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Transcript of Anestesia Ocular
Ophthalmol Clin
Preface
Ocular Anesthesia
Marlene R. Moster, MD Augusto Azuara-Blanco, MD, PhD, FRCS (Ed)
Guest Editors
The goal of this volume is to provide practical
clinical information about anesthesia for ocular sur-
gery. These articles have been written for both anes-
thetists and ophthalmologists, and so we have tried
to integrate the most commonly used techniques
and important recent developments, especially in lo-
cal anesthesia.
We have dedicated an article to each of the types
of anesthesia (eg, general, orbital regional, sub-
Tenon’s) and to different types of ocular surgery
(eg, cataract, glaucoma, vitreoretinal, pediatric) to
help incorporate the latest updated material with cur-
rent usage. The practical approach of this volume
is also reflected in the articles on preparation for
anesthesia and preoperative medical testing, seda-
tion techniques, anesthesia for the open globe, treat-
ment of the blind painful eye, and management of
complications. Numerous illustrations have been
used to provide a natural and easily understandable
flow of information. We believe this volume has
been greatly enriched by the inclusion of articles on
history, pharmacology, and cost-effectiveness of ocu-
lar anesthesia.
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.017
We are indebted to the contributors to this volume
for giving so generously of their time and work. They
are all recognized leaders in ophthalmic anesthesia
and surgery. Our expert collaborators have written
comprehensive articles and have also shared their
personal preferences. We are also extremely grate-
ful to Maria Lorusso, our commissioning editor at
Elsevier, for her help, patience, and advice, and to
Yvette Williams for her expert editorial assistance.
Marlene R. Moster, MD
Wills Eye Hospital
Glaucoma Service
900 Walnut Street
Philadelphia, PA 19107, USA
E-mail address: [email protected]
Augusto Azuara-Blanco, MD, PhD, FRCS (Ed)
Department of Ophthalmology
Aberdeen University Hospital
Foresterhill Road
Aberdeen, AB25 2ZN, UK
E-mail address: [email protected]
N Am 19 (2006) xi
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ophthalmology.theclinics.com
Ophthalmol Clin N
Seeing an Anesthetic Revolution: Ocular Anesthesia
in History
Douglas R. Bacon, MD, MA
Department of Anesthesiology, Mayo Clinic College of Medicine, Ch1-140, 200 First Street, SW, Rochester, MN 55905, USA
Each surgical procedure places unique demands
on the anesthesiologist to create surgical anesthesia
with minimal physiologic trespass on the patient as
well as the surgical repair. In surgery of the eye, the
quest for an anesthetic that does not harm the eye or
the patient can be a challenge. The removal of cata-
racts is one of the most frequently performed opera-
tions in the United States, and the majority of patients
requiring the procedure are elderly and often have
other significant medical conditions.
Early ocular anesthesia
Historically, ocular procedures have had an enor-
mous influence on the discovery of anesthetic mo-
dalities. Before the discovery of surgical anesthesia in
the 1840s, operations on the eye were difficult, as the
sensitive organ would not willing yield to the sur-
geon’s knife. On October 16, 1846, William Thomas
Green Morton demonstrated the anesthetic effects of
diethyl ether as a jaw tumor was removed from
Gilbert Abbott at the Massachusetts General Hospital
[1]. News of this event traveled around the world, and
operations were soon performed that had only been
dreamed about for centuries before. When Lister
conquered infection some 20 years later, surgery
began an explosive growth, with new, more invasive
operations successfully done around the world.
Ocular surgery began to grow. For example, both
William J. and Charles H. Mayo began to perform
procedures on the eye shortly after their respective
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.014
E-mail address: [email protected]
graduations from medical school. In fact, the first
operation done at St. Mary’s Hospital was an eye
operation [2]. But there was a problem. Before thin
suturing material was available to close the eye, the
wound was left open. Ether was notorious for causing
postoperative retching, and therefore damage to the
eye. A solution was needed.
In Vienna, Sigmund Freud began working with
cocaine. He shared some of the crystals with Carl
Koller (Fig. 1) just before leaving to go on vacation.
Koller noticed that his lips became numb when he put
a solution of cocaine crystals on his tongue. In a
eureka moment, Koller realized that this same
solution ought to make the surface of the cornea
numb. Going into the laboratory, he placed drops of
the cocaine solution on the eyes of several experi-
mental animals, and was able to touch the eye with-
out any reaction. Koller then numbed his own eye,
and that of an assistant. He realized he now had a
topical anesthetic for the eye [3].
Koller quickly took this new anesthetic to the
ophthalmology clinic. He was successful in its use in
eye surgery in a large number of patients. Putting
the results together in a paper, which was accepted
for presentation at the prestigious Congress of Ger-
man Ophthalmologists meeting, September 15 and
16, 1884 in Heidelberg, Koller was anxious to tell his
colleagues of his discovery. Koller, however, could
not afford to go. His friend, Josef Brettauer presented
the paper, which caused a number of people to begin
to see the potential of cocaine as an anesthetic, and a
‘‘rival’’ to ether [4].
William Halstead, who traveled to Europe and
was at the Allgemiene Krankenhouse at the time of
Koller’s discovery, came back to the United States
Am 19 (2006) 151 – 154
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ophthalmology.theclinics.com
Fig. 1. Carl Koller. (Courtesy of the Wood Library-Museum,
Park Ridge, IL.)
bacon152
and began to work with cocaine. He would infiltrate
the cocaine into the skin and dissect down to nerve
trunks. While looking at the dissected nerve, Halstead
instilled a solution of cocaine to cause blockage in
nerve transmission—the first regional anesthesia. Hal-
stead published the results of his experience [5] be-
fore he entered treatment for a cocaine addiction [6].
Koller’s fellow Europeans picked up on the idea
of regional anesthesia. Schleich began infiltrating
cocaine into the spinal cord when attempting a lumbar
puncture [7]. Bier and Hildenbrand were successful in
injecting cocaine intrathecally, and producing spinal
anesthesia [8]. James Corning, in New York, produced
the first epidural anesthetic [9]. Thus, the quest for
better anesthesia for ophthalmologic surgery resulted
in a new form of anesthesia—regional! And its
founder, Carl Koller, was forced to leave Vienna after
a duel, settled in New York City, and practiced as an
ophthalmologist [4].
Regional blockade of the eye
The blocks in use for ophthalmologic surgery
today have developed in the years since Koller’s
remarkable discovery. Most interestingly, H. Knapp
described a block in the eye using a needle and
syringe, very similar in technique to the retrobulbar
block. Writing in 1884, months after the discovery of
cocaine’s local anesthetic quality, Knapp’s work
never gained popularity [10], most likely because of
the unique properties of cocaine. Blocks are often
patchy, and absorption of the agent causes hyper-
tension and tachycardia, as well as a feeling of
euphoria [11]. Increasing blood pressure may have
contributed to an increase in intraocular pressure, and
without fine suture to close the incision, intraocular
contents may well have been extruded.
However, in 1905, a new local anesthetic,
procaine, was synthesized and used clinically. An
ester, this agent had a predicable onset and duration
of action [12]. Yet this did not change ocular
anesthesia. Gaston Labat, writing in the first textbook
of regional anesthesia published in the United States
believed topical anesthesia was sufficient and com-
mented, ‘‘The following operations need no other
form of anesthesia: superficial interventions on the
conjunctiva, treatment of corneal ulcers by cautery,
removal of foreign bodies from the conjunctiva and
cornea, plastic on the cornea, cataract operations,
iridectomy and other operations on the lens and iris’’
(p. 141) [13].
In 1934, W. S. Atkinson described the classic
retrobulbar block [14]. Atkinson had the patients look
upward and inward before the block was performed.
Using procaine, this form of regional anesthesia of
the eye was very successful and slowly gained
popularity across the United States [15].
However, the retrobulbar block had some signifi-
cant complications associated with it, including dam-
age to the optic nerve. Other options were sought, and
cadaveric study demonstrated that local anesthetics
placed outside intraorbital muscle cone would pene-
trate and create an anesthetic eye. First described in
1986, the peribulbar block is felt to be safer than the
retrobulbar block as the needle is placed at a greater
distance from the eye and optic nerve than with the
retrobulbar block [15].
In the early 1990s, an additional technique was
rediscovered. First described by K. C. Swan in 1956
[16], sub-Tenon’s block involves the injection of
local anesthetic into the episcleral space, which will
create acceptable anesthetic conditions for operations
on the eye. An injection of 6 to 11 milliliters of local
anesthetic is enough to both anesthetize the eye and
the muscles around it, thus making the eye motion-
less. Since the eye muscles are paralyzed, there is no
need for any additional blocks [17].
Since its reintroduction in the 1990s, Koller’s
topical anesthesia for eye surgery has gained in popu-
larity. With improved local anesthetics, the anesthetic
produced by this method was equal, in many
surgeons’ and anesthesiologists’ hand, to that
produced by block, without some of the complica-
tions. However, studies indicate that there may be
some slight increase in postoperative discomfort
ocular anesthesia in history 153
when topical anesthesia is used alone. The experience
of the surgeon is critical in ensuring that the
anesthetic is successful [18].
General anesthesia
In ocular surgery, general anesthesia has been
used, especially since the rise of regional and topical
anesthetics, for those who cannot cooperate in the
operating room or who may have medical conditions,
such as Parkinson’s disease, which cause tremors that
would interfere with the operation. However, in many
ocular trauma cases, the globe is open, and repair
may take longer than regional anesthesia will last.
Thus, a general anesthetic is necessary. In most
trauma cases, because of a ‘‘full stomach’’ rapid se-
curing of the airway is necessary, and the use of
succinylcholine as a quick onset, ultrashort-acting
neuromuscular blocking agent has been recom-
mended. Succinylcholine, however, raises intraocular
pressure [19].
In the 1950s, shortly after the clinical introduction
of succinylcholine, concerns were raised about its use
in open globe procedures. Experimentally, it was
noted that vitreous humor could be extruded while
the eye muscles fasciculated. This potentially had
devastating consequences for the patient. In several
letters to the editor, anecdotal case reports of just such
phenomena occurring were reported. It soon became
widely accepted that succinylcholine was contra-
indicated in the indication of anesthesia when an
open globe was present. Indeed, the combination of
penetrating eye trauma, difficult airway, and a full
stomach became one of the anesthesiologist’s least
favorite nightmares [19].
In the 1990s, however, the trend toward evidence-
based medicine made many physicians’ questions
accepted teaching in anesthesiology. In fully review-
ing the literature, there were no peer-reviewed case
reports of ocular damage when succinylcholine was
used for induction. In point of fact, there were several
large series that pointed in just the opposite direction
[19]. The subject remains controversial.
Subspecialty society
In 1986, the Ophthalmic Anesthesia Society was
formed to ‘‘ensure that the highest quality anesthesia
care is provided to patients undergoing cataract and
other ophthalmic surgical procedures’’ (p. 1) [20].
The society holds 2-day annual meetings where
matters of importance to the field, new research,
and education are presented. More importantly, there
is a community of anesthesia professionals who
can interact with each other and develop this sub-
specialty area. The society’s newsletter, posted on
their Web site, is a marvelous reference for those in-
terested in the field. In 2006, the society will cele-
brate its 20th anniversary with an exciting meeting in
Chicago, Illinois.
Summary
The history of ocular anesthesia reflects the
broader history of anesthesiology and has made
important contributions to the field. Carl Koller’s
search for an anesthetic that was superior to the
general anesthesia available to him led to the creation
of an entire new division of anesthesia. Regional
anesthesia has been used successfully in countless
cases. Specifically, Koller’s demonstration of topical
anesthesia of the eye has remained in use, although
slightly modified, since its inception. The popularity
of cutaneous regional anesthesia in the first four
decades of the twentieth century may have been
responsible for Atkinson’s description and the sub-
sequent popularity of the retrobulbar block. Further
research and cadaveric demonstrations have de-
veloped additional regional anesthetic techniques
including the peribulbar and sub-Tenon’s blocks.
Finally, the use of succinylcholine in open globe
anesthesia is a marvelous example of the continuing
examination of the evidence within medicine. New
conclusions drawn from old data, supplemented by
new investigations can successfully challenge old
accepted ideas in medicine.
References
[1] Fenster J. Ether day. New York7 HarperCollins Pub-
lishers, Inc; 2001.
[2] Clapesattle H. The doctors Mayo. Minneapolis (MN)7
University of Minnesota Press; 1941. p. 252.
[3] Koller C. Personal reminiscences of the first use of
cocain as local anesthetic in eye surgery. Curr Res
Anesth Analg 1928;7:9–11.
[4] Wyklicky H, Skopec M. Carl Koller (1857–1944)
and his time in Vienna. In: Scott DB, Mc Clure J,
Wildsmith JAW, editors. Regional anesthesia 1884–
1984. Sodertalje, Sweden7 ICM; 1984. p. 12–6.
[5] Halstead WS. Practical comments on the use and abuse
of cocaine; suggested by its invariably successful
employment in more than a thousand minor surgical
operaitons. New York Medical Journal 1885;42:294.
bacon154
[6] Olch PD, William S. Halstead and local anesthesia.
Contributions and complications. Anesthesiology
1975;42:479–86.
[7] Goerig M, Schulte am Esch J. Carl-Ludwig Schleich
and the scandal during the annual meeting of the
German Surgical Society in Berlin in 1892. In: Fink
BR, Morris LE, Stephen CR, editors. The history of
anesthesia. Park Ridge (IL)7 The Wood Library-
Museum; 1992. p. 216–22.
[8] Goerig M, Argarwal K, Schulte am Esch J. The
versatile August Bier (1861–1949)—father of spinal
anesthesia. J Clin Anesth 2000;12:561–9.
[9] Marx GF. The first spinal anesthesia. Who deserves the
laurels? Reg Anesth 1994;19:429–30.
[10] Knapp H. On cocaine and its use in ophthalmic and
general surgery. Arch Ophthal 1884;13:402–8.
[11] Bacon DR. Regional anesthesia and chronic pain ther-
apy: a history. In: Brown DL, editor. Regional
anesthesia and analgesia. Philadelphia7 W.B. Saunders
Co; 1996. p. 10–22.
[12] Calatayud J, Gonzalez A. History of the development
and evolution of local anesthesia since the coca leaf.
Anesthesiology 2003;98:1503–8.
[13] Labat G. Regional anesthesia: its techniques and
clinical application. Philadelphia7 WB Saunders; 1924.
[14] Atkinson WS. Retrobulbar injection of anesthetic
within the muscular cone. Arch Ophthal 1936;16:494.
[15] McGoldrick KE, Gayer SI. Anesthesia and the eye.
In: Barash PG, Cullen BF, Stoelting RK, editors.
Clinical anesthesia. 5th edition. Philadelphia7 Lippen-
cott Williams & Wilkins; 2006. p. 974–96.
[16] Swan KC. New drugs and techniques for ocular
anesthesia. Trans Am Acad Ophthalmol Otolaryngol
1956;60:368–75.
[17] Ripart J, Nouvellon E, Chaumeron A. Regional
anesthesia for eye surgery. Reg Anesth Pain Med
2005;30:72–82.
[18] Crandall AS. Anesthesia modalities for cataract sur-
gery. Curr Opin Ophthalmol 2001;12:9–11.
[19] Vachon CA, Warner DO, Bacon DR. Succinylcholine
and the open globe: tracing the teaching. Anesthesiol-
ogy 2003;99:220–3.
[20] Ophthalmic Anesthesia Society. Available at: http://
www.eyeanesthesia.org/index.html. Accessed January
16, 2006.
Ophthalmol Clin N
Pharmacology of Local Anesthetics
Tim Jackson, MB, ChB, MRCP, FRCAT, Hamish A. McLure, MB, ChB, FRCA
Department of Anesthesia, St James’s University Hospital, Beckett Street, Leeds LS7 9TF, UK
The stimulus for the development of regional
anesthesia was the retreat from poor surgical con-
ditions afforded by primitive general anesthesia in the
latter half of the 19th century. Karl Koller, an eager
young ophthalmic surgeon, was investigating the ef-
fects of cocaine. He found that a few drops instilled
into his own conjunctival fornix produced insensi-
tivity to injury. These magical properties made it pos-
sible to perform painful procedures on patients who
were awake, in quiet surgical conditions without the
systemic toxicity of general anesthesia. However, co-
caine is not without serious adverse effects and
reports of toxicity limited universal uptake by the
ophthalmic community. Two events brought new life
to the field of ophthalmic local anesthesia: (1) the
development of procaine, a much safer alternative to
cocaine, and (2) the description of retrobulbar an-
esthesia by Atkinson [1]. The agents and injection
methods have since been refined and local anesthesia
is now the most common technique used to provide
anesthesia for ocular surgical procedures. Despite
improvements, there is still the potential for compli-
cations, both local and systemic, during routine pro-
cedures. To reduce risks, it is vital for the practitioner
to have a thorough understanding of the physiology
of neuronal function, the chemistry of various local
anesthetic agents, and the pathogenesis of toxicity.
Physiology of nerve conduction
Impulses are transmitted along the nerve in the
form of a wave of electrical activity called an action
potential. This rapid process (1–2 msec) is mediated
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.006
T Corresponding author.
E-mail address: [email protected]
(T. Jackson).
by alterations in the permeability of the neuronal
membrane to various cations, notably sodium and
potassium. In the non-excited resting state, chemical
and electrical gradients exist across the neuronal
membrane. These gradients are established by various
ion channels, which may be passive, active, or voltage
gated. The nerve membrane is relatively imperme-
able to the passage of sodium (Na), but permeable to
potassium (K). In addition to these passive move-
ments, active Na/K-ATPase channels pump potassium
into the cell and sodium outwards, in a molar ratio
of 3:2 respectively. The net effect of these two pro-
cesses, active and passive, is to create a resting po-
tential across the neuronal membrane, in which the
interior is negatively charged (�70 to �90 mV).
The membrane also contains voltage-gated so-
dium channels, which open and close based upon the
membrane potential. Each channel molecule consists
of a pore formed of one a subunit and one or two bsubunits. The a subunit is in turn composed of four
domains (D1–4), each of which comprises six trans-
membrane helical segments (S1–6). These channels
are able to cycle through four states or phases: rest-
ing, activated, inactivated, and deactivated (Fig. 1).
Functionally, the channel can be considered to pos-
sess two gates, an outer m gate and an inner h gate.
At the resting membrane potential, the m gate is
closed, but the h gate is open. On stimulation (ac-
tivation) the m gate opens, and there is an influx of
sodium ions down their electrochemical gradient,
which causes a rise in the membrane potential. If this
occurs with sufficient magnitude, a threshold poten-
tial of about �60 mV is reached, there is widespread
opening of sodium channels, and even greater influx
of sodium ions such that the membrane potential
overshoots neutral to reach a peak of +20 mV. At this
point the h gate closes, which inactivates the channel
and prevents further sodium flux. This process of
Am 19 (2006) 155 – 161
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ophthalmology.theclinics.com
Fig. 1. Diagramatic representation of sodium channel in three main conformational states.
jackson & mclure156
depolarization produces a potential difference rela-
tive to neighboring areas of the neuronal membrane,
which in turn generates an electrical current that tends
to depolarize those neighboring areas of membrane.
Thus, a wave of depolarization flows along the nerve,
propagating the initial stimulus.
During the inactivated phase there is no inward
movement of sodium through the voltage gated chan-
nels, and the resting membrane potential is restored
by continued action of the Na/K-ATPase and pas-
sive potassium leakage. When the membrane potential
reaches �60 mV, the m gate closes and the channel is
said to be deactivated. During these latter two phases
the nerve is refractory to further stimulation, which
prevents rapid re-depolarization of that section of neu-
ronal membrane and retrograde conduction.
Mechanism of action
Local anesthetics reversibly block conduction of
action potentials by interacting with the D4–S6 por-
tion of thea subunit of the voltage-gated sodium chan-
nels. This site of action is intracellular, so the local
anesthetic must first diffuse through the lipophilic
nerve membrane. Local anesthetics are administered
in an acidic solution that causes most of the drug to be
present in the ionized form, which is lipophobic.
Therefore, the drug must first be converted to the un-
ionized form in sufficient quantity to enter the nerve
cell. This depends upon the pKa of the local anesthetic
and the pH of the tissue. Once inside the nerve cell, the
lower pH converts the drug back into the ionized
form, which is then able to block the sodium channels.
This reduces the influx of sodium ions and sub-
sequently, the depolarization of the membrane poten-
tial slows. If sufficient channels are blocked, it will
prevent the threshold potential from being reached,
and prevent propagation of an action potential, with-
out affecting either the resting membrane potential
(which is independent of voltage-gated sodium
channels) or the threshold potential itself.
In addition to the action of the ionized local an-
esthetic moiety on the intracellular portion of the
trans-membrane sodium channel, the non-ionized
form also affects the intra-membrane areas of the
channel: it has direct physical effects on the ex-
pansion of the lipid bilayer. The action of local an-
esthetics is augmented by the blockade of potassium
channels, calcium channels, and G-protein coupled
receptors [2–4].
Local anesthetic agents exhibit differing affinities
with their binding site depending on the state of the
channel, as the conformational changes in the channel
inherent in the cycling of these states reveal or
obscure the binding site. Affinity is greatest when the
channel is open (activated or inactivated) and least
when it is closed (deactivated and resting). Although
this suggests that access of the local anesthetic to its
binding sites will differ based on the frequency of
nerve stimulation, there is no evidence that this use-,
phase-, or frequency-dependent block can be manip-
ulated to alter the quality of the block [5].
In addition to these state-dependent differences in
channel affinity, there are also differences between
local anesthetic agents. Lidocaine binds and disso-
ciates rapidly, whereas bupivacaine dissociates more
slowly. This difference is relatively unimportant for
neuronal conduction, but is crucial to cardiac toxicity.
Conduction of the cardiac impulse is mediated by
voltage-gated sodium channels. Lidocaine binds and
dissociates from these channels quickly; there is little
chance that a frequency-dependent block of the im-
pulse would occur. However, bupivacaine, and part-
icularly the R-isomer, which dissociates more slowly
than the S-isomer, can produce a more profound
frequency-dependent block [6]. Cardiac conduction is
slowed and lethal arrhythmias may occur.
Chemistry
The molecular structure of the standard local an-
esthetics conforms to a similar pattern of a lipophi-
Fig. 2. Generic structure of local anesthetic agents.
pharmacology of local anesthetics 157
lic aromatic ring, linked to a hydrophilic tertiary
or quarternary amine derivative. The intermediate
hydrocarbon chain is joined to the amine moiety by
an ester, amide, ketone or ether, and may be used to
classify the drug as such (Fig. 2). Other dissimilar
compounds may also possess local anesthetic prop-
erties, although they are seldom used in ophthalmic
regional anesthesia (eg, amitryptiline, meperidine)
[7,8]. The clinically used agents are the ester and
amide local anesthetics. The ester bond is relatively
unstable, during hydrolysis, which ensures rapid me-
tabolism in vivo, but shelf life is dramatically short-
ened and autoclave sterilization is impossible.
Ionization
Local anesthetics are weak bases (pKa 7.6–8.9)
(Table 1); poorly soluble in water and therefore
usually presented in acidic hydrochloride salt sol-
utions (pH 3–6). In this form, the local anesthetic
rapidly becomes reduced to a cationic form. This
process is readily reversible, and the relative propor-
tions of neutral base and ionized form develop equi-
Table 1
Physicochemical and clinical properties of local anesthetics
Agent
pKa
(25�C) Speed of onset
Partition
coefficienta
Amide agents
Bupivacaine 8.1 Intermediate 346
Levobupivacaine 8.1 Intermediate 346
Etidocaine 7.7 Fast 800
Lidocaine 7.7 Fast 43
Mepivacaine 7.6 Fast 21
Prilocaine 7.8 Fast 25
Ropivacaine 8.2 Intermediate 115
Ester agents
Cocaine 8.7 Slow Ub
Amethocaine 8.5 Slow 221
Procaine 8.9 Slow 1.7
a Partition coefficient with n-octanol/buffer.b U unknown.
librium as described by the Henderson-Hasselbach
equation. The proportions of each form of the drug
depend on the pH of the solution and the pKa of the
particular drug in question, which is the dissociation
constant and denotes the pH at which the ionized and
neutral forms are present in equal amounts.
pH ¼ pKa þ log base½ �= acid½ �
For a base pH=pKa + log [un-ionized] / [ionized]
Because the pKa for a given local anesthetic agent
is constant, the clinical relevance is in comparing the
speed of onset. Most clinically available local anes-
thetics have pKa values in excess of the pH of extra-
cellular fluid; therefore, the ionized form dominates
after injection, which makes it unable to penetrate the
cell. Those agents with pKa values at the lower end of
the range will have a greater proportion present in the
neutral form, which diffuses more rapidly into the
nerve cell and their site of action. Increasing the pH
of the carrier solution will similarly favor the
formation of a more neutral base, although chemical
stability is reduced by this maneuver. The converse is
true for inflamed tissue, which inherently has a lower
Potency Toxicity
Protein
bound (%) Duration
High High 95 Long
High Intermediate 96 Long
High High 94 Long
Intermediate Low 64 Intermediate
Intermediate Low 75 Intermediate
Intermediate Low 55 Intermediate
Intermediate Intermediate 94 Long
High Very high 98 Long
Intermediate Intermediate 76 Intermediate
Low Low 6 Short
jackson & mclure158
pH than the usual physiological value (7.4), and
renders the local anesthetic less effective.
Lipid solubility
Lipid solubility is a property of the hydrocarbon
chain and aromatic group, and is represented by the
partition coefficient which is a measure of the rela-
tive distribution of agent between an aqueous phase
(eg, buffer at pH 7.4) and non-ionized solvent phase
(eg, octanol, heptane, hexane). As the partition coeffi-
cient gets higher, the drug becomes more lipid solu-
ble, and the concentration of the drug within the
nerve membrane goes up. This is a major determinant
of potency; agents that have high partition coeffi-
cients (eg, bupivacaine, etidocaine) have correspond-
ingly high potency (see Table 1).
Protein binding
Local anesthetics bind to tissue and plasma pro-
teins (albumin, a1-acid glycoprotein). Albumin is
considered high volume, low affinity binding,
whereas, a1-acid glycoprotein is low volume, high
affinity. These proteins represent a reservoir of the
drug, although it is the free drug that is active. The
amount of protein binding correlates well with du-
ration of action of local anesthetic agents; however,
other factors such as potency, dose, presence of vaso-
active substances, and vascularity of the tissue also
have effects. As local anesthetics are absorbed sys-
temically, the binding sites are occupied gradually,
and have apparent stability in free plasma concen-
trations. However, once the binding sites are satu-
rated, toxic levels can be rapidly reached and have
disastrous consequences. This may also occur with
more modest doses in the presence of acidosis, when
local anesthetic dissociates from the binding sites.
Chirality
Organic molecules contain asymmetric carbon
atoms, which may exist as mirror image or stereo-
isomers. They can be identified by the way they
rotate polarized light, and are either R or L, � or + for
dextro- or levorotatory respectively. Bupivacaine,
etidocaine, mepivacaine, prilocaine, and ropivacaine
all have such carbon atoms, and most are produced as
racemic mixtures: composed of equal amounts of
both dextrorotatory and levorotatory isomers. The
exceptions are S-ropivacaine and S-bupivacaine,
which have been marketed separately. They have
similar physicochemical properties, including those
relating to their pharmacokinetics, but behave differ-
ently at biological receptors. As previously men-
tioned, S-bupivacaine (and indeed S-ropivacaine)
demonstrates significantly reduced toxicity.
Metabolism
Ester local anesthetics are hydrolyzed very rapidly
by tissue and plasma cholinesterases. The metabolites
are inactive as local anesthetics, but include para-
aminobenzoic acid (PABA) which can be allergenic.
The rapidity of this metabolism provides some degree
of safety from toxicity, because plasma levels fall so
rapidly. The exception, although no longer used di-
rectly in ophthalmology, is cocaine, which is metab-
olized more slowly in the liver.
Amides are much more stable in plasma than
esters. They are initially absorbed, then distributed to
the pulmonary circulation, where they are temporarily
sequestered by ion-trapping because of the relatively
low pH of extravascular lung water. They are pre-
dominantly cleared by hepatic microsomal phase I
and II reactions, although a small percentage is
cleared by renal mechanisms. The rate of metabolism
depends heavily on liver blood flow, and differs be-
tween agents. Prilocaine and etidocaine are the most
rapid, lidocaine and mepivacaine are intermediate,
and bupivacaine and ropivacaine are the slowest. The
clearance of prilocaine exceeds what the liver could
do alone, which suggests that extra-hepatic mecha-
nisms are also involved, most likely in the lung [9].
Toxicity
Toxic reactions may be local or systemic. Local
toxicity occurs when local anesthetic is injected di-
rectly into a structure, such as a nerve or muscle,
whereas systemic toxicity follows absorption of ex-
cessive amounts or inadvertent intravascular injec-
tion. An exaggerated effect with systemic toxicity may
also occur following accidental sub-dural injection.
Neurotoxicity
Local anesthetics may cause damage to neural
tissue, either by direct injection into a nerve, or in
situations where highly concentrated local anesthetic
solutions bathe nerves for a prolonged period. It
may also occur with concentrations of lidocaine that
would be used in clinical practice. An in vitro squid
pharmacology of local anesthetics 159
axon model showed neurotoxicity with lidocaine 2%
[10]. Lidocaine-induced neurotoxicity has also been
seen in patients with the use of spinal micro catheters
and 5% lidocaine [11]. The presumed mechanism is
relatively concentrated lidocaine that bathes vulner-
able nerves for a prolonged period of time. Fortu-
nately, in ophthalmic regional anesthesia, neither the
concentration, nor the duration of proximity to nerves
of the local anesthetic is sufficiently high, so the local
anesthetic is unlikely to be the sole culprit in neu-
rological damage. In these cases many patients have
coexistent vascular pathology. Highly concentrated
local anesthetic is often used with vasoconstrictors,
and high orbital pressures may develop. It is not sur-
prising that nerve ischemia and subsequent damage
may occur in this adverse environment.
Myotoxicity
Direct injection into muscle can cause muscle
necrosis. The subsequent fibrosis and contracture of
the muscle can significantly impair function and
cause diplopia, which could require surgery. This can
be particularly devastating in elderly patients whose
balance and mobility may already be compromised.
The inferior oblique, inferior rectus, and medial rec-
tus muscles are most frequently involved. This injury
may occur by direct injection into the muscle, but it
has also been reported with sub-Tenon’s injection,
where the mechanism of action may be caused by
local anesthetic that pools around or penetrates the
muscle through small fenestrations in Tenon’s fascia.
It has been suggested that the risks of local anesthetic
induced myotoxicity may be reduced by the addition
of hyaluronidase, which allows dispersal of local
anesthetic away from the muscle [12].
Systemic toxicity
Systemic reactions are uncommon, but may prove
disastrous. In ocular regional anesthesia, systemic re-
actions may occur when anesthetic agent is injected
through the dural cuff into cerebrospinal fluid around
the optic nerve. Brainstem anesthesia could occur
along with loss of consciousness and respiratory and
cardiovascular depression. Supportive treatment is
aimed at securing the airway, providing positive pres-
sure ventilation, and using fluids and vasopressors to
support the circulation. Systemic reactions may also
result from administration of an inappropriately large
dose, or follow intravascular injection of even a small
dose. Intravenous injections of an appropriate dose
may cause significant effects. Reactions can also oc-
cur when much smaller doses are injected at high
pressure into the arterial system, which results in the
retrograde spread of high concentrations of local an-
esthetic solution direct to the brain. The effect of these
mishaps depends upon the drug injected, the speed of
injection, the total dose administered, and the phys-
iology of the patient. Methods aimed at reducing these
complications include techniques to carefully position
the injecting needle, aspiration before every injection
(although a negative aspiration does not exclude the
possibility of intravascular injection), the use of a
test dose, fractionated doses, adequate time between
doses, the use of a less toxic local anesthetic, aware-
ness of maximum doses in different settings, and the
addition of other agents (opioids, clonidine, hyal-
uronidase, bicarbonate, epinephrine) to reduce the
amount of local anesthetic required.
The sequence of toxic phenomena depends upon
the rate of increase in plasma concentration. If the
plasma concentration rises slowly, symptoms develop
such as circumoral and tongue paraesthesiae, a me-
tallic taste, and dizziness, followed by slurred speech,
diplopia, tinnitus, confusion, agitation, muscle twitch-
ing, and convulsions. At even higher plasma levels,
the effects become depressive, and lead to coma and
death. As with direct subarachnoid injection, the treat-
ment is supportive and anticonvulsants are adminis-
tered to control seizure activity.
As plasma levels of local anesthetics increase, neu-
rological effects are accompanied by cardiovascular
complications, which can be difficult to treat. Im-
pending toxicity may be signaled by bradycardia with
prolonged PR interval (the time, in seconds, from the
beginning of the onset of atrial depolarization to the
beginning of the onset of ventricular depolarization)
and broad QRS complex (the EKG representation of
the heart’s electrical impulse as it passes through the
ventricles). This may be followed by a range of dys-
rhythmias, such as heart block, multifocal ectopics,
tachycardia, and ventricular fibrillation. Again, treat-
ment is supportive, but is likely to involve the use of
antiarrhythmics such as amiodarone, phenytoin, and
bretyllium. There is evidence that suggests lipid emul-
sion infusions (intralipid) and clonidine may also
have a supportive role. Although lidocaine has a role
in the treatment of ventricular tachydysrrhythmias, it
would be sensible to avoid it if local anesthetic car-
diotoxicity has been established. Resuscitation is
difficult and may require prolonged efforts, but clini-
cians should remember that the local anesthetic-
induced neuronal depression may be protective
against brain injury.
jackson & mclure160
Increasing laboratory data suggest that modern,
single-isomer local anesthetic preparations provide
improved safety profiles. Nancarrow and colleagues
[13] compared the toxic effects of intravenous bu-
pivacaine, ropivacaine, and lidocaine in sheep, and
found a ratio of lethal doses of 1:2:9. The group that
received lidocaine died with respiratory depression,
bradycardia, and hypotension, but without arrhyth-
mias, whereas, three of four sheep treated with bu-
pivacaine died because of ventricular arrhythmias in
the absence of hypoxia or acidosis. The group treated
with ropivacaine died from a combination of these
causes, or as a result of sudden onset ventricular ar-
rhythmias alone. The arrhythmias precipitated by local
anesthetics are caused by depression of the rapid
depolarization phase (Vmax) of the cardiac action
potential. This leads to slowed conduction, re-entrant
rhythms, and predisposition to ventricular tachycardia.
The effects of arrhythmias on cardiac output are
augmented by myocardial depression, although this
may be offset by the myocardial stimulation asso-
ciated with seizures [14]. In an attempt to isolate the
cardiovascular effects, Chang and colleagues [15]
infused bupivacaine, levobupivacaine, and ropiva-
caine directly into the coronary arteries of conscious
sheep. No significant differences were found in sur-
vival or fatal doses, which indicate that these agents
may have equal cardiac toxicity [16]. Using an
anaesthetised swine model, Morrison and colleagues
[17] administered intracoronary injections of bupiva-
caine, levobupivacaine, and ropivacaine. They found
little difference in fatal dose between levobupivacaine
and ropivacaine, but racemic bupivacaine had greater
cardiotoxicity. Feldman and colleagues [18] showed
that similar doses of ropivacaine and bupivacaine
caused convulsions in dogs, but that the mortality rate
was lower in the animals treated with ropivacaine.
Isolated organ experiments have linked local anes-
thetic toxicity in the brain to disturbances in the heart
[19]. The varied results of these studies may reflect
inter-species variation, or may be a reflection of the
complex interplay between the central nervous sys-
tem, the myocardium, and general anesthesia during
local anesthetic toxicity.
Although the conclusions of these animal studies
are compelling, it is difficult to confirm their results
in human subjects, particularly with respect to lethal
doses. Scott [20] administered a maximum of 150 mg
of ropivacaine and racemic bupivacaine to healthy
volunteers. Of the 12 subjects, 7 tolerated the maxi-
mum dose of ropivacaine, whereas only 1 subject was
able to tolerate 150 mg of bupivacaine. Plasma levels
showed that central nervous system and cardiovas-
cular symptoms occurred at lower plasma levels with
bupivacaine than ropivacaine. In addition, ropiva-
caine reduced myocardial depression and widening of
the QRS (wave) complex. Bardsey and colleagues
[21] used intravenous infusions of lidocaine to fa-
miliarize 12 healthy volunteers with the central ner-
vous system effects of local anesthetic toxicity. A few
days later the volunteers received intravenous infu-
sions of levobupivacaine or bupivacaine at a rate of
10 mg/min until they had received 150 mg, or had
begun to experience central nervous system toxic ef-
fects. Cardiovascular monitoring demonstrated that,
despite higher plasma levels, levobupivacaine de-
pressed myocardial function significantly less than
bupivacaine. Equal doses of intravenous levobupiva-
caine were compared with ropivacaine by Stewart
and colleagues [22]. No differences were found in
terms of central nervous system symptoms or car-
diovascular effects.
Animal and human studies have shown improved
safety with the single-isomer local anesthetics levo-
bupivacaine and ropivacaine. However, they may still
provoke severe toxic reactions. In addition, the mar-
ginally reduced potency of ropivacaine requires a
larger total dose and may reduce any benefit of the
single isomeric form.
Allergy
The first reports of allergy to local anesthesia were
from a dentist who developed contact dermatitis after
repeated exposed to apothesin, an ester local anes-
thetic [23]. Further minor reactions were reported, but
very few individuals developed anaphylaxis. The
trigger for these reactions was found to be PABA, an
intermediate metabolite of ester hydrolysis. Sensitiv-
ity to PABA may also occur as a result of exposure to
certain foodstuffs or cosmetics, and because sulpho-
namides structurally resemble PABA, cross-reactivity
to all these substances may occur.
The development of amide local anesthetics in the
1940s effectively reduced reports of allergic reac-
tions. Amides are now considered to be very rare
allergens; only about 1% of alleged reactions are be-
lieved to be caused by a truly immune-mediated
process [24]. Reports of previous allergic reactions
come largely from the dentist’s surgery. This is likely
to have been a vagal response in a patient who was
anxious and in a semi-upright position, or an in-
advertent intravascular injection of local anesthetic
solution and its associated vasopressor, which pro-
duced some unpleasant cardiovascular effects. Never-
theless, it is important to exclude allergy by referral to
an allergist, who will perform skin-prick tests for
pharmacology of local anesthetics 161
mild reactions or in-vitro testing for patients who
have suffered an anaphylactoid reaction.
Summary
Local anesthesia forms the backbone of all oph-
thalmic anesthetic techniques. From its inception in
the 19th century to the modern era, developments
in the chemistry of local anesthetic agents and im-
provements in operative conditions have led to
reductions in the incidence of adverse reactions. Ne-
vertheless, use of this powerful group of agents is
not without hazard, and it is vital to have a thorough
understanding of the underlying chemistry, and
their potential to cause local and systemic toxicity
when they are used for ophthalmic regional anesthe-
sia. The single-isomer preparations show great pro-
mise in the laboratory, but have yet to demonstrate a
clinical difference.
References
[1] Atkinson WS. Retrobulbar injection of anesthetic within
the muscular cone. Arch Ophthalmol 1936;16:494–503.
[2] Xiong Z, Strichartz G. Inhibition by local anesthetics
of Ca 2+ channels in rat anterior pituatary cells. Eur J
Pharmacol 1998;363:81–90.
[3] Hollman M, Wieczorek K, Berger A. Local anesthetic
inhibition of G protein-coupled receptor signaling by
interference with Galpha(q) protein function. Mol
Pharmacol 2001;59:294–301.
[4] Olschewski A, Hemplemann G, Vogel W. Blockade of
Na + currents by local anesthetics in the dorsal horn
neurons of the spinal cord. Anesthesiology 1998;88:
172–9.
[5] Courtney K. Mechanism of frequency-dependent
inhibition of sodium currents in frog myelinated nerve
by the lidocaine derivative GEA 968. J Pharmacol Exp
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[6] Vanhoutte F, Vereecke J, Verbeke N, et al. Stereo-
selective effects of the enantiomers of bupivacaine on
the electrophysiological properties of the guuinea-pig
papillary muscle. Br J Pharmacol 1991;103:1275–81.
[7] Sudoh Y, Cahoon E, Gerner P, et al. Tricyclic anti-
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[8] Acalovschi I, Cristea T. Intravenous regional anesthe-
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[11] Lambert L, Lambert D, Strichartz G. Irreversible con-
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lopia cases after periocular anesthesia without hyal-
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[14] Rutten A, Nancarrow C, Mather L, et al. Hemody-
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effects of intracoronary bupivacaine, levobupivacaine
and ropivacaine in sheep. Br J Pharmacol 2001;132:
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[16] Huang Y, Pryor M, Mather L, et al. Cardiovascular and
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[17] Morrison S, Dominguez J, Frascarolo P, et al. A
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Ophthalmol Clin N
Preoperative Medical Testing and Preparation for
Ophthalmic Surgery
Bobbie Jean Sweitzer, MD
University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA
As the practice of medicine becomes more
outcome-driven and cost-conscious, clinicians need
to reevaluate and streamline methods of patient care.
A preoperative evaluation is important to
Screen for and optimize co-morbid conditions.
Assess and lower the risk of anesthesia
and surgery.
Establish baseline results to guide perioperative
decisions.
Facilitate timely care and avoid cancellations on
the day of surgery.
The Australian Incident Monitoring Study (AIMS)
found that adverse events were unequivocally related
to insufficient (3.1%; 197 of the first 6271 reports)
and inadequate (11%) preoperative assessments [1].
More than half the incidents were considered pre-
ventable. Delays, complications, and unanticipated
postoperative admissions have been significantly re-
duced by preoperative screening and patient contact.
Ophthalmologic procedures are considered low
risk because of their general lack of physiologic dis-
turbances such as hemodynamic perturbations, sig-
nificant stress response, hypercoagulable state, blood
loss, or postoperative pain [2]. However, ophthalmic
patients are often elderly and have multiple co-
morbid conditions that are a constant threat to well-
being, even without surgery. If general anesthesia
(GA) is necessary, the risk of the procedure may
increase. In a study of patients who had cataract sur-
gery, there was significantly more myocardial ische-
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.007
E-mail address: [email protected]
mia in the group that was given GA compared with
the group that was given local anesthesia. There
was a surprisingly high incidence (31%) of peri-
operative ischemia detected by Holter monitoring for
24 h after surgery. Interestingly, there was no dif-
ference in occurrence of ischemia between the two
groups (probably because of the high rate of coronary
heart disease in this elderly population) but the GA
group had more episodes per patient, especially intra-
operatively [3]. Patients who undergo retinal surgery
have a particularly increased risk because of their
associated co-morbid conditions [4].
Preoperative assessment
At a minimum, a preoperative visit should include
the following:
Interview the patient to review medical, anesthe-
sia, surgical, and medication history.
Conduct an appropriate physical examination.
Review the pertinent diagnostic data (laboratory,
electrocardiogram).
Refer the patient to primary care or specialist
physicians to manage new or poorly
controlled diseases.
Formulate and discuss care plan with patient or
responsible adult.
Several studies have proven the utility of a pa-
tient history and physical examination when making
a diagnosis. A study of patients in a general medical
clinic found that 56% of correct diagnoses were made
based on the history alone, and rose to 73% based on
Am 19 (2006) 163 – 177
reserved.
ophthalmology.theclinics.com
sweitzer164
history plus physical examination [5]. In patients who
have cardiovascular disease, the history established
the diagnosis two-thirds of the time, and the physical
examination contributed to one-quarter of diagnoses.
Routine investigations, mainly chest radiographs and
ECG, helped with only 3% of diagnoses, and special
tests, mainly exercise ECG, assisted with 6% [5].
History is also the most important diagnostic method
in respiratory, urinary, and neurologic conditions.
The patient’s medical problems, past surgeries,
previous anesthesia or surgical-related complications,
medications, allergies, and use of tobacco, alco-
Patient's Name
Planned Operation
Surgeon Primary Doctor
1. Please list all operations (and approximate dates) a.
b.
c.
d
e
f.
2. Please list any allergies to medicines, latex or other (a.
b.
c
d
3. Please list all medications you have taken in the las drugs, inhalers, herbals, dietary supplements and asp
Name of Drug Dose and how often Na. f.
b. g.
c. h.
d. i.
e. j.
(Please check YES or NO and circle specific problems4. Have you seen your primary care doctor within the las5. Have you ever smoked? (Quantify in packs/day f
Do you still smoke? Do you drink alcohol? (If so, how much?)Do you use or have you ever used any illegal drugs? (
6. Can you walk up one flight of stairs without stopping?7. Can you lie flat (or with only 1-2 pillows) for at least 8. Have you had any problems with your heart? (circle)
abnormal EKG, heart murmur, palpitation, heart failu9. Do you have high blood pressure? 10. Have you had any problems with your lungs or your c
emphysema, bronchitis, asthma, TB, abnormal chest 11. Are you ill now or were you recently ill with a cold, f
Fig. 1. Sample patient preo
hol, or illicit drugs should be documented (Fig. 1).
A screening review of systems should emphasize air-
way abnormalities, personal or family history of ad-
verse events related to surgery, and cardiovascular,
pulmonary, endocrine, or neurologic symptoms. In
addition to identifying the presence of a disease, it
is equally important to establish the severity, the sta-
bility, and any prior treatment of the condition. The
patient’s medical problems, previous surgeries, and
responses, will elicit further questions to establish
the extent of disease, current or recent exacerbations,
and recent or planned interventions.
Age Sex
Date of Surgery
Cardiologist?
.
.
and your reactions to them) .
.
t month (include over-the-counter irin)
ame of Drug Dose and how often
) YES NOt 6 months? or years)
we need to know for your safety)
one hour? (chest pain or pressure, heart attack, re)
hest? (circle) (shortness of breath, x-ray) ever, chills, flu or productive cough?
perative history form.
preoperative assessment & management 165
Knowledge of the patient’s cardiorespiratory fit-
ness or functional capacity can help guide additional
preoperative evaluation, and help predict outcome
and perioperative complications [2,6]. An ability to
exercise is two-pronged; better fitness decreases dis-
eases such as diabetes and hypertension, as well as
mortality, and a patient’s inability to exercise may
be a result of cardiopulmonary disease and therefore
may identify a patient who warrants further inves-
tigation [7]. Several studies have shown that inabil-
ity to perform average levels of exercise (walking
1–2 flights of stairs) identifies patients at risk of
perioperative complications [8].
The important components of the patient history
are shown in Fig. 1. The form can be completed by
the patient in person (paper or electronic version), by
way of web-based programs, by a telephone inter-
view, or by office staff. This form can be used to
identify patients who may be in need of referral to a
primary care physician, an anesthesiologist, or a spe-
cialist, for further evaluation or management be-
fore surgery. Alternately, the form can be forwarded
13. Have you ever had problems with your: (circle)Liver (cirrhosis, hepatitis, jaundice)? Kidney (infection, stones, failure, dialysis)?
14. Have you ever had: (circle)Seizures, epilepsy, or fits? Stroke, facial, leg or arm weakness, difficulty speakin
15. Have you ever been treated for cancer with chemothera16. Women: Could you be pregnant?
Last menstrual period began: 17. Have you ever had problems with anesthesia or surgery (in blood relatives or self) or problems during placemen
12. Have you had any problems with your blood (circle) (ablood clots, transfusions within the last 6 months)?
18. Do you snore? 19. Please list any medical illnesses not noted above:
22. Additional comments or questions for nurse or doctor?
Describe recent changes
Fig. 1 (conti
for an anesthesiologist or a primary care physician to
review and make the determination if an appointment
is needed. A more detailed discussion of important
components of the patient history for specific medical
conditions is presented below.
At a minimum, the preoperative examination
should include vital signs (blood pressure, pulse and
room air oxygen saturation), and a heart and lung
examination. If general anesthesia is not planned,
the ability of the patient to lie flat for the estimated
duration of the procedure is extremely important.
A guide to help determine the patient’s ability to lie
recumbent follows:
Disease. Certain conditions such as heart failure,
lung disease, chronic cough, musculoskeletal
disease like kyphoscoliosis, or a movement dis-
order such as a tremor, may prevent a patient
from lying still during the planned procedure.
Dementia. If the patient’s mental capacity pre-
cludes being able to stay still and follow sim-
ple commands, local anesthesia will likely fail.
g? py or radiation therapy? (circle)
? (circle) (malignant hyperthermia t of a breathing tube)
nemia, leukemia, sickle cell disease,
nued ).
sweitzer166
Dialect. Patients who are unable to communi-
cate because they speak a language different
than operating room personnel may not
be cooperative.
Deafness. Patients who have hearing problems
may have difficultly communicating.
The physical examination contributes one-quarter
of diagnoses in patients who have cardiovascular
disease [5]. Auscultation of the heart, palpation of the
pulses, and inspection of the extremities for the
presence of edema are important diagnostically and
for risk assessment when care plans are developed.
The practitioner should auscultate for murmurs,
rhythm disturbances, and signs of volume overload.
Murmurs, without a previous diagnosis, warrant fur-
ther evaluation. The pulmonary examination should
include auscultation for wheezing, decreased or ab-
normal breath sounds, and notation of cyanosis or
clubbing and effort of breathing. Observing whether
the patient can walk up 1–2 flights of stairs can
predict a variety of medical conditions and post-
operative complications including pulmonary and
cardiac events and mortality.
Preoperative testing
Preoperative testing is performed to evaluate exist-
ing medical conditions and screen for asymptomatic
conditions based on known risk factors for particular
diseases. Diagnostic tests can help assess the risk of
anesthesia and surgery, guide medical intervention to
lower this risk, and provide baseline results to di-
rect intra- and postoperative decisions. The choice of
laboratory tests should depend on the probable
impact of the test results on the differential diagno-
sis and on patient management. A test should be
ordered only if the results will (1) affect the decision
to proceed with the planned procedure, (2) influence
the type of anesthesia used, or (3) alter the care plans.
The history and physical examination should be used
to direct which tests are ordered. (Fig. 2).
Preoperative tests without specific indications lack
clinical utility and may actually lead to patient in-
jury because of unnecessary interventions, delay of
surgery, anxiety, and perhaps even inappropriate
therapies. The patient history is responsible for the
diagnosis 75% of the time and is more important than
the physical examination and laboratory investiga-
tions combined [9]. In addition, the evaluation of
abnormal results is costly. Many studies have eval-
uated the benefits of disease- or condition-indicated
testing versus batteries of screening tests [10]. For-
tunately, without specific clinical indication, few ab-
normalities detected by nonspecific testing have been
shown to result in changes in management and rarely
have such changes been shown to have a beneficial
patient effect [11]. It has been suggested that not
following up on an abnormal test result is a greater
medico-legal risk than not identifying the abnormal-
ity to begin with.
A preoperative ECG is one of the most frequently
ordered and costly noninvasive tests. A preoperative
ECG might be ordered because
Occult heart disease is common in a middle-aged
population and increases with advancing age
Pre-existing heart disease increases periopera-
tive risk
It is useful to establish a baseline.
However, a resting ECG is not a reliable screen
for coronary artery disease and is a poor predictor of
heart disease (without a supporting history) in non-
surgical patients. There is evidence that only some
ECG abnormalities are important in the perioperative
period (eg, new Q waves and arrhythmias). One study
found only 2% of patients had one or both of these
abnormalities [12]. Gold [13] found that in ambu-
latory surgical patients, the incidence of abnormal
ECGs was quite high (43%). However, only 1.6%
had an adverse perioperative cardiac event, and the
preoperative ECG was of potential value in only half
(6/751) of these. It has been suggested that routine
preoperative ECG testing is not indicated in patients
who do not have a history of cardiovascular disease
or significant risk factors [14].
Even though ECG abnormalities are increasingly
more common with advanced age, abnormalities
alone have not been shown to predict postoperative
cardiac complications in the elderly [13,15]. Al-
though abnormal ECG findings are common in the
elderly, significant abnormalities that impact care are
low in the absence of a history or symptoms of car-
diac disease [13]. Centers for Medicare and Medicaid
Services will not provide coverage for age-based
ECGs or ECGs performed simply as a preoperative
test. A practitioner must provide a supporting diag-
nosis with an acceptable ICD-9 code [16]. ECGs are
acceptable if performed within 6 months and the pa-
tient has had no change in symptoms.
Indications for ECG testing include
History of coronary artery disease, myocardial in-
farction, angina or chest pain
History of congestive heart failure
Disease /Therapy/Procedure based Indications
(applies to all patients scheduled for general anesthesia, or newly diagnosed
or unstable conditions only)
Possible pregnancy
BUN; Diabetes; Heart failure; Renal disease; Sickle cell anemia; Use of Diuretics Creatinine
ECG Alcohol abuse; Cardiovascular, Cerebrovascular, Peripheral vascular,
Pulmonary, or Renal disease; Diabetes; Morbid Obesity; Murmurs; Poor exercise
tolerance (unable to walk up a flight of stairs); Poorly controlled hypertension
(BP >180/110 mmHg); Rheumatoid arthritis; Sickle cell anemia; Sleep apnea;
Smoking >40 pk-yr; Systemic lupus; Radiation therapy to chest or left breast; Use
of Digoxin
Electrolytes Cerebrovascular, Hepatic or Renal disease; Diabetes; Sickle cell anemia; Use of
Digoxin, or Diuretics
Glucose Cerebrovascular Disease; Diabetes; Morbid obesity; Steroid use
Platelets; PT; Alcohol abuse; Hepatic disease; Personal or Family history of bleeding; Use of aPTT*
Anticoagulants.
Thyroid Tests Thyroid disease; Use of Thyroid medications
* Only indicated for these conditions if peri- or retrobulbar blocks are planned or bleeding is an issue
Abbreviations: β-hCG=pregnancy test; BUN= blood urea nitrogen; ECG=electrocardiogram; PT= prothrombin time; a-PTT=
activated partial thromboplastin time;
All tests are valid for 6 months before surgery unless abnormal, or patients condition has changed; with the exception of β-hCG for
pregnancy, glucose in diabetics and blood tests in patients with renal failure.
Guidelines may not apply for low-risk procedures without general anesthesia where testing is only
indicated if the medical condition is newly diagnosed or unstable.
β-hCG
Fig. 2. Sample preoperative diagnostic testing order form.
preoperative assessment & management 167
sweitzer168
History of atrial fibrillation, arrhythmias, irregular
or skipped beats, heart block
History or presence of murmur
Presence of a pacemaker or implantable cardio-
verter-defibrillator
Chronic lung disease, >40 pack-years of tobacco
use or significant shortness of breath
Diabetes mellitus
Cerebrovascular (stroke, TIA) or peripheral vas-
cular disease (claudication)
Renal insufficiency or failure
Age-based recommendations for testing are based
on few data. No correlation has been established,
independent of co-existing disease, a positive history,
or findings on physical examination, between age
and abnormalities in hemoglobin (Hgb), serum chem-
istries, radiographs, or pulmonary function testing
[17–19]. Hemoglobin and hematocrit (Hct) levels are
frequently abnormal in otherwise healthy patients but
rarely impact anesthetic care or management, unless
the planned procedure involves the potential for sig-
nificant bleeding.
Coagulation studies (platelet count, prothrombin
time [PT], or activated partial thromboplastin time
[a-PTT]) are not recommended unless the patient
history is suggestive of a coagulation disorder. It is
generally accepted that the cost of screening co-
agulation tests before minor surgery outweighs the
benefit of non-life threatening bleeding (because of
the minor nature of the procedure) in the rare patient
with what would have to be a minor bleeding dis-
order, if there is a negative history [20].
Healthy patients of any age who undergo low or
intermediate risk procedures (without expected sig-
nificant blood loss) are unlikely to benefit from any
tests. Patients who have stable, well-controlled,
mild to moderate severity co-existing diseases, and
who follow up regularly with primary care or spe-
cialist physicians are unlikely to benefit from addi-
tional diagnostic testing before surgery. In general,
tests are only recommended if they will result in
A change, cancellation, or postponement of the
surgical procedure
A change in anesthesia and medical management
A change in monitoring or guidance of intra- or
post-operative care
Confirmation of a suspected abnormality based on
the patient’s history and physical examination
Generally, test results are valid and acceptable for
up 6 months before surgery if the medical history has
not substantially changed [21]. Suggested tests are
shown in Fig. 2.
Patients who undergo cataract surgery are often
elderly and have extensive co-morbid disease. The
procedure is minor, however, and systemic physio-
logic disturbances or significant postoperative pain
are not expected. Topical anesthesia is commonly
used and because general anesthesia is rarely re-
quired, the risk is lessened. The cost of routine medi-
cal testing before cataract surgery is estimated at
$150 million annually. In one study, more than
18,000 patients were randomly allocated to either a
group that received no routine testing before cataract
surgery or a a group that received a battery of tests
(ECG, complete blood cell count, electrolytes, serum
urea nitrogen, creatinine and glucose levels). No dif-
ferences in postoperative adverse events were found
between the two groups [10].
The study of cataract patients eliminated routine
tests, not tests indicated for a new or worsening
medical problem. All patients underwent a preop-
erative medical assessment. The group that crossed
over from no testing to some testing had significantly
more coexisting illnesses and poor self-reported
health status. This finding suggests that the preop-
erative care provider screen patients to order tests for
those who require them. In the study described, ex-
clusion criteria were general anesthesia or a myocar-
dial infarction within 3 months. More than 85% of
subjects enrolled in the study reported good to ex-
cellent health status, almost 25% reported no coex-
isting illnesses (including hypertension, anemia,
diabetes, and heart or lung disease), almost 30%
were <70 years, and 65% were American Society of
Anesthesiologists physical status (ASA-PS) 1 or 2
(Table 1); all of which suggests a fairly healthy
group. The results of this study do not suggest that
patients who undergo cataract surgery require no
laboratory testing [10]. If patients are comparable to
those in the study, are routinely evaluated by primary
care physicians, have stable mild disease, and will
undergo cataract surgery under topical or bulbar
block, then no special testing is required for cataract
surgery. Serious, poorly controlled conditions must
be normalized before surgery, and selective test-
ing suggested by history and physical examination
may be necessary. Rarely is testing necessary be-
cause of cataract surgery, but patients with limited
access to health care services may benefit from
medical evaluation.
Often physicians are concerned about their failure
to diagnose a condition because a diagnostic screen-
ing test was not ordered, for which legal action can be
brought. The traditional system of ordering routine
Table 1
American Society of Anesthesiologists physical status
classification
Class Description
ASA 1 Healthy patient without organic, biochemical,
or psychiatric disease.
ASA 2 A patient with mild systemic disease
(eg, mild asthma or well-controlled
hypertension). No significant impact on daily
activity. Unlikely impact on anesthesia
and surgery.
ASA 3 Significant or severe systemic disease that
limits normal activity (eg, renal failure on
dialysis or class 2 congestive heart failure).
Significant impact on daily activity. Likely
impact on anesthesia and surgery.
ASA 4 Severe disease that is a constant threat to
life or requires intensive therapy (eg, acute
myocardial infarction, respiratory failure
that requires mechanical ventilation).
Serious limitation of daily activity. Major
impact on anesthesia and surgery.
ASA 5 Moribund patient who is equally likely to die
in the next 24 hours with or without surgery.
ASA 6 Brain-dead organ donor.
preoperative assessment & management 169
preoperative tests evolved from the mistaken belief
that more information, no matter how irrelevant or
expensive, will improve care, enhance safety, and
decrease liability. In reality, non-selective screening
may actually increase legal culpability. Unanticipated
abnormalities (ie, not suggested by the history or
physical examination) are uncommon and the rela-
tionship between these abnormalities and surgical and
anesthetic morbidity is weak at best. In addition, it
has been documented that over half of all abnormal
test results obtained in routine preoperative screening
are ignored or at least not noted in the medical record,
which is the document of interest to the courts.
Failure to follow up an abnormal result is, from a
legal point of view, probably riskier than failure to
order the test in the first place. AIMS found that
communication problems were predominant in most
reported incidents that involved a failure of preoper-
ative preparation [1].
Risk assessment
Risk assessment is useful to compare outcomes,
control costs, allocate compensation, and assist with
the difficult decision to cancel or recommend that a
procedure not be done when the risks are too high.
Yet risk assessment, at its best, is hampered by in-
dividual patient variability. One of the most com-
mon risk assessment tools used perioperatively is
the ASA-PS scoring system (see Table 1). Though
ASA-PS is usually determined by anesthesiologists
for patients having anesthesia, it is often used for any
comparison of surgical patients. Studies have cor-
roborated an association of mortality and morbidity
with ASA-PS. The other important risk assessment
tool is the joint guideline published by The Ameri-
can College of Cardiology and the American Heart
Association (ACC/AHA), which identifies risk fac-
tors and cardiac complications in noncardiac surgery.
Cardiac complications are the most common cause of
significant perioperative morbidity and mortality. For
the purposes of this article, the ACC/AHA guideline
considers ophthalmic procedures to be low risk and
therefore, further risk assessment is only necessary
for high-risk comorbid conditions [2].
Hypertension
Poorly controlled hypertension (HTN) is one of
the most common reasons for ophthalmic procedures
to be cancelled on the day of surgery. HTN, defined
by two or more measurements of blood pressure (BP)
greater than 140/90 mmHg, affects one billion in-
dividuals worldwide and increases with age. In the
United States, 25% of adults and 70% of patients
older than 70 years have HTN and less than 30% are
adequately treated [22]. The degree of end-organ
damage and morbidity and mortality correlate with
the duration and severity of HTN. Heart failure, renal
insufficiency, and cerebrovascular disease are more
common in hypertensive patients. Ischemic heart dis-
ease is the most common form of organ damage
associated with HTN. Uncontrolled HTN is only a
minor cardiac risk factor and the odds ratio for an
association between HTN and perioperative cardiac
risk is 1.31 [2,23]. There is little evidence of an as-
sociation between preoperative BPs <180/110 mmHg
and perioperative cardiac risk [23].
It is generally recommended that elective surgery
be delayed for severe HTN (diastolic blood pressure
>115 mmHg; systolic blood pressure >200 mmHg)
until BP <180/110 mmHg. If severe end-organ
damage is present, the goal should be to normalize
BP as much as possible before surgery [23]. For BP
<180/110 mmHg there is no evidence to justify can-
cellation of surgery, although if time allows, inter-
ventions preoperatively are appropriate. Severely
elevated BP should be lowered over several weeks.
Box 1. Preoperative medication guidelines
Continue on the day of surgerya
Antidepressant, anti-anxiety, andpsychiatric medications
Anti-hypertensive medicationsAnti-seizure medicationsAspirin, unless the risk of minor bleed-
ing is significantAsthma medicationsBirth control pillsCardiac medications (eg, digoxin)Cox-2 inhibitorsDiuretics (eg, triamterene or hydrochlo-
rothiazide) for hypertensionHeartburn or reflux medicationsInsulin- all intermediate, combination,
or long-acting insulin, orinsulin pumps� Type 1 diabetics should take asmall amount (one-third to one-half) of their usual morning long-acting insulin (eg, lente or NPH) onthe day of surgery� Type 2 diabetics should take onethird to one-half dose of long-acting (eg, lente or NPH) or com-bination (70/30 preparations) insu-lin on the day of surgery� Patients with an insulin pumpshould continue only their basalrate on the day of surgery
Narcotic pain medicationsStatinsSteroids, oral or inhaledThyroid medications
Discontinue 7 days before surgery
Clopidogrel (Plavix), except patientsscheduled for cataract surgery withtopical or general anesthesia
Herbals and non-vitamin supplementsHormone replacement therapy
Discontinue 4 days before surgery
Warfarin (Coumadin), except for pa-tients scheduled for cataract surgerywith topical or general anesthesia
Discontinue 24 hours before surgery
Erectile dysfunction medications
Discontinue on the day of surgery
Diuretics, except triamterene or hydro-chlorothiazide for hypertension,which should be continued
Insulin- all regular insulin (see insulin tocontinue on day of surgery above)
IronOral hypoglycemic agentsTopical medications (eg, creams
or ointments)Vitamins
Special considerations before surgery
Monoamine oxidase inhibitors: patientstaking these antidepressant medi-cations need an anesthesia consul-tation before surgery (preferably3 weeks before) if general anesthe-sia is planned
a Patients should take medications witha small sip of water even if otherwise in-structions are nothing per mouth.
sweitzer170
Guidelines suggest that cardioselective beta-blocker
therapy is the best treatment preoperatively because
of a favorable profile in lowering cardiovascular risk
[2]. It may take 6–8 weeks of therapy to effectively
lower the risk and to allow regression of vascular
changes, because too rapid or extreme lowering of
BP may increase cerebral and coronary ischemia. The
Antihypertensive and Lipid-Lowering Treatment to
Prevent Heart Attack Trial showed that effective
treatment of HTN is not simply a matter of lowering
BP [24]. Continuation of antihypertensive treatment
preoperatively is critical (Box 1).
Testing should be determined by the history and
physical examination and may include ECG, elec-
trolytes, serum urea nitrogen, and creatinine if gen-
eral anesthesia is planned (see Fig. 2). An elevated
BP during the ophthalmology visit or a history of
poorly controlled HTN should prompt a referral to a
primary care physician for BP control before elec-
tive surgery.
preoperative assessment & management 171
Cardiac disease
The goals of the ophthalmologist should be to
identify the presence and severity of heart disease
(HD) or significant risk of HD based on associated
conditions, such as diabetes, renal insufficiency or
failure, cerebrovascular or peripheral vascular dis-
ease, and determine the need for preoperative con-
sultation and interventions (almost always medical,
not invasive) to modify the risk of perioperative
adverse events. The basis of cardiac assessment is
the history, physical examination, and ECG. The
most recent guidelines for the cardiac evaluation
for noncardiac surgery from the ACC/AHA have
become the national standard of care [2]. These
guidelines indicate that patients without high-risk co-
morbid conditions defined as unstable or new onset
angina, decompensated heart failure, significant ar-
rhythmias (ventricular tachycardia or atrial fibrilla-
tion with a rapid rate, >100 bpm) or severe valvular
disease (regurgitation or stenosis) can safely undergo
low-risk procedures without stress testing or cardiol-
ogy intervention.
Currently, the benefits of coronary revasculariza-
tion before noncardiac surgery, versus medical risk
modification are controversial [25]. Unless patients
will benefit from revascularization regardless of the
planned procedure, or have unstable angina, revas-
cularization is not indicated before ophthalmic sur-
gery. Noncardiac surgery soon after revascularization
(bypass grafting and percutaneous coronary interven-
tion with or without stents) is associated with high
rates of perioperative cardiac morbidity and mor-
tality [26,27]. Patients who have recently had an-
gioplasty with stent placement (within 6 months),
especially with newer, drug-eluting stents, require
several months of anti-platelet therapy to avoid re-
stenosis or acute thromboses. These patients need to
be identified and close management with a cardiolo-
gist is required. Case reports have indicated that pa-
tients can have stent thromboses perioperatively even
if anti-platelet agents are continued [28].
Patients who have a history of coronary artery
disease or significant risk factors (diabetes, renal in-
sufficiency, cerebrovascular or peripheral vascular
disease) need an ECG within 6 months of a planned
GA (see Fig. 2).
Heart failure affects 4–5 million people in the
United States and is a significant risk factor for post-
operative adverse events [29]. The goal for the
ophthalmologist is to identify patients who have
decompensated heart failure. Recent weight gain,
complaints of shortness of breath, fatigue, orthopnea,
paroxysmal nocturnal dyspnea, edema, hospitaliza-
tions, and recent changes in medication are impor-
tant. Physical findings should focus on examination
for third or fourth heart sounds, rales, jugular ve-
nous distention, ascites, hepatomegaly, and edema
[30]. Decompensated heart failure requires referral
to a cardiologist for optimization preoperatively.
Minor procedures can be done with little risk as
long as heart failure is stable. If GA is planned an
ECG, electrolytes, BUN, and creatinine are required
(see Fig. 2).
New onset or poorly controlled atrial fibrillation
(HR >100 bpm), symptomatic bradycardia, or high-
grade heart block (second or third degree) warrants
postponement of elective procedures and referral to
cardiology for further evaluation. Left bundle branch
block (LBBB) is highly associated with coronary
artery disease and a recent onset, or a patient with-
out a previous evaluation of a LBBB requires stress
testing or cardiology consultation. Right bundle
branch block (RBBB) is more likely to be congenital,
a result of calcification and degeneration of the
conduction system or secondary to pulmonary dis-
ease. If the history and physical examination are
not suggestive of significant pulmonary disease, no
further evaluation is warranted just because of a
RBBB. Patients who have a history of arrhythmias
should be queried about syncope, chest pain, dyspnea
or light-headedness. An ECG is necessary within
6 months or more recently if there has been a change
in symptoms (see Fig. 2).
The quandary with heart murmurs is to distin-
guish between significant murmurs and clinically
unimportant ones. Diastolic murmurs are always
pathologic and require further evaluation. Regurgitant
disease is tolerated perioperatively better than ste-
notic disease.
Aortic stenosis is the most common valvular le-
sion in the United States and affects 2%–4% of
adults >65 years of age; severe stenosis is associated
with a high risk of perioperative complications with
GA [2]. Aortic stenosis was once considered to be a
degenerative lesion that increased with age or a con-
genital bicuspid valve, but is now believed to have
much in common with coronary heart disease and is
an independent marker of ischemic disease [31]. The
classic symptoms of severe aortic stenosis are an-
gina, heart failure, and syncope, though patients
are much more likely to complain of a decrease in
exercise tolerance and exertional dyspnea. Aortic ste-
nosis causes a systolic ejection murmur, which is
best heard in the right upper sternal border and often
radiates to the neck. Any patient with a previously
undiagnosed murmur needs an ECG, and any ECG
abnormality warrants an echocardiogram or a car-
sweitzer172
diology consultation. Current guidelines recommend
echocardiography annually for patients who have
severe aortic stenosis, every 2 years for moderate
stenosis, and every 5 years for mild stenosis [32].
Aortic sclerosis, which causes a systolic ejection
murmur similar to that of aortic stenosis, is present in
25% of people 65–74 years of age and almost half of
those >84 years. However, there is no hemodynamic
compromise with aortic sclerosis. Aortic sclerosis
is associated with a 40% increase in the risk of
myocardial infarction and a 50% increase in the risk
of cardiovascular death in patients who do not have a
history of heart disease [31].
It is estimated that more than 100,000 pacemakers
and implantable cardiac defibrillators (ICDs) are
implanted annually in the United States. Electro-
magnetic interference (EMI) is likely to occur with
electrocautery and radiofrequency ablation, and result
in malfunction or adverse events [33]. Some patient
monitors and ventilators may cause EMI in patients
who have rate-adaptive pacemakers. The preoperative
evaluation should determine the type of device and
the features (eg, rate-adaptive mechanisms) likely
to malfunction if perioperative EMI should occur.
Consultation with the device manufacturer, cardiolo-
gist, or the electrophysiology service is necessary.
Ideally, patients should have these devices interro-
gated preoperatively. Special features such as rate
adaptive mechanisms and anti-tachyarrhythmia func-
tions need to be disabled or be reprogrammed to an
asynchronous pacing mode before surgical proce-
dures and anesthesia where EMI is anticipated [33].
Newer generation devices are more complex and
reliance on a magnet, except in emergency situations,
is not recommended.
Disabling ICDs will prevent unanticipated dis-
charges during delicate procedures. However, exter-
nal defibrillators must be immediately available. A
baseline ECG is needed in patients who have pace-
makers and ICDs (see Fig. 2).
Pulmonary disease
Patients who have significant chronic obstructive
pulmonary disease (COPD), asthma, or a cough, may
not be able to lie supine for an extended period.
Treating exacerbations of their disease (eg, infection,
bronchospasm) may make it possible for them to
remain recumbent and still, and is necessary to
decrease complications if GA is planned. However,
routine chest radiographs, arterial blood gases, and
the degree of airway obstruction measured by pul-
monary function tests, are not predictive of pulmo-
nary complications.
Sleep-disordered breathing affects up to 9% of
middle-aged women and 24% of middle-aged men;
less than 15% of these cases have been diagnosed.
Obstructive sleep apnea (OSA), the most common
serious manifestation of sleep-disordered breathing,
is caused by intermittent airway obstruction. Car-
diovascular disease is common in patients who have
OSA. These patients have an increased incidence of
hypertension, atrial fibrillation, bradyarrhythmias,
ventricular ectopy, endothelial damage, stroke, heart
failure, dilated cardiomyopathy, and atherosclerotic
coronary artery disease (CAD) [34]. Patients who
have moderate to severe OSA are unlikely to be able
to lie flat without general anesthesia. Mask ventila-
tion, direct laryngoscopy, endotracheal intubation,
and even fiberoptic visualization of the airway are
more difficult in patients who have OSA than in
healthy patients.
The Berlin Questionnaire is useful to identify pa-
tients who have undiagnosed OSA [35]. The presence
of any two of the following is considered a high risk
for sleep apnea: snoring, daytime sleepiness, hyper-
tension, and obesity. Preoperative evaluation should
focus on identifying patients who are at risk for OSA
and improving associated co-morbid conditions. ECG
and echocardiography may be indicated if heart
failure or pulmonary hypertension is suspected or
GA is required (see Fig. 2). Patients should be in-
structed to bring their continuous positive airway
pressure devices to the hospital on the day of surgery.
Obesity
It is estimated that 64% of adults in the United
States are overweight or obese and 4.7% are ex-
tremely obese. Obesity is an independent risk factor
for heart disease. Hypertension, stroke, hyperlipid-
emia, diabetes mellitus, and OSA are more common
in obese people. Morbidly obese patients require spe-
cial operating room tables and gurneys to support
excessive weight. Venous access and invasive and
noninvasive monitoring may be difficult, and air-
ways may require specialized equipment, techniques,
and personnel. Preoperative identification and plan-
ning for these contingencies will avoid delays on the
day of surgery. Preoperative evaluation should be
directed toward identifying significant co-existing
diseases such as OSA, pulmonary hypertension, and
heart failure. Many of these patients will not be able
to lie flat and will require general anesthesia. An
preoperative assessment & management 173
ECG is indicated preoperatively if GA is required
(see Fig. 2).
Diabetes
An estimated 18 million US adults have diabetes
mellitus, which increases the risk of coronary artery
disease and is considered equivalent to angina for
predicting heart disease [2]. Heart failure is twice as
common in men and five times as common in women
who have diabetes as in individuals who do not have
diabetes. Poor glycemic control is associated with an
increased risk for heart failure and both systolic and
diastolic dysfunction may be present.
Recent studies suggest that tighter perioperative
control is warranted, especially to reduce the risk
of infections. Patients who have poor preoperative
management of glucose are likely to be more out of
control perioperatively. Aggressive management of
hyperglycemia decreases postoperative complications.
The American College of Endocrinologists position
statement recommends a target fasting glucose of
< 110 mg/dL in non-critically ill patients [36].
The focus of the preoperative visit should be
to assess organ damage and control blood sugar.
Cardiovascular, renal, and neurologic systems should
be evaluated. Ischemic heart disease is often asymp-
tomatic in the diabetic patient. An ECG should
be done within 6 months of surgery. Electrolytes,
BUN, and creatinine levels need to be determined
(see Fig. 2). The goal of perioperative diabetic man-
agement should be to avoid hypoglycemia and
marked hyperglycemia (see Box 1).
Anticoagulated patients
There is no consensus on the optimal periopera-
tive management of patients who are taking war-
farin. There are risks if therapy is continued and
risks if it is stopped [37]. The location and extent of
surgery is important and the ability to compress the
bleeding site is a consideration. Warfarin may be
associated with increased bleeding, except for minor
procedures such as cataract surgery without peri- or
retrobulbar blocks. One study found grade 1 hemor-
rhages in 2.3% of patients, grade 2–3 hemorrhages in
2%, and no grade 4 hemorrhages in patients who
were undergoing a variety of ophthalmic procedures
with retro- or peribulbar blocks. However, they con-
cluded that preoperative use of aspirin, other anti-
platelet drugs, and warfarin, (whether they were
continued or not) was not associated with significant
hemorrhage [38]. There have been reports of bleeding
in the anterior eye chamber and subconjunctival
hemorrhages in patients who undergo ophthalmic
surgery while on warfarin. No studies of long-term
visual acuity have been done in patients who con-
tinued warfarin therapy during eye surgery.
A survey of 135 surgeons in the United States
found that 75% stopped anticoagulation 3–5 days
preoperatively. They reported two deaths that were
caused by cerebrovascular accidents, and 7 nonfatal
thromboembolic episodes in the group in which anti-
coagulants were discontinued. No complications were
reported by the 7.4% of surgeons who continued
anticoagulants [39].
There is little harm in continuing aspirin through-
out the perioperative period for ophthalmic patients
and evidence suggests benefit for patients at high risk
for cardiovascular and cerebrovascular complica-
tions [37]. More potent antiplatelet therapy such as
clopidogrel (Plavix) may have a risk of bleeding
intermediate between aspirin and warfarin. Clopidog-
rel or similar drugs should probably be discontinued
for procedures in which one would discontinue war-
farin but do not need to be stopped before cataract
surgery performed with topical anesthesia.
Anemia
Consequences from moderate levels of anemia
and Hgb levels >7.0 g/dL in patients without CAD
are minimal. Transfusion is rarely indicated when the
Hgb is >10 mg/dL and is almost always needed when
the Hgb is <7 mg/dL. The focus of the preoperative
visit is to determine the etiology, duration, and
stability of the anemia, and the patient’s co-morbid
conditions that may impact oxygenation, such as
pulmonary, cerebrovascular, or cardiovascular disease.
Sickle cell disease is a hereditary hemoglobinop-
athy and vaso-occlusion is responsible for most of the
associated complications. Preoperative assessment
should focus on identification of organ dysfunction
and acute exacerbations. Frequent hospitalizations or
a recent increase in hospitalizations, advanced age,
preexisting infections, and pulmonary disease predict
perioperative vaso-occlusive complications [40]. The
preoperative history and physical examination should
focus on the frequency, severity, and pattern of vaso-
occlusive crises and the degree of pulmonary, cardiac,
renal, and central nervous system damage. An ECG,
electrolytes, BUN, and creatinine are necessary
before GA (Table 2). Patients who have significant
pulmonary or cardiac symptoms need an echocar-
diogram. Prophylactic transfusion may be beneficial
Table 2
Guidelines for food and fluids before elective surgery
Time before surgery Food or fluid intake
Up to 8 hours Food and fluids as desired
Up to 6 hoursa Light meal (eg, toast and clear
liquidsb); infant formula; non-
human milk
Up to 4 hoursa Breast milk
Up to 2 hoursa Clear liquidsb only; no solids or
foods that contain fat in any form
During the 2 hours No solids, no liquids
a This guideline applies only to patients who are not
at risk for delayed gastric emptying. Patients who have
the following conditions are at risk for delayed gastric
emptying: morbid obesity, diabetes mellitus, pregnancy,
a history of gastroesophageal reflux, a surgery that limits
stomach capacity, a potentially difficult airway; opiate anal-
gesic therapy.b Clear liquids are water, carbonated beverages, sports
drinks, coffee or tea (without milk). The following are not
clear liquids: juice with pulp, milk, coffee or tea with milk,
infant formula, any beverage with alcohol.
From American Society of Anesthesiologists Task Force on
Preoperative Fasting. Practice guidelines for preoperative
fasting and the use of pharmacologic agents to reduce the
risk of pulmonary aspiration: application to healthy patients
undergoing elective procedures. Anesthesiology 1999;90:
896–905; Available at: http://www.asahq.org. Accessed
October 25, 2005.
sweitzer174
before general anesthesia. Preoperative prophylactic
transfusion is controversial and the decision to
transfuse should be made in concert with a hematol-
ogist who is familiar with sickle cell disease.
Renal or hepatic disease
The focus of the preoperative evaluation of pa-
tients with renal insufficiency or failure should be on
the cardiovascular and cerebrovascular systems, fluid
volume, and electrolyte status. Chronic metabolic
acidosis is common but usually mild and compen-
sated for by chronic hyperventilation. Chronic renal
disease is a significant risk factor for cardiovascular
morbidity and mortality and is an intermediate
cardiac risk factor equal to a history of known
CAD [2]. The annual incidence of death from CAD
in patients with both diabetes and end stage renal
disease and on hemodialysis is 8.2%. In elective
cases, hemodialysis should be performed within
24 hours of surgery but not immediately before.
Hemodialysis is associated with fluid and electrolyte
(sodium, potassium, magnesium, phosphate) imbal-
ance and shifting of electrolytes between intra- and
extracellular compartments. Hemodialysis should be
performed to correct volume overload, hyperkalemia,
and acidosis. Patients with renal insufficiency or
failure undergoing GA need an ECG, BUN, creati-
nine and electrolytes before surgery (see Fig. 2).
It is appropriate to delay elective surgery until
after an acute episode of hepatitis or an exacerbation
of chronic disease has resolved. If GA is planned for
patients who have hepatic or renal disease, electro-
lytes, BUN, and creatinine levels need to be evalu-
ated. If retro- or peribulbar blocks, or a procedure
where bleeding may compromise vision are planned
for patients who have cirrhosis, a PT and a-PTT need
to be determined (see Fig. 2).
Neurologic patients
A history focused on recent events, exacerbations,
or evidence for poor control of the medical condition
is necessary for a patient who has neurologic dis-
ease (eg, stroke, seizure disorder, multiple sclerosis,
Parkinson’s disease). If a stroke or transient neuro-
logic deficit has not been fully evaluated or has oc-
curred within 1 month, elective surgery should be
delayed pending complete evaluation. Patients who
have significant movement disorders or poorly con-
trolled seizures may require general anesthesia.
Consultations
Collaborative care of patients is often neces-
sary and beneficial. Consultation initiated by the
preoperative physician should seek specific advice
regarding diagnosis and status of the patient’s con-
dition(s). The first step is to ask specific questions
such as, ‘‘Is this patient in the best medical condi-
tion for planned vitrectomy under general anesthe-
sia’’? Letters or notes that state ‘‘cleared for surgery’’
are rarely sufficient to design a safe anesthetic. A
letter that summarizes the patient’s medical problems
and condition, along with the results of diagnostic
tests, is necessary.
In many practices, the cardiology service is most
frequently consulted perioperatively. In one survey,
however, the utility of such consultations was ques-
tioned. Forty percent of the consultations contained
only the recommendation to ‘‘proceed with the
case,’’ ‘‘cleared for surgery,’’ or ‘‘continue with cur-
rent medications’’ [41]. Part of this responsibility lies
with the consulting physicians (surgeons or anes-
thesiologists) and the long-standing practice of asking
preoperative assessment & management 175
for, or receiving cardiac clearance. This is a vague
request and often results in a vague response. In gen-
eral, preoperative consultations should be sought for
diagnosis, evaluation, and improvement of a new or
poorly controlled condition.
Close coordination and good communication
among the anesthesiologist, surgeon, and consultant
is vitally important. Miscommunication among care
providers was central to most reported incidents in
the Australian Incident Monitoring Study whenever
preoperative assessment was implicated [1].
Medication instruction
Most medications should be continued on the day
of surgery because of their beneficial effects, al-
though some may be harmful or contraindicated.
Box 1 details classes of drugs and varying protocols
of continuation before surgery. Medications associ-
ated with withdrawal effects (eg, beta-blockers, cen-
trally acting sympatholytics, benzodiazepines, and
opioid analgesics) should be continued through the
preoperative period [42]. Medications used by pa-
tients who have a history of or are at risk for heart
disease, such as beta blockers, digoxin, anti-arrhyth-
mics, and statins should not be withdrawn before
surgery. Not only are they beneficial but risk may
increase when they are not taken [2,42].
Oral hypoglycemic agents should be held the day
of surgery to avoid hypoglycemia unless only local
anesthesia is planned and the patient is instructed to
eat. Patients who have type 1 and type 2 diabetes
mellitus should discontinue all short-acting insulins
on the day of surgery. Type 1 and type 2 diabetics
should take one-third to one-half the dose of long-
acting (eg, lente or Neutral Protamine Hagerdorn) or
combination (70/30 preparations) insulins on the day
of surgery. Small amounts of long-acting insulin on
the day of surgery present little risk of hypoglycemia
but improve perioperative control and avoid diabetic
ketoacidosis. Patients who have an insulin pump
should continue their basal rate only.
It is usually not necessary to discontinue aspi-
rin before ophthalmic surgery [37]. More potent
antiplatelet agents such as clopidogrel (Plavix) need
to be stopped 1 week before surgery if bleeding is a
concern. There is general agreement that aspirin,
nonsteroidal anti-inflammatory drugs and potent
antiplatelet agents (eg, clopidogrel) and warfarin
should be continued in patients who are scheduled
for cataract surgery with general or topical anesthesia.
Most surgeons discontinue warfarin for retinal sur-
gery and practices vary widely as to whether warfa-
rin is discontinued when peri- or retrobulbar blocks
are planned.
If warfarin is stopped it is usually necessary to
withhold four doses before surgery to allow the
International Normalized Ratio to decrease to <1.5, a
level considered safe for surgical procedures. Sub-
stitution with shorter acting anticoagulants such as
unfractionated or low molecular weight heparin,
referred to as bridging, is controversial and should
be individualized [43]. Kearon and Hirsh [43] only
recommend preoperative bridging with intravenous
heparin for patients who have had an acute arterial or
venous thromboembolism within 1 month before
surgery, if surgery cannot be postponed. Patients who
take narcotic pain medications should be told to
continue these medications. Missed doses may result
in withdrawal symptoms and significant pain with the
associated stress response and hemodynamic pertur-
bations. For similar reasons, anti-anxiety and psychi-
atric medications should be continued up until the
time of the procedure.
Herbals and supplements may interact with anes-
thetic agents, alter the effects of prescription medi-
cations, and increase bleeding. Many patients do not
consider supplements medications and will not report
them unless specifically asked. Gingko, echinacea,
garlic, ginseng, kava, St. John’s wort and valerian
may be associated with bleeding and interactions
with anesthetic and sedative medications. It is rec-
ommended that herbals and supplements be stopped
7–14 days before surgery. The exception is valerian,
a central nervous system depressant which may cause
a benzodiazepine-like withdrawal when discontinued.
Patients who are particularly anxious should be
offered a prescription for a short course of benzo-
diazepines such as lorazepam to be taken in the days
preceding surgery as well as on the day of surgery.
Fasting guidelines
If GA is planned, patients should be instructed to
follow the ASA guidelines for preoperative fasting as
shown in Table 2 [44]. Many practitioners allow food
and fluids ad lib if the patient will receive topical or
local anesthesia without sedation.
Future developments
The ophthalmologist is in a unique position during
an ophthalmologic examination to identify patients
who have an increased risk of systemic disease. One
study found an association between retinal arteriolar
sweitzer176
narrowing and coronary heart disease [45]. Another
study found that diabetic retinopathy was associated
with a higher risk of renal failure and death in patients
who had type 2 diabetes mellitus [46]. Ophthalmolo-
gists need to identify at-risk patients and not only
inform the patient of the implications of their findings
but ensure the patient receives appropriate referral
and follow-up.
Summary
The prevention of complications during and after
procedures is the most important goal of preoperative
evaluation. Identification of risk requires fundamen-
tally good medicine, systems of care, clinical and
laboratory assessment, and experienced, knowledge-
able, and dedicated health care providers. Risk
reduction is the ultimate goal of preoperative assess-
ment and management.
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Ophthalmol Clin N
General Anesthesia for Ophthalmic Surgery
Kathryn E. McGoldrick, MDa,b,T, Peter J. Foldes, MDb
aDepartment of Anesthesiology, New York Medical College, Valhalla, NY 10595, USAbWestchester Medical Center, Valhalla, NY 10595, USA
Anesthetic management plays a vital role in con-
tributing to the success or failure of ophthalmic sur-
gery. Patients with eye conditions are often at the
extremes of age, ranging from tiny, fragile infants
with retinopathy of prematurity or congenital cata-
racts to nonagenarians with submacular hemorrhage,
and may have extensive associated systemic or meta-
bolic diseases [1]. Moreover, with more than 13% of
Americans characterized as elderly (older than
65 years), we must acknowledge that the increased
longevity typical of developed nations has produced a
concomitant increase in the longitudinal prevalence
of major eye diseases, including diabetic retinopathy,
primary open-angle glaucoma, and age-related mac-
ular degeneration [2]. Clearly, the challenges of
caring for an aging population with complex coex-
isting diseases undergoing sophisticated and techni-
cally demanding ophthalmic procedures require a
high level of anesthetic expertise.
The objectives of anesthesia for ophthalmic sur-
gery include safety, akinesia, satisfactory analgesia,
minimal bleeding, avoidance or obtundation of the
oculocardiac reflex, prevention of intraocular hyper-
tension, and awareness of potential interactions be-
tween ophthalmic drugs and anesthetic agents. Other
exigencies include an understanding of the anesthetic
implications intrinsic to delicate ophthalmic proce-
dures, including the necessity for an especially
smooth induction, maintenance, and emergence from
anesthesia. Indeed, a closed claims analysis by Gild
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.005
T Corresponding author. Westchester Medical Center,
Macy Pavilion, Room 2389, Valhalla, NY 10595.
E-mail address: [email protected]
(K.E. McGoldrick).
and colleagues [3] disclosed that 30% of eye injury
claims related to anesthesia management were asso-
ciated with patient movement during ocular surgery.
Most of the problems transpired during general an-
esthesia, but in one fourth of the cases the patients
were receiving monitored anesthesia care during pro-
cedures performed under local or regional anesthesia.
Tragically, the outcome was blindness in all cases.
Clearly, strategies to ensure patient immobility during
ophthalmic surgery are mandatory. Moreover, safety
issues are complicated by the logistic necessity for
the anesthesiologist frequently to be positioned at a
considerable distance from the patient’s face, thus
preventing immediate, direct access to the airway. It
is axiomatic that open, clear, and effective commu-
nication among the anesthesiologist, ophthalmologist,
and patient is integral to optimal outcome of oph-
thalmic surgery.
Indications for general anesthesia
In selecting the anesthetic technique for eye sur-
gery, numerous issues must be considered. General
anesthesia remains the technique of choice for chil-
dren, mentally retarded individuals, and demented
or psychologically unstable patients. It is also the
favored technique for patients with suspected or ap-
parent open-globe injuries, although recent literature
supports the use of regional eye blocks in selected
patients with open-eye trauma. Recognizing that there
are several distinct permutations of eye injuries, Scott
and colleagues [4] developed techniques to safely
block patients with certain open-globe injuries. In a
4-year period, 220 disrupted eyes were repaired via
regional anesthesia at Bascom Palmer Eye Institute.
Am 19 (2006) 179 – 191
reserved.
ophthalmology.theclinics.com
mcgoldrick & foldes180
Many of these injuries were caused by intraocular
foreign bodies and dehiscence of cataract or corneal
transplant incisions. Blocked eyes tended to have
smaller, more anterior wounds than those repaired
via general anesthesia. There was no outcome differ-
ence—that is, change of visual acuity from initial
evaluation until final examination—between the eyes
repaired with regional versus general anesthesia.
Additionally, combined topical analgesia and seda-
tion for selected patients with open-globe injuries has
also been reported [5].
General anesthesia is the technique of choice for
removal of infected scleral buckles or for patients
with very high myopia, where a perforating injury
from peribulbar or retrobulbar block is feared. Other
indications may include claustrophobia, deafness, a
language barrier, Parkinson’s disease, and intractable
arthritis or orthopnea, which impair the patient’s abil-
ity to lie flat and remain motionless during surgery.
Furthermore, the anticipated duration of the proce-
dure must be factored into the selection process, be-
cause few geriatric patients under regional anesthesia
can remain comfortable on a narrow, hard operating
table for procedures that exceed 2 or 3 hours.
With general anesthesia the risks of retrobulbar or
peribulbar hemorrhage, globe perforation, myotox-
icity, central spread of local anesthetic with possible
brain stem anesthesia, and inadequate intraoperative
analgesia are virtually eliminated. Nonetheless, gen-
eral anesthesia may be associated with a greater like-
lihood of airway complications and postoperative
nausea and vomiting. Although regional and topical
anesthetic techniques have gained enormous popular-
ity in recent years, it is imperative to appreciate the
vital role that general anesthesia maintains in the care
of certain ophthalmic patients. Major retrospective
and prospective nonrandomized studies have failed to
demonstrate the superiority of one anesthetic ap-
proach over the other in terms of morbidity and mor-
tality [6–10]. Accordingly, the risks, benefits, and
alternatives of all anesthetic options should be ex-
plained clearly to the patient, with the choice deter-
mined after discussion among patient, anesthesiologist,
and surgeon.
Preoperative evaluation
The preoperative evaluation of the geriatric patient
characteristically is more complex than that of the
younger patient owing to the heterogeneity of seniors
and the increased frequency and severity of comor-
bid conditions associated with aging. The process of
aging is highly individualized. Different people age at
varying rates and often in different ways. Typically,
however, virtually all physiologic systems decline
with advancing chronological age. Nevertheless,
chronological age is a poor surrogate for capturing
information about fitness or frailty. Moreover, peri-
operative functional status can be difficult to quanti-
tate because many elderly patients have reduced
preoperative function related to deconditioning, age-
associated disease, or cognitive impairment. Thus, it
is challenging to satisfactorily evaluate the patient’s
capacity to respond to the specific stresses associated
with anesthesia and surgery. How, for example, does
one determine cardiopulmonary reserve in a patient
severely limited by osteoarthritis and dementia? Even
‘‘normal’’ aging results in alterations in cardiac, re-
spiratory, neurologic, and renal physiology that are
linked to reduced functional reserve and ability to
compensate for physiologic stress. Moreover, the con-
sumption of multiple medications so typical of the
elderly can alter homeostatic mechanisms.
Preoperative testing
In the general population there is strong consensus
that most so-called ‘‘routine’’ tests are not indicated.
In the subset of geriatric patients our knowledge is
somewhat more limited. Nonetheless, a recent study
on routine preoperative testing in more than 18,000 pa-
tients undergoing cataract surgery is worthy of com-
ment. Patients were randomly assigned to undergo or
not undergo routine testing (ECG, complete blood
cell count, electrolytes, serum urea nitrogen, cre-
atinine, and glucose) [11]. The analysis was stratified
by age and disclosed no benefit to routine testing for
any group of patients. Similar conclusions were
drawn in a smaller study of elderly noncardiac sur-
gical patients by Dzankic and colleagues [12]. Some
physicians and lay people, however, misinterpreted
the results of Schein and colleagues’ [11] study, be-
lieving that patients having cataract surgery need no
preoperative evaluation. It is vital to note that all
patients in this trial received regular medical care
and were evaluated by a physician preoperatively;
they simply were not subjected to a robotic battery
of routine laboratory testing. Patients whose medical
status indicated a need for preoperative laboratory
tests were excluded from the study. Because ‘‘rou-
tine’’ testing for the more than 1.5 million cataract
patients in the United States is estimated to cost
$150 million annually, the favorable economic im-
pact of this ‘‘targeted’’ approach is obvious.
From these investigations and others, a few con-
cepts emerge. First, routine screening in a general
population of elderly patients does not significantly
general anesthesia for ophthalmic surgery 181
augment information obtained from the patient’s
history and physical examination. Testing should be
selective, based on abnormalities found from the pa-
tient’s history and physical examination. Second, the
positive predictive value of abnormal findings on
routine screening is limited. Third, positive results on
screening tests have modest impact on patient care.
The preoperative period is not the appropriate time to
screen for asympotomatic disease.
The dearth of population studies of perioperative
risk and outcomes specifically addressing the geri-
atric population can make selecting the most appro-
priate course of care challenging. Because age itself
adds very modest incremental risk in the absence of
comorbid disease, most risk-factor identification and
risk-predictive indices have focused on specific dis-
eases [13–15].
Considerations for patients with cardiac disease
It is well known that normal aging produces
structural changes in the cardiovascular system, as
well as changes in autonomic responsiveness/control,
that can compromise hemodynamic stability. The su-
perimposition of such comorbid conditions as angina
pectoris or valvular heart disease can further impair
cardiovascular performance, especially in the periop-
erative period.
According to the guidelines of the American Col-
lege of Cardiology (ACC) and the American Heart
Association (AHA) for preoperative cardiac evalua-
tion, the patient’s activity level, expressed in meta-
bolic units, is a primary determinant of the necessity
for further evaluation, along with the results obtained
from history and physical examination [13]. These
findings are then evaluated in conjunction with due
consideration for the invasiveness of the planned
surgical procedure. Fortunately, most ophthalmic pro-
cedures are typically considered to represent rela-
tively noninvasive, low-risk surgery.
Clearly, the goal of the preoperative evaluation
should be the identification of major predictors of
cardiac risk such as unstable coronary syndromes (for
example, unstable angina or myocardial infarction
[MI] less than 30 days ago), decompensated conges-
tive heart failure (CHF), severe valvular disease, and
significant arrhythmias. These patients have a pro-
hibitive rate of perioperative morbidity and mortality,
and are inappropriate candidates for elective outpa-
tient surgery. They deserve the benefit of further car-
diology consultation and optimization. In patients
with intermediate clinical predictors (mild angina,
previous MI more than 30 days ago, compensated or
prior CHF, diabetes mellitus, or renal insufficiency),
the invasiveness of the surgery and the functional
status of the patient will play major roles in de-
termining the nature and extent of preoperative
testing or intervention. Importantly, no preoperative
cardiovascular testing should be performed if the
results will not change perioperative management.
Patients with minor clinical predictors, such as ad-
vanced age, ECG abnormalities, rhythm other than
sinus, low functional status, history of stroke, or hy-
pertension, who are having low- or intermediate-risk
surgery typically will not require further cardiovas-
cular testing.
For those in whom further testing is warranted,
there are several options including Holter monitor-
ing, radionuclide ventriculography, thallium scintigra-
phy, dobutamine stress echocardiography, and coronary
angiography. The use of perioperative b-blockade in
intermediate or high-risk patients undergoing vascu-
lar surgery can be beneficial and may obviate the
need for more invasive interventions [16]. A recent
study demonstrated that perioperative b-blockertherapy is associated with a reduced risk of in-
hospital death among high-risk, but not low-risk,
patients undergoing major noncardiac surgery [17].
However, there is an absence of data pertaining to the
use of perioperative b-blockade in patients under-
going less invasive outpatient surgery that is charac-
teristic of most ophthalmic procedures.
Increasingly, patients with coronary artery disease
are undergoing stent placement. A frequently asked
question in this context is how long should one wait
after stent placement before scheduling a patient for
elective surgery under general anesthesia. Kaluza and
colleagues [18] in 2000 published a recommendation
(based on a study of 40 patients) that elective surgery
should be postponed for 2 to 4 weeks after stent
placement to allow completion of the antiplatelet pro-
tocol. A few years later, however, Wilson and col-
leagues [19] studied more than 200 patients and
recommended that nonemergency surgery should be
delayed for 6 weeks after stent insertion to permit
completion of the antiplatelet therapy and to allow for
endothelialization of the stent.
It should be emphasized that diabetes mellitus is
an intermediate predictor of such adverse cardiac
outcomes as perioperative MI and CHF after elective
surgery because of the accelerated atherosclerosis that
occurs with associated aberrations of lipid and cho-
lesterol metabolism. The Diabetes Control and Com-
plications Trial, a clinical study of young (average
age 27 years) diabetic patients, showed that intensive
treatment delayed the onset and severity of retinop-
athy, nephropathy, and neuropathy [20]. However, the
cohort was probably too young to demonstrate a
mcgoldrick & foldes182
reduction in cardiovascular complications with ag-
gressive insulin therapy, but the results suggest that a
well-controlled diabetic patient may be at lesser risk
than a poorly controlled diabetic patient. Nonetheless,
this issue is not addressed in the ACC/AHA guide-
lines. It is important to appreciate that the diagnosis
of myocardial ischemia may be more challenging in
a diabetic patient owing to the high incidence of au-
tonomic neuropathy. Patients with autonomic neu-
ropathy may not complain of chest pain even when
experiencing an acute MI.
General anesthesia: physiologic principles and
pharmacologic agents
Those patients who require or prefer general an-
esthesia for eye surgery experience a favorable
outcome provided the airway is satisfactorily main-
tained, hemodynamic stability is achieved, and the
eye is kept motionless with a constant intraocular
pressure (IOP). The latter is especially critical during
open-eye operations such as corneal transplantation
or open-sky vitrectomy procedures when the risk of
vitreous loss or expulsive choroidal hemorrhage is
present. Moreover, it is important to appreciate that
drugs administered to produce pupillary dilation or to
reduce IOP may be absorbed systemically from the
conjunctiva or (predominantly) from the nasal mu-
cosa after drainage through the nasolacrimal duct.
Such systemic absorption has important anesthetic
implications. Nasolacrimal duct occlusion is an ef-
fective way to minimize systemic absorption, and this
maneuver is important in small children who are ex-
tremely vulnerable to the toxic effects of such drugs
as scopolamine or phenylephrine. Additionally, top-
ical administration of these drugs should be avoided
in eyes with open conjunctival wounds. Examples
of potentially worrisome topical ocular drugs include
cyclopentolate, echothiophate iodide, epinephrine,
and timolol.
Intraocular drugs also have important anesthetic
implications. Nitrous oxide, for example, should not
be used concomitantly in eyes that receive intraocular
air or gas. To avoid significant changes in the volume
of the injected bubble and associated dangerous
changes in IOP, nitrous oxide should be discontinued
15 to 20 minutes before an intravitreous air or gas
injection administered to tamponade a detached retina
[21]. Furthermore, if a patient requires a repeat op-
eration after intravitreous gas injection, the typical
recommendation is that nitrous oxide should be
omitted for 5 days after an air injection and for
10 days after a sulfur hexafluoride injection [22]. In
cases where perfluoropropane has been injected, the
nitrous oxide proscription should be in effect for
longer than 30 days [23]. It is important to point out,
however, that resorption time is not uniform or al-
ways predictable. For example, reports have appeared
where a 19-year-old woman with type 1 diabetes
injected with sulfur hexafluoride 25 days before sub-
sequent surgery and a 37-year-old male with insulin-
dependent diabetes injected with perfluoropropane
gas 41 days before subsequent surgery were given
nitrous oxide and developed central retinal artery
occlusion and permanent blindness in the affected eye
[24]. Because the pressure in retinal arterial vessels is
lower in patients with diabetes, the elderly, and those
with atherosclerosis, these patients are probably at
higher risk for this devastating complication [25–29].
The international distributor of medical-grade gases,
in cooperation with the American distributors and the
US Food and Drug Administration (FDA), has begun
to provide hospital band-type warning bracelets for
patients who receive intraocular gas injection to alert
other health professionals to the presence of the bub-
ble and the need to avoid nitrous oxide administration.
Because many eye surgery patients are elderly,
they may have arthritic involvement of the cervi-
cal spine and the temporomandibular joint, which
can make laryngoscopy difficult or, occasionally,
impossible. Thus, equipment designed to facilitate
intubation, such as gum elastic bougies, fiberoptic
endoscopes, laryngeal mask airways, and a variety of
laryngoscope blades and endotracheal tube sizes,
should be readily available.
The logistic exigencies of ophthalmic anesthesia
are such that the anesthesiologist is positioned remote
from the patient’s airway. It is, therefore, essential to
meticulously secure the endotracheal tube. Addition-
ally, the anesthetic tubing should be positioned so that
torsional strains do not occur that might inadvertently
occlude the endotracheal tube by causing it to kink
or twist. All connections should be firmly secured
because movement of the head by the surgeon might
dislodge a weak connection. Finally, the eye that is
not undergoing surgery should be taped shut and a
shield applied to prevent injury. Many ophthalmolo-
gists request that the patient’s nares be packed with
gauze to prevent nasal secretions from contaminating
the eye during surgery.
The laryngeal mask airway (LMA) has gained
great popularity in the past 15 years. Having the
advantage of being easy to position without laryngos-
copy or muscle relaxants, the LMA does not produce
the same marked degree of vasopressor and oculo-
tensive reflexes associated with endotracheal intuba-
tion and is less apt to cause dental damage. Initially, it
general anesthesia for ophthalmic surgery 183
was thought that the LMA was less likely to produce
a sore throat [30,31], but more recent prospective
investigations question the purported advantage of
the LMA versus an endotracheal tube in regard to
minor laryngopharyngeal morbidity [32]. The classic
LMA does not protect against aspiraton, however,
and many geriatric patients have an incompetent
esophagogastric junction that may allow reflux of
gastric contents. Moreover, many patients with dia-
betes mellitus also have gastroparesis. These patients,
and others with significant risk factors for aspiration,
are managed prudently by intubation with a cuffed
endotracheal tube to protect the lungs.
A wide assortment of anesthetic agents can be
administered safely and effectively in ophthalmic
surgery. Virtually any of the inhalation agents can be
administered after intravenous induction with a
barbiturate or propofol. Similarly, a total intravenous
anesthetic technique with a propofol infusion and
other intravenous medications as needed can be ad-
ministered. Because it is consistently associated with
less postoperative nausea and vomiting than other
agents [33–35], propofol is an excellent drug for
patients undergoing ophthalmic surgery. Recovery
from propofol is rapid and typically associated with a
sense of well-being [36], even euphoria, making it a
very suitable drug for ambulatory surgery. Moreover,
propofol attenuates the hypertensive response to
intubation and reduces IOP, similar to most intra-
venous anesthetic drugs commonly used during eye
surgery, such as narcotics and other sedative-hypnotics
[37,38]. Propofol, however, frequently produces dis-
comfort or pain when injected into small veins. This
complication can be minimized or prevented by
preadministration of, or admixing with, 20 mg li-
docaine. Moreover, new formulations of propofol
designed to be less irritating to veins are currently
being evaluated. In patients with significant coronary
artery or other types of heart disease, the cardiode-
pressant effects of barbiturates or propofol are un-
welcome. Induction with intravenous etomidate may
be more benign in terms of the cardiovascular system
but, unfortunately, can trigger postoperative nausea
and vomiting and possibly also result in short-term
depression of adrenocortical function. The selection
of the optimal muscle relaxant to facilitate intubation
is made after assessing the patient’s airway and the
probable degree of difficulty of intubation, the pres-
ence of symptomatic reflux, the hemodynamic con-
sequences of the neuromuscular blocking agent, and
the estimated duration of the surgery.
Satisfactory control of arterial blood pressure is
always important, but it has special implications for
retinal perfusion in patients having vitreoretinal sur-
gery. If the patient’s mean arterial pressure is mark-
edly reduced, the retinal perfusion may be inadequate
and compromise the visual outcome of surgery.
Alternatively, marked elevation of retinal arteriole
pressure can be dangerous. Therefore, it behooves the
anesthesiologist to be cognizant of the patient’s nor-
mal blood pressure and endeavor to maintain hemo-
dynamic variables within an acceptable range for
each individual patient.
Various inhalation agents are available for intra-
operative maintenance of anesthesia, including iso-
flurane, desflurane, and sevoflurane. All these agents
lower IOP in a dose-dependent fashion, provided
oxygenation and ventilation are satisfactorily main-
tained. Desflurane and sevoflurane, the two newest
inhalation agents in widespread use, have lower
blood-gas solubilities than all previously used potent
inhaled agents. In theory, this solubility advantage
allows greater control of anesthetic depth and more
rapid recovery from general anesthesia. Desflurane
has the lowest blood-gas solubility of all volatile
agents and is associated with the fastest immediate
awakening after surgery. Data indicate that desflurane
resists in vivo degradation more than any other potent
halogenated agent. The limited biodegradation that
does occur appears to be approximately one tenth that
of isoflurane, the least degraded of the other available
halogenated agents. This lack of significant biotrans-
formation suggests relative safety in terms of po-
tential toxicity from metabolites.
The cardiovascular effects of desflurane involve
the direct effects of the agent, and a transient response
linked to sympathetic nervous system activation. The
direct hemodynamic effects of desflurane are quite
similar to those of isoflurane, including a reduction in
peripheral vascular resistance and blood pressure.
Prolongation of the QTc interval has been reported
with many anesthetic drugs including isoflurane,
sevoflurane, and desflurane [39]. However, the tran-
sient sympathetic activation seen with desflurane
administered in combination with nitrous oxide is not
encountered with isoflurane, but had been reported
with diethyl ether. Although the precise mechanism
responsible for this response has not been definitively
established, beta-adrenergic activation leading to
major increases in blood pressure and heart rate
through increased plasma epinephrine and norepi-
nephrine levels has been postulated [40]. The extent
of sympathetic activation is related, at least partially,
to the absolute concentration of desflurane as well as
to the rapidity of increase in the concentration of
desflurane. Thus, an extremely rapid progression to
high concentrations of desflurane triggers more dra-
matic sympathetic stimulation [40,41]. This sympa-
mcgoldrick & foldes184
thetic response can be attenuated by pretreatment
with clonidine or intravenous fentanyl, esmolol, or
propofol. Nonetheless, many clinicians think it is best
to avoid desflurane in patients with a history of myo-
cardial ischemia, or else to administer only relatively
low concentrations of the agent and to increase the
concentration gradually as indicated.
Many of the physicochemical characteristics and
pharmacologic properties of sevoflurane suggest that
it is well suited for use in ophthalmic surgery. Com-
pared with desflurane, sevoflurane has the advantage
of being nonirritating to the airway. Inhalational in-
duction of anesthesia with sevoflurane is accom-
plished smoothly and quickly, making it the agent of
choice in young children who are afraid of needles
and would, therefore, prefer to avoid an intrave-
nous induction. Coughing, laryngospasm, and breath-
holding are lesser problems than they are with
isoflurane or desflurane, even with so-called single
breath inductions. Additionally, sevoflurane, unlike
desflurane, has a cardiovascular profile that is quite
predictable, and it does not activate the sympathetic
nervous system [42]. The incidence of bradycar-
dia and arrhythmias during inhalation induction in
children is also much lower than with halothane
[43]. Occasionally, the occurrence of opisthotonic
and seizurelike activity with sevoflurane has been
noted [44–46]. The seizurelike activity has been re-
ported at variable sevoflurane concentrations and
during induction, maintenance, and recovery. The
phenomenon has been observed in adults as well as
children. It is reassuring that all of the patients who
demonstrated the seizurelike activity recovered with-
out incident. Nonetheless, clinicians should be aware
of this problem, which is listed in the drug insert
provided by Abbott Pharmaceuticals [47].
Sevoflurane is unstable under in vitro and in
vivo conditions, producing compound A and fluo-
ride. Compound A has been shown to be nephro-
toxic in rats, and high fluoride concentrations can be
nephrotoxic in humans. However, despite extensive
clinical investigations, multiple studies have not
demonstrated any clinically significant renal or he-
patic dysfunction in humans, even at very low gas
flows [48,49]. Indeed, sevoflurane has been admin-
istered to more than 120 million patients worldwide
with an impressive safety record. It appears that the
likelihood of long-term toxicity in humans from
sevoflurane administered according to the guidelines
in the package insert is extremely low, even when
given for prolonged procedures. Similar to desflur-
ane, awakening and emergence from sevoflurane are
rapid and complete. However, emergence excitement
or agitation is not uncommon with desflurane and
sevoflurane. The times until discharge for ambulatory
patients in whom desflurane or sevoflurane was used
are comparable with more soluble agents like iso-
flurane or enflurane [50]. Whether this finding re-
flects a true lack of improvement in recovery time, or
merely inertia in the ambulatory center system, re-
mains to be determined.
Regardless of which agent is selected, it should be
carefully titrated and, because akinesia is important
for delicate ocular surgery, administration of a non-
depolarizing muscle relaxant is advised, in conjunc-
tion with peripheral nerve monitoring to ensure a
twitch height suppression of 90% to 95% during
open-eye surgery. Ventilation should be controlled
and continuously monitored by end-tidal CO2 deter-
mination to avoid hypercarbia and its ocular hy-
pertensive effect as well as to detect inadvertent
disconnection of the endotracheal tube from the an-
esthesia circuit, a dangerous event that can be ob-
scured by the surgical drapes. Continuous monitoring
of arterial oxygen saturation by pulse oximetry is also
essential. After completion of surgery, any residual
neuromuscular block should be reversed. Intravenous
lidocaine can be administered a few minutes before
extubation to prevent or attenuate periextubation
coughing. Depending on such factors as the patient’s
airway anatomy, NPO (nil per os) status, and history
of reflux, either awake or deep extubation may be
selected. In skilled hands, either technique is sat-
isfactory for patients who were fasting, who have
normal airway anatomy, and who have no risk factors
for reflux.
Postoperative nausea and vomiting: prevention
and therapy
Postoperative nausea and vomiting (PONV) ac-
count for a major proportion of unanticipated ad-
missions to the hospital after intended ambulatory
surgery, especially in children. Fortunately, after age
50 the incidence of PONV declines by more than
10% during each subsequent decade. The incidence
of PONV is higher with narcotic-based anesthesia and
with volatile agents. The incidence is lowest with a
total intravenous anesthetic technique using propofol.
The emetic effect of anesthetics are modulated in the
chemoreceptor trigger zone, where serotonergic, his-
taminic, muscarinic, and dopaminergic receptors are
found [34]. Input also comes from vagal and other
stimulation directly to the emetic center.
Although pharmacologic agents that act on the
chemoreceptor trigger zone are well represented
in our antiemetic armamentarium, the neurokinin1
general anesthesia for ophthalmic surgery 185
(NK1) antagonists are the only available antiemetics
that act on the vomit center. Traditional antiemetics
include benzamides such as metoclopramide, buty-
rophenones such as droperidol, and phenothiazines
such as prochlorperazine. These three classes of drugs
antagonize dopamine receptors. Scopolamine and
atropine are anticholinergics that antagonize musca-
rinic receptors. Dimenhydrinate, diphenhydramine,
and hydroxyzine antagonize histamine receptors.
Other useful antiemetics include steroids such as
dexamethasone and assorted agents such as ephedrine
and propofol. Newer drugs include the 5-HT3 sero-
tonergic receptor antagonists, such as ondansetron,
tropisetron, and granisetron, which are expensive but
generally effective. The 5-HT3 blockers are attractive
because of the paucity of side effects associated with
their use. Unlike many other antiemetics, which can
cause drowsiness, dry mouth, or extrapyramidal
symptoms, the 5-HT3 antagonists have a clean profile,
except for headache and mild effects on liver function
tests. However, similar to droperidol, some of the
drugs in this category can prolong the QT interval.
Unlike droperidol, however, these drugs have not
been subject to a black box warning from the FDA.
Our knowledge concerning the pathophysiology
and management of PONV has grown impressively in
the past 15 years. We now believe, for example, that
universal PONV prophylaxis is not cost-effective.
Rather, prophylactic treatment should be directed to-
ward those at increased risk for the complication.
Apfel and colleagues have developed a simplified
risk score that identifies four major risk factors: fe-
male gender, nonsmoking status, history of PONV,
and opioid use [51]. In this investigation of inpatients
receiving balanced inhaled anesthesia the incidence
of PONV with none, one, two, three, or all four risk
factors was approximately 10%, 20%, 40%, 60%, and
80%, respectively. Apfel and colleagues claimed that,
for inpatients, the type of surgery was not an inde-
pendent risk factor. Sinclair and colleagues, however,
reported that certain ophthalmic procedures, such as
strabismus correction, were predictive of an increased
risk of PONV [52].
Recently, guidelines have been developed to pro-
vide a comprehensive, evidence-based reference tool
for the management of patients at moderate or high
risk for PONV [53]. Double and triple antiemetic
combinations (each with a different mechanism of
action) are recommended prophylactically for pa-
tients at high risk for PONV. All prophylaxis in chil-
dren at moderate or high risk for postoperative
vomiting should be with combination therapy using
a 5-HT3 antagonist and a second drug from a different
category. Antiemetic rescue therapy should be admin-
istered to patients who have an emetic episode after
surgery. If PONVoccurs within 6 hours after surgery,
patients should not receive a repeat dose of the pro-
phylactic antiemetic(s). Rather, a drug from another
class should be given.
Guidelines for diabetic patients undergoing
general anesthesia
Estimates reflect that as many as 15 million
people in the United States have diabetes mellitus.
Ninety percent of diabetic individuals have non-
insulin-dependent, or type 2, diabetes mellitus, and
10% have insulin-dependent, or type 1, diabetes mel-
litus requiring exogenous insulin to prevent keto-
acidosis. Diabetes affects virtually every tissue of the
body and shortens average life expectancy by up to
15 years. The emotional toll and financial costs
of diabetes and its complications are an estimated
$132 billion annually. This estimate reflects both
direct health care costs as well as lost productivity.
More than one of every four Medicare dollars is spent
on people with diabetes. It is sobering to realize that
diabetes and its complications rank as the third lead-
ing cause of death by disease in the United States.
Given the pandemic of obesity currently afflicting our
country, one can anticipate that the number of dia-
betic individuals will continue to climb.
End-organ disease
The renal, neurologic, cardiovascular, and oph-
thalmic complications of diabetes mellitus have been
well described. Both the presence and extent of end-
organ disease in an individual diabetic patient and the
metabolic perturbations induced by the stress of
anesthesia and surgery must be thoroughly compre-
hended if one is to formulate a rational and effective
perioperative management plan.
Cardiovascular abnormalities include coronary
artery disease, hypertension, cardiac autonomic neu-
ropathy, and impaired ventricular function. Occa-
sionally, unexpected sudden death may occur in
association with autonomic nervous system dysfunc-
tion. Because atherosclerosis and microangiopathy
occur at an earlier age in diabetic patients compared
with nondiabetic individuals, a diabetic patient’s
physiological age is much older than the stated
chronologic age. Thus, coronary artery disease is
common in long-standing type 1 diabetes, even at age
25 or 30 years. Myocardial infarction is 5 to 10 times
more common in type 1 and type 2 diabetic in-
dividuals with end-organ disease than in the general
mcgoldrick & foldes186
population. Because diabetic adults are considered at
high risk for perioperative myocardial ischemia, a
baseline ECG should be obtained on all adult diabetic
individuals. Anesthetic management is then adjusted
appropriately to the results of preoperative assess-
ment and intraoperative hemodynamic performance.
Hypertension is extremely common in diabetic
patients, and may be a marker for possible coronary
artery disease. The presence of left ventricular hy-
pertrophy suggests impaired autoregulation of coro-
nary perfusion, rendering these patients vulnerable to
ischemia with even a moderate reduction in blood
pressure. Satisfactory control of blood pressure be-
fore surgery should foster stable intraoperative and
postoperative hemodynamic function. However,
perioperative hemodynamic instability may occur ow-
ing to altered sympathetic tone, reduced barorecep-
tor function, relative hypovolemia associated with
chronic vasoconstriction, and anesthetic interactions
with some antihypertensive medications. Because of
the diabetic patient’s limited ability to autoregulate
coronary perfusion, the anesthesiologist should
attempt to maintain blood pressure within ±20% of
baseline values.
The presence of orthostatic hypotension, an ele-
vated resting heart rate, or a reduction or absence of
a normal beat-to-beat variation of heart rate during
deep breathing suggests the possibility that the patient
may have cardiac autonomic neuropathy. This con-
dition manifests as an impaired cardiovascular stress
response and may be accompanied by painless
myocardial ischemia. Additionally, diabetic patients
with autonomic neuropathy may have abnormal
hypoxic drive mechanisms centrally or peripherally
and hence are at greater risk for sudden, unexpected
cardiac and respiratory arrest in the setting of hypoxia
[54,55].
Those with painless myocardial ischemia may
also have occult left ventricular dysfunction, which
can result in CHF if the patient is given a volume
overload perioperatively. Impaired gastric emptying
is also a consequence of autonomic dysfunction, and
can increase the risk of perioperative aspiration and
PONV. Administration of IV metoclopramide to fa-
cilitate gastric emptying may be helpful.
Diabetic renal disease, including renal papillary
necrosis and glomerulosclerosis, renders the diabetic
patient susceptible to perioperative acute renal failure.
Additionally, a diabetic patient is at greater risk for
urosepsis, which may contribute to systemic sepsis
and acute renal failure.
Fixation of the atlanto-occipital joint with limi-
tation of head extension may make endotracheal
intubation difficult [56]. ‘‘Stiff joint syndrome’’ typi-
cally occurs in type 1 diabetic patients and is as-
sociated with short stature, small joint contractures,
and tight, waxy skin. The etiology is thought to be
abnormal collagen cross-linking by nonenzymatic
glycosylation, which may occur in up to 25% of
juvenile diabetic individuals [57]. This abnormal
collagen glycosylation may also lead to possible
atlanto-occipital dislocation. A defective palm print
or ‘‘prayer sign’’ in these patients (owing to an in-
ability to approximate the interphalangeal joints of
the hand) is often associated with difficult intubation
and, therefore, should be assessed preoperatively so
that appropriate airway management can be planned,
enabling the necessary equipment to be immedi-
ately available.
Clearly, meticulous attention must be paid to a
thorough preoperative assessment and optimization
of the patient’s medical condition, as well as careful
titration of the drugs and fluids administered peri-
operatively. Attention must also be paid to proper
positioning and padding intraoperatively, because the
diabetic patients are especially vulnerable to pressure
ischemia of nerves and vasculature.
A retrospective study assessed perioperative risk
of nonocular surgery in diabetic patients [58]. Over-
all, 15% of patients had significant complications,
and there were major differences in outcome depend-
ing on the presence or absence of end-organ damage.
Patients with serious cardiac disease were more prone
to major perioperative cardiac complications. Non-
cardiac complications, including infection, renal in-
sufficiency, and cerebral ischemia, occurred in 24% of
patients with end-organ disease (retinopathy, neu-
ropathy, or nephropathy), in 29% of those with CHF,
and in 35% of those with peripheral vascular disease.
In patients without preexisting conditions, noncardiac
complications (6%) and cardiac complications (4%)
were rare. Moreover, the type of anesthetic selected
was not predictive of risk of complications. The study
emphatically underscored, however, that increased
morbidity and mortality occur in diabetic patients
with cardiac and end-organ disease.
Control of glucose
Despite the known advantages of ‘‘tight’’ or near
euglycemic control in the chronic diabetic state, the
concept of rigidly tight control is controversial in the
perioperative period. Aggressive attempts to achieve
euglycemia may result in dangerous episodes of
hypoglycemia that may be masked by anesthesia
and sedation. Therefore, the perioperative blood
sugar level should be maintained in the range of ap-
proximately 100 to 180 mg/dL. Patients with insulin-
general anesthesia for ophthalmic surgery 187
dependent diabetes mellitus (type 1) tend to be more
‘‘brittle’’ than those with type 2 diabetes, and surgery
for type 1 patients should be scheduled as early in the
day as possible. Several regimens for insulin and
substrate infusions have been advocated, but one of
two protocols is generally followed. All treatment
options require frequent measurement of blood glu-
cose and treatment of hypoglycemia and hyper-
glycemia as needed. The blood glucose level is
determined preoperatively, and an intravenous infu-
sion of dextrose 5% (D5) and 0.25 normal saline
is begun. One half of the usual neutral protamine
Hagedorn (NPH) insulin dosage is administered,
provided the blood sugar level is above 150 mg/dL.
Blood glucose levels are monitored frequently (usu-
ally hourly) during the intraoperative period. Regular
insulin doses of 0.1 unit/kg are given when the
plasma glucose level exceeds 200 mg/dL. In contrast,
if the blood glucose level is below 100 mg/dL, more
intravenous dextrose is administered.
Alternatively, a simultaneous insulin and glucose
infusion may be given to a type 1 patient after a
preoperative blood sugar level has been established.
The infusion contains 1 to 2 units of insulin per
100 mL of 5% dextrose in water, and the infusion rate
allows for 0.2 to 0.4 units of insulin per gram of
glucose. Blood glucose levels are maintained in the
desired range by titrating the infusion rate.
Type 2 diabetic patients taking daily insulin are
managed in a manner analogous to that for type 1
diabetic individuals. Those patients on oral hypogly-
cemics should refrain from taking the hypoglycemic
agent on the day of surgery. After the fasting blood
sugar level has been established an appropriate intra-
venous infusion is initiated. A postoperative blood
sugar level is determined, with therapeutic and die-
tary instructions provided accordingly. An ophthal-
mic patient is usually able to tolerate oral intake
within a relatively brief period after surgery. When
oral intake is adequate, the patient may resume his or
her usual diabetic regimen.
Considerations for select high-risk patients
Marfan syndrome
Marfan syndrome is a disorder of connective
tissue, involving primarily the cardiovascular, skel-
etal, and ocular systems. However, the skin, fascia,
lungs, skeletal muscle, and adipose tissue may also be
affected. The etiology is a mutation in FBNI, the gene
that encodes fibrillin-1, a major component of extra-
cellular microfibrils, which are the major compo-
nents of elastic fibers that anchor the dermis, epi-
dermis, and ocular zonules [59]. Connective tissue in
this disorder has decreased tensile strength and elas-
ticity. Marfan syndrome is inherited as an autosomal
dominant trait with variable expression.
Ocular manifestations of the syndrome include
severe myopia, spontaneous retinal detachment, lens
displacement, and glaucoma. Cardiovascular mani-
festations include dilation of the ascending aorta and
aortic insufficiency. The loss of elastic fibers in the
media may also account for dilation of the pulmonary
artery and mitral insufficiency resulting from ex-
tended chordae tendinae. Myocardial ischemia owing
to medial necrosis of coronary arterioles as well as
dysrhythmias and conduction disturbances have been
well documented. Heart failure and dissecting aortic
aneurysms or aortic rupture are not uncommon.
The patients are tall, with long, thin extremities
and fingers (arachnodactyly). Joint ligaments are
loose, resulting in frequent dislocations of the man-
dible and hip. Possible cervical spine laxity can also
occur. Kyphoscoliosis and pectus excavatum can
contribute to restrictive pulmonary disease. Lung
cysts have also been described, causing an increased
risk of pneumothorax. A narrow, high-arched palate
is commonly found.
The early manifestations of Marfan syndrome
may be subtle, and therefore the diagnosis may not
yet have been made when the patient comes for initial
surgery. The anesthesiologist, however, should have a
high index of suspicion when a tall young patient
with a heart murmur presents for repair of a spontane-
ously detached retina. These young patients should
have a chest radiograph as well as an electrocardio-
gram and echocardiogram before surgery. Antibiotics
for subacute bacterial endocarditis prophylaxis
should be considered, as well as b-blockade to miti-
gate increases in myocardial contractility and aortic
wall tension (dP/dT).
The anesthesiologist should be prepared for a
potentially difficult intubation. Laryngoscopy should
be carefully performed to circumvent tissue damage
and, especially, to avoid hypertension with its atten-
dant risk of aortic dissection. The patient should be
carefully positioned to avoid cervical spine or other
joint injuries, including dislocations. The dangers of
hypertension in these patients are well known.
Clearly, the presence of significant aortic insuffi-
ciency warrants that the blood pressure (especially
the diastolic pressure) be high enough to provide
adequate coronary blood flow but should not be so
high as to risk dissection of the aorta. Maintenance
of the patient’s normal blood pressure is typically a
good plan. No single intraoperative anesthetic agent
mcgoldrick & foldes188
or technique has demonstrated superiority. If pulmo-
nary cysts are present, however, positive pressure ven-
tilation may lead to pneumothorax [60]. At extubation,
one should take care to avoid sudden increases in
blood pressure or heart rate. Adequate postoperative
pain management is vitally important to avoid the
detrimental effects of hypertension and tachycardia.
Myotonic dystrophy
Myotonic dystrophy, also known as myotonia
dystrophica or Steinert’s disease, is a genetically trans-
mitted autosomal dominant disease with variable and
unpredictable penetrance and phenotypic presenta-
tion. Myotonia denotes a characteristic persistent
contracture after cessation of voluntary contraction or
electrical or percussive stimulation. This inability of
skeletal muscle to relax is diagnostic. Electromyog-
raphy is corroborative and pathognomonic, showing
continuous, low-voltage activity with high-voltage,
fibrillation-like potential bursts. Myotonia can be
initiated or exacerbated by exercise or cold temper-
ature and a host of other conditions and drugs. The
most common form of myotonic dystrophy is lo-
calized to chromosome 19, locus q12.3, the gene that
codes for serine/threonine kinase. An abnormally
long trinucleotide repeat is thought to lead to the
disease. Moreover, within a given patient there is
mosaicism in the aberrant repeat sequences in differ-
ent tissues. A defect in sodium and chloride channel
function produces electrical instability of the muscle
membrane and self-sustaining runs of depolarization.
Additionally, abnormal calcium metabolism may be
involved. In contrast to most myopathies, the distal
muscles are more affected than proximal muscles.
Although patients can present at any age from infancy
to late life, typically myotonic dystrophy manifests in
the second or third decade. Myotonia is the predom-
inant manifestation early in the disease, but as the
condition progresses, muscle weakness and atrophy
become more apparent. Facial muscles (orbicularis
oculi and oris, masseter, and so forth) frequently
develop marked atrophy, producing a characteristic
expressionless facial appearance sometimes described
as ‘‘hatchet face.’’
Multiple organ systems are affected. Cardiac mani-
festations, which are often noted before the appear-
ance of other clinical symptoms, consist of atrial or
ventricular tachyarrhythmias, conduction abnormal-
ities including varying degrees of heart block, and,
less frequently, impaired ventricular function [61,62].
Mitral valve prolapse is said to occur in approxi-
mately 15% of myotonic patients [62]. Respiratory
involvement consists of a restrictive pattern of dis-
ease, with respiratory and sternocleidomastoid mus-
cle weakness leading to reduced vital capacity.
Patients typically develop a weak cough, dyspnea,
and frequent episodes of pneumonia. Alveolar hypo-
ventilation is caused by either pulmonary or central
nervous system dysfunction. Chronic hypoxemia may
result in cor pulmonale. Assorted other stigmata in-
clude presenile cataracts, ptosis, strabismus, and pre-
mature frontal balding. Endocrine dysfunction leads
to adrenal [63], thyroid, pancreatic [64], and gonadal
insufficiency. Central nervous system manifestations
include mental retardation, central sleep apnea, and
hypersomnolence, as well as psychiatric aberrations.
Delayed esophageal and gastric emptying [65], in
combination with compromised ability to swallow
[66], can predispose patients to pulmonary aspiration.
Moreover, uterine atony can retard labor and increase
the likelihood of retained placenta.
Treatment of myotonic dystrophy can be under-
taken with membrane-stabilizing medications, such
as phenytoin, quinine sulfate, and procainamide. Al-
though phenytoin has not been implicated in the
exacerbation of cardiac conduction abnormalities,
quinine and procainamide may prolong the P-R inter-
val. A cardiac pacemaker should be inserted in pa-
tients with significant conduction defects, even if they
appear to be asymptomatic.
Patients with myotonic dystrophy offer multiple
challenges to the anesthesiologist because they are at
high risk for serious perioperative respiratory and
cardiac complications. (Apparently, this condition can
also complicate surgical results. Three case reports,
for example, describe seemingly uneventful cataract
surgery that was complicated postoperatively by re-
current opacifications and intraocular fibrosis [67].) It
is vital to appreciate that a small number of patients
with this condition may be presymptomatic and un-
diagnosed. Indeed, although rare, there are reports of
patients with myotonic dystrophy in whom the diag-
nosis was made only after an episode of prolonged
apnea occurred following general anesthesia. Typi-
cally, however, the patient’s diagnosis is known, and
that individual suffers from a host of associated con-
ditions including restrictive lung disease, conduction
defects, cardiomyopathy, hypothyroidism, diabetes,
dysphagia, and delayed gastric emptying.
Patients with myotonic dystrophy have altered re-
sponses to a vast spectrum of anesthetic drugs. They
are frequently extremely sensitive to even small doses
of opioids, sedatives, and inhalation agents, all of
which may trigger prolonged apnea. Succinylcholine
is considered relatively contraindicated because it can
precipitate intense myotonic contractions. Moreover,
trismus can abolish the ability to open the mouth for
general anesthesia for ophthalmic surgery 189
oral intubation. Myotonic contraction of respiratory,
chest wall, or laryngeal muscles can render ven-
tilation difficult or impossible. Additionally, hypo-
thermia, shivering, struggling during an inhalation
induction, application of a tourniquet, performing a
painful needle stick for intravenous induction, surgi-
cal manipulation, and using electrocautery or a pe-
ripheral nerve stimulator can all trigger myotonic
contractions. Other drugs that act at the motor end
plate, such as neostigmine and physostigmine, can
exacerbate myotonia. Regional anesthesia can be ad-
ministered but does not reliably prevent myotonic
contractions, which do respond to intramuscular
injection of procaine or intravenous administration
of 300 to 600 mg quinine hydrochloride. Even non-
depolarizing muscle relaxants do not consistently
prevent myotonic contractions. Because reversal
agents can theoretically trigger myotonic contrac-
tions, the use of relatively short-acting nondepolariz-
ing drugs, such as mivacurium, is recommended.
Small doses of meperidine may be judiciously ad-
ministered to prevent the shivering commonly asso-
ciated with hypothermia and the use of volatile
anesthetics. Short-acting opioids, such as alfentanil
or remifentanil, are recommended to avoid prolonged
postoperative respiratory depression and obtundation.
Obviously, temperature monitoring is important, as is
the use of warmed IV fluids, warmed humidified
inhaled gases, and use of a warming blanket. More-
over, aspiration prophylaxis is probably prudent.
Aggressive pulmonary hygiene with physical ther-
apy, incentive spirometry, and vigilant postopera-
tive monitoring are warranted. In the past, there was
speculation about an association between myotonic
dystrophy and malignant hyperthermia. This possible
link has not been confirmed, however. Interestingly,
both conditions map to chromosome 19, but have
different loci.
The literature suggests that there is no association
between the type of anesthesia administered and any
postoperative complications. Risk of pulmonary com-
plications appears to be greatest in those with severe
disability and those having upper abdominal surgery.
Because a variety of approaches have been used
successfully, there is no single best method. The risks
and benefits should be assessed individually to tailor
an appropriate anesthetic plan.
Summary
Skillful anesthetic management is integral to op-
timal outcomes after ophthalmic surgery. Although
the majority of ophthalmic operations in the United
States are performed with local anesthetic techniques,
nonetheless general anesthesia may be either nec-
essary or advisable in several challenging circum-
stances. Ophthalmic patients are often at the extremes
of age, and not uncommonly have extensive asso-
ciated systemic or metabolic diseases. Because the
complications of ophthalmic anesthesia can be vision
threatening or life threatening, it is imperative that the
ophthalmologist and the anesthesiologist understand
the complex and dynamic interaction among patient
disease(s), anesthetic agents, ophthalmic drugs, and
surgical manipulation. Effective communication and
planning among all involved are essential to safe
and efficient perioperative care.
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Ophthalmol Clin N
Sedation Techniques in Ophthalmic Anesthesia
Shireen Ahmad, MD
Northwestern University, Feinberg School of Medicine, Department of Anesthesiology, 251 East Huron Street, F5-704,
Chicago, IL 60611, USA
The majority of ophthalmologic surgeries are
performed with regional nerve block anesthesia.
Preoperatively, sedation may be required during the
placement of the nerve block to decrease the dis-
comfort of the injection, limit patient motion, relieve
anxiety, and produce amnesia about the procedure.
Intraoperatively, sedatives may also be administered
to relieve anxiety and prevent uncontrolled and
unexpected movement. However, it is also important
during surgery for the patient be calm, cooperative,
and aware; reflexes should not be obtunded; and the
airway should not be obstructed. Ideal sedation levels
can be achieved by careful intravenous titration of
suitable agents while monitoring the effect of the
sedative and analgesic agents.
Evidence-based medicine
Sedation practices for ophthalmologic surgery
range from none to multiple drug combinations that
result in a level of sedation that borders on general
anesthesia. There are limited data regarding the
question of whether there is a sedation strategy that
is safer and more effective, with most studies, despite
being randomized and placebo controlled, not having
a large enough sample size to detect any adverse
medical event with a low incidence. One study of
90 subjects who underwent cataract surgery follow-
ing intramuscular analgesic agents found that intra-
muscular sedation was associated with a higher
incidence of bradycardia compared with no sedation
[1], and another found an increased need for sup-
plemental oxygen when intramuscular sedative use
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.004
E-mail address: [email protected]
was compared with placebo [2]. Oral sedatives were
not associated with any adverse events in two studies
[3,4], neither was intravenous propofol [5,6]. Barbi-
turates have been evaluated also and revealed no
hemodynamic complications [7,8]. A large cohort
study of 19,354 patients reported a 1.95% and 1.23%
incidence of intraoperative and postoperative adverse
events, respectively [9]. There was a strong associa-
tion between the use of intravenous agents in con-
junction with topical or nerve block anesthesia and
intraoperative adverse medical events after adjusting
for age, gender, length of surgery, and American
Society of Anesthesiologists Physical Status classi-
fication [10]. Use of more than one agent also was
associated with an increased risk of adverse events,
suggesting that use of multiple agents may not be
advisable. Most of the events were bradyarrhythmias
and hypertension.
Levels of sedation
The American Society of Anesthesiologists has
defined the levels of sedation [11,12] that are
commonly used to monitor patients perioperatively
and have also been used by the Joint Commission on
Accreditation of Healthcare Organizations (JCAHO)
to establish standards and guidelines on sedation.
These levels of sedation are as follows.
Minimal sedation (anxiolysis)
Minimal sedation (anxiolysis) produces a drug-
induced state during which patients respond normally
to verbal commands. Although cognitive function
and coordination may be impaired, ventilatory and
cardiovascular functions are unaffected.
Am 19 (2006) 193 – 202
reserved.
ophthalmology.theclinics.com
ahmad194
Moderate sedation or analgesia (‘‘conscious
sedation’’)
Moderate sedation or analgesia (‘‘conscious seda-
tion’’) is a drug-induced depression of conscious-
ness during which patients respond purposefully to
verbal commands, either alone or accompanied by
light tactile stimulation. No interventions are required
to maintain a patent airway, and spontaneous venti-
lation is adequate. Cardiovascular function is usu-
ally maintained.
Deep sedation and analgesia
Deep sedation and analgesia is a drug-induced
depression of consciousness during which patients
cannot be easily aroused but respond purposefully
following repeated or painful stimulation. The ability
to independently maintain ventilatory function may
be impaired. Patients may require assistance in main-
taining a patent airway and spontaneous ventilation
may be inadequate. Cardiovascular function is usu-
ally maintained.
Anesthesia
General anesthesia is a drug-induced loss of con-
sciousness during which patients are not arousable,
even by painful stimulation. The ability to indepen-
dently maintain ventilatory function is often impaired.
Patients often require assistance maintaining a patent
airway, and positive-pressure ventilation may be re-
quired because of depressed spontaneous ventilation
or drug-induced depression of neuromuscular func-
tion. Cardiovascular function may be impaired.
The JCAHO standards require that moderate or
deep sedation be administered by a practioner with
‘‘appropriate credentials’’ who can ‘‘rescue’’ the pa-
tients from deep sedation and general anesthesia.
Monitoring level of sedation
Patients undergoing surgery may become sedated
as a result of the effects of regional blockade. Spinal
anesthesia is known to be accompanied by significant
sedation [13] and both spinal and epidural anesthesia
reduce hypnotic requirements for midazolam [14,15]
and thiopental [16]. Patients undergoing ophthal-
mologic surgery under regional block may also fall
asleep during the procedure. The mechanism for this
effect is not completely understood, but it has been
demonstrated that temporary peripheral denervation
decreases the excitability of the cuneate nucleus in the
brainstem [17] and acute block of retinal discharges
results in synchronization of cortical electroencepha-
logram (EEG), which is normally desynchronized
[18]. More recently it has been suggested that de-
crease in ascending somatosensory transmission can
modulate the activity of the reticulo-thalamo-cortical
mechanisms that regulate arousal [19,20] and thus
neuraxial blockade could result in a reduced level
of consciousness.
Ongoing assessment of the level of conscious-
ness throughout the surgical procedure is essential
to prevent the patient from progressing into deep
sedation with loss of protective airway reflexes. The
accurate assessment of the depth of sedation re-
quires a tool that is reliable and valid, and at the same
time is easy to use in the clinical arena. Various such
tools have been developed [21–29]. The Ramsay
sedation scale is a commonly used subjective assess-
ment of level of consciousness that uses an ordinal
scaling system to describe the level of conscious-
ness [21]:
� Level 1: Patient awake, anxious/restless, or both� Level 2: Patient awake, cooperative, orientedand tranquil� Level 3: Patient awake responds to
commands only� Level 4: Patient asleep, brisk response to light
glabellar tap or loud auditory stimulus� Level 5: Patient asleep, sluggish response to
light glabellar tap/loud auditory stimulus� Level 6: Patient asleep, no response to light
glabellar tap or loud auditory stimulus
The Observer’s Assessment of Alertness/Sedation
Scale (OAA/S) was designed to measure changes
in the level of consciousness during procedures,
but it is limited with deeper levels of sedation
(Table 1) [22].
The Neurobehavioral Assessment Scale [23] and
the Vancouver Sedative Recovery Scale (VSRS) [30]
are better at assessing the patient at the two extreme
ends of the scale. Children may progress rapidly from
light to deeper levels of sedation and greater vigilance
is necessary. The University of Michigan Sedation
Scale (UMSS) [31] is a validated scoring system that
has been used in children undergoing nonpainful
procedures and may be useful in the child undergoing
minor ophthalmologic surgery:
� 0, Awake and alert� 1, Minimally sedated: tired/sleepy, appropriate
response to verbal conversation and/ or sound
sedation techniques in ophthalmic anesthesia 195
� 2, Moderately sedated: somnolent/sleeping,
easily aroused with light tactile stimulation or a
simple verbal command� 3, Deeply sedated: deep sleep, arousable only
with significant physical stimulation� 4, Unarousable
Conscious sedation versus sedation/analgesia
The term conscious sedation was coined by
the American Dental Association to describe the
practice of using sedatives and analgesics to alleviate
the fear, anxiety, and pain of dental surgery. Deeper
levels of sedation induced by an anesthesiologist are
referred to as sedation/analgesia or ‘‘monitored
anesthesia care.’’
Route of administration
The intravenous route is the preferred method of
administration, however in some very young chil-
dren, oral and inhalation agents may be necessary.
The enteral, subcutaneous, or intramuscular routes
are best avoided whenever possible because of unpre-
dictability of absorption and distribution of the drugs.
Choice of drugs
The drugs commonly used fall into two main
categories, namely sedatives and analgesics. When
Table 1
Observer’s Assessment of Alertness/Sedation Scale
(OAA/S) [22]
Subscore Responsiveness Speech
5 Responds readily to
name in normal tone
Normal
4 Lethargic response to
name spoken loudly
repeatedly
Mild slowing
or thickening
3 Responds only after
name spoken loudly
or repeatedly
Slurring or slowing
2 Responds after mild
prodding or shaking
Few recognized
words
1 Does not respond to
mild prodding or shaking
used in combination these drugs have a synergistic
effect and need to be titrated carefully [32–34].
Additionally, it is important to differentiate between
patient movement as a result of anxiety and that as a
result of pain. Administration of additional sedatives
in the presence of pain resulting from inadequate
regional block will only worsen the situation and
result in a deeply sedated, uncooperative patient with
uncontrolled movement.
Sedative agents
Benzodiazepines
Benzodiazepines are the most commonly used
drugs for peri-operative sedation. They act by binding
to the g-aminobutyric acid (GABA) complex and in-
hibit neuronal transmission. These drugs exhibit hyp-
notic, anxiolytic, and amnestic properties and lower
intraocular pressure. Cardiovascular and respiratory
depression is seen with excessive doses. Diazepam
has a long half-life, which is further prolonged in the
elderly. Its original formulation (Valium; Roche
Laboratories, Nutley, NJ), which contained propylene
glycol, was associated with venous irritation and phle-
bitis [35]. The newer lipid-based formulation (Dizac;
Ohmeda, Liberty Corner, NJ) is less irritating [36].
Midazolam is a water-soluble imidazo-benzodia-
zepine, with a rapid onset and short duration of effect.
The half-life of midazolam is 1.7 to 2.6 hours,
whereas that of diazepam is 20 to 50 hours [37].
Midazolam is metabolized in the liver by hydrox-
ylation to 1-hydroxy-midazolam, which has 20% to
30% the activity of midazolam and a shorter dura-
tion of action. It is excreted by the kidneys and could
have a prolonged effect in patients with renal failure
[38]. Respiratory depression and apnea occurs with
all benzodiazepines and is more likely to occur in the
presence of opioids, old age, and debilitating dis-
ease. Low doses of midazolam (0.075 mg/kg) do not
affect the ventilatory response to carbon dioxide,
suggesting that clinically significant respiratory
depression is unlikely at that dose range [39]. In a
study of midazolam in male volunteers, the elimi-
nation half-life was prolonged more than twofold in
the elderly group as compared with the young males
[40]. This study also revealed that the volume of
distribution was increased in the elderly, the obese,
and in women. Used alone, the benzodiazepines have
modest hemodynamic effects. The predominant
hemodynamic change is a slight reduction in arterial
blood pressure that results from a decrease in sys-
temic vascular resistance. The hemodynamic effects
of midazolam are dose related: the higher the plasma
level, the greater the decrease in systemic blood
ahmad196
pressure [41]. The amnesic effect of midazolam has
been compared with diazepam and it was found to
produce better antegrade amnesia and faster recovery,
making it a more suitable drug for the elderly patient
having outpatient surgery than diazepam [42]. Mid-
azolam has been administered in small doses in the
range of 0.015 mg/kg, before administration of local
anesthetic in patients undergoing phacoemulsification
and lens implant surgery [43–45] and resulted in
high patient satisfaction scores and low levels of in-
traoperative anxiety.
In children ranging from 2 to 10 years of age,
midazolam has been administered orally (0.5 mg/kg)
before diagnostic and minor ophthalmologic surgical
procedures [46]. Administration of intranasal midazo-
lam has been reported in pediatric patients aged
3.5 months to 10 years for sedation before ocular
examination. This method of administration was as-
sociated with a rapid onset and was preferable to the
rectal route [47].
Lorazepam has twice the sedative potency of
midazolam, a slower onset of action, and longer du-
ration of action. A prospective randomized placebo-
controlled study of sublingual lorazepam 1 mg
administered an hour before peribulbar block for
cataract or glaucoma surgery resulted in good patient
comfort and amnesia related to the injection [48].
Propofol
Propofol (2, 6-di-isopropylphenol) is an alkylphe-
nol nonbarbiturate sedative-hypnotic that modulates
the GABAA receptor. It is rapidly metabolized in
the liver by conjugation to glucuronide and sulfate to
produce water-soluble compounds, which are ex-
creted by the kidneys [49]. The elimination half-life
of propofol is 4 to 23.5 hours [50,51]. Propofol phar-
macokinetics are affected by age, with elderly hav-
ing decreased clearance rates [52] and children a
more rapid clearance [53]. The degree of sedation and
reliable amnesia, as well as preservation of respira-
tory and hemodynamic function, are better overall
with benzodiazepines than with other sedative-
hypnotic drugs used for conscious sedation. When
midazolam is compared with propofol for sedation,
the two are generally similar except that emergence
or wake-up is more rapid with propofol. Because of
the potential for significant respiratory depression it
is recommended that propofol be administered under
close medical supervision by physicians with airway
management skills [54].
Propofol in small incremental intravenous doses
(20 mg) has been used to achieve amnesia for re-
gional eye blocks [55]; however, propofol provides
no analgesia for insertion of the block needle and
therefore semiconscious patients may have a startle
response to needle insertion. A single dose of pro-
pofol (0.98 mg/kg) has been shown to reduce intra-
ocular pressure (IOP) by 17% to 27%, which is
also beneficial during ophthalmologic surgery [56].
This change occurs immediately following injec-
tion and may be related to relaxation of the ex-
traocular muscles. Continuous infusion of propofol
(1.5 mg/kg/hour) has been found to be effective
during cataract surgery under topical anesthesia
but does require close monitoring for signs of respi-
ratory depression [57]. Patient-controlled sedation
using propofol (0.3 mg/kg, lockout interval of
3 minutes) in 55 elderly patients undergoing cataract
surgery has been reported [58]. Patients used less
than 1 mg/kg and reported a high degree of satis-
faction. One patient developed excessive sedation and
transient respiratory depression, which responded to
patient stimulation.
Ketamine
Ketamine is a phenylcyclidine derivative and dif-
fers from other sedative-hypnotic agents in that it also
has significant analgesic effects. It is metabolized by
hepatic microsomal enzymes to form norketamine
(metabolite I), which has been shown to have sig-
nificantly less (between 20% and 30%) activity than
the parent compound [59]. Ketamine produces a dis-
sociative state in which patients have profound anal-
gesia but keep their eyes open and maintain their
corneal, cough, and swallow reflexes. Ketamine ad-
ministration results in pupillary dilation, nystagmus,
lacrimation, salivation, and increased skeletal muscle
tone, often with coordinated but seemingly purpose-
less movement of the arms, legs, trunk, and head.
Ketamine is associated with psychic emergence reac-
tions, including excitement, confusion, euphoria, and
fear, which usually abate within 1 to several hours
[60]. The incidence of emergence reactions is higher
in adults [61], women [62], and with larger doses [63]
and can be reduced by concomitant use of benzodiaze-
pines [64].
Ketamine has minimal effect on the central respi-
ratory drive [65] and does not usually depress the
cardiovascular system [63]. Early studies reported an
increase in IOP after intramuscular or intravenous
administration of ketamine. However, subsequent
studies of ketamine given with diazepam and meper-
idine showed no affect on IOP, and intramuscularly
administered ketamine may even lower IOP in chil-
dren [66]. The use of ketamine in conjunction with
droperidol and diazepam has been reported to be a
useful adjunct in patients undergoing cataract surgery
with regional block [67].
sedation techniques in ophthalmic anesthesia 197
Barbiturates
Barbiturate compounds such as methohexital and
thiopental have been used for sedation in ophthalmo-
logic surgery in the past, but have been replaced by
newer agents such as propofol and midazolam, which
have better pharmacologic profiles and fewer side
effects. Methohexital is administered in incremental
doses of 10 to 20 mg [68]. Residual sedation is
greater with methohexital than with propofol [69].
Chloral hydrate
Chloral hydrate has been used in children under-
going diagnostic procedures in offices and outpatient
clinics [70] and in elderly patients before cataract
surgery [71]; however, midazolam was found to be
preferable for the amnesic properties.
Dexmedetomidine
Dexmedetomidine is an a2-adrenergic agonist andproduces a sedative-hypnotic effect by an action on
a2-receptors in the locus ceruleus and an analgesic
effect by its action on a2-receptors within the locus
ceruleus and the spinal cord [72]. In volunteers, dex-
medetomidine sedation reduced minute ventilation
but did not alter the slope of the ventilatory response
to increasing CO2 [73]. The effects on the cardiovas-
cular system are a decreased heart rate; decreased
systemic vascular resistance; and indirectly decreased
myocardial contractility, cardiac output, and systemic
blood pressure [74]. Used as a premedicant at intra-
venous doses of 0.33 to 0.67 mg/kg given 15 minutes
before surgery, dexmedetomidine appears to be effi-
cacious with minimal cardiovascular side effects [75].
When used for intraoperative sedation, dexmedeto-
midine (0.7 mg/kg/hr) had a slower onset than pro-
pofol but had similar cardiorespiratory effects. With
continuous infusion sedation after termination of the
infusion was more prolonged, as was recovery of
blood pressure; however, lower doses of opioid were
needed in the first hour postoperatively [76]. A
double-blind placebo-controlled comparative study of
intramuscular dexmedetomidine (1 mg/kg) and mid-
azolam (20 mg/kg) before peribulbar block for cata-
ract surgery revealed comparable sedation in both
groups, but dexmedetomidine was more effective at
lowering IOP [77].
Opioid Analgesic Agents
Analgesic agents may be administered before
performing regional nerve block to decrease the pain
associated with the injection. Additionally, pain may
occur intraoperatively as a result of the light from the
operating microscope, iris manipulation, irrigation-
aspiration, and intraocular lens manipulation [78,79]
necessitating intraoperative analgesics.
Fentanyl
Fentanyl is the opioid analgesic most commonly
used to supplement regional blockade. It is usually
administered intravenously, in small doses in the
range of 50 to 100 mg. Onset of action is within 3 to
5 minutes but fentanyl has a relatively long half-life,
in large part because of this widespread distribution
in body tissues. The elimination half-life is 2 to
3 hours. Fentanyl is primarily metabolized in the liver
by N-dealkylation and hydroxylation to norfentanyl,
which is detectable in the urine for up to 48 hours
after intravenous administration [80]. Elderly pa-
tients are more sensitive to fentanyl and lower doses
(0.7 mg/kg) have been recommended in this age
group [81,82].
Fentanyl is available for oral transmucosal admin-
istration and results in reasonably rapid absorption,
with peak blood levels achieved within 15 to 30 min-
utes [83]. A recent study found that the liquid
intravenous formulation administered orally was rap-
idly absorbed and may be a reasonable substitute for
intramuscular opioid administration in children who
do not have intravenous access. An advantage of this
method may be the shorter and less variable con-
sumption time and greater versatility in dosing in
comparison to the Fentanyl Oralet [84].
Alfentanil
Alfentanil is a more rapid and shorter-acting
analog of fentanyl [85].The main metabolic pathways
of alfentanil include oxidative N-dealkylation and
O-demethylation, aromatic hydroxylation, and ether
glucuronide formation. The degradation products of
alfentanil have little, if any, opioid activity. Human
alfentanil metabolism may be predominantly, if not
exclusively, by cytochrome P-450 3A4 /5. Alfentanil
has been reported to have fewer side effects and simi-
lar or shorter recovery times than fentanyl [86,87].
Onset of action is in 1 to 3 minutes and the elimi-
nation is 1 to 2 hours [80]. The elderly exhibit an
increased sensitivity to the opioids and the dose of
alfentanil should be reduced by half [88].
Remifentanil
Remifentanil is chemically related to the fentanyl
congeners, but it is structurally unique because of
its ester linkages that render it susceptible to hydroly-
sis—primarily by enzymes within the erythrocytes—
resulting in its rapid metabolism. Remifentanil has a
30- to 60-second onset time and a 5- to 10-minute
ahmad198
duration. The primary metabolic pathway of remifen-
tanil is de-esterification to form a carboxylic acid
metabolite, GI90291, which is 0.001 to 0.003 times as
potent as remifentanil. Excretion of GI90291 is
dependent on renal clearance mechanisms [89]. Its
pharmacokinetics are not appreciably influenced by
renal or hepatic failure [90,91]. Remifentanil (0.3 to
0.6 mg/kg IV) has been used to prevent the pain
associated with placement of the peribulbar block
[92]. A double-blind, randomized study of remi-
fentanil (remifentanil 1 mg/kg, remifentanil 1 mg/kg +
infusion of 0.2 mg/kg/min) administered before per-
forming peribulbar block found it to be more effective
than alfentanil (0.7 mg/kg) [93]. It was noted that the
patients were calm and cooperative, although aware
during the eye block and did not move or startle. In
this study the group that had the bolus dose followed
by an infusion had a higher incidence of respiratory
depression; however, in clinical situations the bolus
dose alone would be adequate.
Combinations of sedatives and analgesics
It is a common practice to combine sedatives and
analgesics in an attempt to minimize the side effects
of the individual agents by using smaller doses than
would be necessary if they were used alone. In most
situations the drugs have synergistic effects and may
result in significant hemodynamic and respiratory
depression, especially in the elderly patient. Propofol
has been used in combination with alfentanil [94] and
a combination of midazolam, propofol, and alfentanil
revealed the increased risk of apnea with multiple
drug combinations [95]. A combination of propofol
and ketamine provided better analgesia and sedation
than propofol alone and was not associated with an
increase in IOP [96].
Patient-controlled sedation and analgesia
The level of stimulation and discomfort may vary
during the peri-operative period and the need for
sedation/analgesia varies considerably among pa-
tients, making the patient-controlled administration a
useful alternative [97,98]. Successful use of the tech-
nique in patients undergoing ophthalmologic surgery
has been reported [99–101]. The main advantage with
this technique is the increased patient satisfaction;
however, it is important that patients be appropriately
monitored to prevent excessive sedation.
Nonpharmacologic measures
It has been suggested that music may be able to
modulate the human stress response [102] and studies
have suggested that music may be used as an adjunct
to sedatives. It has also been shown that music can
reduce pain reported by patients [103] and may
decrease analgesic requirements. The music selected
needs to have specific characteristics, namely, the
music needs to be of the patients choice, tracks need
to be mixed to convey homogeneous ambience, and
the playing device needs to be of good quality to
avoid auditory fatigue [104–106].
Type of surgery
Besides cataract surgery, regional anesthesia and
sedation has been used for trabeculectomy [107],
keratoplasty [108], vitreoretinal surgery [109], open
globe injuries [110], and enucleations and eviscera-
tions [111].
Summary
Sedation/analgesia for ophthalmologic surgery is
safe and effective [9]. The choice of sedation/an-
algesia strategy should be based on patient preference
and the assessment of risk for adverse events. Pre-
operative screening and preparation of the patient
is most important in obtaining cooperation and pa-
tient acceptance.
Despite the obvious effectiveness of the various
strategies, there is a small group of patients who are
not suitable for regional anesthesia with sedation.
Patients with chronic spontaneous cough, shortness
of breath while lying flat, parkinsonian head tremor,
Alzheimer’s disease, or claustrophobia may be very
difficult to manage with regional anesthesia and light
sedation. These patients may best be managed with a
general anesthetic.
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Ophthalmol Clin N
Choices of Local Anesthetics for Ocular Surgery
Gary D. Cass, MD
Tampa Eye and Specialty Surgery Center, 4302 N. Gomez Avenue, Tampa, FL 33607, USA
The choice of local anesthetic solution to perform
either topical anesthesia or conduction blockade for
ocular surgery is made based on the specific require-
ments of the patient, the surgical procedure, and the
properties of the local anesthetic. It is important for
clinicians to be aware of the options before selecting
an ophthalmic anesthetic delivery system. This arti-
cle discusses the rationale for using different local
anesthetics, anesthetic combinations, and additives, in
different clinical situations and with different anes-
thetic deliveries.
Topical ocular anesthesia
Topical ocular anesthesia has been demonstrated
to be a safe and effective alternative to retro or peri-
bulbar anesthesia [1]. However, topical anesthesia
does not provide ocular akinesia and may provide
inadequate sensory blockade for the iris and ciliary
body. Therefore, topical techniques are best reserved
for short surgeries and cooperative patients who have
low to moderate anxiety. Sedation should be carefully
administered to help relieve anxiety but not affect the
patient’s cooperation and movement. Topical anes-
thesia can be successfully achieved by several dif-
ferent methods and combinations of these methods. A
few popular approaches to topical ocular anesthesia
will be discussed, although there are many variations
of these practices.
The first approach simply involves administering
local anesthetic eye drops, most commonly pro-
paracane, tetracaine, lidocaine, or bupivacaine, to the
operative eye three or four times, usually separated by
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.011
E-mail address: [email protected]
a few minutes just before surgery. The choice of which
anesthetic to use can be based on concerns regarding
corneal epithelial toxicity, patient comfort, and the
patient’s history of local anesthetic allergies.
High doses or prolonged use of local anesthetics
are toxic to the corneal epithelium, which prolongs
wound healing and causes corneal erosion [2,3]. All
of these local anesthetics are safe and effective in
brief perioperative exposure. Tetracaine is the most
irritating of the eye drop anesthetics mentioned; it is
an ester anesthetic and should be avoided in patients
allergic to that family of local anesthetics. Propara-
cane is also an ester anesthetic, but it is not metabo-
lized to the p-aminobenzoate (PABA) moiety and,
therefore, may be safely used in patients who are al-
lergic to other ester anesthetics.
It is common practice to administer topical anes-
thesia using viscous lidocaine gel instead of drops.
Often this gel is mixed with dilating medications,
antibiotics, and non-steroidal anti-inflammatory
agents. An anecdotal description of such a mixture
is 5 mL 2% lidocaine gel with 4 gtts tropicamide
(Mydriacyl), 4 gtts 1% cyclopentolate (Cyclogel),
4 gtts 10% phenylephrine (Neosynephrine), 10 gtts
moxifloxacin (Vigamox) and 4 gtts ketorlac (Acular).
This mixture applied to the operative eye twice before
surgery reportedly achieves excellent results in both
dilation and anesthesia [4]. Predictability of drug ab-
sorption or corneal epithelial safety with this mixture
has not been well investigated.
A common adjunct to topical anesthetic eye drops
is intracameral injection of local anesthetics. Intra-
cameral anesthetics have included preservative free
1% lidocaine and preservative free 0.5% bupivacaine
injected in doses of 0.1 to 0.5 mL instilled into the
anterior chamber. Intracameral injection may provide
sensory blockade for the iris and ciliary body, which
Am 19 (2006) 203 – 207
reserved.
ophthalmology.theclinics.com
cass204
relieves discomfort that patient’s may have when the
intraocular lens is placed.
This topic has been the subject of many studies.
In 2001, in a report by the American Academy of
Ophthalmology, Karp and colleagues [5] reviewed
over 180 literature citations to address questions
about intracameral anesthesia’s efficacy and safety in
regard to possible corneal endothelial and retinal
toxicity. Regarding efficacy, the ideal timing and
placement of intracameral anesthesia was not deter-
mined. Some of the articles reviewed in this report
showed efficacy of intracameral injection whereas
others did not. The authors concluded that because
topical anesthesia alone is effective, surgeons may
elect to use intracameral anesthesia to manage
patients that had incremental pain with topical anes-
thesia alone.
Regarding the safety of intracameral anesthesia,
short-term studies seem to indicate that preservative-
free 1% lidocaine is well tolerated by the corneal
endothelium, whereas higher concentrations are
toxic. Retinal toxicity is another concern because
local anesthetics diffuse posteriorly to the retina.
There have been reports of patients loosing light per-
ception temporarily after intracameral anesthesia.
Several in vitro studies suggest lidocaine and bupiva-
caine may be toxic to the retina. This report suggests
that minimal amounts and concentrations of local
anesthetic be used. Preservative-free 1% lidocaine in
doses of 0.1ml to 0.5 mL has not been associated
with corneal endothelial toxicity, but studies suggest
that higher concentrations may be toxic. Intracameral
bupivacaine is not as well studied as lidocaine and
it may be more toxic to the corneal endothelium than
1% lidocaine. The authors suggested, therefore, that
the local anesthetic of choice for intracameral
anesthesia is preservative-free 1% lidocaine.
Intracameral lidocaine alone has been shown to
dilate the pupil well [6]. This may be because of
its direct action on the iris which causes muscle
relaxation. A recent practice of using intracameral
preservative-free 1% lidocaine with 1:100,000 epi-
Table 1
Properties of local anesthetics for ocular conduction blockade
Generic name Brand name Class
2-chloroprocaine Nesacaine Ester
Articaine Septocaine Amide
Lidocaine Xylocaine Amide
Ropivacaine Naropin Amide
Bupivacaine Marcaine Amide
Levobupivacaine Chirocaine Amide
nephrine is reported to enhance the pupillary dilation
more than 1% lidocaine alone, and may obviate the
need for preoperative dilating drops [7].
Conduction ocular anesthesia
The most common choices of local anesthetics for
either retro or peribulbar (intra or extraconal) or sub-
Tenon’s (episcleral) technique are bupivacaine, lido-
caine, ropivacaine, levobupivacaine, articaine, and
2-chloroprocaine. The following discussion considers
the pros and cons of each of these local anesthetics
and the indications for their use. Considerations
include cardiovascular and central nervous system
safety, family of local anesthetics, and onset and
duration of each agent. Properties of local anesthetics
for ocular conduction blockade are summarized in
Table 1.
When reviewing the literature about onset and
duration times of local anesthetics in ocular anes-
thesia, it is very difficult to make comparisons be-
cause shorter acting local anesthetics with faster onset
times are often combined with longer acting anes-
thetics. In addition to combining local anesthetics,
hyaluronidase is frequently added to the mix, which
also confounds the true onset time and duration of a
specific local anesthetic. Hyaluronidase shortens the
onset and duration of local anesthetics used for ocular
conduction blockade. Another variable from study to
study is the volume and concentration of anes-
thetic injected.
Bupivacaine and lidocaine are familiar local anes-
thetics that have been used for many years in retro
and peribulbar anesthesia as well as sub-Tenon’s
technique. Studies regarding the onset and duration
of lidocaine and bupivacaine in ocular anesthesia
compare them to the newer local anesthetics. The
onset time to ocular akinesia of a 50:50 mixture of
2% lidocaine and 0.5% bupivacaine with 1:200,000
epinephrine and 30 IU/mL hyaluronidase is reported
to be 7.2 minutes with a 5.7 minute standard devia-
Onset Duration Toxicity
Rapid Short Low
Rapid Short Intermediate
Rapid Intermediate Intermediate
Slow Long Intermediate
Slow Long High
Intermediate Long Intermediate
local anesthetics 205
tion [8]. The duration is not so well investigated.
A patient can usually remove their eye patch in 4 to
6 hours after a block where bupivacaine was used
and not be troubled by diplopia. Many practitioners,
however, report instances where the diplopia did not
resolve until the next day.
Ropivacaine is a long-acting, pure S-enantiomer,
amide local anesthetic similar to bupivacaine in
duration. The use of ropivacaine is attractive because
it is less cardiotoxic than equal concentrations of
racemic bupivacaine and has a significantly higher
threshold for central nervous system toxicity than
bupivacaine. Ropivacaine and bupivacaine were
compared with each other when mixed with 2% lido-
caine and hyaluronidase and both mixtures were
equally effective in peribulbar anesthesia [9]. In this
study, the median time at which the block was
adequate to start surgery was 8 minutes. This com-
paratively quick onset is representative of the quicker
acting lidocaine with hyaluronidase rather than the
ropivacaine. Another recent study compared onset
and duration of different concentrations of ropiva-
caine with hyaluronidase. At 15 minutes ropivacaine
0.75% had an 82% complete motor block, whereas
the 0.5% ropivacaine had a 55% complete motor
block. Complete recovery of motor function 1 hour
after surgery was 37% with 0.5% ropivacaine with
hyaluronidase, whereas complete motor recovery was
only 5% in the 0.75% ropivacaine with hyaluroni-
dase group [10]. Another study reported that diplopia
lasted up to 30 hours past peribulbar block when
1% ropivacaine was used [11]. Ropivacaine would be
a good clinical choice when longer anesthesia is
needed and a large enough dose will be used that
there is concern about toxicity.
Levobupivacaine is the S enantiomer of racemic
bupivacaine. Because of findings that cardiotoxicity
observed with racemic bupivacaine, although infre-
quent, is based on entantioselectivity, the S enan-
tiomer, levobupivacaine, was developed for use as a
long acting, local anesthetic that shows reduced
cardiotoxicity. Recently McLure and colleagues [12]
compared the onset of 2% lidocaine with 0.75%
levobupivacaine, both with hyaluronidase, in sub-
Tenon’s block. The speed of onset for the lidocaine
group was 3.02 minutes, which statistically was
significantly faster then the onset time for the
levobupivacaine group, which was 5.06 minutes.
The authors concluded, however, that this difference
in onset time was not clinically significant. Levo-
bupivacaine 0.75% was compared with bupivacaine
0.75%, each with hyaluronidase, in peribulbar anes-
thesia [13]. After a 5 cc injection, both agents re-
portedly achieved satisfactory anesthesia in a median
time of 2 minutes. The authors concluded that both
levobupivacaine and bupivacaine are equally suc-
cessful in achieving clinically satisfactory peribulbar
anesthesia with few adverse effects. The most com-
mon post operative adverse effect reported was
prolongation of the block in 15% of the patients.
Bupivacaine, ropivacaine, and levobupivacaine all
have clinically acceptable onset times when mixed
with lidocaine. However, the duration can be up to
30 hours when most surgeries last only 15 minutes.
Prolonged diplopia is disturbing to the patients and
dissatisfying to the clinician.
Articaine is a comparatively new local anesthetic.
It is chemically unique and offers a shorter duration
than the previously discussed drugs. In a number of
European countries, articaine is the most widely used
local anesthetic in dentistry. Articaine is classified as
an amide local anesthetic but is structurally different
from other amide local anesthetics in that it contains
a thiophene ring. It also contains an ester linkage
which is quickly hydrolyzed by esterase to inactive
artinic acid.
In 2001, Allman and colleagues [14] compared
the onset of 2% articaine mixed with epinephrine
(1:200,000), with the onset of a mixture of 0.5%
bupivacaine and 2% lidocaine in peribulbar anes-
thesia, where a single medial canthus injection is
used. Hyaluronidase was added to both solutions.
The degree of akinesia was measured at 1, 5, and
10 minutes after block, at the end of surgery, and at
discharge from the day unit. At 1 minute the score in
both groups was the same, but at 5 minutes articaine’s
onset was significantly greater. At discharge it was
apparent that the articaine group regained extraocular
motion quicker. The authors, however, don’t specify
how much time elapsed between initial injection and
discharge. Eyelid motion was the same for both
groups at all measurements. A similar study [8] was
repeated at the same institution and compared the
same agents, but used an inferotemporal injection
with similar results. In 2004, 2% articaine was com-
pared with a mixture of 0.5% bupivacaine and 2%
lidocaine in a sub-Tenon’s approach, and once again
articaine had the faster onset times and appeared to be
a safe agent to use [15].
Articaine appears to have a desirable onset and
duration for shorter ocular surgeries. In the United
States articaine is prepared in a solution that contains
both epinephrine and sodium metabisulfate as a pre-
servative. Currently articaine has only been approved
in the United State for dental use.
For shorter surgeries, 2-choloroprocaine is a desir-
able choice of a local anesthetic for conduction block-
ade. Cass and colleagues [16] compared 2% versus 3%
cass206
preservative-free 2-cholroprocaine in peribulbar anes-
thesia. Onset time of ocular akinesia and surgical
anesthesia was <4 minutes in the 2% group and 6 min-
utes in the 3% group. Full recovery of extraocular
muscle and eyelid motion was less than 85 minutes in
the 2% group and was less than 100 minutes in the 3%
group. Both 2% and 3% 2-cholroprocaine were safe
and effective in peribulbar aesthesia.
Modern ophthalmic surgeries are being performed
faster and faster. At the typical outpatient surgery
center where cataract surgery takes 20 minutes or
less, a patient can be blocked in a preoperative area,
moved to the operating room, have surgery, then go
to a recovery area where they can have a cup of
coffee or juice. By the time postoperative instructions
are given, the patient has regained full extraocular
and eyelid motion. This allows the patient to be
discharged without an eye patch and with good vi-
sion. Although the duration of 2-cholroprocaine is
relatively short, it still affords the surgeon enough
time to handle circumstances such as an unanticipated
anterior vitrectomy. A particular circumstance where
rapid vision recovery is extremely advantageous is in
the monocular patient having surgery on their better
seeing eye. This is very satisfying to both the patient
and the clinical staff.
Because it is an ester anesthetic, 2-choloropro-
caine is quickly hydrolyzed by plasma cholinester-
ase, which makes it a safe local anesthetic that has
a high therapeutic index. Clinicians should avoid
2-choloroprocaine in patients who report allergies to
ester local anesthetics.
Use of additives
Anesthetic solutions often contain preservatives,
enzymes that aid the spread of the local anesthetic,
and drugs that increase the duration of action. It is
important for clinicians to choose whether or not to
use these additives because they can affect local
anesthetic toxicity both locally and systemically.
Preservatives in local anesthetics are considered
to be toxic to the retina. In many ophthalmology
practices all local anesthetics used are preservative-
free, although in many other practices, with the
exception of intracameral administration, topical and
injected local anesthetics are used with preservatives
and without apparent retinal problems.
Hyaluronidase is a proteolytic enzyme which is
often added to local anesthetic solutions to aid the
spread of the anesthetic. The enzyme hydrolyses
hyaluronic acid which limits diffusion by binding
cells together. The addition of hyaluronidase shortens
the time of onset of the local anesthetic solution as
well as its duration. In retro or peribulbar anesthesia,
the addition of hyaluronidase is presumed to decrease
the time of exposure of the local anesthetic to the
extraocular muscles, which decreases the incidence
of myotoxicity that results in diplopia. In a retro-
spective chart review, Brown and colleagues [17]
postulated that the absence of hyaluronidase was
responsible for a cluster of diplopia. In a response
to this paper, Miller [18] reported a series of over
7000 cases of periocular injections without hyal-
uronidase which resulted in no incidence of diplopia.
It is important to point out that anesthetic myotoxicity
is not the only cause of diplopia after periocular
block. The extraocular muscle can be directly in-
jured by the injection or indirectly injured by ische-
mia secondary to pressure on the muscle from a high
volume of injectate.
Epinephrine is a common additive to local anes-
thetic solutions for periocular block. It augments
anesthetic duration. In the borderline patient small
amounts of epinephrine can cause untoward hemody-
namic consequences.
Clonidine has also been added to local anesthetic
solutions used for periocular block to lengthen the
duration of the anesthesia [19]. Vecuronium has been
added to periocular local anesthetic solutions to en-
hance the ocular and eyelid akinesia [20]. Adding
these medicines to periocular anesthetic solutions is
potentially harmful because these agents have power-
ful systemic actions.
Summary
There are many choices of local anesthetic solu-
tions and additives for both topical anesthesia and
conduction blockade. The differing onset and dura-
tion, toxicity, and pharmacology of local anesthetics
must be considered when making a choice of which
agent to use. Additives to local anesthetic solutions
must also be considered. Clinicians should make their
ocular anesthetic plan based on the specific require-
ments of the patient, the surgical procedure, and the
properties of the local anesthetic.
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[18] Miller RD. Hyaluronidase and diplopia [letter]. J Cata-
ract Refract Surg 2000;26:478.
[19] Bharti N, Madan R, Kaul HL, et al. Effect of addition
of clonidine to local anaesthetic mixture for peribulbar
block. Anaesth Intensive Care 2002;30(4):438–41.
[20] Reah G, Bodenham AR, Braithwaite P, et al. Peribulbar
anaesthesia using a mixture of local aneaesthetic and
vecuronium. Anaesthesia 1998;53(6):551–4.
Ophthalmol Clin N
Sub-Tenon’s Anesthesia
Chandra M. Kumar, MBBS, MSc, FFARCS, FRCAa,b,T,Chris Dodds, MBBch, MRCGP, FRCAa,b
aSchool of Health and Social Science, University of Teesside, Middlesbrough, TS4 3BW, UKbDepartment of Anaesthesia, The James Cook University Hospital, Middlesbrough, TS4 3BW, UK
The sub-Tenon’s anesthesia block was reintro-
duced as a simple, safe, effective, and versatile alter-
native to a sharp needle block for orbital anesthesia.
After topical anesthesia has been instilled, Tenon’s
capsule is dissected, a blunt cannula is introduced
into the sub-Tenon’s space, and a local anesthetic
agent is administered [1]. It is not known how fre-
quently this technique has been used. Seven percent
of ophthalmic departments in the United Kingdom
used this technique in 1997 [2] but its use appears to
have increased [3]. In the United Kingdom, only
trained ophthalmologists or anesthesiologists perform
needle orbital local anesthetic injections [2], but in
some centers nurses have been trained to perform the
sub-Tenon’s block [4]. It is essential for any practi-
tioner to have a comprehensive understanding of the
basic sciences and techniques behind regional orbital
blocks. Before any technique is used, the knowledge
of globe anatomy, especially Tenon’s capsule and the
surrounding structures, must be mastered.
The regional orbital block was first described by
Turnbull in 1884 [5]. More recently Mein and
colleagues [6], Hansen and colleagues [7] and
Stevens [8] have popularized this block. The tech-
nique is also known as pinpoint anesthesia [9],
parabulbar block [10], and episcleral block [11].
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.008
T Corresponding author. Department of Anaesthesia,
The James Cook University Hospital, Middlesbrough, TS4
3BW, UK.
E-mail address: [email protected]
(C.M. Kumar).
Anatomy
There are many excellent books on ophthalmic
anatomy [12–15] and these are recommended as a
source of reference.
Globe movements are controlled by both the
rectus muscles (inferior, lateral, medial, and superior)
and the oblique muscles (superior and inferior). The
rectus muscles arise from the annulus of Zinn near
the apex of the orbit and insert anterior to the equator
of the globe to form an incomplete muscle cone.
The optic nerve (II), oculomotor nerve (III, contains
both superior and inferior branches), abducens nerve
(VI), nasociliary nerve (branch of nerve V), ciliary
ganglion, and vessels all lie within the muscle cone.
The superior branch of the oculomotor nerve supplies
the superior rectus and the levator palpebrae mus-
cles. The inferior branch of the oculomotor nerve
supplies the medial rectus, the inferior rectus, and
inferior oblique muscles. The abducens nerve sup-
plies the lateral rectus. The trochlear nerve (IV) runs
outside and above the annulus, and supplies the
superior oblique muscle (the anesthetic agent may
fail to block this nerve and the oblique muscle will
retain activity).
Corneal and perilimbal conjunctival sensation and
the superonasal quadrant of the peripheral conjunc-
tival sensation are mediated through the nasociliary
nerve. The remainder of the peripheral conjunctival
sensation is supplied through the lacrimal, frontal,
and infraorbital nerves which run outside the muscle
cone. Intraoperative pain may be experienced if these
nerves are not blocked.
The fascial sheath (Tenon’s capsule) is a thin
membrane that envelops the eyeball and separates it
Am 19 (2006) 209 – 219
reserved.
ophthalmology.theclinics.com
Fig. 1. Sub-Tenon’s space shows multiple connective tissue bands (From Gray, H. Anatomy of the human body. Philadelphia:
Lea & Febiger; 1918; Bartleby.com, 2000. Available at www.bartleby.com/107/. Accessed September 14, 2005; with permission.)
kumar & dodds210
from the orbital fat [14]. It thus forms a socket for the
eyeball. The inner surface is smooth and shiny and is
separated from the outer surface of the sclera by a
potential space, the episcleral space (sub-Tenon’s
space). Numerous delicate bands [15] of connective
tissue (Fig. 1) cross the space and attach the fascial
sheath to the sclera. Anteriorly, the fascial sheath is
firmly attached to the sclera (Fig. 2) about 3–5 mm
posterior to the corneoscleral junction [16,17].
Posteriorly, the sheath fuses [13] with the meninges
around the optic nerve and with the sclera around the
exit of the optic nerve (see Fig. 1). However, the
description varies and a major textbook of anatomy
[15] suggests that the space under the Tenon capsule
Fig. 2. Tenon’s capsule is shown underneath the conjunctiva
when dissected 5 mm posterior to limbus.
is a lymph space, and this follows the optic nerve and
continues with the subarachnoid space. The tendons
of all six extrinsic muscles of the eye pierce the
sheath as they pass to their insertion on the globe. At
the site of perforation, the sheath is reflected back
along the tendons of these muscles to form a tubular
sleeve. The superior oblique muscle sleeve extends as
far as the trochlea, and the inferior oblique muscle
sleeve extends to the origin of these muscles. The
tubular sleeves for the four recti muscles have
expansions. Expansions for the medial and lateral
recti are strong, are attached to the lacrimal and
zygomatic bones, and are called medial and lateral
check ligaments respectively. The superior rectus
expansion is thinner, less distinct, and extends from
the superior rectus tendon to the levator palpebrae
superioris. Similarly, the expansion from the inferior
rectus extends to the inferior tarsal plate. The inferior
part of the fascial sheath is thickened and is con-
tinuous, both medially and laterally, with the medial
and lateral check ligaments.
Assessment of patients
The preoperative assessment and preparation of
patients who have ophthalmic surgery under local
anesthesia varies worldwide. There are evidence-
based guidelines [18] and reports [19] available on
this subject. The Joint Colleges Working Party Report
Fig. 3. Essential (right) and non-essential (left) equipment which may be required during sub-Tenon’s anesthesia.
sub-tenon’s anesthesia 211
[18] has recommended that patients not be starved but
starvation policies vary considerably [20]. Complica-
tion rates as a result of starvation or aspiration in
ophthalmic regional anesthesia are unknown but
dangers remain if a patient vomits while undergoing
anesthesia and surgery. According to guidelines and
evidence reports, routine investigation of patients who
undergo cataract surgery is not essential and does not
improve health or outcome of surgery, but tests can
be done to improve general health of the patient
if required.
The preoperative assessment should always in-
clude specific enquiry about bleeding disorders and
drugs. There is increased risk of hemorrhage in pa-
tients receiving anticoagulants and a clotting profile
assessment is required before injection. Patients who
receive anticoagulants are advised to continue medi-
cation [21]. Clotting results should be within the
recommended therapeutic range [21,22]. Because of
a lack of data, currently there are no recommenda-
tions for patients who receive antiplatelet agents [22].
Sub-Tenon’s block is a favored technique for these
patients [21].
Fig. 4. Upwards and outwards rotation helps to expose the
area of dissection.
Monitoring during block
Once the decision is made to operate, anesthetic
and surgical procedures are explained to the patient,
and informed consent is obtained and recorded. All
monitoring and anesthetic equipment in the operating
environment should be fully functional [18]. Blood
pressure, oxygen saturation, and ECG leads are
connected to the patient, and baseline recordings are
obtained [18]. Although, the insertion of an intra-
venous line has been questioned [23], it is always a
good clinical practice to secure an intravenous line,
because serious complications can occur regardless of
the anesthetic technique being used (eg, anaphylactic
reaction to antibiotics).
Standard sub-Tenon’s technique
Access to the space by the inferonasal quadrant is
the most commonly described approach, because the
placement of the cannula in this quadrant allows good
fluid distribution superiorly, avoids the area of
surgery, and reduces the risk of damage to the vortex
veins [1]. The equipment that may be required during
sub-Tenon’s blocks is shown in Fig. 3. After instil-
lation of local anesthetic eye drops (proxymetacaine
Fig. 5. The place of incision for dissection during infero-
nasal sub-Tenon’s anesthesia.
kumar & dodds212
0.5% or tetracaine 1%), the eye is cleaned with spe-
cially formulated 5% aqueous povidone iodine solu-
tion. An eyelid speculum or an assistant’s finger is
used to keep the eyelids apart. The patient is asked to
look upwards and outwards, to expose the inferonasal
quadrant (Fig. 4). The conjunctiva and Tenon’s cap-
sule are gripped with non-toothed forceps 5–10 mm
away from the limbus. A small incision is made
Fig. 6. Different types of sub-Tenon’s cannulas. (A) A standard pos
mid sub-Tenon’s cannula, 21 gauge and 1.8 cm long; (C) an anter
ultra-short cannula, 14 gauge and 0.6 cm long.
through these layers with scissors and sclera is ex-
posed (Fig. 5).
A blunt, curved (Fig. 6A), metal sub-Tenon can-
nula, (19 gauge, 25 mm long, curved, a flat profile
with end hole) that is securely mounted onto a 5 mL
syringe, which contains the local anesthetic solution,
is inserted through the hole along the curvature of the
sclera. If resistance is encountered, a gentle pressure
is applied and hydro-dissection usually helps to ad-
vance the cannula. The resistance felt during insertion
of the cannula is caused by the intermuscular septum,
but usually the cannula passes into the posterior sub-
Tenon’s space. If the hydro-dissection does not help,
or the resistance encountered is too great, it is ad-
visable to reposition or reintroduce the cannula.
Muscle insertions vary and the cannula may be tran-
versing the muscle’s Tenon’s sheath rather than
following the globe surface. The local anesthetic
agent of choice is injected slowly and the cannula is
removed. A gentle pressure is applied over the globe
to help spread the local anesthetic agent.
There are many variations of the sub-Tenon’s
technique that relate to route of access, type of can-
nula, local anesthetic agent, volume of anesthetic, and
the adjuvant used.
terior sub-Tenon’s cannula, 19 gauge and 2.54 cm long; (B) a
ior sub-Tenon’s cannula, 14 gauge and 1.2 cm long; (D) an
sub-tenon’s anesthesia 213
Variations of technique
Access to sub-Tenon’s space
Access to all other quadrants has been reported:
the superotemporal by Fukasaku [9], the superonasal
and inferotemporal by Roman and colleagues [24]
and McLure and colleagues [25], and the medial
canthal side by Ripart [11]. It is not known how
frequently these quadrants are used for access. In
addition, there are no comparative data to support the
ease of access to any particular quadrant. However,
the supernasal route is potentially more hazardous
because of the vascular, neuronal, and muscular
contents in that area.
Varieties of cannulae
There are several alternative cannulae available
for this block. Some are specifically designed for this
purpose while others have a different primary pur-
pose. The specifically designed cannulae may be
made of either metal or plastic. The metal cannulae
vary in gauge, length, curvature, and the position of
the end holes. A plastic cannula advocated by Green-
baum [10] is known as an anterior sub-Tenon’s can-
nula and is 15 gauge, 1.2 cm long, blunt, D shaped,
and has a flat bottom (see Fig. 6C). The opening on
the flat bottom is designed to face the sclera after
insertion. Non-specific sub-Tenon’s cannulae include
the metal Southampton cannula [8], metal ophthalmic
irrigation cannula [26], plastic intravenous cannula
[27], and plastic mid sub-Tenon’s cannula [28] (see
Fig. 6B). Recently an ultrashort metal cannula,
(16 gauge, 6 mm with blunt end hole) has been de-
scribed [29] (see Fig. 6D). The placement of a poly-
ethylene catheter into sub-Tenon’s space has been
described for long surgeries [30]. Additionally, access
to the sub-Tenon space through the medial canthal
approach has been described using needles without
dissection [11,31]. The selection of a cannula or
needle depends on the availability, cost, and the skills
and expertise of the clinician. However, the commer-
cially manufactured, posterior metal sub-Tenon’s
cannula is the type that is most commonly featured
in published studies.
Choice of local anesthetic agent
Anesthesia and akinesia are determined by the
properties of the local anesthetic agent, but more
directly, by the proximity to the sensory and motor
nerves. Lidocaine 2% is the most commonly used
agent and is considered the gold standard [32]. Vari-
ous local anesthetic agents such as articaine 2% [33],
etidocaine [34], prilocaine [35], mepivacaine [36],
levobupivacaine [37], and a mixture of lidocaine and
bupivacaine [38], have been used but there are few
comparative data available on the relative effec-
tiveness of various agents.
Volume of local anesthetic agent
There is a wide variation in the volume of local
anesthetic used in sub-Tenon’s block and this has
been a subject of debate. The volumes vary from 1 to
11 mL [10,39] but 3 to 5 mL are generally used [40].
Smaller volumes will usually provide globe anes-
thesia but larger volumes are required if akinesia is
desirable [41].
Adjuvant and sub-Tenon’s block
Vasoconstrictor
Vasoconstrictors are commonly mixed with local
anesthetic solution to increase intensity and duration
of the block, and to minimize bleeding from small
vessels [32]. Because vasoconstrictors reduce absorp-
tion of local anesthetic, a surge in plasma levels is
avoided. However, epinephrine may cause vasocon-
striction of the ophthalmic artery, which compromises
the retinal circulation [32]. The use of solutions that
contain epinephrine is usually avoided in elderly
patients who suffer from cerebrovascular and car-
diovascular diseases. The role of epinephrine in sub-
Tenon’s block has been questioned [42]. This is
because ophthalmic surgery does not usually take a
long time and the duration of the block achieved
by lidocaine without epinephrine suffices for modern
minimally invasive cataract surgery.
Hyaluronidase
Hyaluronidase is an enzyme, which reversibly
liquefies the interstitial barrier between cells by depo-
lymerization of hyaluronic acid to a tetrasaccharide,
and enhances the diffusion of molecules through tis-
sue planes [32]. The amount of hyaluronidase
mixed with the local anesthetic varies from 0.5 to
150 IU/mL. There is conflicting evidence that hyal-
uronidase (30 IU/mL) improves the effectiveness and
the quality of sub-Tenon’s block [43,44]. If hyal-
uronidase is to be used, 15 IU/mL is the recom-
mended amount in the United Kingdom [45]. It is an
expensive drug [46] and although side effects are
rare, allergic reactions [47], orbital cellulites [48], and
the formation of pseudotumors [49] have been re-
ported after its use.
kumar & dodds214
pH alteration
Commercial preparations of lidocaine and bupiva-
caine are acidic solutions in which the basic local
anesthetic exists predominantly in the charged ionic
form [32]. It is only the non-ionized form of the agent
that traverses the lipid membrane of the nerve to
produce the conduction block. At higher pH values a
greater proportion of local anesthetic molecules exist
in the non-ionized form, which facilitates more rapid
influx into the neuronal cells. Alkalinisation of the
local anesthetic agent has been shown to decrease the
onset and prolong the duration of needle blocks
[50,51] but no such benefit has been observed in sub-
Tenon’s block [52].
Passage of local anesthetic agent during injection
The passage of the local anesthetic during sub-
Tenon’s block has been studied using different
imaging techniques [53–55]. These studies confirm
that when the anesthetic agent is injected into the sub-
Tenon’s space, it opens the space to form a character-
istic T sign (Fig. 7). As the local anesthetic agent
spreads through the sub-Tenon’s space, it diffuses
into intraconal and extraconal areas and results in
anesthesia and akinesia of the globe and eyelids.
Intense analgesia is produced by blockade of the
short ciliary nerves as they pass through the Tenon’s
capsule [53]. Akinesia is caused by a blockade of
the motor nerves present in the intraconal and extra-
conal compartments.
Fig. 7. Ultrasound image shows the opening of the s
Complications of sub-Tenon’s anesthesia
Minor complications
Pain during injection
The pain experienced during ophthalmic blocks is
multi-factorial. Up to 44% of patients report pain
during sub-Tenon’s injection in which a posterior
metal cannula is used [8]. Pain scores on a visual ana-
log scale [0 = no pain, 10 =worst imaginable] have
been reported as high as 5, and smaller cannulae offer
a marginal benefit [56]. Premedication or sedation
of patients during sub-Tenon’s injection does not
seem to be beneficial [57]. To reduce the patient’s
discomfort and anxiety, it is important to give a thor-
ough preoperative explanation of the procedure, use a
good surface anesthesia, use gentle technique, slowly
inject the warm local anesthetic agent, and pro-
vide reassurance.
Chemosis
Chemosis signifies anterior injection of the anes-
thetic agent. This usually occurs if a large volume of
local anesthetic is injected and if the Tenon’s cap-
sule is not dissected properly [41]. The incidence of
chemosis varies from 25% to 60% [24,58] with
posterior cannula and to 100% with shorter cannulae
[41]. Chemosis may not be confined to the site of
injection and has been known to spread to other
quadrants [8,41]. This usually resolves after the
application of digital pressure, and no intraoperative
problems have been reported. Surgeons who per-
ub-Tenon’s space and the characterstic T-sign.
sub-tenon’s anesthesia 215
form glaucoma surgery may believe that significant
chemosis compromises the surgical procedure.
Subconjunctival hemorrhage
Fine vessels are inevitably severed during the
conjunctival dissection, which causes a degree of
subconjunctival hemorrhage. The incidence (and
severity) of subconjunctival hemorrhage varies from
20% to 100% and depends on the cannula used
[8,41]. This can be minimized by careful dissection
that avoids damage to fine vessels. The use of cau-
tery has been advocated [10] but no benefit was
seen when a disposable diathermy was used by
anesthesiologists [59]. Patients should receive ade-
quate warning about the possibility of subconjunc-
tival hemorrhage.
Overspill of anesthetic
Overspill of the local anesthetic agent during its
administration is commonly observed [8,41]. This is
likely to occur if the dissection of the sub-Tenon’s
capsule is not complete or if there is a resistance to
injection. Traction during injection may cause en-
largement of the initial dissection and large injection
volume also cause overspill. Careful dissection and
use of diathermy may minimize the loss. Gentle pres-
sure over the insertions site with a surgical sponge
might also help [1].
Akinesia and anesthesia
Akinesia is volume dependent and if 4–5mL of
local anesthetic agent is injected, most patients de-
velop akinesia [41]. However, superior oblique mus-
cle and lid movements may remain active in a small
but significant number of patients. Many published
studies on the subject report good results when an-
esthesia accompanies sub-Tenon’s block. However,
akinesia is variable and may not be complete [41,57].
Serious complications
Sight- and life-threatening complications have
been reported. These include short-lived muscle
paresis [60] as well as orbital and retrobulbar hem-
orrhage [61,62]. Recently, a scleral perforation during
sub-Tenon’s block was reported in a patient who had
previously undergone retinal surgery [63]. Damage to
the inferior and medial rectus muscles, caused by
trauma from metal cannula, has led to restrictive
functions that result in diplopia [64]. Other compli-
cations relate to optic neuropathy [65], afferent
papillary, and accommodation defects [66]. Retinal
and choroidal vascular occlusion has been reported
[67] as has one case where central spread of the local
anesthetic agent led to cardio-respiratory collapse
[68]. The mechanism of central spread is not clear but
possible explanations include spread of the injected
anesthetic agent into the subarachnoid space (see
discussion above) through the optic nerve sheath, or
back-tracking of the local anesthetic agent through
one of the orbital foramina [1]. The later can happen
if there is an unintentional perforation of the Tenon’s
capsule, which leads to the deposition of the local
anesthetic agent into the intraconal compartment.
Retained visual sensations
Published studies have reported that patients who
have phacoemulsification cataract surgery under topi-
cal, retrobulbar, peribulbar, and sub-Tenon’s blocks,
experience light and other visual sensations during
surgery [69]. Although most of the patients felt
comfortable with the visual sensations they experi-
enced, a proportion of patients (up to 16%) found the
experience to be unpleasant or frightening [70,71].
Preoperative counseling benefits these patients [69].
Patients who receive sub-Tenon’s block should be
offered preoperative advice which may alleviate fear
of this experience.
Intraocular pressure and role of ocular
compression
The rise in intraocular pressure (IOP) after ad-
ministration of sub-Tenon’s block is small or even
insignificant [72,73]. There was a numerically sig-
nificant reduction in intraocular pressure using a
Honan balloon, but this did not make a clinical
difference in the effectiveness of anesthesia [74].
Pulsatile ocular blood flow during sub-Tenon’s
block
It is known that retrobulbar and peribulbar
injections decrease pulsatile ocular blood flow, at
least for a short time [75]. In a recent study [73], the
changes in IOP and ocular pulsatile amplitude (OPA)
were compared during peribulbar and sub-Tenon’s
blocks. The IOP remained stable with both blocks
throughout the study. One minute after injection of
the anesthetic agent, the OPA decreased significantly
in the injected eyes in both the sub-Tenon’s (24%)
and peribulbar (25%) groups. The OPA decrease in
the sub-Tenon’s group (14%) was also detectable
kumar & dodds216
after 10 minutes in the control group. Therefore,
caution is required in the management of patients
whose ocular circulation may be compromised and an
alternative anesthesia, such as general anesthesia,
may be desirable.
Presence of anesthesiologists
The presence of anesthesiologists during sub-
Tenon’s block may not be required [18] but the
ability to manage life-threatening cardio-respiratory
events must be available from the other staff in
theater. A member of the staff whose sole responsi-
bility is to the patient, should be responsible for
monitoring and should remain with the patient at all
times throughout the monitoring period. This person
must be trained to detect and act on any adverse
events, and may be an anesthesiologist, nurse, or
operating department practitioner who is trained in
life support [18].
Intraoperative monitoring
The patient should be comfortable and soft pads
should be placed under the pressure areas. All
patients who experience major eye surgery under
local anesthesia should be monitored with pulse
oximetry, ECG, non-invasive blood pressure mea-
surement, and verbal contact [18]. Patients should
receive an oxygen-enriched breathing atmosphere to
prevent hypoxia, and a flow rate high enough to
prevent hypercarbia if enclosed in surgical drapes.
ECG and pulse oximetry should be continued. Once
the patient is under the drapes, verbal and tactile
contacts are maintained [18].
Sedation during sub-Tenon’s block
A patient who undergoes ophthalmic surgical
procedures, regardless of the type of regional
anesthesia used, should be fully conscious; respon-
sive; and free of anxiety, discomfort, and pain [18].
The aim of sedation is to minimize anxiety and pro-
vide the maximum degree of safety. Sedation is com-
monly used during cataract surgery under topical
anesthesia [76], but selected patients who receive a
sub-Tenon’s or another type of orbital regional block,
may benefit from sedation if explanation and
reassurance are inadequate [17]. Short acting benzo-
diazepines, opioids, or intravenous anesthetic agents
in minimum dosages are used. However, there is an
increased risk of an intraoperative event when seda-
tion is used [77,78]. A means of providing sup-
plemental oxygen must be available when sedation
is administered.
Advantages of sub-Tenon’s block
A sub-Tenon’s block eliminates the risks of sharp
needle techniques, provides reliable anesthesia, can
be supplemented for prolonged anesthesia and post-
operative pain relief, and can be safely used in pa-
tients who have a long globe [1]. There are numerous
studies that demonstrate its effectiveness compared
with retrobulbar, peribulbar, and topical anesthesia
alone [1]. Sub-Tenon’s block has been used mainly
for cataract surgery, but also vitreoretinal surgery
[79–81], panretinal photocoagulation [82], strabis-
mus surgery [83], trabeculectomy [42,84], optic nerve
sheath fenestration [85], chronic pain management
[86], and therapeutic delivery of drugs [87]. Recent
reviews suggest that sub-Tenon’s block may be used
safely in patients who receive anticoagulants and
antiplatelet agents, as long as clotting results are in
the normal therapeutic range [21,22]. Despite reports
of a few major complications, sub-Tenon’s block has
one of the highest safety profiles of any regional
anesthetic technique.
Limitations of sub-Tenon’s block
Subconjunctival hemorrhage and chemosis are
common. Residual muscle movement or incomplete
akinesia do not cause intraoperative difficulties and
are generally acceptable to surgeons. The block may
be difficult to perform in patients who have had
previous sub-Tenon’s block in the same quadrant,
previous retinal detachment and strabismus surgery,
eye trauma, and infection to the orbit. Some
glaucoma surgeons may dislike sub-Tenon’s block,
although it has been used successfully for glaucoma
surgery [1].
Summary
Currently there is no absolutely safe orbital re-
gional block technique. Sub-Tenon’s block is a
simple, effective, safe, and versatile technique,
although rare complications can occur. To perform a
sub-Tenon’s block, a thorough knowledge of anat-
omy and understanding of the underlying principles
is essential.
sub-tenon’s anesthesia 217
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Ophthalmol Clin N
Orbital Regional Anesthesia
Gary L. Fanning, MD
Hauser-Ross Eye Institute, P.O. Box 406, Sycamore, IL 60178-0406, USA
Topical and sub-Tenon’s local anesthetic tech-
niques have rapidly gained popularity for cataract [1]
and other ophthalmic surgical procedures (ie, stra-
bismus and retinal surgery) both here and abroad,
largely because of their perceived margins of safety.
In Great Britain, sub-Tenon’s anesthesia in particular
has risen in popularity and now is used for a large
percentage of cataract surgeries. However, there re-
mains a place for orbital regional anesthesia or gen-
eral anesthesia in ophthalmic surgery, because topical
and sub-Tenon’s techniques are not suitable for every
patient, every procedure, nor every surgeon.
The goals of this article are to examine the no-
menclature of orbital blocks, to review orbital anat-
omy as it relates to the safe performance of orbital
regional anesthesia, and to describe two specific
block techniques and contrast them with others.
Nomenclature
Nomenclature for orbital blocks is imprecise and
can be confusing [2]. Currently, the term retrobulbar
is applied to a block for which a long, apically
directed needle is used. Actually, all orbital blocks are
retrobulbar because the term simply means behind the
globe. In many patients it is possible to be behind the
globe with a 0.5-in needle. Similarly, the term peri-
bulbar is used to describe a block in which the intent
is to stay out of the muscle cone with the needle. In
fact, all blocks should be peribulbar (ie, around the
globe), because the only alternative is transbulbar,
something to avoid. More recently, the term para-
bulbar has been used to describe sub-Tenon’s blocks.
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.009
E-mail address: [email protected]
This seems reasonable, because parabulbar has the
connotation of being next to and close to the globe.
Use of the terms retrobulbar and peribulbar to
describe different block techniques seems unsuitable
on at least two grounds: they are imprecise and they
do not actually describe the anatomical spaces they
are meant to describe. It would be more precise and
anatomically correct to substitute the term intraconal
for retrobulbar, because the block is designed to go
into the muscle cone. Instead of peribulbar, the term
extraconal better describes the type of block intended
to inject anesthetic into the extraconal space. In this
article, therefore, the terms intraconal and extraconal
will be used instead of the more widely used
expressions retrobulbar and peribulbar, respectively.
Anatomy for orbital regional anesthesia
To best understand the anatomy of the orbit for the
purpose of doing blocks, one should have a thorough
knowledge of the frontal anatomy of the orbit at
various depths from the orbital rim back to the optic
canal. This anatomy is best illustrated in the works of
Leo Koornneef [3] and Jonathan Dutton [4].
The orbit is an irregularly shaped pyramid; the
base faces anteriorly, roughly on the frontal plane.
The apex (the optic canal) lies at the posterior end of
the medial wall. Because of the irregular shape of the
orbit, the lateral wall is longer than the medial wall.
As a result, a long (1.5 in) needle that is inserted
along the medial wall can easily reach the optic canal
in most patients.
The globe is situated in the orbit such that it is
slightly closer to the roof and lateral wall than to the
floor and medial wall. The lateral rectus muscle lies
against the orbital wall until quite far anteriorly
Am 19 (2006) 221 – 232
reserved.
ophthalmology.theclinics.com
Fig. 1. A frontal section through the posterior half of the
globe. The open star indicates the fat-filled space at the
extreme inferotemporal corner of the orbit. The inferior
rectus muscle is located at the junction of the lateral one-
third and medial two-thirds of the inferior orbital rim. The
neurovascular bundle to the inferior oblique lies just lateral
to it. The filled star lies in the medial canthal fat-filled
space, another relatively safe entry point for an orbital
block. IRM, inferior rectus muscle; LPM, levator palpebrae
muscle; LRM, lateral rectus muscle; MRM, medial rectus
muscle; SOM, superior oblique muscle; SRM, superior
rectus muscle. (Adapted from Dutton JJ. Atlas of clinical
and surgical orbital anatomy. Philadelphia: W.B. Saunders
Company; 1994; with permission.)
Fig. 2. Frontal section at a level about 5–10 mm behind the
hind surface of the eye. The tip of a 1-in needle should just
reach this level and lie in the fat medial to the lateral rectus,
and lateral and inferior to the optic nerve. It is unnecessary
to be deeper than this in the orbit to achieve an excellent
block. IRM, inferior rectus muscle; LRM, lateral rectus
muscle; MRM, medial rectus muscle; OA, ophthalmic
artery; ON, optic nerve; SOM, superior oblique muscle;
SRM, superior rectus muscle. (Adapted from Dutton JJ.
Atlas of clinical and surgical orbital anatomy. Philadelphia:
W.B. Saunders Company; 1994; with permission).
fanning222
where its tendon then passes medially to insert on the
globe. The medial rectus muscle, in contrast, begins
to angle laterally to join the globe relatively close to
its origin at the annulus of Zinn. As a result, there is a
sizable fat-filled space between the medial rectus
muscle and the medial orbital wall for most of its
length, especially in the anterior half of the orbit
(Fig. 1). This extraconal space is an excellent site for
the injection of local anesthetic, as it communicates
freely with the intraconal space and is virtually devoid
of easily damaged structures if appropriately ap-
proached. Some practitioners use this as the site of their
primary orbital block.
At the extreme inferotemporal corner of the orbit
there is another extraconal, fat-filled space that is
easily entered and is devoid of other structures. It,
too, communicates with the intraconal space between
the lateral rectus muscle and inferior rectus muscle. A
frontal section just posterior to the equator of the
globe (see Fig 1) invariably shows this space to be
large and filled with fat. Actually, both the inferior
rectus muscle and the neurovascular bundle to the
inferior oblique are quite close to this spot. This can
be seen by looking at the junction of the lateral third
and medial two-thirds of the lower orbital rim. For
decades, this point has been recommended as the
needle entry point for an orbital block. Atkinson [5] is
often credited with suggesting this entry point, but in
his original 1936 paper, he recommended ‘‘. . .theinferior temporal margin of the orbit.’’ An illustration
in his paper shows a skin wheal at the inferotemporal
margin of the orbit.
It is not surprising that the inferior rectus com-
monly suffers dysfunction after orbital regional anes-
thesia. This point is significantly closer to the globe
than a point at the inferotemporal corner of the orbit.
Thus, for clear anatomical reasons, the classic inser-
tion point for orbital regional anesthesia (junction of
the lateral third and medial two-thirds of the lower
orbital rim) would seem to be a less desirable entry
point than the extreme inferotemporal corner of
the orbit.
A frontal section of the orbit 5–10 mm behind the
hind surface of the eye (Fig. 2) shows a fat-filled,
intraconal space that is relatively devoid of structures
other than the optic nerve; the bellies of the extra-
ocular muscles are close to the orbital walls at
this level. Vascular structures are small and widely
spread. The space between the lateral rectus and
Fig. 3. Frontal section 15–20 mm behind the hind surface of
the eye shows how closely packed structures become as the
apex of the orbit is approached. There is little room for error
here and a needle can damage any of the structures seen in
this section. A 1.5-in needle can reach this level in at least
20% of patients. There is no need to be this deep in the orbit
when doing orbital regional anesthesia. IRM, inferior rectus
muscle; LPM, levator palpebrae muscle; LRM, lateral rectus
muscle; MRM, medial rectus muscle; ON, optic nerve;
SOM, superior oblique muscle; SRM, superior rectus
muscle. (Adapted from Dutton JJ. Atlas of clinical and sur-
gical orbital anatomy. Philadelphia: W.B. Saunders Com-
pany; 1994; with permission.)
Fig. 4. The white line in this drawing divides the orbit
into superior and inferior halves. Most large arterial vessels
are seen in the superior and deep areas of the orbit. To
avoid injuring them, keep needles out of these areas. Note
the course of the ophthalmic artery that leaves the optic
canal and goes into the superonasal quadrant. (Adapted
from Dutton JJ. Atlas of clinical and surgical orbital
anatomy. Philadelphia: W.B. Saunders Company; 1994;
with permission.)
orbital regional anesthesia 223
inferior rectus muscles is fairly large, but the space
between the medial rectus muscle and the medial
orbital wall is narrower than in the previous section.
These spaces behind the globe are reachable with
a 1-in needle. If a sufficient volume of anesthetic is
injected, it is unnecessary to place a needle any
further back into the orbit to achieve a good block.
There is no intermuscular septum between the rectus
muscles to define the intraconal from the extraconal
space. In fact, anesthetic injected into either space
flows readily into the other, as clearly demonstrated
by Ripart and coworkers [6]. Some practitioners rely
on feeling a pop when the needle is inserted, and
believe that they have traversed the (non-existent)
septum. When a sharp needle is inserted into a fat-
filled space, little, if any, sensation will be felt. A
popping sensation may mean that one of the tiny
connective tissue septa described by Koornneef [3]
and that are found throughout the orbit, has been
punctured. It may also indicate, however, a punctured
vessel, nerve, muscle, optic nerve, or globe.
A frontal section, about 20 mm behind the hind
surface of the globe (Fig. 3), shows that the amount
of fat in the intraconal space is now much less and
there are other structures that fill it. These include the
branches of the motor nerves that supply the ex-
traocular muscles, the arteries and veins to those
muscles, and the optic nerve. The subarachnoid space
between the dural sheath and optic nerve is impres-
sive in this section. The bellies of the extraocular
muscles are also much larger at this level. Myotox-
icity, which is often irreversible, may occur when
local anesthetic is injected directly into a muscle belly
[7,8]. The part of the orbit where the structures are
closely packed and easily impaled is reached by a
1.5-in needle in at least 15%–20% of eyes, as dem-
onstrated by Katsev and colleagues [9]. To avoid
damage to any of the structures seen in the frontal
section, it would seem wise to use a shorter needle.
Three special anatomical details are worth dis-
cussion. First is the vascular tree of the orbit. Both the
largest arteries (Fig. 4) and largest veins (Fig. 5) lie in
the superior half of the orbit. In addition, the vessels
that have the largest diameter lie in the deep portion
of the orbit. To avoid a major retrobulbar hemorrhage
or intravascular injection, the needle tip should be
kept out of the upper half and out of the deep portion
of the orbit. Second is the superonasal quadrant of the
orbit, which is an especially dangerous place to put a
needle. The terminal branches of the ophthalmic
artery are here, an artery that is often large and tor-
tuous in elderly, hypertensive individuals. A needle
placed in this artery may result in a sight-threatening
Fig. 5. This figure shows the venous drainage of the orbit.
The major vessels are in the superior and deep portions of
the orbit. The superior ophthalmic vein begins in the su-
peronasal quadrant. Needles should not enter that quadrant.
(Adapted from Dutton JJ. Atlas of clinical and surgical or-
bital anatomy. Philadelphia: W.B. Saunders Company; 1994;
with permission.)
fanning224
hematoma or intravascular injection of anesthetic that
causes immediate seizure activity. In addition, the
terminal branches of the nasociliary nerve lay in the
superonasal quadrant and can be damaged. The supe-
rior oblique muscle and its trochlear mechanism
are also located in the superonasal quadrant. Third is
the dural sheath that surrounds the optic nerve. A
needle tip placed within that sheath will result in
local anesthetic being injected retrograde into the
cerebrospinal fluid surrounding the brainstem, caus-
ing brainstem anesthesia. This complication may
largely be avoided by the use of short needles that
are not apically directed.
Patient preparation
Before performing an orbital block, it is wise to
review the patient’s medical history and conduct a
directed physical examination to be sure that the
patient is a suitable candidate on the day of surgery.
Routine assessment of vital signs and an ECG moni-
tor will help determine if patients have fevers,
arrhythmias, or hypertension, conditions that may
require the procedure to be cancelled. At the Hauser-
Ross Eye Institute patients are routinely treated who
have blood pressures >170 mm Hg systolic and/or
105 mm Hg diastolic. Judicious doses of intravenous
labetalol (10–20 mg) are commonly used, but other
agents are available to patients who must avoid beta-
blockers. Great care is taken to avoid suddenly low-
ering the blood pressure in patients who have angina,
aortic stenosis, renal vascular disease, or carotid ste-
nosis. In order to prevent hypotension, administer
small, divided doses and monitor carefully.
It is also important to examine the eyes for in-
fectious, traumatic, or even malignant lesions. The
patient’s record should be examined for evidence of
the length of the eye. In the case of cataract sur-
gery, each patient should have had an axial length
measurement and this should be noted and recorded
by the person who performs the orbital block. If the
anesthesia provider is performing the block, the
ophthalmologist should be certain that they know
the axial length. If the axial length is not available,
the spherical equivalent in the patient’s eyeglass
prescription should be reviewed. High myopes tend
to have exceptionally long eyes, so when the
spherical equivalent is as high as �6.00 or �7.00,it is advisable to measure the axial length before
performing an orbital block. Fig. 6 demonstrates the
relationship between axial length and spherical
equivalent as measured in 1325 eyes. Patients who
have axial lengths �27 mm are at risk for posterior
staphylomata [10] and should have been carefully
examined for their presence preoperatively. After the
patient’s eye length has been determined or estimated,
the relationship of the eye within the orbit should be
examined. Is it a long eye sunk deeply into a very
tight orbit? Is it a short, proptotic eye in a large but
potentially shallow orbit? Knowledge of this relation-
ship is used to determine the angle of the block
needle as it enters the desired orbital space in order to
avoid penetrating the sclera.
Sedation
An orbital block can result in a great deal of pain
and many practitioners use deep sedation, equivalent
to a brief period of general anesthesia, when they
perform a block. Pain on injection is likely to occur
when a needle is placed deeply into the orbit, because
pressure is generated when the anesthetic is injected
rapidly into a tight space that is filled with delicate
structures. Deep sedation is not without its risks, and
a number of unwanted events can occur, including ap-
nea, hypoxemia, uncontrolled movements, and even
vomiting or aspiration. Some practitioners believe
that it is important not to sedate the patient deeply for
an orbital block, because they want the patient to be
Fig. 6. Axial length versus spherical equivalent in 1325 eyes. Patients who are highly myopic (and have eyeglass prescriptions
with large negative spherical equivalents), tend to have very long eyes. Axial length is plotted against spherical equivalent. The
bars represent two standard deviations from the averages. When performing a block on a patient who has not had an their axial
length measured, it is useful to look at the spherical equivalent in the eyeglass prescription to estimate the length of the eye.
(Gary L. Fanning, MD, unpublished data, 2000.)
orbital regional anesthesia 225
able to give notice if excessive pain occurs. Such pain
might indicate that the anesthetic is not being injected
into a fat-filled space but rather into an extraocular
muscle, the globe, a nerve, or under the periosteum. It
is possible to have a patient who is sedated to the
point of anxiolysis and still remain cooperative. Small
intravenous doses of midazolam (1–2 mg) coupled
with small, divided doses of a short-acting barbiturate
(thiopental [Pentothal] 25–75 mg or methohexital
[Brevital] 10–30 mg) or with a rapid, short-acting
opioid (remifentanil [Ultiva] 20–40 mcg, alfentanil
[Alfenta] 250–500 mcg, or fentanyl [Sublimase]
50–100 mcg) can produce a patient who is re-
laxed, submissive, and cooperative. Sedative doses
of propofol are preferred by many, but it can be dif-
ficult to titrate due to its slow onset of action, and in
some patients it results in a great deal of unwanted
movement unless sleep doses are given. Nonetheless,
it is an appropriate agent for many patients when
administered by those skilled in its use. Strict attention
to the patient’s reaction to the sedatives is important to
avoid over-sedation. The patient’s response to sedation
for the block provides advanced knowledge of their
reaction to the sedatives before the onset of surgery. If
additional sedation is believed to be required during
surgery, the practitioner will be able to avoid excessive
sedation and its attendant dangers. To render the in-
jection of a block virtually painless in a patient who
is awake, three precautions must be taken: (1) use a
fine, short needle (ie, 25 gauge, 1 in), (2) use an anes-
thetic solution that has been heated to about 35�C, and(3) inject the anesthetic at a slow rate (15–20 s/mL).
Studies [11,12] that have examined warming the
anesthetic solution have often failed to include the
other two precautions, and over-warming the solution
often produces increased pain. Any solution injected
deeply and rapidly into the orbit will cause intense
pain. Warmed solutions injected slowly and more
anteriorly do not. Conscious sedation along with a
painless injection technique has another benefit:
patients may be allowed to have a light breakfast
before cataract surgery. The author has used this
technique in more than 22,000 patients without a
single instance of regurgitation or aspiration. When
a painless injection technique is used, only small
amounts of sedation, if any, are necessary.
Needles
Before discussing the details of block techniques,
it is necessary to examine what kind of needle should
be used to perform a block. Many, if not most,
practitioners still use the 23-gauge, 1.5-in needle that
has been used for decades. In 1989, Katsev and
fanning226
coworkers [9] published an anatomical study of the
orbit with regard to needle length. They measured the
distance from the junction of the lateral third and
medial two-thirds of the inferior orbital rim to the
optic canal. In the 120 skulls that were examined, this
measurement varied from about 42 mm to 54 mm
(Fig. 7). They postulated that the most dangerous part
of the orbit, where structures are densely packed and
vulnerable to damage, is the portion within 7 mm of
the annulus of Zinn. Thus, the tip of a 1.5-in needle
(38 mm) would reach this dangerous portion in any
orbit shorter than 45 mm. In their specimens this
would be about 15%–20% of the total. If a needle
�1.25-in (32 mm) in length is used, the danger area
would not be reached in any of the skulls examined
by Katsev and coworkers. Although the study was
published in a prominent journal, many practitioners
still use a long needle. Having used a 1-in needle
for 2 years with great success and having used a
1.25-in needle for 12 years before that, it is the au-
thor’s opinion that the incidence of all of the fol-
lowing complications of orbital regional anesthesia
would be significantly reduced by using a shorter
needle: retrobulbar hemorrhage, brainstem anesthe-
sia, optic nerve damage, intravascular injection, and
extraocular muscle dysfunction. With regard to nee-
dle gauge, the needle should be 25 gauge, no bigger.
Some prefer a 30-gauge, 1-in needle although others
find it too flexible. Many would prefer a 27- or
Fig. 7. Orbital length in 120 skulls. Orbital length is plotted again
20% of orbits are short enough that a 1.5-in needle can reach within
(Adapted from Katsev DA, Drews RC, Rose BT. An anatomical st
96:1221–4; with permission.)
28-gauge, 1-in needle, but these are no longer avail-
able commercially in the United States; a 25-gauge,
1-in needle is a compromise.
There is a great debate about whether the bevel of
the needle should be sharp or blunt. Some of this
discussion revolves around feel: many practitioners
believe that a blunt-beveled needle offers a better tac-
tile signal than the sharp-beveled one; others believe
just the opposite. Proponents of the blunt-beveled
needle believe that it is less likely to inadvertently
puncture the sclera than is the sharp-beveled needle.
Although this may be true, it is also true that any
needle that is capable of going through the intact skin
is also able to go through the sclera of the eye in situ
(as opposed to an enucleated eye, where it can be
demonstrated that a blunt-beveled needle requires
more force than a sharp one to penetrate the globe).
There is some evidence that scleral puncture with a
blunt-beveled needle results in more retinal damage
than puncture with a sharp-beveled one [13]. One
group has suggested that in patients with a long eye,
the blunt-beveled needle should always be used
because it is less likely to puncture the sclera [14].
However, the longest eyes have the most delicate
sclera, which makes it easy for any needle to pene-
trate. If penetration did occur, it would seem pref-
erable to have used a needle that would result in less
retinal damage. Furthermore, it is not rational to rely
on the shape of the needle to avoid penetration of
st the percentage of orbits that have specific lengths. About
7mm of the optic canal where structures are tightly packed.
udy of retrobulbar needle path length. Ophthalmology 1989;
orbital regional anesthesia 227
the sclera. Instead, thorough knowledge of orbital
anatomy and examination of the patient’s globe-orbit
relationship should prevent this complication. One
thing that is not disputed is that the sharp needle
enters the skin more easily and with less pain. No
matter what needle the practitioner uses, the length,
gauge, and bevel shape must be documented in the
patient’s record.
Fig. 9. Line A represents the diagonal of the orbit from the
superotemporal to the inferotemporal corner. The block
needle is aligned with line A and is inserted at the infero-
temporal corner. Dotted line B represents a sagittal plane
that goes through the lateral limbus. The block needle is
angled (angle C) so that the tip will just intersect plane B
about 5–10 mm behind the hind surface of the eye when
inserted. The value of this angle is different for each patient.
Technique
Intraconal block
For an intrconal block, the patient should be in the
supine position, the chin held up, and the eyes in a
neutral gaze. A skin wheal is made with a 0.5-in,
30-gauge needle using 0.1% lidocaine solution in-
jected at the extreme inferotemporal corner of the
orbit (Fig. 8). The lidocaine solution is prepared by
adding 1.5 mL 2% lidocaine with preservative to a
30 mL bottle of 0.9% saline solution with preserva-
tive. The final solution contains about 0.1% lido-
caine, which provides excellent anesthesia for about
5–10 min but is virtually painless to inject. This
solution given through a 30-gauge 0.5-in needle is
also used to anesthetize the intravenous catheter’s
insertion site, which makes starting the intravenous
line painless as well. In many patients a distinct notch
is felt in the lower orbital rim at the inferotempo-
ral corner. It is worthwhile to search for this notch,
Fig. 8. A skin wheal is raised at the inferotemporal corner of
the orbit. A 30-gauge needle is used to inject 0.1% lidocaine
solution, which is virtually painless on injection. The same
solution also is used before starting an intravenous to render
it painless.
because inserting the needle here increases one’s
chances of entering into the intraconal space keeping
well away from the extraocular muscles and the
globe. While an assistant steadies the patient’s head
and holds the upper lid open, a 25-gauge 1-in needle
is inserted through the skin wheal at the inferotem-
poral corner (notch) of the orbit on a line that con-
nects the inferotemporal corner with the superonasal
corner (line A, Fig. 9) and is aimed posteriorly to pass
tangential to the globe and intersect a sagittal plane
(line B, Fig. 9) to pass through the lateral limbus. The
angle formed by the needle shaft and the frontal
plane on which line A lies (angle C, Fig. 9) will vary
in each patient. The degree of angulation is deter-
mined by the eye’s axial length and how deeply set
or proptotic the eye is. In Fig. 10, the two deep-set
eyes can be compared with two more proptotic eyes.
The angulation necessary to pass tangentially to the
globe will differ in each of these patients. The
patient’s eye should be watched constantly during
the initial insertion, at which time it should not move
at all as the needle passes the globe. Although the
patient’s eye should be in neutral gaze during the
initial insertion and should not move, it is helpful to
have the patient gaze toward the ipsilateral side once
the needle is slightly beyond the equator. This insures
that the globe is free and also moves the posterior
pole of the eye away from the needle tip. Some
practitioners prefer to have the patient continue in
neutral gaze, which is also acceptable. It is not ac-
Fig. 10. The depth of the eye with respect to the lower orbital rim varies from patient to patient. The length of the eye, how
deeply it is set, and how tightly it is placed within the orbit constitute the globe-orbit relationship. This relationship must be
carefully considered for each patient in order to angle the needle safely to pass tangentially to the globe.
Fig. 11. The tip is more anterior when a short needle is used
and injection may cause anesthetic solution to pass retro-
grade into the lower eyelid instead of behind the eye. To
lessen this tendency, the assistant is directed to place two
fingers along the lower orbital rim and to apply gentle
pressure to encourage flow of the injectate behind the globe.
It is an easy and harmless maneuver that results in a higher
rate of successful blocks.
fanning228
ceptable to move the needle back and forth in order
to see if it is in the globe or not. This has been termed
by some as stirring the orbital contents, a practice to
be avoided. For most patients, the tip of the fully
inserted 1-in needle will lie just behind the posterior
surface of the globe and no deeper than 5–10 mm
behind it. The bevel of the needle should at first be
pointing toward the globe so that during insertion the
tip of the needle will tend to move away from the
globe. After the tip of the needle is well beyond
the equator of the globe (about half inserted), the
needle can be spun 180� so that the bevel faces
away from the globe. This will tend to move the tip
medially into the intraconal space behind the globe.
Properly placed, the tip of the needle should now be
in the intraconal space of the inferotemporal quadrant
of the orbit, just behind the globe. Before injecting,
the assistant places two fingertips along the lower
orbital rim to bolster the inferior orbital septum
(Fig. 11). Gentle pressure applied here during injection
promotes flow of anesthetic upward and posteriorly
instead of retrograde into the lower lid through the
ever-present gaps in the orbital septum. Local anes-
thetic is injected slowly (1 mL every 15–20 seconds)
and the globe is periodically palpated to insure that
there is no excessive pressure. In most patients 7 mL
can be injected safely, a volume that will provide total
akinesia and anesthesia in well over 90% of patients.
After injection, an orbital compression device is ap-
plied for 10 min. This can be a soft plastic ball or a
Honan balloon [15]. This compression helps to
disperse the anesthetic throughout the orbit and helps
to prevent excessive intraocular pressure caused by the
presence of the anesthetic within the orbit.
Fig. 12. If a supplemental block is required to achieve
complete akinesia, a medial canthal block is performed.
First, identify the small tunnel or dimple that lies anterior
to the caruncle and just behind the medial canthus. The tip
of the needle is placed in that tunnel.
orbital regional anesthesia 229
It is important to emphasize the insertion point
described in this technique. For decades, common
practice has been to insert the needle at the junction
of the lateral third and medial two-thirds of the lower
orbital rim (the classic point). As explained above,
this insertion site is nearer the globe, is close to
the inferior rectus muscle, and is also close to the
neurovascular bundle of the inferior oblique. Because
it is so close to the globe, it is also difficult from
this point to place the needle tip within the muscle
cone without trying to redirect it after insertion.
From the extreme corner, it is easier to stay far away
from the globe and the angle of insertion does not
have to change to enter the intraconal space. In fact,
a needle only has to be angled 10� medial to a sagit-
tal plane tangential to the globe (ie, to the optic axis)
to enter the intraconal space [16]. If the needle is
angled as described in the paragraph above, this
should happen virtually every time. When performing
an extraconal block, it is acceptable to enter at the
classic point if the needle remains low and parallel to
the orbital floor and is not redirected once inserted.
A large volume of anesthetic injected through a
short needle in this way will often provide a satis-
factory block.
Some practitioners prefer to insert the needle into
the orbit through the inferior conjunctiva instead of
transcutaneously as described above. This is an ac-
ceptable technique, especially since the conjunctiva
can be anesthetized with topical anesthetic, which
avoids the need to inject a skin wheal. Transconjunc-
tival injection can be difficult for some patients,
however, especially for those who are very protective,
have short palpebral fissures, or have exceptionally
deep-set eyes. In these patients, the transcutaneous
approach may be easier and perhaps safer.
The block technique described above should be
contrasted with the classic technique that has been
taught, practiced, and described in the literature
[17]. In the older technique, the needle enters more
medially, as has been mentioned, and is redirected
to be aimed toward the apex of the orbit when it is
an inch or so into the orbit. It is during this redi-
rection of the needle, especially in patients with long
eyes (26–27 mm or longer), that perforation of the
globe probably occurs. Perforation is less likely to
occur if the needle is inserted further away from
the globe, not aimed at the apex, and not redirected.
In the apex, structures are tightly packed together,
and a long needle aggressively aimed in that di-
rection has a real chance of causing a major com-
plication. The complication rate is, in fact, relatively
low, but it could be even lower with the use of im-
proved techniques.
Extraconal block
After 10 min, the patient’s eye should be evalu-
ated for movement. When significant movement
occurs, it is most often medial, torsional, or superior.
If there is a lot of movement, it may be wise to re-
peat the inferotemporal, intraconal injection, which is
often necessary in patients with large orbits. If there is
less movement, a supplement in the medial canthal
extraconal space is recommended. The purpose of
this injection is to deposit anesthetic into the fat-filled
space between the medial rectus muscle and the
medial orbital wall (see Fig. 1). Anesthetics placed
here flow unimpeded into the posteromedial aspect of
the intraconal space as well as into the posterosu-
perior extraconal space. This block, described by
Hustead and colleagues [18], is preferred by some for
the primary block. For this procedure, a 25-gauge,
1-in needle (some practitioners use a 30-gauge 0.5-in
needle) is inserted into the tunnel that lies between
the caruncle and the medial canthus (Fig. 12). This is
usually painless because of the inferotemporal block.
The needle tip is directed at first toward the medial
wall (Fig. 13). The orbital wall is extremely thin here
and is called the lamina papyracea (paper layer). If
inserted too aggressively, the needle tip ends up in the
ethmoid sinus and after injection the patient will feel
the anesthetic running down the back of the nose and
into the throat. After touching the wall, the needle is
withdrawn slightly (1 mm) and is redirected so that it
can be inserted into the orbit parallel to the medial
wall and the floor (Fig. 14). The needle should be
Fig. 14. The needle has been redirected and inserted into the
fat-filled space medial to the medial rectus. The shaft of the
needle should be parallel to the medial wall and to the floor
of the orbit. No attempt should be made to angle it supe-
riorly or inferiorly. No needle longer than 1 in should be
used, and the shoulder (where hub and shaft meet) of the
needle should not go deeper than the plane of the iris.
Fig. 13. The tip of a 1-in needle is inserted into the tun-
nel until it just touches the periosteum of the medial wall
(lamina papyracea). The tip is then withdrawn just 1–2 mm,
and the needle is redirected.
fanning230
aimed straight posteriorly to stay in the fat-filled,
avascular space medial to the medial rectus muscle. A
needle longer than 1 inch should never be used here,
because the optic canal lies directly posterior and can
be impacted by overly aggressive insertion. The
shoulder (where the hub and shaft join) of a 1-in
needle should not go deeper than the plane of the iris.
The bevel of the needle during insertion should face
the orbital wall to keep the tip of the needle away
from the wall. It is not unusual to see the globe move
medially and then move back to neutral gaze during
insertion of the needle. This is because the needle will
pass through the medial check ligament, and, in some
patients, the globe will turn. Properly placed, how-
ever, the needle is safely medial to the globe in
spite of the movement. After aspirating, 2–5 mL is
injected while the globe is frequently palpated to in-
sure that excessive pressure does not develop. The
orbital compression device is reapplied for another
5–10 min. It is rare to have to give more than one
supplement and then only when absolute akinesia is
required. As mentioned, some practitioners use this
approach for their primary block, inject up to 10 mL,
and are happy with their results.
An alternative approach to the medial canthal
block has been suggested by Jacques Ripart and his
colleagues in Nimes, France [19,20]. Instead of in-
serting the needle in front of the caruncle, they insert
it between the caruncle and the globe. The globe turns
severely medially during insertion and then pops
suddenly back to neutral gaze as the needle goes back
further. They have promoted this technique as a way
of entering the sub-Tenon’s space, which they un-
doubtedly do when short needles (0.5 in) are used. If
longer needles are used, the needle probably enters
the medial canthal space [21]. Ripart and colleagues
have reported excellent results with their blocks, and
their technique should be respected and considered.
Block mixtures
A variety of anesthetic agents are acceptable for
performing orbital regional anesthesia; they range
from 1% lidocaine for short procedures that do not
require complete akinesia to 0.75% bupivacaine for
long procedures that do. The higher concentrations of
local anesthetics are known to be significantly myo-
toxic in laboratory investigations [7,8] and may be
so in selected patients [22]. They will certainly be
toxic if injected directly into a muscle. In addition,
bupivacaine may exhibit significant neurotoxicity
and cardiotoxicity when injected intravascularly.
Although 4% lidocaine has been marketed and used
for deep intraconal blocks for many years, some [23]
believe that it is too myotoxic and should be avoided
when doing orbital regional anesthesia. For the most
part, however, the choice of anesthetic agent is only
critical when deciding how long the patient needs to
be anesthetized.
Hyaluronidase has been used for years in orbital
regional anesthesia, perhaps the only regional block
where it has been shown to be beneficial, although
not all investigators agree regarding its effectiveness
[24–26]. Hyaluronidase does slightly speed the on-
set of block and perhaps improves the quality of the
orbital regional anesthesia 231
block, but it also facilitates more rapid diffusion of
the anesthetic bolus within the orbit, which reduces
vitreal pressure during cataract and other intraocular
procedures [27]. In addition, during a recent lack of
hyaluronidase in the commercial market in America,
a rise in extraocular muscle dysfunction was noted in
some institutions [28,29]. Lack of the agent may have
caused high concentrations of anesthetic to remain
close to a muscle for a longer period, which resulted
in toxicity, although such a mechanism is hypotheti-
cal. Nonetheless, the question remains as to whether
or not myotoxicity is seen more frequently when
hyaluronidase is not added to orbital block mixtures.
The amount of hyaluronidase needed has been
the subject of clinical investigations. Many practi-
tioners use large amounts of the agent: 150 units per
5–10 mL of anesthetic mixture (15–30 units per mL).
A study from Finland [30] showed that a mixture
containing 3.5 units per mL is quite effective. This
author has used 1 unit per mL for many years
[31]. Hyaluronidase is also an expensive agent and
150 units is more than sufficient for a dozen patients,
a significant savings compared with giving 150 units
to each patient.
The use of epinephrine in the block mixture is
controversial. Some believe that it is dangerous and
results in retinal vascular problems [23,32]. High
concentrations (�1:200,000) are to be avoided and it
should probably not be used for patients who have
known severe, generalized peripheral vascular dis-
ease. The reasons to add epinephrine are to prolong
the block and to improve its quality. In the author’s
experience, small quantities of epinephrine (1:300,000
or 1:400,000 concentrations) have not resulted in
retinal vascular problems in over 22,000 patients and
have added significant duration to the block. Epi-
nephrine, however, is not absolutely necessary to
obtain a good block, and high concentrations should
not be used.
Summary
Orbital regional anesthesia is a useful and safe
modality to provide excellent operating conditions for
the surgeon and painless, pleasant circumstances for
the patient. It is especially suited for patients who are
extremely sensitive and who could not tolerate topi-
cal anesthesia or a sub-Tenon’s block without deep
sedation. Both intraconal and extraconal techniques
can be used safely and effectively if proper precau-
tions are taken to enter the safest areas of the orbit in
order to avoid the vascular areas and the deep orbit
where structures are tightly packed and thus more
easily harmed. Thorough knowledge of orbital anat-
omy and understanding of the globe-orbit relation-
ship of every patient are necessary to perform this
form of regional anesthesia. In addition, knowledge
of the effects and side effects of the anesthetics and
adjuvants is also required.
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Ophthalmol Clin N
Choosing Anesthesia for Cataract Surgery
Joselito S. Navaleza, MDa, Sagun J. Pendse, MDa, Mark H. Blecher, MDb,TaWills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA
bCataract and Primary Eye Care Service, Wills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA
Advances in cataract surgery techniques have pre-
sented surgeons with new options for ocular anes-
thesia. As cataract removal has become faster, safer,
and less traumatic, the need for akinesia and anes-
thesia has declined significantly. The use of general
anesthesia or retrobulbar block has largely been re-
placed with other safer and equally effective means of
local anesthesia, including peribulbar, sub-Tenon’s,
and topical. These newer and less invasive methods
have not only reduced the potential for catastrophic
surgical complications, but also increased the effi-
ciency of cataract surgery and hastened the process of
visual rehabilitation. Today there are numerous modes
of anesthesia from which a surgeon can choose. There
is not one type of anesthesia right for all cases. The
best choice varies from surgeon to surgeon, and pa-
tient to patient. The goal of this article is to review
the current choices for ocular anesthesia, compare
their efficacies, and provide a framework, helping to
select the most appropriate type of anesthesia for
each patient.
Although general anesthesia was first used in
surgery in 1846 by William Morton, it was not used
for cataract surgery until 1954 [1]. Retrobulbar block
was first described in 1884 by Knapp who injected
4% cocaine before enucleation surgery [2]. The mod-
ern technique used by most ophthalmologists today
was described by Atkinson in 1948, and until re-
cently served as the most commonly used technique
for intraocular surgery [3]. Davis and Mandel are
credited with introducing the peribulbar block in
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.001
T Corresponding author. Cataract and Primary Eye Care
Service, Wills Eye Hospital, 840 Walnut Street, Philadel-
phia, PA 19107.
E-mail address: [email protected] (M.H. Blecher).
1986 as a less dangerous alternative to retrobulbar
anesthesia [4].
The decision between retrobulbar anesthesia and
peribulbar anesthesia presents the surgeon with a
choice between speed and safety. With a retrobulbar
block a surgeon can ensure that adequate akinesia and
anesthesia will result for cataract surgery; however, a
blind injection into the orbit poses several potential
complications, including, but not limited to retro-
bulbar hemorrhage, globe perforation, optic nerve
damage, and brainstem anesthesia. Peribulbar anes-
thesia, involving the injection of local anesthetic
external to the muscle cone, is thought to decrease the
likelihood of optic nerve and globe perforation while
maintaining the desirable qualities of excellent
akinesia and anesthesia. However, the potential need
for reinjection, the higher volume of injectate re-
quired, and the longer duration of onset associated
with peribulbar blocks may make it a less attractive
alternative. In a prospective, randomized controlled
trial involving 100 patients undergoing elective cata-
ract surgery, Whitsett and colleagues compared retro-
bulbar anesthesia with one injection site peribulbar
anesthesia [5]. They evaluated the two methods based
on three criteria that were considered critical to in-
traocular surgery: lid akinesia, globe akinesia, and
ocular anesthesia. Following administration of the
block, an independent observer rated each of these.
The authors concluded that one injection site peri-
bulbar anesthesia appeared to have a similar range
of efficacy in all three categories as compared with
standard retrobulbar anesthesia. There were no
anesthetic-related complications in either group.
As documented by Leaming [6] in his annual
surveys of ASCRS members, the current trend for
cataract surgery has shifted away from retrobulbar
and peribulbar anesthesia toward topical anesthesia.
Am 19 (2006) 233 – 237
reserved.
ophthalmology.theclinics.com
navaleza et al234
Karl Koller was the first to describe the use of
cocaine as a topical anesthetic for ocular surgery
in 1884 [7]. Topical anesthesia, however, did not
gain popularity until recently when it was reintro-
duced in the early 1990s by groups that used topical
medications. Subsequently, topical anesthesia was
modified by Gills and colleagues in 1997 with the
introduction of nonpreserved intracameral lidocaine
[8,9] and by Barequet et al [10] with the introduction
of lidocaine gel.
Given the recent trend toward the use of topical
anesthesia, perhaps of more significance would be
a comparison of retrobulbar and topical anesthesia
for cataract surgery. In 1993, Kershner evaluated
100 patents undergoing cataract surgery with topical
anesthesia and concluded that topical anesthesia was
safe, decreased complication rates, and hastened
patients’ return to normal vision [11]. However, the
following year, however, Fukasaku and Marron
[12] compared topical and retrobulbar anesthesia
and found that patients had unacceptable amounts of
intraoperative pain with the topical technique and
abandoned its use altogether. They, however, did not
mention the use of preoperative counseling or IV
sedation. Patel and collegaues completed a random-
ized controlled trial comparing the clinical efficacy of
retrobulbar versus topical anesthesia in patients
undergoing temporal clear corneal cataract extraction
[13]. Patients were given IV sedation (Midazolam)
in this study. They used a visual pain analog scale to
evaluate patient discomfort preoperatively, intraop-
eratively, and postoperatively, and concluded that the
degree to which patients experience pain is only
marginally higher for the topical group during the
administration of the anesthetic, intraoperatively, and
postoperatively. There was no statistically significant
difference in pain scores (P=.35). They also con-
cluded that no statistically significant (P=.5) differ-
ence in operative conditions were experienced by the
surgeon because of lack of globe akinesia. The im-
portance of careful patient selection with regard to
patient anxiety and cooperation was emphasized.
In a follow-up study by Crandall and colleagues,
the efficacy of topical anesthesia with and without
intracameral lidocaine was assessed [14]. In this
study no intravenous sedation was used. The authors
found that there was no statistically significant
difference in patients’ assessments of pain preopera-
tively, intraoperatively or postoperatively between
those who received intracameral lidocaine and those
in the control group. There did exist, however, a
statistically significant difference in patients’ percep-
tion of tissue handling (P=.021). This outcome
measure did not incorporate pain, but rather the
sensation that the eye or surrounding tissue is being
manipulated. Of perhaps greatest importance was the
finding of a statistically significant difference in the
surgeon’s assessment of patient cooperation (P = .043)
between the two groups. Those patients who received
intracameral lidocaine more readily followed sur-
geon commands. It was postulated that this ability
to cooperate was a result of the patient being less
bothered by tissue manipulation. The authors argue
that this finding alone justifies the use of intracameral
lidocaine to enhance topical anesthesia given the
importance of patient cooperation to successful topi-
cal cataract surgery. And to take the current trend
of less anesthesia to its most absolute, Pandey and
associates compared no anesthesia to topical and
topical with intracameral and found that for a highly
experienced surgeon, with a carefully selected patient
population, the pain scores for all three groups were
the same. The only difference was the discomfort
level of the surgeon [15].
In the most recent published study of the practice
styles and preferences of ASCRS members [6], it was
found that retrobulbar block without facial block was
used by 11% of surgeons and retrobulbar injection
with facial block by 9% (down from 76% in 1985,
32% in 1995, and 14% in 2000). The peribulbar
block was used by 17% of surgeons (down from
38% in 1995). Topical anesthesia was used by 61%
(up from 8% in 1995 and 51% in 2000). Of those
surgeons electing to use topical, 73% of surgeons also
used concomitant intracameral lidocaine. The use of
topical also varied with surgical volume. Those per-
forming 1 to 5 cataract procedures per month used
topical 38% of the time and those doing more than
75 procedures used it in 76% of cases. Clearly the
trend has been to transition from retrobulbar anes-
thesia to topical, and this pattern parallels the increase
in the use of temporal clear corneal incisions.
Given the choices for ocular anesthesia today, one
thing remains clear: no single mode of anesthesia can
serve as a universal choice for all patients and all
surgeons. The literature reveals that each of the major
modes of ocular anesthesia—retrobulbar, peribulbar,
and topical—are essentially equally effective in con-
trolling patient pain and allowing a surgeon to have
a successful surgical outcome. The decision to choose
one of these methods ultimately falls on the surgeon,
and the surgeon should carefully tailor his or her
approach to each individual patient. The decision of
which type of anesthesia to use is not only dependent
on a number of patient factors, but is also dependent
on the surgeon and the surgeon’s level of expertise
and facility with the surgery to be performed. With
this in mind, we present a short discussion that
choosing anesthesia for cataract surgery 235
addresses the decisions involved in choosing the
mode of anesthesia best suited for each patient.
The ideal surgery is conducted under the safest
conditions, is cost- and time-efficient, and ultimately
results in excellent outcomes as well as patient sat-
isfaction. These are our goals with regard to the use
of anesthesia for cataract surgery as well. We group
anesthesia into three categories: general, regional
(retrobulbar, peribulbar, and sub-Tenon’s), and topical
(with and without intraocular anesthetics).
Risks and benefits
General anesthesia provides excellent anesthesia,
analgesia, and akinesia. In addition, the duration of
anesthesia can be varied to accommodate the length
of surgery. This provides the most controlled environ-
ment for surgery and may result in fewer ocular
complications and, ultimately, a satisfied patient.
Systemic risks include malignant hyperthermia,
hemodynamic fluctuation, postoperative nausea and
vomiting, and allergic reactions. There may also be
increased risk of cardiac complications under general
anesthesia. In 1980, Backer and colleagues [16]
published a study suggesting elderly patients with a
history of myocardial infarction were at a higher risk
for another myocardial infarction under general
anesthesia. Lang [17] did not find similar results in
their review of 15,000 cases between 1977 and 1979
comparing regional with general anesthesia. There
was one death in each group and the only two myo-
cardial infarctions occurred in the regional group.
Lynch and colleagues [18] found similar rates of
mortality and major complications including vitreous
loss with general and regional anesthesia in 2217
consecutive patients. Ocular complications such as
intraocular pressure fluctuation, Valsalva retinopathy,
corneal abrasions, and chemical injury also occur
more frequently.
General anesthesia requires more medication,
equipment, and personnel than topical anesthesia.
As a result, it is the most costly form of anesthesia.
The time required for induction, intubation, and ex-
tubation also contributes to its inefficiency. Modern
health care, where time and cost efficiency are sig-
nificant factors, renders general anesthesia unlikely
for the bulk of cataract surgeries.
Regional anesthesia also provides excellent anes-
thesia, analgesia, and akinesia. The duration of effect
varies with the anesthetic mixture used but can easily
last for most cataract surgeries. While the eye is not
able to move, the patient may still move, as a result, it
is not quite as controlled as general anesthesia. The
cost of the medications and equipment are much less
than with general anesthesia. Injections themselves take
very little time, making this method more time and cost
efficient than general anesthesia. There are systemic
risks such as allergic reactions, brainstem anesthesia,
and oculocardiac reflex. In addition, the complications
of a blind injection into the orbit present additional
risks discussed earlier. The incidence of retrobulbar
hemorrhage has been reported as low as 0.44% of cases
[19], up to 3% of cases [20]. Peribulbar anesthesia,
involving the injection of local anesthetic external to
the muscle cone, is thought to decrease the likelihood
of optic nerve and globe perforation while maintaining
the desirable qualities of excellent akinesia and
anesthesia. However, the higher volume of injectate
required and the longer duration of onset may make it a
less attractive alternative. Sub-Tenon’s injections with
blunt cannulas have an even lower risk of local
complications [21]. With all orbital block anesthesia,
cosmetic complications such as localized swelling,
bruising, and subconjuctival hemorrhage may lead to
reduced patient satisfaction. In addition, eye movement
and vision are affected for some time after surgery.
Topical anesthesia is the most cost and time
efficient. Topical does not affect vision or motility, so
patients may have improved and useful vision almost
immediately after surgery. There are also minimal
cosmetic changes. As a result, if patients have no pain
or discomfort during surgery, patient satisfaction may
be improved. Topical also avoids the systemic risks
of general anesthesia and the risk of local trauma that
occurs with regional blocks. Rare local allergic reac-
tions do occur. The disadvantage to topical anesthesia
is that it provides the least controlled environment for
cataract surgery. Patients are able to move their eyes
as well as any other part of their bodies. They per-
ceive visual phenomena as the case proceeds. Pain
and pressure may be experienced with intraocular
pressure changes as the lens– iris diaphragm move.
These sensations may be reduced with intravenous
sedation or analgesia, maneuvers such as entering the
eye with low bottle height, or with the use of intra-
cameral anesthetics [22]. However, even with all of
the above, patients may still experience some dis-
comfort. In addition, the duration of anesthetic effect
is typically less than an hour. Even in uncomplicated
cases there may be a loss of effect by the end of a case.
Choosing anesthesia
It is essential that the surgeon, patient, and
anesthesia staff work together and be involved in
navaleza et al236
the selection and execution of anesthesia during the
surgery. Involving the patient in this decision by
describing the patient experience before and during
surgery is critical. Fear and anxiety result when things
are unknown or unexpected. If patients are prepared,
they are better equipped to cope with the sensations
they may feel during and after surgery. Anesthesia
staff, whether a physician or nurse anesthetist should
also be involved and know the patient. Modulation
of intravenous sedation can play a key role during
surgery. Increasing sedation as needed during surgery
can reduce discomfort, provide akinesia, and ulti-
mately may result in some amnesia that can result in
better outcomes. This may be particularly important
with topical anesthesia, and the degree of intravenous
sedation may vary widely from surgeon to surgeon,
and from case to case.
Some of the indications for general anesthesia for
cataract surgery include pediatric patients, patients
who are unable to cooperate, lengthy procedures
(> 3 hours), and patient or surgeon preference. Most
surgery in children is performed under general anes-
thesia. Patients with psychiatric disorders, dementia,
tremor, and inability to lie flat are at risk to move
or even attempt to sit up during surgery. Longer pro-
cedures may exceed the duration of action of regional
blocks; some complex anterior segment surgeries
such as suturing lenses can take hours in some hands.
Patients may ultimately feel that they will not be able
to cooperate during surgery and request general anes-
thesia. Finally, the surgeon may choose general an-
esthesia for certain patients. Again, general does
provide the most controlled environment. This may
be ideal for the beginning surgeon. In teaching
institutions, it would also allow the attending surgeon
and the resident surgeon to communicate more freely
during surgery.
General and topical anesthesia should also be
considered in patients on anticoagulation treatment;
general is preferable when complete ocular akinesia is
desired. Patients with nystagmus may not be able to
fixate and ocular akinesia can only be attained with
regional or general anesthesia. Anatomic abnormali-
ties such as an abnormally long axial length may
make topical or general anesthesia a safer alternative.
There are patients in which general anesthesia is
contraindicated or should be undertaken with caution.
Myotonic dystrophy patients develop cataracts at a
younger age; these patients are at risk of cardiac and
respiratory complications under general anesthesia
[23,24]. Marfan’s patients are subject to lens sub-
luxation and dislocation; they are also at increased
risk of cardiac and pulmonary complications under
general anesthesia [25,26]. Other modes of anesthesia
should be considered in patients with a family his-
tory of malignant hypertension. Thorough review
of medications is necessary, because some ocular
medications may interfere with general anesthesia.
Topical epinephrine used to treat glaucoma may
interact with halogenated hydrocarbon anesthetics
leading to ventricular fibrillation [27]. Echothiophate,
which in the past was used to treat glaucoma, inhibits
plasma pseudocholinesterase, which also metabolizes
anesthetics including succinylcholine leading to over-
dosing [28].
Regional blocks provide some benefit over topical
for patients who are unable to follow directions, such
as when the patient is hearing impaired or there is a
language barrier. It obviously does not prevent patient
movement. The ocular akinesia and longer duration of
effect make it a more ideal mode of anesthesia in cases
in which the primary surgeon is a physician in training.
Topical anesthesia provides the least controlled
environment for cataract surgery. The surgeon must
be able to tolerate some ocular motility, the patient
should be able to follow directions, and the anesthe-
sia staff must be willing to modulate intravenous
sedation. Topical has the shortest duration of action.
If the surgeon anticipates that he or she can complete
the case in a reasonable time frame and the other
conditions are met, topical anesthesia may ultimately
be the safest mode of anesthesia as it avoids the
systemic risks of general anesthesia and the risk of
local trauma that accompanies regional blocks. For
many patients and surgeons this mode of anesthe-
sia fulfills all of the goals of anesthesia in cataract
surgery. This is perhaps the reason that it has become
the most popular form of anesthesia.
It seems every few years we further perfect the
cataract operation. We make it safer, faster, better, and
more atraumatic. And just when we think we cannot
improve it any more, we do. Hand in hand with our
evolving surgical technique has come concepts in
ocular anesthesia that bring these surgical advances to
our patients in the safest and most efficient manner.
While it seems unbelievable that we can further re-
duce the stress of cataract surgery and cataract sur-
gery anesthesia any further, our history should tell
us otherwise.
References
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Ophthalmol Clin N
Anesthesia Considerations for Vitreoretinal Surgery
Steve Charles, MDa,b,T, Gary L. Fanning, MDc
aUniversity of Tennessee, College of Medicine, 6401 Poplar Avenue, Suite 190, Charles Retina Institute,
Memphis, TN 38119, USAbColumbia University, New York, NY, USA
cHauser-Ross Eye Institute, 2240 Gateway Drive, Sycamore, IL 60178, USA
Regardless of the type of anesthesia contemplated
for vitreoretinal (VR) surgery, the patient should
undergo a thorough preoperative evaluation before
the procedure. Under most circumstances this eval-
uation should occur well before the day of surgery so
that required adjustments can be performed in ad-
vance to help ensure that the patient is in optimal
condition before surgery. Specific investigations, such
as chest radiography, electrocardiogram, and blood
chemistries, should be performed only when dic-
tated by the findings of thorough history and physical
examinations. So-called ‘‘screening labs’’ are not in-
dicated when the appropriate history and physical
examinations are negative [1].
General versus local anesthesia
Both general and local anesthetic techniques are
acceptable for VR surgery; however, many retinal
surgeons prefer to do the vast majority of these cases
using monitored local anesthesia for the following
reasons: (1) local anesthesia offers increased safety
for patients, especially those in high-risk categories;
(2) local anesthesia saves time and reduces cost; and
(3) local anesthesia provides rapid recovery and pro-
longed analgesia, both of which are especially im-
portant in the outpatient population.
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.002
T Corresponding author. University of Tennessee, Col-
lege of Medicine, 6401 Poplar Avenue, Suite 190, Charles
Retina Institute, Memphis, TN 38119.
E-mail address: [email protected] (S. Charles).
Not all patients are appropriate candidates for VR
surgery under local anesthesia. Immature, mentally
deficient, claustrophobic, and uncooperative patients
are best managed with general anesthesia. Patients
with language barriers, however, can frequently be
managed extremely well with local anesthesia if a
competent translator can be found. Estimated surgical
time is an additional consideration when choosing
general versus local anesthesia. Surgeons requiring
more than 90minutes for a given VR procedure should
consider general anesthesia over local anesthesia,
because patients may become restless and uncomfort-
able when asked to lie completely still for such long
periods. An additional indication for general anesthesia
is the patient who insists on it, although these patients
will be rare if properly informed and reassured by a
sympathetic surgical team.
Monitoring during surgery
Regardless of the type of anesthesia used, the
patient must be carefully monitored during surgery.
Appropriate monitoring begins with the continuous
presence of an anesthesiologist or certified registered
nurse anesthetist (CRNA) during the entire proce-
dure. If sedation is being given, it is not in the pa-
tient’s best interest to have the surgeon or circulating
nurse monitoring the patient, as may be the case in
a brief procedure performed under strictly local
anesthesia without sedation. Basic monitoring in-
cludes continuous electrocardiogram, noninvasive
blood pressure (NIBP), and pulse oximetry. End-tidal
CO2 monitoring is additionally essential during
Am 19 (2006) 239 – 243
reserved.
ophthalmology.theclinics.com
charles & fanning240
general anesthesia and can also be helpful during
local anesthesia, especially when continuous sedation
techniques are used. Core temperature monitoring is
indicated during longer procedures under general
anesthesia to help ensure that thermal preservation
procedures are successful and to help in monitoring
for the rare occurrence of malignant hyperthermia.
In diabetic patients, the ability to monitor blood
glucose in the intra- and perioperative periods is also
important to recognize and treat extremes of both
hyper-and hypoglycemia.
Blood pressure considerations during general
anesthesia
It is common for VR surgeons to become
angry if the patient moves at all during surgery. An
unintended consequence of this tendency is for the
anesthesia provider to maintain deeper levels of
anesthesia to prevent movements, which may result
in systemic blood pressures that are low enough to
compromise cerebral, myocardial, and retinal perfu-
sion. During VR surgery, intraocular pressure (IOP)
should be controlled in the 35-45 mm Hg range.
Ocular ischemia and central retinal artery occlusion
can occur if low systemic blood pressures are allowed
to persist during the procedure. To ensure adequate
levels of general anesthesia and immobility of the
patient, adequate, monitored muscular paralysis com-
bined with processed electroencephalogram (ie, bi-
spectral analysis) monitoring should be considered
so that excessively deep levels of general anesthesia
can be avoided.
Sedation during local anesthesia
In general, patients having VR surgery under local
anesthesia should have minimal sedation, most of
which should be given at the time of the block.
Patients should not be sedated too deeply during VR
surgery for a number of reasons. In the first place,
airway obstruction may occur, requiring manual
support and interruption of the procedure. This has
been described as AWAC (anesthesia without airway
control). Second, respiratory movements during sleep
or near sleep often result in magnified movements of
the head, which greatly hinder the progress of the
surgeon who is seeing these movements magnified
20 to 40 times through the operating microscope.
Third, some patients become quite talkative and social
when overly sedated. It may be impossible for them to
quit talking and moving despite the most vigorous
admonitions to do so. The only way to manage these
patients is to stop all sedation completely or to convert
to general anesthesia. Finally, patients who are asleep
or nearly asleep are prone to awakening suddenly
and completely unpredictably and being totally
disoriented, resulting in movements that can be devas-
tating, even in the hands of the finest surgeon.
Judicious amounts of sedatives or opioid agents can
be helpful during local anesthesia for VR surgery,
especially in the patient who is very apprehensive
or slightly claustrophobic. Methohexital, thiopental,
midazolam, propofol, alfentanil, remifentanil, keta-
mine, and others have been promoted to provide good
operating conditions and acceptable patient satisfac-
tion for a variety of procedures performed under lo-
cal anesthesia. For VR surgery, the emphasis must be
placed on balancing patient comfort and satisfaction
while providing the most stable conditions for surgery.
In general this means using small doses of rapid- and
short-acting drugs given continuously with very care-
ful monitoring of effect. The goals are to assist the
patient in lying perfectly still for 60 to 90 minutes
without falling asleep, to enhance analgesia, and to
provide a measure of amnesia. These goals are not
easily achieved, but they can be accomplished in most
patients by an experienced and knowledgeable anes-
thesia team.
Psychological preparation for local anesthesia
In preparing patients for VR surgery under some
form of local anesthesia, it is important to give them
specific details about the experience so that they will
suffer no surprises. They need to know about the
drape and about not being able to see during the
procedure. They also need to know that plenty of fresh
air will be provided for them under the drape and that
breathing under the drape will not be a problem. This
is the perfect opportunity to discuss the patient’s fears,
such as claustrophobia, positional dyspnea, positional
pain, and similar concerns. One may discover during
these discussions that a particular patient might be
better managed with general anesthesia.
The patient should also be given a realistic es-
timate of the length of time for the procedure and the
need for lying extremely still. Almost anyone can lie
still for 30 to 45 minutes, but for longer procedures
the patient must be reassured that short ‘‘time outs’’
can be arranged to allow for some movement.
Patients must also be aware that an anesthesia
provider will be constantly present and dedicated to
monitoring their condition and to act as liaison with
the rest of the team. It is extremely important for the
anesthesia considerations for vitreoretinal surgery 241
anesthesia provider and surgeon to communicate
freely during the procedure, both with each other
and with the patient. Simple means for communica-
tion with minimal movement, such as hand-holding
or hand-held signaling devices, give the patient a
feeling of comfort in knowing that it is possible to
alert the team to a problem while not jeopardizing the
surgical field. If the patient cannot speak English, it
is imperative to have a translator in the room who
is fluent in the patient’s native language.
Choice of local anesthesia
There are essentially four types of local anesthesia
commonly used in ophthalmic surgery: topical, retro-
bulbar, peribulbar, and sub-Tenon’s. Topical anesthe-
sia is useful in a variety of operations, but it has
limitations in VR surgery because of the need for
complete akinesia during many VR procedures, such
as macular surgery and membrane peeling. The terms
retrobulbar and peribulbar are confusing and impre-
cise, and they should perhaps be replaced by the
terms intraconal and extraconal, which more accu-
rately describe the intended location of the needle in
the orbit. These techniques carry a risk, albeit small,
of major complications, such as ocular perforation,
bleeding, and brainstem anesthesia, but both are very
useful for VR surgery, providing excellent akinesia,
anesthesia, and prolonged postoperative analgesia.
Sub-Tenon’s anesthesia offers an increased level
of safety over intraconal and extraconal techniques.
Sub-Tenon’s may not be appropriate for patients who
have had previous scleral buckling, as scleral per-
foration with a sub-Tenon’s cannula has been re-
ported in such a patient [2]. A recent report by Lai
et al [3] compared the use of orbital regional anes-
thesia with sub-Tenon’s anesthesia for retinal surgery
and found that both had similar efficacy profiles.
Technique for intraconal anesthesia
A 25- or preferably a 27-gauge sharp needle is
preferred over larger needles and blunt so-called
‘‘retrobulbar’’ needles, which cause much more pain
when entering the orbit. [4] In addition, retrobulbar
needles often penetrate the septum abruptly after
considerable force is applied and may then perforate
the eye. The conventional 1.5-inch needle is too long
for many orbits and should be replaced by a 1- to
1.25-inch needle to avoid impaling the optic nerve in
the orbital apex. The entry point should be at the
outer ‘‘corner’’ of the orbital rim, not at the outer one
third, inner two thirds junction to reduce potential
damage to the eye and inferior oblique muscle. The
needle should not be directed apically but rather
posteromedially to intersect a sagittal plane through
the lateral limbus about 5 to 10 mm behind the pos-
terior surface of the eye [4]. The authors use 2% plain
lidocaine without epinephrine to reduce the risk of
arrhythmias and hypertension and avoid using bicar-
bonate because of reports and personal experience
with lateral rectus paralysis for months after surgery.
The author recommends applying pressure on the
entire orbit with the palm of the hand immediately
after withdrawing the needle to reduce bleeding and
disperse the anesthetic agent. If hyaluronidase is used
in the block mixture, its concentration should be
limited to 1 unit per milliliter, as higher concentra-
tions are not necessary [5].
Reblocking during the procedure
Sometimes local anesthesia must be supplemented
during surgery. This can occasionally be accomplished
with topical anesthesia, but we most commonly
supplement intraoperatively by placing a flexible
cannula into Tenon’s space and injecting additional
local anesthetic. An additional intraconal injection can
also be performed by placing the needle between
Tenon’s capsule and the sclera to enter the intraconal
space. Most often reblocking is necessary when the
block has been inadequate, when the patient is a
reoperation, and when the procedure is prolonged.
Facial nerve blocks
Separate facial nerve blocks are rarely indicated,
especially if a well-performed extraconal or high-
volume intraconal block is used. Avoiding a facial
nerve block spares the patient a painful injection and
prevents the bleeding, swelling, and other complica-
tions that occasionally accompany these blocks. If the
patient is a marked ‘‘squeezer,’’ the orbicularis oculi
can be easily and effectively blocked by inserting a
one-half-inch 30-gauge needle transconjunctivally
into the lower lid just beneath the orbicularis and
injecting about 1.5 mL of local anesthetic.
Sources of pain during VR surgery
Local anesthesia needs to be quite complete if the
experience is to be pain-free. Manipulation of the iris,
ciliary body, and sclera can all be painful, especially
charles & fanning242
if blunt instruments are being used. Thermal stim-
ulation is also an important source of discomfort.
Cryopexy is very painful, more so than laser or even
radiofrequency cautery (bipolar diathermy). Lasers in
the near-infrared range are more painful than the ar-
gon laser at 514 nm or the diode-pumped, frequency-
doubled CW YAG laser at 532 nm. As one or
more of these modalities may be used during VR sur-
gery, it is important that the patient receives ade-
quate anesthesia.
Carbon dioxide issues
Patients lying awake under the drape frequently
complain that they ‘‘cannot get enough air.’’ Because
pulse oximetry routinely records normal oxygen
saturation in these patients, their complaints are
frequently attributed to anxiety. In fact, CO2 often
builds up under the drape, resulting in hypercarbia
and a feeling of air hunger. This may be noted by a
rise in the baseline if capnography is being used,
even though the peak expired CO2 may be normal
or only slightly elevated. An easy solution to this
problem is to ensure adequate air/oxygen supplemen-
tation near the patient’s nose and mouth as well as
active evacuation of the exhaled gases by way of a
large bore vacuum line placed under the drapes. The
vacuum line also facilitates cooling, which can be an
issue as well. If laser or electrocautery are to be
used, it is important to use only air under the drape to
avoid the dangers of fires attended by an oxygen-
enriched atmosphere.
Air/gas and general anesthesia
If gas or air are introduced into the eye during VR
surgery, nitrous oxide should be turned off at least
10 minutes beforehand and fresh gas flow into the
anesthesia machine should be increased to ensure
adequate washing out before introduction of the gas.
Failure to do so results in a smaller-than-desired gas
bubble within the eye and lower-than-desired IOP
postoperatively when nitrous oxide diffuses out of the
bubble. Conversely, if a patient has a bubble in the
eye from a previous procedure, nitrous oxide should
be avoided from the beginning to prevent expansion
of the bubble by diffusion of nitrous oxide into it,
thus raising IOP. In fact, patients must be warned
both verbally and in writing to alert physicians to the
presence of the bubble should they require emergency
surgery for a nonophthalmic condition and of the
dangers of air travel for as long as the bubble is
present [6].
Anesthetic considerations for specific procedures
Endophthalmitis
Endophthalmitis is an acute situation in which
cultures must be taken and therapy instituted as
quickly as possible. In many situations, cultures and
even core vitrectomy can be performed under topical
anesthesia. If general anesthesia is required, surgery
cannot be delayed to allow the stomach to empty.
The open globe
Each patient must be thoroughly evaluated, as
choice of anesthesia will depend on the extent of the
injury and the ability of the patient to cooperate.
Often initial wound closure can be accomplished
under topical and intracameral anesthesia. In cooper-
ative patients with limited damage, orbital regional
anesthesia can be safely used [7], provided that the
person performing the block has had sufficient
experience, uses limited volumes of anesthetic, and
injects very slowly (ie, 1 mL every 30 to 60 seconds)
while closely watching the eye. When general
anesthesia is required, the issue of whether or not to
use a depolarizing muscle relaxant arises. Because
there are advocates on both sides of this issue, the
choice must be left to the anesthesia provider who
will make a decision based on the total clinical pic-
ture. If general anesthesia is required, allowing suf-
ficient time (6 to 8 hours) for the stomach to empty
should be seriously considered.
Scleral buckles
Many presenting for scleral buckling procedures
will be high myopes. These patients have long axial
lengths, often accompanied by posterior staphylomata
and scleral thinning. Sub-Tenon’s cannula techniques
might be considered in these patients to lessen the
risk of perforation, provided that long cannulae ap-
proaching the posterior half of the globe are avoided.
Regional anesthesia for scleral buckling proce-
dures may be complicated by the fact that the orbital
retractor can cause significant orbital rim pain even in
the presence of complete ocular anesthesia. Addi-
tionally, with traction of the extraocular muscles the
oculocardiac reflex may occur. Most commonly the
resulting bradycardia will return to normal when
traction is released, and the reflex will diminish over
anesthesia considerations for vitreoretinal surgery 243
time. Intravenous atropine is more effective than gly-
copyrrolate in blocking the reflex, but its use is as-
sociated with the higher incidence of subsequent
tachyarrhythmias. Local anesthetic injection may
block the bradycardia, but the reflex is also seen in
the presence of a complete block.
Patients who have had previous scleral buckles
and present for another procedure may be difficult to
block. Because the buckling may slightly elongate
the eye, one must be aware of an increased danger
for perforation. Because scarring occurs, normally
‘‘safe’’ procedures may be come less safe, and ocular
perforation has been reported with sub-Tenon’s anes-
thesia in a patient with a previous scleral buckle [2].
Anticoagulation issues
In our practice we virtually never stop anti-
coagulation before VR surgery, although it is wise
to ensure that the patient taking warfarin compounds
has an International Normalized Ratio in the thera-
peutic range (generally 2 to 3). Stopping anticoagu-
lants risks causing morbidity or mortality from a
variety of causes, including stroke, myocardial in-
farction, pulmonary embolism, and deep venous
thrombosis. In our opinions the dangers of intra-
operative hemorrhage are grossly overemphasized
when compared with the dangers of stopping thera-
peutic anticoagulation. Use of cannula techniques for
local anesthesia greatly reduces the risk of hemor-
rhage in these patients, as does the use of short
needles (1 to 1.25 inches) placed in the less vascular
areas of the orbit (ie, avoiding the superior half of
the orbit in general and especially the superonasal
quadrant) for orbital blocks.
Postoperative pain
One source of postoperative pain is the injection
of antibiotics and steroids into the periocular tissues
at the end of the procedure. This pain can be reduced
by injecting these substances into the sub-Tenon’s
space with a cannula if conjunctival incisions have
been made, which is not the case with 25-gauge,
sutureless surgery. In addition, injection of a long-
acting local anesthetic, such as bupivacaine, at the
end of the procedure with a flexible cannula can
greatly reduce postoperative pain. This is especially
important in the occasional patient who requires
general anesthesia for VR surgery and those under-
going scleral buckles.
Summary
The vast majority of VR procedures can be safely,
comfortably, and efficiently performed under local
anesthesia with minimal sedation. Compared with
general anesthesia, properly performed monitored
local anesthesia offers the patient an increased level
of safety, reduced recovery times, and prolonged
postoperative pain relief. Nonetheless, the choice of
anesthesia technique must be based on the needs of
the patient, the requirements of the surgeon, and the
skills of the anesthesia provider, ever keeping in mind
that our ultimate goal is a satisfied patient with a good
visual outcome.
References
[1] Schein OD, Katz J, Bass EB, et al. The value of routine
preoperative medical testing before cataract surgery.
Study of medical testing for cataract surgery. N Engl J
Med 2000;342:168–75.
[2] Frieman BJ, Friedberg MA. Globe perforation asso-
ciated with subtenon’s anesthesia. Am J Ophthalmol
2001;131:520–1.
[3] Lai MM, Lai JC, Lee WH, et al. Comparison of retro-
bulbar and sub-Tenon’s capsule injection of local anes-
thetic in vitreoretinal surgery. Ophthalmology 2005;112:
574–9.
[4] Kumar CM, Fanning GL. Orbital regional anaesthesia.
In: Kumar CM, Dodds C, Fanning GL, editors. Oph-
thalmic anaesthesia. Lisse (The Netherlands)7 Swets &
Zeitlinger B.V.; 2002. p. 61–88.
[5] Fanning GL. Hyaluronidase in ophthalmic anesthesia
[letter]. Anesth Analg 2001;92:560.
[6] Seaberg RR, FreemanWR, GoldbaumMH, et al. Perma-
nent postoperative vision loss associated with expansion
of intraocular gas in the presence of a nitrous oxide-
containing anesthetic. Anesthesiology 2002;97:1309–10.
[7] Scott IU, Gayer S, Voo I, et al. Regional anesthesia with
monitored anesthesia care for surgical repair of selected
open globe injuries. Ophthalmic Surg Lasers Imagining
2005;36:122–8.
Ophthalmol Clin N
Anesthesia for Glaucoma Surgery
Tom Eke, MA (Cantab), MD, FRCOphth
Norfolk & Norwich University Hospitals NHS Trust, Colney Lane, Norwich NR4 7UY, UK
Glaucoma surgery can be done using any of
the established anesthesia techniques. Each technique
has its advantages and disadvantages, as outlined in
Tables 1 and 2. Retrobulbar and peribulbar injections
are particularly associated with the risk of sight-
threatening and life-threatening complications, in any
patient. Glaucoma patients may be at increased risk of
sight-threatening complications from orbital injec-
tions because the optic nerve is already compromised
and vulnerable to pressure/ischemic damage (Table 3).
Therefore, there has been much interest in the less
invasive techniques of local anesthesia for glaucoma
patients, with anterior placement of local anesthesia
(anterior sub-Tenon, subconjunctival, topical, and
intracameral techniques) [1]. These ‘‘newer’’ tech-
niques appear to be successful in terms of safety and
patient acceptability. However, there is some uncer-
tainty regarding the effect of different anesthesia
techniques on complication and failure rates for
glaucoma surgery.
Factors influencing the choice of anesthesia
In planning any ocular surgery, it is appropriate to
ask ‘‘which is the most appropriate anesthetic, for this
operation, for this patient?’’ Numerous factors must
be considered, including nature of the operation to be
done; efficacy of the various anesthetic techniques;
acceptability to both patient and surgeon; safety is-
sues (ocular, orbital, and systemic complications of
anesthesia or per-operative and later surgical compli-
cations associated with each anesthetic technique);
demand on staff, hospital beds, and other resources;
speed, efficiency, and throughput of patients in the
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.003
E-mail address: [email protected]
operating room; and financial issues (Tables 1 and 2).
The patient’s general health may influence the choice
of anesthesia, particularly the choice between general
anesthesia (GA) and local anesthesia (LA). Ocular
conditions themselves may also influence the choice
of anesthetic technique, and this is especially true in
the case of glaucoma (Table 3). Glaucoma is a
chronic condition characterized by progressive pres-
sure/ischemic damage to the optic nerve head, so it
would be logical to choose an anesthetic technique
that has a low risk of causing further damage to the
optic nerve. It is common for glaucoma patients to
require filtering surgery (eg, trabeculectomy) and
also cataract surgery, and many eyes with glaucoma
will require two or more operations. Therefore, the
long-term functioning of any previous or future
filtering surgery should also be considered when
deciding on the appropriate anesthesia technique for a
glaucoma patient.
In this article, the issues specific to glaucoma
patients are discussed. Other articles have discussed
the generic problems associated with each of the
LA techniques, which can be briefly summarized as
sight-threatening complications, life-threatening com-
plications, and surgical complications related to the
LA technique used (Table 2). General anesthesia has
the potential for various life-threatening complica-
tions, as discussed in any textbook of anesthesia.
Table 3 summarizes the concerns related to anesthesia
and glaucoma surgery, and the relative merits and
demerits of the various anesthesia techniques.
Optic nerve damage from anesthesia
If anesthetic agents are placed into the orbit be-
hind the globe, there is potential for damage to the
optic nerve. This damage could occur as a result of
Am 19 (2006) 245 – 255
reserved.
ophthalmology.theclinics.com
Table 1
Factors influencing the choice of anesthesia technique for
any ocular surgery
Operation
to be done
How much of the eye/orbit needs to
be anesthetised?
Is total akinesia needed?
Any specific anesthetic requirements
for this operation? (see Tables 2, 3)
Patient factors
and comorbidity
General (eg, child; adult with very
poor general health)
Ocular (eg, glaucoma (see Table 3),
severe nystagmus)
Acceptability
of technique
To patient
To surgeon
To managers/providers
Use of
resources
Efficiency
Staff (eg, anesthetist, trained
assistants)
Hospital accommodation (eg, beds for
GA patients)
Back-up facilities required (eg, cardiac
arrest team, intensive care)
Cost (consumables, staffing costs, and
so forth)
Time taken per case
Number of cases done per operating
list
Safety Ocular/orbital complications of
LA/GA technique
Systemic complications of LA/GA
technique
Surgical complications related to
LA/GA technique
Late complications related to LA/GA
technique
Abbreviations: GA, general anesthesia; LA, local anesthesia.
eke246
direct trauma from a retrobulbar or peribulbar needle,
pressure on the nerve, or ischemia [2]. Potential
mechanisms are summarized in Table 3. For patients
whose optic nerve is already damaged by glaucoma,
this could result in further loss of vision.
The phenomenon of severe visual loss after sur-
gery, with no obvious cause, is known as ‘‘wipe-out’’
or ‘‘snuff syndrome.’’ Wipe-out is generally seen in
patients who already have a severe glaucomatous
visual field defect [3,4]. Local anesthetic injections
into the orbit have been postulated as a likely cause
for many cases of wipe-out [4]. Possible mechanisms
include unnoticed trauma to the optic nerve from the
anesthetic needle, or pressure on the optic nerve
owing to either a hematoma in the optic nerve sheath,
a retrobulbar hematoma, or simply from the volume
of anesthetic injected. High pressure around the nerve
could potentially occur even with a low volume of
LA, if the LAwere to become trapped between fascial
layers to give a ‘‘compartment syndrome.’’ This pres-
sure may also induce ischemia of the nerve, as may
epinephrine (adrenaline) in the LA mixture. While the
term ‘‘wipe-out’’ is reserved for severe loss of vision
after surgery, glaucoma patients are also at risk of
suffering a milder form of this condition.
There is a wealth of indirect evidence to support
the concept of orbital LA as a cause for wipe-out
syndrome. There have been numerous case-reports of
visual loss as a result of direct needle trauma to the
optic nerve, or secondary to high orbital pressure
from LA-induced orbital hemorrhage [2]. In a series
of 3 cases of hyaluronidase-associated orbitopathy,
the most severe and long-lasting visual loss occurred
in the one patient who had glaucoma [5]. Doppler
imaging studies have shown that retrobulbar injec-
tions can cause a marked reduction in blood flow
in the arteries supplying the anterior optic nerve,
particularly if epinephrine is included in the LA
mixture [6,7]. This effect is not seen with anterior
placement of LA, for example by subconjunctival
anesthesia [8]. A retrospective study of 508 trabecu-
lectomies identified four cases of wipe-out, all of
which had retrobulbar anesthesia [3].
The problems described above could potentially
occur with retrobulbar, peribulbar, or posterior sub-
Tenon’s LA. It would be very difficult to prove a
definite association between LA technique and wipe-
out or increasing field defects, because of difficulties
in case definition, the rarity of the condition, and the
problems encountered with any large randomized
prospective trial. However, the high index of suspi-
cion means that many glaucoma specialists now try to
avoid using these LA techniques for any surgery on
glaucoma patients [1]. Preferred techniques are GA,
anterior sub-Tenon’s, subconjunctival, topical, and
intracameral anesthesia. Small case-series indicate
that these techniques are acceptable to patients and
surgeons, but data are lacking as regards long-term
pressure control, complications, and visual field.
Effect of LA on the conjunctiva, and outcome of
filtering surgery
Conjunctival scarring, as a result of previous sur-
gery or topical medication, may significantly increase
the risk of trabeculectomy failure [9,10]. These
insults initiate an inflammatory response in the con-
junctiva and Tenon’s capsule, making a trabeculec-
tomy more likely to fail because of further scarring.
It would be logical to infer that any LA technique
that induces chemosis or subconjunctival hemorrhage
could increase the risk for failure for any future
trabeculectomy. Chemosis and hemorrhage are fre-
Table 2
Safety factors to be considered when choosing an anesthesia technique for any patient undergoing intraocular surgery, and relative risk of each anaesthesia technique
General anesthesia
(GA)
Peribulbar local
anesthesia (LA)
Retrobulbar
LA
Sub-Tenon’s
LA
Subconjunctival
LA
Topical
LA
Topical-intracameral
LA
Sight-threatening
complications
Globe penetration or perforation � ++ ++ +/� + � �Optic nerve penetration or perforation � ++ ++ � � � �Severe orbital hemorrhage � ++ ++ +/� � � �Hyaluronidase orbitopathy � + + + � � �
Life-threatening
complications
Brainstem anesthesia � ++ ++ � � � �Oculo-cardiac reflex + �? �? �? +? +? +?
Other life-threatening adverse event ++ � � � � � �See text for fuller discussion.
Abbreviations: ++, significant potential risk of sight-threatening or life-threatening adverse event; +, lower potential risk; +/�, this adverse event is very rare with this technique, or
theoretical risk only; �, ‘no risk’ of this event occurring.
anesthesiaforglaucomasurgery
247
Table 3
Additional safety concerns for the glaucoma patient when choosing anesthesia techniques for ocular surgery, and relative risk for each anesthesia technique
General
anesthesia
Peribulbar local
anesthesia (LA)
Retrobulbar
LA
Sub-Tenon’s
LA
Sub-conjunctival
LA
Topical
LA
Topical-intracameral
LA
Avoid risk of
further damage
to optic nerve
Direct trauma Inadvertent trauma from
LA needle
� ++ ++ � � � �
Pressure damage Volume effect of periocular LA � ++ + +/� � � �‘compartment syndrome’
(esp. if no hyaluronidase)
� + + +/� � � �
Hyaluronidase orbitopathy � + + + � � �Severe orbital haemorrhage � ++ ++ +/� � � �
Ischemic damage Pressure (see above) � ++ ++ +/� � � �Epinephrine � + + + � � �Systemic hypotension ++ � � � � � �
Consider functioning
of filtering surgery
Future filter Induction of conjunctival
scarring
� +/� +/� +? +? � �
Previous filter Re-activation of conjunctival
scarring
� +/� +/� +? +? � �
Filtering surgery
today
Induced scarring? (controversial,
see text)
� �? �? �? +? �? � �
See text for fuller discussion, and see also Table 2.
Abbreviations: ++, significant potential risk of sight-threatening adverse event; +, lower potential risk; +/�, very rare, or theoretical risk only; �, ‘no risk’ of this event occurring.
eke
248
anesthesia for glaucoma surgery 249
quently seen with peribulbar, retrobulbar, and sub-
Tenon’s injections [2], particularly if the sub-Tenon’s
injection is more anterior or of larger volume [11].
For this reason, many glaucoma specialists prefer to
avoid these LA techniques for any surgery in patients
who may need filtering surgery in the future.
Some studies have suggested that the outcome of
trabeculectomy surgery itself may be influenced by
the anesthetic technique used, although published evi-
dence is inadequate at present. Observational studies
have suggested that subconjunctival LA may be
associated with an increased risk of bleb failure or
leakage, although there is no definite evidence to sup-
port this and some of the evidence is contradictory.
Noureddin and colleagues [12] published a study
that appeared to show a link between subconjunctival
anesthesia and thin-walled, leaking trabeculectomy
blebs. In a retrospective, nonrandomized observa-
tional study, they looked at 29 patients who had under-
gone trabeculectomy with GA approximately 1 year
previously, and compared them with 19 patients who
had LA with 2 mL of subconjunctival 2% lidocaine.
Intraocular pressure (IOP) control was good in both
groups, with better IOP in the subconjunctival anes-
thesia group. However, the incidence of thin-walled,
leaky (Seidel-positive) blebs was higher, at 77% in
the subconjunctival lidocaine group as opposed to
25% in the GA group. Leaky blebs are undesirable,
because they predispose the eye to bleb-related infec-
tion and potential blindness. The authors postulated
that lidocaine might have an inhibitory effect
on fibroblasts.
Edmunds and colleagues [13–16] found a possi-
ble link between subconjunctival anesthesia and poor
IOP control, although they did not report any
problems with late bleb leakage. They performed a
large prospective observational study of routine prac-
tice, which looked at 1450 primary trabeculectomies
performed by 382 surgeons [13]. ‘‘Success’’ was de-
fined as a one-third reduction in IOP, without the use
of antiglaucoma medications. At 1 year, ‘‘success’’
rate was 65.6% for the 555 peribulbar LA cases,
69.5% for the 424 GA cases, 65.7% for the 105 ret-
robulbar LA cases, 69.0% for the 59 sub-Tenon’s
cases, 39.5% for the 38 subconjunctival LA cases,
and 100% for the 6 topical LA cases. Multiple lo-
gistic regression compared ‘‘success’’ rates for sub-
conjunctival and peribulbar LA, and indicated an odds
ratio of 0.172 (95% confidence interval: 0.065–0.459,
P<.0001) [16], suggesting that subconjunctival anes-
thesia is associated with worse surgical outcome.
There was no further detail on the number of surgeons
who did the 38 cases (possibly as few as 10 surgeons),
or the specific techniques used for subconjunctival
LA. The authors speculated that subconjunctival LA
could possibly stimulate conjunctival fibroblasts or
cause hemorrhage, thus predisposing to a higher
failure rate. They concluded that the association
deserved further examination, and suggested a pro-
spective randomized trial of the type of LA in
trabeculectomy [16]. Edmunds and colleagues’ series
appears to have a much lower rate of bleb leak than
Noureddin and colleagues’. The actual rate of bleb
leakage at 1 year is not given, although the paper
implies that the overall rate was below 3% [15]. In
another study, Vicary and colleagues [17] looked at
1-year outcomes for phaco-trabeculectomy using
small volume (0.1- to 0.2-mL) subconjunctival 2%
lidocaine with epinephrine: IOP control was described
as ‘‘excellent,’’ with 72% of patients requiring no
glaucoma medication at 1 year. Thus, there appears to
be no agreement between these studies that looked at
anesthesia technique and trabeculectomy outcomes.
Each of these studies is observational in nature with
small numbers of subconjunctival anesthesia cases, so
these results should be interpreted with caution. In a
recent clinical audit, my colleagues and I looked at
results of primary trabeculectomy, using the same
criteria as Edmunds and colleagues’ study. We looked
retrospectively at the 1-year outcomes for two glau-
coma surgeons at the same institution, one of whom
routinely used peribulbar anesthesia, the other sub-
conjunctival lidocaine 0.5% (Rai C et al, submitted for
publication). Both techniques showed 1-year ‘‘suc-
cess’’ rates that were better than Edmunds’ series.
There was no bleb leakage at 1 year, but the
subconjunctival anesthesia group did appear to have
a higher rate of early leakage. We will be conducting a
prospective audit to see if this is a genuine phenome-
non, or simply reflects a higher degree of concern
about bleb leakage in patients who have had subcon-
junctival anesthesia.
There is some evidence that subconjunctival lido-
caine may indeed have an inhibitory effect on con-
junctival healing, as suggested by Noureddin and
coworkers. Studies on other tissues have found a
dose-dependent effect of lidocaine on wound
strength. The tensile strength of skin wounds has
been studied, following infiltration of the wound with
lidocaine 2%, 1%, 0.5%, and saline. Wound strength
was the same when 0.5% lidocaine or saline was
used, but 1% and 2% lidocaine gave significantly
weaker wounds [18,19]. Lidocaine 1% infiltration
was associated with decreased vascularity and fewer
collagen fibers, when compared with saline [18].
These findings could possibly explain Noureddin
and colleague’s high rate of bleb leakage with large
volumes (2 mL) of strong (2%) lidocaine [12]. It may
eke250
be that lidocaine exhibits a dose-dependent inhibi-
tory effect on conjunctival healing, analogous to
the antimetabolites.
Data on specific LA techniques
Since the early 1990s, there have been numerous
papers describing ‘‘less invasive’’ LA techniques for
glaucoma surgery. Most have been either case-series
or small randomized trials of a few dozen patients.
Numerous techniques have been described, mainly
for trabeculectomy or combined cataract and tra-
beculectomy (phaco-trabeculectomy) surgery. They
include various methods of administering topical,
subconjunctival, anterior sub-Tenon’s, and intra-
cameral anesthesia. Most publications concentrate on
per-operative complication rates and acceptability to
patient and surgeon.
Studies on patient/surgeon acceptability should be
interpreted with caution, because it is difficult to
avoid bias. Even in prospective randomized studies,
both patient and surgeon are likely to be aware
whether they are using a periocular injection or one of
the ‘‘newer’’ techniques. This lack of masking may
influence acceptability scores. It is best if pain/
acceptability data are collected by an independent
person, who is unaware of the LA technique used and
without the presence of the surgeon or other person-
nel connected with the surgery. This means that pain
scores collected at the time of surgery may be biased
by the patient not wanting to displease the surgical
team, and pain scores collected after surgery may be
subject to recall bias. Most or all published studies
show good acceptability to the surgeon, but this may
simply reflect that the authors want to prove the
effectiveness of their favored technique, and tend to
recruit surgeons who feel likewise. In addition,
there is publication bias in that unfavorable studies
are less likely to be submitted and published. Despite
these caveats, it does appear that the ‘‘newer’’ LA
techniques are acceptable to most patients, and to
many surgeons.
The current literature should be considered in-
adequate, for several reasons. Terminology is not
consistent, with some authors using the terms ‘‘sub-
conjunctival’’ and ‘‘sub-Tenon’s’’ for what appears to
be the same technique, and others creating new terms
for minor variations on established techniques (peri-
limbal, contact, and so forth). Most of the safety
concerns outlined in Tables 2 and 3 cannot be ad-
dressed by these small studies, although it is possible
to infer from the larger studies of cataract patients that
these ‘‘newer’’ techniques ought to be safer than pe-
riocular injections [20,21]. Most studies have looked
at LA for trabeculectomy, with very few studies
looking at other glaucoma procedures such as cyclo-
ablation, glaucoma drainage devices, or nonpenetrat-
ing surgery. There is no direct evidence regarding the
possible effect of LA technique on the visual field, as
discussed in the section ‘‘Optic nerve damage from
anesthesia.’’ There is a definite need for studies that
look at success rates for filtering surgery and late
complication rates.
Subconjunctival anesthesia and anterior
sub-Tenon’s anesthesia
These two techniques will be considered together,
because of confusing use of terminology in the
glaucoma literature. In the literature related to cata-
ract surgery, there is a clear difference between the
two techniques, but the terms ‘‘sub-conjunctival’’ and
‘‘sub-Tenon’s’’ appear to be used interchangeably by
some authors in the glaucoma literature.
Both techniques were popularized by publications
in the early 1990s. Sub-Tenon’s LA for cataract
surgery was described by several authors, all of
whom used similar techniques [22–24]. A small cut
is made through conjunctiva and Tenon’s capsule, so
that a blunt cannula can be passed into the sub-
Tenon’s space, between Tenon’s capsule and sclera.
The LA agent can easily reach the back of the globe,
even with an anterior injection [25], and chemosis is
unlikely if small volumes are injected posteriorly via
a long cannula [11]. By contrast, subconjunctival LA
[26,27] is administered by means of a sharp needle,
the aim being to infiltrate the conjunctiva/Tenon’s
layer with the anesthetic agent. Therefore, subcon-
junctival LA will always induce chemosis in the area
where the LA is injected, and the LA is not expected
to reach the back of the globe. A sharp-needle sub-
Tenon’s (episcleral) LA technique has been described
[28], although some have raised concerns about the
risk of globe penetration by the needle. Many of
the descriptions of ‘‘sub-Tenon’s’’ anesthesia in the
glaucoma literature would be more accurately de-
scribed as ‘‘sub-conjunctival’’ anesthesia.
Ritch and Liebmann [29] were among the earliest
to describe this technique for glaucoma surgery. Their
original report was entitled ‘‘Sub-Tenon’s anesthesia
for trabeculectomy,’’ although they later referred to it
as a ‘‘subconjunctival’’ technique [30]. They used a
lid block, topical tetracaine, and then injected about
1 mL of 2% lidocaine or 2% mepivacaine via a
anesthesia for glaucoma surgery 251
30-gauge needle, ‘‘beneath Tenon’s capsule over the
anterior portion of the superior rectus muscle,’’ with
smaller injections over the medial and lateral recti.
They wrote that ‘‘concerns regarding sensation
during iridectomy have proven to be unfounded,
and only rarely do patients complain of pain at
the time.’’
Buys and Trope [31] used a similar technique to
that of Ritch and Liebmann, and performed a
prospective randomized comparison with retrobulbar
anesthesia. All 39 patients had sedation using a
standard technique. Pain scores collected during and
after surgery were similar, and ‘‘creation of an
iridectomy was not associated with discomfort or a
response in the sub-Tenon’s group.’’ The ‘‘sub-
Tenon’s’’ group was less likely to require additional
LA during surgery (9% versus 60%), or analgesia
after surgery (32% versus 71%), and these differences
were both statistically significant.
Azuara-Blanco and colleagues [32] reported a
prospective randomized trial of ‘‘sub-conjunctival
versus peribulbar anesthesia in trabeculectomy.’’ All
patients had intravenous sedation and a facial nerve
block, using an identical technique. The LA agent
was the same for the 30 peribulbar and 30 subcon-
junctival injections (2% mepivacaine with 0.75%
bupivacaine), except for the omission of hyaluroni-
dase from the subconjunctival group. Subconjuncti-
val injections were given in the supero-temporal
quadrant, 8 to 10 mm posterior to the limbus, ‘‘bal-
looning the superior conjunctiva.’’ During surgery,
patients were asked to grade their pain as none, mild,
moderate, or severe. There was a low pain score for
both groups, with all episodes of pain (20% in the
subconjunctival group and 7% in the peribulbar
group) rated as mild. This difference did not reach
statistical significance. The authors concluded that
their technique was well tolerated, although ‘‘mild
intra-operative discomfort and eye movements should
be expected.’’
Anderson [33] described a modification of the
subconjunctival LA technique, which he called
‘‘circumferential perilimbal anesthesia.’’ A small in-
jection of 0.25 mL lidocaine 4% was injected through
the inferior conjunctiva, ‘‘to avoid the possibility of a
button-hole in the superior conjunctiva.’’ The anes-
thetic was then spread subconjunctivally around the
limbus for 360 degrees, using smooth forceps. All pa-
tients were sedated, and 1 of 34 phaco-trabeculectomy
patients complained of pain during surgery.
Vicary and colleagues [17] looked at surgical
outcomes 1 year after phaco-trabeculectomy using
subconjunctival anesthesia. They used topical lido-
caine 4% and a small volume (0.1 to 0.2 mL) of
subconjunctival 2% lidocaine with 1:200,000 epi-
nephrine. Charts were reviewed retrospectively for 38
consecutive cases. At 1 year, 72% of patients had
‘‘controlled IOP without additional medication’’ and
overall IOP control was described as ‘‘excellent.’’
Bleb leak is not mentioned.
Bellucci and colleagues [34] described a ‘‘true’’
sub-Tenon’s anesthesia technique for phaco-
trabeculectomy. A conjunctival limbal incision was
commenced as for a standard fornix-based trabecu-
lectomy using topical lidocaine 4% anesthesia. A
plastic cannula was then passed into the sub-Tenon’s
space near to the superior rectus, to inject 1.5 mL of
mepivacaine 2%. Retrospective review of 50 cases
showed that only one patient required supplementary
sub-Tenon’s anesthesia, and the per-operative and
early complication rates were similar to a cohort of
50 patients who had peribulbar anesthesia.
Kansal and colleagues [35] describe a similar
technique in which ‘‘true’’ sub-Tenon’s anesthesia is
augmented with intracameral anesthesia. This is
discussed in the ‘‘Combined LA techniques’’ section
later in this article.
Topical anesthesia techniques
Several studies have described using topical
anesthesia for trabeculectomy, with or without the
use of sedation. Techniques include LA drops alone,
application of LA in gel form, or via an applicator
made of spongelike material. Topical anesthesia may
be combined with any of the other LA techniques
discussed below.
Jonas [36] describes using topical oxybuprocaine
0.4% (Benoxinate) eyedrops, followed by topical
cocaine 10%, for all of his routine trabeculectomy
surgery. Patients are instructed to gaze in the desired
direction, so that superior rectus or corneal traction
sutures are not used. An earlier study compared this
technique with retrobulbar anesthesia in a prospective
randomized study of 20 patients [37]. Intravenous
infusion was set up, but the authors do not state
whether the patients had any sedation. Pain scores
were similarly low in both groups, and none of the
topical anesthesia patients thought that the surgery
was more painful than having the intravenous needle
put into the back of their hand. In a subsequent series
of 69 consecutive cases, there were no per-operative
complications that could be attributed to a mobile
eye, and ‘‘when asked which type of anesthesia they
would prefer if the same type of surgery would have
to be repeated, the patients answered they preferred
topical anesthesia’’ [36].
eke252
Ahmed and colleagues published randomized
trials comparing topical bupivacaine drops with
retrobulbar anesthesia, for trabeculectomy [38] and
for phaco-trabeculectomy [39]. All patients were se-
dated. Different sedative agents were used for each
group and pain scores were collected postoperatively,
therefore the results are difficult to interpret. The
authors felt that both techniques were similarly well
tolerated by patients.
Pablo and colleagues [40] described a technique of
‘‘contact-topical’’ LA for trabeculectomy. An absorb-
able gelatin sponge was soaked in lidocaine 2%
solution, and inserted into the superior fornix for
5 minutes before surgery. Intravenous sedation was
given ‘‘as required,’’ and the technique was compared
with peribulbar LA in a randomized trial of 100 cases.
Pain scores and use of sedation were similarly low in
both groups.
Lai and colleagues [41] looked at using 2% lido-
caine gel without sedation. They prospectively eval-
uated 22 consecutive cases of phaco-trabeculectomy,
all of whom had surgery under topical anesthesia
without sedation. Lidocaine 2% gel was applied to
the conjunctival fornices for 5 minutes before sur-
gery. They looked at patients’ pulse rate and blood
pressure, and per-operative pain scores were recorded
immediately after surgery. Using a pain scale of 0 to
10, mean reported pain was 0.9, with a range of 0 to
3, and only three patients reported having pain
or discomfort during surgery. They concluded that
the technique provided adequate analgesia for
the surgery.
Carrillo and colleagues [42] reported a prospec-
tive randomized trial comparing topical lidocaine 2%
gel with ‘‘sub-Tenon’s’’ LA for trabeculectomy. As
discussed in the previous section, the LA technique
for the control group would be described as ‘‘sub-
conjunctival’’ by some other authors. All 59 cases
received a standardized sedative, and the ‘‘topical’’
group received about 1 mL of nonpreserved lidocaine
2% gel to the conjunctival fornices 5 minutes before
surgery commenced. The control group LA was
similar to the ‘‘sub-conjunctival’’ technique described
by Azuara-Blanco and colleagues [32] (see previous
section). Mean pain scores (recorded postoperatively)
and surgeon satisfaction scores were similar in the
two groups. Supplemental anesthesia (as determined
by the surgeon) was required in 4 of the 29 sub-
Tenon’s cases, and none of the lidocaine gel cases.
The authors concluded that topical 2% lidocaine gel
was ‘‘as effective’’ as the sub-Tenon’s (subconjunc-
tival) technique.
Lidocaine 2% gel has also been used for implan-
tation of glaucoma drainage devices. Rebolleda and
colleagues [43] describe using lidocaine 2% gel
without sedation for implanting Ahmed valves. In a
prospective randomized trial, the technique was com-
pared with retrobulbar anesthesia. Pain scores were
similarly low, although surgical times were longer in
the topical group and the authors concluded that
lidocaine 2% gel offered ‘‘a reasonably safe and
comfortable surgical environment’’ for experienced
surgeons and selected patients.
Topical-intracameral anesthesia
Rebolleda and colleagues [44] described topical-
intracameral LA for phaco-trabeculectomy. Tetracaine-
oxybuprocaine drops were supplemented with 1%
nonpreserved intracameral lidocaine; sedation was
not used. The technique was compared with retro-
bulbar anesthesia in a prospective randomized study
of 60 patients. Pain scores were significantly higher in
the topical-intracameral group, in that 93% of the
topical-intracameral anesthesia patients required fur-
ther LA in the form of extra drops or application of a
sponge soaked in 1% lidocaine. By contrast, only
17% of the retrobulbar LA group needed any addi-
tional LA. Pain scores showed that discomfort was
rated as none/mild by 67% of the topical group and
93% of the retrobulbar group. Four patients had
retrobulbar anesthesia for their first eye and topical-
intracameral for the second; three of these pa-
tients stated that they preferred topical-intracameral
anesthesia. The authors concluded that, despite
the higher levels of per-operative discomfort, the
technique was well tolerated and ‘‘provides a safe
and comfortable surgical environment for experi-
enced surgeons.’’
Pablo and colleagues [45] described a technique
of ‘‘contact-topical plus intracameral’’ LA for phaco-
trabeculectomy. An absorbable gelatin sponge was
soaked in lidocaine 2% and inserted into the superior
fornix for 5 minutes before surgery, and intracameral
lidocaine 1% was used for phaco-emulsification. No
sedation was used. In a prospective trial, 80 patients
were randomized to topical-intracameral or peribul-
bar LA. During surgery, there were no significant
differences in vital signs, patients’ pain evaluation, or
surgeon stress.
If intracameral anesthesia is used for trabecu-
lectomy surgery, it may cause the pupil to dilate in
many patients [46]. This may make it difficult
to do the peripheral iridectomy, but the phe-
nomenon can be prevented by using pilocarpine
drops preoperatively.
anesthesia for glaucoma surgery 253
Combined LA techniques
Kansal and colleagues [35] described a combined
sub-Tenon’s (subconjunctival), topical, and intracam-
eral LA with intravenous sedation. The technique,
referred to as ‘‘blitz’’ anesthesia, involved topical
bupivacaine or mepivacaine, intracameral 1% lido-
caine, and a sub-Tenon’s injection of 1% lidocaine
via a 30-gauge needle (for limbus-based filters) or
via a cannula in fornix-based filters. Acceptability was
assessed in a prospective series of 139 consecutive
cases of trabeculectomy, phaco-trabeculectomy, and
aqueous shunt surgery. Results were compared with a
parallel case-series of 139 patients who had similar
surgery by different surgeons using retrobulbar
anesthesia and sedation. Pain scores were similarly
low in both groups, with no intraoperative complica-
tions. The authors concluded that the technique was
‘‘a safe and effective alternative to retrobulbar
anesthesia’’ for glaucoma surgery.
This author’s favored technique for trabecu-
lectomy surgery is a combined subconjunctival-
intracameral anesthesia without sedation (Burnett
and Eke, submitted for publication). After instilling
topical oxybuprocaine or tetracaine, around 0.5 mL
of 0.5% lidocaine is infiltrated subconjunctivally in
the area of the proposed drainage bleb. The bleb of
anesthetic is then massaged (through the lid), so that
it covers the entire surgical area. Additional tetracaine
drops are instilled onto the sclera before cautery, and
intracameral 0.5% lidocaine is used before the
peripheral iridectomy. Patients’ acceptability is good,
with low pain scores for the surgery. Average pain
scores for surgery are lower than the average pain
scores for removing the sticky surgical drape at the
end of the procedure. When asked, all patients stated
they would have the same LA technique again if
further surgery was required.
Summary
While glaucoma surgery can be done using any of
the established anesthesia techniques, many glau-
coma specialists prefer to avoid using retro-ocular
injections (peribulbar, retrobulbar, posterior sub-
Tenon’s) for their glaucoma patients. Peribulbar and
retrobulbar injections can have sight-threatening or
life-threatening complications in any patient (Table 2),
and glaucoma patients may be at further risk of vision
loss because of more subtle pressure/ischemic effects
of LA injected around the optic nerve (Table 3). For
this reason, anterior application of LA agents has
become popular, using combinations of topical, sub-
conjunctival, anterior sub-Tenon’s, and intracameral
LA. These ‘‘newer’’ LA techniques should avoid the
potential for optic nerve damage, and they have been
shown to be acceptable to patients and surgeons.
However, there have been some concerns regarding
long-term outcomes of trabeculectomy surgery, par-
ticularly with subconjunctival anesthesia. There is
little evidence in the literature regarding this, and
further research is needed.
The author’s personal practice is to use LA with-
out sedation for virtually all patients. Filtering sur-
gery is performed using a combined subconjunctival/
intracameral technique, with 0.5% nonpreserved lido-
caine as described in ‘‘Combined LA techniques.’’
Cyclo-ablation (cyclo-diode laser) is performed using
a small volume posterior sub-Tenon’s LA. Cata-
ract surgery is performed using topical-intracameral
LA and a clear-corneal incision. This approach is
designed to give a good balance of safety and pa-
tient acceptability.
The doctor-patient relationship is particularly im-
portant in glaucoma. Treatment goals are, first,
lifelong maintenance of normal vision, and second,
freedom from concern regarding eyes and vision. A
painful operation could result in a breakdown in trust
between the patient and his or her ophthalmologist,
so it is important to use an appropriate mode of
anesthesia for each individual patient. Preopera-
tive counseling should therefore include an expla-
nation of the degree of awareness that the patient
should expect.
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Ophthalmol Clin N
Oculoplastic and Orbital Surgery
Adam J. Cohen, MDT
Eyelid and Facial Aesthetic and Reconstructive Surgery, Craniofacial Surgery, Elmhurst Hospital, Elmhurst, IL 60126, USA
Successful surgical outcomes are not based solely
on the knowledge and skill level of a surgeon. Pa-
tient comfort and cooperation along with minimiz-
ing bleeding are paramount to achieving successful
surgical outcomes. Few things in a surgeon’s life
can be more frustrating than a patient who is not
adequately anesthetized and is uncooperative during
an operation.
The majority of oculoplastic and facial surgical
procedures are performed in outpatient settings under
local or regional anesthesia with sedation via oral or
intravenous routes. To achieve maximal patient com-
fort, familiarity with regional neuroanatomy, anes-
thetic agents, and techniques of delivery are salutary.
Because large numbers of these procedures are
performed with an anesthesiologist, this article will
be geared toward delivery of anesthesia from the
surgeon’s standpoint.
Anatomy
Sensory innervation of the craniofacial region is
most easily broken down by the well-recognized der-
matomes [1]. The major sensory innervation of the
face; a large portion of the scalp, teeth, and oral
and nasal regions; and dura mater is the trigeminal or
fifth cranial nerve. This nerve transmits information
on light touch, pain, temperature, and propioception
to the ventral, mid-lateral pons. After leaving its
nucleus the nerve divides into three branches: the
ophthalmic nerve (V1), the maxillary nerve (V2), and
the mandibular nerve (V3) (Fig. 1).
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.016
T 2720 S. Highland Avenue, Lombard, IL 60148.
E-mail address: [email protected]
The ophthalmic nerve (V1) is the smallest branch
of the trigeminal nerve and is a purely sensory nerve.
After traversing the lateral wall of the cavernous sinus
the ophthalmic nerve divides into the lacrimal, fron-
tal, and nasociliary nerves just before entering the
orbit through the superior orbital fissure (Fig. 2).
The lacrimal nerve enters the orbit laterally via
the superior orbital fissure and travels in proximity
to the lacrimal artery to supply the lacrimal gland
and surrounding conjunctiva, terminating in the upper
eyelid septum.
The frontal nerve enters the orbit through the
superior orbital fissure and continues anteriorly. It lies
between the periosteum of the orbital roof and the
levator palpebralis superioris and divides into the
supraorbital and supratrochlear bundles.
The supraorbital branch of the frontal nerve con-
tinues along the orbital roof exiting from the supra-
orbital notch radiating branches to the upper eyelid
and conjunctiva. The supraorbital notch can usually
be palpated at the medial one third of supraorbital
rim. Moving cephalad it ascends with the supraorbital
artery to a level in the vicinity of the lambdoid su-
ture supplying sensation to the forehead and a large
portion of the scalp (Fig. 3). An in-depth study of
this nerve by Knize [2], found two distinct branches
after it exits the supraorbital foramen: a superficial
(medial) branch, which supplies the anterior scalp
margin and forehead skin, and a deep (lateral) branch
supplying the frontoparietal scalp. In addition, this
nerve also supplies the mucosa of the frontal sinus.
The supratrochlear nerve exits the orbit medial to
the supraorbital notch and travels along the frontal
bone to supply the upper eyelid skin and conjunctiva.
Moving superiorly below the corrugator supercilii
and frontalis muscles it terminates to innervate the
glabelar region.
Am 19 (2006) 257 – 267
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ophthalmology.theclinics.com
Fig. 1. The distribution of ophthalmic and maxillary nerves.
The mandibular nerve is not shown because it is usually not
of consequence during oculoplastic procedures. (Courtesy of
Mark R. Levine.)
Fig. 3. Deep branch of supraorbital nerve with artery.
cohen258
The nasociliary branch of the ophthalmic nerve
(V1) enters the orbit through the annulus of Zinn and
travels to the medial orbital wall. Here it enters the
cranium via the anterior ethmoidal foramen and canal
as the anterior ethmoidal nerve. Before entering the
anterior ethmoidal foramen, the infratrochlear nerve
offshoots to supply the skin of the medial canthal
region including the caruncle and nasal skin superior
to the medial canthal tendon along with nasolacrimal
sac. Moving extracranially it then enters the nasal
cavity innervating the mucosa and upper lateral nasal
sidewall terminating as the external nasal nerve to par-
tially supply the skin of nasal columella, ala, and tip.
Before leaving the orbit this nerve provides sev-
eral branches of the long ciliary nerves that supply the
ciliary body, iris, cornea and post-ganglionic sym-
pathetic fibers of the dilator pupillae.
The posterior ethmoidal nerve innervates the mu-
cosa of ethmoidal and sphenoid sinuses.
Fig. 2. The ophthalmic nerve exiting the superior orbital
fissure and its branches. (Courtesy of Mark R. Levine.)
The maxillary nerve (V2) provides sensory neural
branches emanating at four distinct craniofacial sites:
the cranial cavity, pterygopalatine fossa, infraorbital
canal, and face. Because the oculoplastic surgeon
rarely performs intracranial surgery I will limit my
description to the latter three.
At the pterygopalatine fossa the maxillary nerve
gives off the zygomatic nerve, which enters the or-
bit through the inferior orbital fissure. Before leaving
the orbit it divides into the zygomaticotemporal and
zygomaticofacial nerves. Both of these nerves emerge
through their respective foramina with the zygo-
maticotemporal nerve supplying the skin of the tem-
poral region and the zygomaticofacial supplying the
skin of malar region.
Within the infraorbital canal the superior alveolar
nerves (anterior, middle, and posterior) arise before
the infraorbital nerve and its accompanying vessels
exit the infraorbital foramen located approximately
6 mm below the inferior orbital rim and parallel to the
mid-pupillary axis. They supply the lower eyelid and
lateral canthal region; the skin of the nasal sidewall
and anterior portion of its mucosa; the nasal septum;
maxillary sinus; upper gingiva and teeth; and the skin
of the anterior cheek, upper lip, and oral mucosa
(Fig. 4).
The palatine branch of the maxillary nerve is of
importance to the oculoplastic surgeon when harvest-
ing hard palate grafts for eyelid reconstruction.
It should be recognized that there is overlap of
the ophthalmic and maxillary nerve branches in the
medial and lateral canthal regions. This overlap may
explain patients’ discomfort when operating in these
areas after local anesthetic infiltration.
The mandibular nerve (V3), the largest division of
the trigeminal nerve, is composed of a large sensory
and smaller motor root. The sensory branch supplies
Table 1
Commonly used ophthalmic topical anesthetic agents
Anesthetic agent
Available
strengths, %
Duration of
action, min
Proparacaine HCL 0.5 5–20
Tetracaine HCL 0.5–2.0 15–20
Lidocaine HCL 2.0 or 5.0 20–30
Abbreviation: HCL, hydrochloride.
Fig. 4. The infraorbital and zygomaticofacial nerves exiting
the infraorbital and zygomaticofacial foramina respectively.
(Courtesy of Mark R. Levine.)
oculoplastic & orbital surgery 259
the teeth and gums of the mandible, the skin of the
temporal region, the otic auricle, the lower lip, and
the lower part of the face. The smaller motor branch
innervates the muscles of mastication. Branches of
the mandibular nerve pertinent to the oculoplastic and
facial surgeon include the inferior alveolar nerve and
its branch the mental nerve.
The largest branch of the mandibular nerve is the
inferior alveolar nerve. Descending with the inferior
alveolar artery, it passes between the sphenomandib-
ular ligament and the ramus of the mandible into
the mandibular foramen. It then passes forward in
the mandibular canal, beneath the teeth, as far as the
mental foramen, where it divides into two terminal
branches, the incisive and mental nerves.
The mental nerve exits at the mental foramen, and
divides into three branches. These branches provide
sensation to the skin of the chin and the skin and
mucous membrane of the lower lip.
Inferior alveolar nerve injury can occur during a
sagittal split osteotomy while dissections for allo-
plastic chin implantation or mandibular protuberance
reshaping can insult the mental nerves.
The cervical plexus is formed by the anterior
divisions of the upper four cervical nerves. Each
nerve, except the first, divides into an upper and a
lower branch, and the branches unite to form three
loops. These branches are divided into superficial and
deep groups.
The great auricular nerve is the largest of the
superficial ascending branches. It arises from the
second and third cervical nerves and divides into an
anterior and a posterior branch. The anterior branch
supplies the skin of the face over the parotid gland
and communicates in the substance of the gland with
the facial nerve. The posterior branch supplies the
skin over the mastoid process and the posterior au-
ricle, except at its superior most aspect. The posterior
branch communicates with the smaller occipital nerve
and the auricular branch, which also supplies the skin
of the upper and back part of auricle. The poste-
rior branch of the greater auricular nerve can be
damaged during elevation of the retroauricular flap
during rhytidectomy.
Pharmacology
Topical anesthetic agents
Commonly used topical ocular anesthetic agents
include proparacaine hydrochloride, tetracaine hydro-
chloride, and lidocaine hydrochloride jelly. Their side
effects include ocular discomfort before onset of ac-
tion and punctate keratopathy [3] (Table 1).
EMLA (Astra Zeneca Pharmaceuticals, Wilming-
ton, Delaware) (lidocaine 2.5% and prilocaine 2.5%)
and ELA-Max (Ferndale Laboratories, Inc., Ferndale,
Michigan) (4% lidocaine) are topical skin anesthetics.
These creams can lessen the discomfort associated
with needle insertions and superficial cutaneous sur-
gery when applied approximately 15 to 60 minutes
before the procedure. Corneal or conjunctival contact
should be avoided with these agents. Ramos-Zabala
and colleagues [4] reported adequate anesthesia with
EMLA cream and remifentanil during full face la-
ser resurfacing with the Erbium:yttrium-aluminum-
garnet (Er:YAG) laser.
Reducing the temperature of the skin with ice or
cool compresses often provides adequate anesthesia
to reduce discomfort associated with needle insertion
and removal of small acrochordons. Placement of ice
for 5 minutes before injection of botulinum toxin to
the lateral orbital region resulted in a statistically
significant decrease in pain when compared with non-
iced regions [5].
Infiltrative anesthetic agents
Local anesthetic agents are usually of the amino
amide class and have a relatively rapid onset of ac-
tion. Commonly used agents include lidocaine, bupi-
Table 2
Commonly used infiltrative anesthetic agents
Anesthetic agent Onset of action Dosage ceiling Duration of action
Lidocaine Rapid 7.0 mg/kg with EPI 2–4 h with EPI
4.5 mg/kg without EPI 1–2 h without EPI
Bupivacaine Slow 3.0 mg/kg with EPI 8 h with EPI
2.5 mg/kg without EPI 4 h without EPI
Prilocaine Moderate 7.5 mg/kg with EPI 6 h with EPI
5.0 mg/kg without EPI 90 min without EPI
Mepivacaine Rapid 7.0 mg/kg with EPI 6 h with EPI
5.0 mg/kg without EPI 3 h without EPI
Etidocaine Rapid 8.0 mg/kg with EPI 8 h with EPI
6.0 mg/kg without EPI 4 h without EPI
Cocaine Rapid 2.8 mg/kg without EPI 45 min without EPI
Abbreviation: EPI, epinephrine.
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vacaine, prilocaine, mepivacaine, and etidocaine. The
potency, onset, toxicity level, and duration of action
of these agents vary (see Table 2) [6].
Local anesthetic agents of the amino ester class
include procaine, chloroprocaine, cocaine, and tetra-
caine. This class of agents is uncommonly used ex-
cept for cocaine during surgery of the lacrimal system.
Toxicity of infiltrative anesthetics is related to sys-
temic absorption, distribution, and metabolism that
vary considerably among individual compounds and
patients. Infiltrative anesthetic adverse reactions are
almost always the result of an excessively large dose
or oversight of an intravascular injection [7].
Toxic signs and symptoms of local anesthetic are
usually limited to cardiovascular and central nervous
system dysfunction. Cardiac dysfunction is related
to direct myocardial depression, which may lead to
arrthymia, hypotension, and asystole. Intravascular
injection of bupivicaine and etidocaine has been
reported to result in cardiovascular collapse unre-
sponsive to resuscitative attempts [8]. Central ner-
vous system signs and symptoms include circumoral
paresthesias, light-headedness, tinnitus, metallic taste,
auditory or visual hallucinations, dysarthria, nystag-
mus, and tremors. At higher toxicity levels grand
mal seizures, apnea, and loss of consciousness may
result [8].
Allergic reactions may occur with infiltrative
anesthetics [9]. Para–aminobenzoic acid (PABA) is
thought to play a role in hypersensitivity [10]. Be-
cause ester amides produce a PABA metabolite the
incidence of hypersensitivity is greater versus amino
amides [11], albeit the overall frequency of these
reactions is uncommon in either class. Preservatives
such as methylparaben are found in the amino amide
class of agents and are metabolized to PABA [10].
One should use preservative-free amino amide agents
when anesthetizing a patient with a known allergy to
ester amide agents to avoid indirect patient exposure
to PABA.
Hypersensitivity reactions can manifest as mild
rashes, hives, angioedema, dyspnea, tachycardia, hy-
potension, or anaphylactia. Antihistamines and corti-
costeroids are usual treatment options in mild cases,
while cardiopulmonary compromise necessitates
ACLS measures [11].
Additives to infiltrative anesthetics
Epinephrine’s vasoconstrictive properties pro-
vide hemostatis and impede the systemic absorption
of infiltrative agents by one third [10], prolonging
their effect. This reduced systemic absorption al-
lows for a greater maximal safe dose. Most commer-
cially available injectable agents contain 1:100,000 or
1:200,000 strengths. Care should be taken to avoid
use of epinephrine in patients with thyroid storm or
advanced cardiac disease.
Sodium bicarbonate has been used to reduce the
acidic pH of infiltrative anesthetics. This is thought to
improve patient comfort associated with irritation of
infiltration of low pH solutions. Risks of alkaliniza-
tion include precipitation of anesthetics [12]. Addi-
tion of 1 cc of a 1 mEq/mL solution of bicarbonate
for every 9 cm3 of local anesthetic can alleviate
burning and improve patient comfort [13]. It should
be remembered that increasing the pH reduces the
shelf life of infiltrative anesthetic agents [14].
Ovine testicular hyaluronidase (Vitrase, Irvine,
CA, USA) increases the permeability of connective
tissue by the hydrolysis of hyaluronic acid [15]. This
allows for more rapid diffusion of injectable solutions
oculoplastic & orbital surgery 261
thereby reducing the amount of anesthetic needed and
increasing the rate of onset. Symptoms of overdose
include edema, urticaria, nausea, chills, and tachy-
cardia [15].
Tumescent anesthesia
Tumescent anesthesia has been well described to
provide excellent anesthesia of superficial and deep
tissue structures and vasoconstriction [16]. This mo-
dality allows for the use of large amounts of anesthetic
solution because of the extremely low concentration
of lidocaine. Klein’s solution is a well- recognized
mixture that includes 50 mL of lidocaine hydro-
chloride, 1 mL of 1:1000 epinephrine, 12.5 mL of
8.4% sodium bicarbonate, and 1000 mL of normal
saline with a final concentration of 0.05% lidocaine
hydrochloride and 1:100,000 epinephrine [17]. Klein
reported a safe upper limit of 35 mg/kg when using
tumescent solution and postoperative analgesia for
up to 18 hours obviating the need for postoperative
analgesic medications [18]. Tumescent solutions are
infused into the subcutaneous adiposity via a cannula
in a subcutaneous plane. This is especially useful
with facial procedures such as rhytidectomy or lipo-
suction because of the creation of a tissue plane that
aids in dissection and a relatively bloodless field
provided by vasoconstriction. Tumescence may also
be used when performing laser or chemical skin re-
surfacing. Because of skin creep, optimal exposure
to laser energy or chemical agents can be achieved.
Although some support the use of tumescent solution
for facial reconstruction with flaps, I personally do
not use this technique [19]. Use of injectable anes-
thetic agents has yielded excellent results in my ex-
perience without compromise of flap vascularity.
Oral sedatives
The use of and selection of these agents are based
on the comfort level of the surgeon. A commonly
used class of medication is the benzodiazepines,
which provide excellent sedative and antianxiety
affects. One must use caution when prescribing these
since age, weight, and history of patient use of these
medications and drug interactions can alter metabo-
lism of these drugs. Diazepam, 5 to 20 mg and
alprozolam 0.25 to 0.50 mg [20] are two commonly
used drugs and can be given to patients on arrival for
their procedure.
Intravenous sedative and anesthetic agents
Because profound cardiovascular and pulmonary
effects are avoided with intravenous sedatives in most
cases, this class of agents is extremely popular. They
produce excellent analgesia and amnesia without the
need for laryngeal mask or general endotracheal
anesthesia. Several are discussed below.
Propofol (Diprivan, AstraZeneca Pharmaceuticals
LP, Wilmington, DE, USA) is a widely used sedative-
hypnotic agent [21]. Its rapid onset of action and
superlative level of hypnosis make for an excellent
choice when coupled with an opioid before local
anesthetic infiltration or as maintenance of monitored
anesthesia care sedation during prolonged proce-
dures. The author has found this agent to be of ex-
cellent value when repairing traumatic eyelid and
facial lacerations in the pediatric population in an
emergency department setting.
Midazolam is a benzodiazepine with a short half-
life. Given in slow, incremental 1-mg doses this agent
produces deep semiconscious sedation [22]. Intra-
venous use of this agent has been described to cause
impairment of memory for several hours [23].
Another useful attribute is its antianxiolytic effect.
Morphine sulfate, alfentanil hydrochloride, and
remifentanil hydrochloride (Ultiva, GlaxoWellcome,
Inc., Research Triangle, NC, USA) can provide out-
standing analgesia. The author has found alfentanil
hydrochloride (Alfenta, Taylor Pharmaceutical, De-
catur, IL, USA) at an induction dose of 3 to 8 mg/kgprovides effective pain control when used in a moni-
tored anesthesia care setting. Maintenance dosing
of 0.25 to 1 mcg/kg/min may be required during
protracted procedures. Care should be taken in pa-
tients with respiratory compromise because decreased
respiratory drive and increased airway resistance oc-
cur with increasing doses of alfentanil. Avramov and
White suggested healthy outpatients premedicated
with 2 mg of intravenous midazolam, receive a prop-
ofol and alfentanil infusion dose as calculated by
their formula for sedation and analgesia during
monitored anesthesia care (MAC) in the ambulatory
setting [24].
Remifentanil hydrochloride is a rapid onset, short-
acting m-opioid. Philip and colleagues [25] compared
this agent to alfentanil. They found remifentanil may
be used in a 1:4 ratio compared with alfentanil for
total IV anesthesia in ambulatory surgery patients pre-
medicated with midazolam. Remifentanil was more
effective in suppression of intraoperative responses
and did not result in prolonged awakening or
discharge times. Another study compared propofol
and remifentanil in patients who received 2 mg of
Fig. 5. Cornwall syringe system.
cohen262
midazolam before the procedure [26]. It found remi-
fentanil to provide comparable intraoperative con-
ditions and patient comfort at a lower sedation level
compared with propofol. Remifentanil did result in
increased respiratory depression and longer discharge
times in these patients.
General anesthetic agents
Familiarity and administration of general inhala-
tion anesthetic agents is not usual practice for the vast
majority of oculoplastic surgeons and is beyond the
scope of this manuscript.
Applied anatomy
The vast majority of oculoplastic procedures are
performed with direct infiltration or regional blocks
in conjunction with conscious sedation. This section
will deal with these direct infiltrative and regional
block techniques in a structured anatomical fash-
ion. Although many commercially available inject-
able anesthetics are available, I prefer a mixture of
0.75% bupivicaine, 1:400,000 epinephrine, and hyal-
uronidase (Vitrase, Ista Pharmaceuticals, Irvine, CA)
(1 unit/mL). In my experience this melange offers
excellent and prolonged analgesia, hemostatis, and
tissue diffusion.
Fig. 6. Local infiltration in a subcutaneous, avascular plane.
Scalp, forehead, and eyebrow surgery
Anesthesia of this region can be achieved by di-
rect infiltration alone or in combination with su-
pratrochlear and supraorbital nerve blocks. Direct
infiltration provides the additional advantage of vaso-
constriction, especially advantageous in this highly
vascular region. A Cornwall syringe system (Becton
Dickinson and Co, Franklin Lakes, NJ) system can
assist in delivering anesthetic agents to large areas
such as the scalp and forehead (Fig. 5).
Usually the supraorbital foramen can be palpated
approximately parallel to the midpupillary axis, al-
though others have described it to be parallel to
the medial iris [27]. Once this landmark is found, a
30-gauage, one-half-inch needle is advanced to a
level beneath the periosteum just lateral to the fora-
men. The foramen itself should not be entered. One
should remember to draw back on the syringe be-
fore injection because inadvertent intravascular place-
ment of the needle may occur. One to 2 mL of
solution is injected and the needle withdrawn followed
by digital pressure.
The supratrochlear nerve may be anesthetized by
inserting a needle in a perpendicular fashion at the
junction of the nasal root, medial orbital wall, and
roof. A similar injection technique as described above
should be used.
Upper eyelid surgery
Anesthetizing the upper eyelid is achieved with
direct infiltration in most cases. The solution should
be injected in a subcuticular plane and unhurriedly to
reduce patient discomfort (Fig. 6). If possible, the
needle should pierce the skin in an avascular region
to avoid hematoma formation, which can lead to
perioperative eyelid distortion. Application of digital
pressure following injection can help to evenly dis-
Fig. 7. Insertion of needle with bevel facing orbital peri-
osteum. Eyelid crease has been exaggerated to better define
the needle placement site.
oculoplastic & orbital surgery 263
tribute the solution and reduce focal swelling. Local
anesthetic agents should be used sparingly to mini-
mize Muller’s muscle overactivity and levator palpe-
bralis superioris underactivity due to epinephrine
and bupivicaine respectively. Focal swelling and mus-
cle under- or overactivity may result in imprecise
results during repair of blepharoptosis. If medial fat
extirpation is planned one should be cognizant that
both the supratrochlear and infratrochlear nerves may
supply this area necessitating additional anesthetic.
Oliva and colleagues [28] reported a case of transient
visual impairment and internal and external ophthalmo-
plegia following injection for blepharoplasty reaffirming
the need for gentle infiltration and minimal anesthetic
doses. In addition, central retinal artery occlusion has
been reported following local anesthesia for blepharo-
plasty [29].
A frontal nerve block is usually performed during
Muller’s muscle-conjunctival resection for blepharo-
ptosis. A 25-gauge, 1.5-inch sharp needle is used. It
is passed below the midsuperior orbital rim with the
needle lumen facing the orbital roof (Fig. 7). One
should feel the needle passing along the orbital roof
to a depth of 1.5 inches. Then, 1.5 to 2 mL of anes-
thetic solution is infiltrated followed by gentle digital
pressure. If the patient is adequately blocked, a com-
plete ptosis will result with the inability to open his
or her eye.
Lower eyelid and midface surgery
Direct anesthetic technique for the lower eyelids is
similar to that for the upper eyelids. If desired, this
direct infiltration of subcutaneous structures can be
combined with a conjunctival approach for lower eye-
lid and upper midface analgesia. After instillation
of a topical anesthetic onto the patient’s eye, a
corneoscleral shield should be placed over the globe.
The lower eyelid should be retracted away from the
globe exposing the tarsal conjunctiva. A 30-gauge
0.5-inch or 25-gauge 5/8-inch needle should be
directed at a 45 degree angle directly below the
inferior tarsal border to a point just anterior to the
inferior orbital rim. Once the initial injection is
performed the needle may be slightly withdrawn
and directed laterally and medially to further anes-
thetize the entire eyelid.
Infraorbital nerve blocks provide excellent anes-
thesia when operating on the lower eyelid, central and
medial midface, lateral aspect of the nose, and upper
lip. Blocking of this nerve may be approached via
a cutaneous or intraoral route. Whichever route is
chosen, one should be certain the needle is placed
beneath the periosteum to achieve the maximum dis-
tribution of the anesthetic.
If a cutaneous route is taken, the infraorbital
foramen is palpated approximately 6 mm below the
inferior orbital rim and parallel to the mid-pupillary
axis. A 30-gauge 0.5-inch or 25-gauge 5/8-inch
needle should be directed perpendicular to, without
entering, the foramen. Several boluses of 0.5- to
1.0-mL injections can be placed around the foramen
by repositioning the needle. Care should be taken to
avoid entering the orbit, which can lead to diplopia,
hemorrhage, and loss of vision.
The intraoral approach begins with palpation of
the infraorbital foramen with the middle finger and
elevation of the lip with the thumb and index finger
of the same hand. A 30-gauge 0.5-inch or 25-gauge
5/8-inch needle should be introduced into the
gingival sulcus above at the superior aspect of the
canine fossa. One to 2.0 mL of anesthetic solution
should be placed around the foramen.
Lower facial and mandibular surgery
Excellent analgesia can be achieved with mental
nerve blocking. The mental nerve exits the mandible
via the mental foramen, which is located approx-
imately within the midpupillary line. This nerve may
be blocked by a cutaneous or intraoral route. Which-
ever route is chosen, one should be certain the needle
is placed beneath the periosteum to achieve the maxi-
mum distribution of the anesthetic as described with
the infraorbital block.
After palpating the mentalis foramen the needle
should be advanced without entering the foramen.
cohen264
Then 1.5 to 2.0 mL of solution anesthetic solution
should be infiltrated. When an intraoral route is taken
a similar technique as describe for the infraorbital
block is used for exposing the injection site.
The needle then pierces the inferior labial sulcus
at the top of the first bicuspid followed by anes-
thetic infiltration.
Fig. 9. Infraorbital nerve block.
Lacrimal system surgery
Innervation of this system stems from the oph-
thalmic and maxillary divisions of the trigeminal
nerve [30]. Achieving adequate anesthesia of medial
canthal and intranasal structures is essential for opti-
mal patient comfort during dacryocystorhinostomy,
conjunctivodacryocystorhinostomy, dacryocystectomy,
balloon dacryoplasty, or lacrimal system intubation.
Nasal passageway anesthesia has typically been
described to consist of preoperative packing of the
middle turbinate region with neurosurgical cottonoids
soaked in a 4% cocaine solution (Fig. 8). Others
espouse the use of a mixture of phenylephrine and
cocaine [31] to reduce untoward side effects while
others support the use of oxymetazoline and lidocaine
[32] for intranasal anesthesia. Pelletier and colleagues
[33] suggest coating the nasal vault with 2% lidocaine
hydrochloride jelly via a 22-gauge angiocatheter to
reduce the discomfort of placement of the nasal
packing and to aid passage of the cottonoids into
the nose.
Blocking of the nasolacrimal sac and duct and
medial canthal and external nasal regions can be
achieved by the elegant technique described by
Fanning [31]. Fanning’s technique is composed of
Fig. 8. Packing of the nasal vault with neurosurgi-
cal cottonoids.
four blocks. The first block is a standard cutaneous
infraorbital block as described previously using a
27-gauage, 1-inch needle (Fig. 9). Following the in-
fraorbital block the needle is withdrawn completely
and is directed toward the medial canthus and placed
beneath the periosteum (Fig. 10). One to 1.5 mL of
anesthetic is instilled and the needle withdrawn
completely. The needle should then be reinserted be-
low the periosteum at a point midway between the
original injection site and the medial canthus, directed
at the medial canthus. Injection at this site results in a
subperiosteal tumescent effect moving toward the
medial canthus (Fig. 11). Once this effect is seen the
injection is stopped. Gentle massage for 1 minute
allows for further anesthetic dissemination and
reduction of edema at the injection site.
The second block is a medial compartment block.
The same caliber and length needle is used as before
and is directed at a 30-degree angle to the coronal
plane between the caruncle and medial canthus
toward the medial wall stopping just at the perios-
Fig. 10. Reinsertion of the needle toward the medial canthus
followed following infraorbital nerve blocking.
Fig. 13. Intranasal injection.
Fig. 11. Reinsertion of the needle at a point half way
between the medial canthus and insertion site depicted in
Fig. 10.
oculoplastic & orbital surgery 265
teum (Fig. 12A). Once this point is reached the
needle is withdrawn 1 or 2 mm and then redirected
becoming parallel with the medial orbital wall. The
bevel of the needle should be facing the orbital bone
and the needle should be inserted until the shoulder
(hub-needle junction) of the needle meets the iris
plane (Fig. 12B). The needle should remain medial to
the medial rectus at all times. Slowly inject 2 to 4 mL
of anesthetic while monitoring the tension of the
globe with your fingertip. This technique will
produce transient extraocular and orbicularis muscle
weakness necessitating gentle patching for several
hours postoperatively.
The third block is an optional lacrimal canal
block. A 30-gauge 0.5-inch needle is inserted per-
pendicular to the coronal plane entering the medial
aspect of the lower eyelid stopping at the level of
the infraorbital rim periosteum. The needle should be
gently rolled until it falls off the posterior aspect
Fig. 12. (A) Insertion of the needle between the medial canthus an
plane. (B) Redirection of the needle in a plane parallel to the med
of the infraorbital rim. The needle is now within
the lacrimal canal and 2 mL of anesthetic should be
injected. If reflux is noted from the punctum the
needle should be slightly withdrawn, removing it
from the lacrimal sac, and the area re-infiltrated.
The fourth block is performed after temporarily
removing the previously placed nasal packing. A
27-gauge 1-inch needle is used to directly infiltrate
anterior to the middle turbinate in a submucosal plane
(Fig. 13). Slow instillation of anesthetic results in a
spreading effect posteriorly along the middle turbi-
nate and lateral nasal wall. The nasal packing is then
replaced and left until intranasal access is needed
during the procedure.
Adequate anesthesia for less invasive procedures
involving the puncta or canaliculi can be realized
with topical and local infiltration in most instances.
d caruncle at a 30-degree angle with respect to the coronal
ial orbital wall.
cohen266
Orbital surgery
Although most orbital surgery is performed with
general anesthesia, several authors have reported
successful outcomes with regional anesthetic blocks.
Burroughs and colleagues [34]described successful
outcomes in 158 patients when performing enucle-
ation and evisceration with retrobulbar blocks and
monitored anesthesia care . In addition, Kezirian and
colleagues [35] reported four cases of successful
orbital floor repair with peribulbar and infratrochlear
nerve blocks.
Postoperative pain control following enucleation,
evisceration and orbital implant placement may
be difficult even with narcotics. Several authors have
described success in such scenarios with placement
of orbital catheters [36,37]. Garg and colleagues
[38] reported one case of death of a patient with
Stickler’s syndrome following placement of a flexible
orbital catheter.
Summary
Awide variety of anesthetic agents and techniques
are available. No one combination of agents or tech-
niques is accepted as dogma. Experience and knowl-
edge with these agents will optimize anesthetic
effects, surgical outcomes, and patient satisfaction
and will reduce the risk of complications.
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Ophthalmol Clin N
Anesthesia for Pediatric Ocular Surgery
Steven Gayer, MD, MBAa,b,T, Jacqueline Tutiven, MDa
aUniversity of Miami Miller School of Medicine, 900 Northwest 17th Street, Miami, FL 33136, USAbDirector of Anesthesia Services, Bascom Palmer Eye Institute, 900 Northwest 17th Street, Miami, FL 33136, USA
Ophthalmic pathology in infants and children un-
dergoing eye surgery ranges from the rare and atypi-
cal to the commonplace. These pathologies include
nasolacrimal duct obstruction, strabismus, congenital
or traumatically induced cataracts, penetrating eye
injuries, glaucoma, retinopathy of prematurity, intra-
orbital tumors, and more. Nasolacrimal duct stenosis,
cataracts, and traumatic eye injuries often occur in
otherwise healthy pediatric patients; however, many
ophthalmopathies can be associated with other con-
genital disorders that may have important anesthesia
implications. In this article, we will review pertinent
anesthesia issues within the context of various
ophthalmic diseases.
The vast majority of adult eye surgery patients
have regional or topical anesthesia with sedation.
Pediatric patients lack the maturity to remain still and
are readily traumatized by unfamiliar environments
and separation from parents, so general anesthesia is
de rigueur. It may be difficult for children up to the age
of 5 or 6 to cooperate for the most basic ophthalmic
examination. Therefore, general anesthesia is also
often used to accomplish simple refraction; measure
intraocular pressure (IOP); and obtain photographs,
ultrasound examination, or electroretinography.
The preoperative anesthesia evaluation is crucial.
The timeline is dependent on degree of prematurity
and existing comorbidities. Congenital aberrancies
and degrees of previously unviable prematurity are
now frequently survivable. Additionally, frail and
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.012
T Corresponding author. University of Miami Miller
School of Medicine, 900 Northwest 17th Street Miami,
FL 33136.
E-mail address: [email protected] (S. Gayer).
sickly neonates often mature to become frail, sickly
children [1]. Societal pressures have caused the venue
for ophthalmic surgery to migrate from hospital oper-
ating room suites to freestanding eye surgery centers.
Many such facilities lack depth of services and may
perform only a modest amount of pediatric surgery
per year. Caring for the infant or child with signifi-
cant comorbidities puts greater demands on the
anesthesiology staff as well as the facility [2]. The
preoperative examination is a key point in the con-
tinuum of care to assess if the perioperative anes-
thesia environment will ensure a safe course for the
individual patient.
Separation anxiety is a well-described concern of
pediatric patients (and their parents). A small dose of
benzodiazepine may be helpful in transitioning a
child into the operating room. Anxiolytics can be
administered intramuscularly, intranasally, by mouth
or rectum, or intravenously. Older children may ac-
quiesce to placement of an IV, particularly if the
cannulation site has been anesthetized with EMLA
(eutectic mixture of local anesthetics) cream. For
younger children, the oral route is more readily ac-
cepted. Because of variability in first-past absorption
through the hepatic circulation, timing and extent of
response to oral midazolam is less predictable. Intra-
nasal midazolam can be painful and is poorly tol-
erated [3]. Premedication with midazolam prolongs
neither emergence from general anesthesia nor dis-
charge from the hospital [4].
Surgical access is improved with pupil dilation.
Because of prolonged latency of onset, drops are
often instilled preoperatively, but may be given in the
operating room as well. They can migrate through the
puncta into the nasolacrimal duct and on to the nasal
mucosa with subsequent absorption into the systemic
Am 19 (2006) 269 – 278
reserved.
ophthalmology.theclinics.com
gayer & tutiven270
circulation. Sequelae from phenylephrine, an alpha
agonist mydriatic, range from transient hypertension
to pulmonary edema and cardiac arrest [5]. Over 100
severe or fatal reports have been documented. Addi-
tionally, intravenous administration of beta-blockers
given in response to iatrogenic hypertension can
induce unopposed alpha-adrenergic stimulation,
exacerbate symptoms, and produce life-threatening
consequences [6]. Therefore, full strength, 10%
phenylephrine should be avoided in pediatric patients
[7,8]. Ideally, parasympatholytic mydriatic agents
should be used instead of phenylephrine. Otherwise
judicious instillation of 2.5% phenylephrine with ac-
tive occlusion of the nasal puncta to minimize
unintentional rerouting of drug through the naso-
lacrimal duct is advisable. Sufficient time for onset of
effect is warranted before placing additional drops.
The anesthesiologist must be informed so that he or
she may monitor for a hypertensive response and
react appropriately.
Retinopathy of prematurity
Retinopathy of prematurity (ROP), a disease of
neovascularization of the retina, is a leading cause of
infant blindness. Primary risk factors for ROP are
birth weight of less than 1500 g and prematurity with
a postconceptual age less than 32 weeks. Together,
the least mature, lowest weight infants are at highest
risk of developing the disease. Oxygen administration
in the first few weeks of life may be associated with
ROP; however, there are confounding case reports of
newly born infants who have never had exposure to
exogenous oxygen yet have evidence of ROP [9–11].
The improved survival rate of very low birth weight
and highly premature infants has increased the inci-
dence of ROP surgery in developed countries [12].
These infants have markedly higher incidence of
bronchopulmonary dysplasia, cardiac anomalies, epi-
sodic bradydysrhythmias, anemia, intraventricular
hemorrhage, and necrotizing enterocolitis.
In normal development, retinal vessel formation
and growth begins at the optic disc and continues
concentrically, reaching the periphery by 36 to
40 weeks of gestation. It is a dynamic process—
vessels develop or resorb as a function of changes in
local tissue oxygen availability. ROP results from
aberrant formation of blood vessels within the eye in
response to fluctuating levels of oxygen. It develops
in a two-step manner: During the period of early
vascular development, blood vessels in the retina
diminish as an autoregulatory response to high
oxygen tension. Later, in response to the increased
metabolic demands of the developing retina in a
milieu of relative avascularity, endothelial growth
factors are secreted that, in turn, induce vasoprolifera-
tion [13,14]. This neovascularity causes poor visual
acuity, tractional retinal detachment, amblyopia, and
ultimately, blindness.
Neonatologists attempt to maintain preterm in-
fants’ oxygen saturation below the level that is usu-
ally considered to be physiologically normal to
prevent further neovascularization and advancement
of ROP [15]. Intraoperatively, anesthesiologists have
adhered to this practice as well. The Supplemental
Therapeutic Oxygen for Prethreshold Retinopathy
(STOP-ROP) multicenter study sought to determine
if use of exogenous oxygen during the ischemic
phase of ROP could correct local tissue hypoxia,
blunt the secretion of vascular endothelial growth
factors, and prevent formation of new vessels [16].
Threshold disease, typically stage 3 retinopathy, is the
point at which treatment should be administered.
Premature infants with prethreshold ROP and oxygen
saturation below 94% were randomized to maintain
oxygen saturation between 89% and 94% or 96%
and 99%. Although the STOP-ROP study did not find
clear evidence that staged oxygen administration
attenuated development of ROP, it was significant
in that it found that provision of supplemental oxygen
to saturations up to 99% did not cause greater
progression to threshold ROP. During surgery and
anesthesia, higher FI O2 reduces the likelihood of
severe hypoxemia, lowers pulmonary arterial pres-
sure, and decreases airway resistance in infants with
chronic lung disease [17]. Thus, one may consider
that if higher oxygenation is warranted because of
other patient comorbidities, maintaining a relatively
hypoxic state intraoperatively may not be crucial to
the management of neonates with ROP. On the other
hand, some studies have found that episodic cycling
between hypoxia and hyperoxia produces greater re-
tinal neovascularization than exposure to either
hypoxic or hyperoxic environments [18,19]. Many
neonatal intensive care units (NICUs) have adopted
policies that strive to keep oxygen saturation within a
restricted, tight range [20]. The anesthesiologist may
consider keeping perioperative oxygen saturations
within the NICU’s proscribed boundary. Thus, since
concentration, duration, timing, and fluctuation of
oxygen all may have a role in ROP; the optimal in-
traoperative oxygen saturation for these patients has
yet to be clearly elucidated.
The same risk factors that predispose a neonate to
develop ROP, namely low birth weight, prematurity,
and exogenous oxygen, may also promote broncho-
pulmonary dysplasia. This form of chronic lung
anesthesia for pediatric ocular surgery 271
disease is associated with increased airway resistance
and reactivity, diminished lung compliance, and hyp-
oxemia. In the operating room, endotracheal intu-
bation has been the traditional means of obtaining
control of premature and ex-premature ROP patients’
airways; however, barring specific contraindications,
supraglottic devices may provide suitable airways,
even for those patients with history of mild to mod-
erate bronchopulmonary dysplasia [21,22]. For short
procedures, placement of a laryngeal mask airway
(LMA) causes less cardiovascular stimulation than
laryngoscopy and endotracheal intubation. It does not
impede the ophthalmologist’s access to the eyes, and
is associated with a reduced incidence of coughing
and Valsalva [23].
Postoperative breath-holding and apnea are poten-
tial serious complications for premature and ex-
premature infants undergoing surgery for ROP. It
may be associated with episodic bradycardia [24].
Perioperative risk of apnea is dependent on post-
conceptual age, gestational age, and prior history of
apnea at home, with the incidence strongly correlat-
ing inversely with postconceptual and gestational
age. Combined analysis of several studies has found
that at 48 weeks postconceptual age, neonates have
an approximately 5% risk of postoperative apnea,
whereas those at approximately 55 weeks have a less
than 1% probability [25]. Apnea at emergence from
anesthesia, periodic breathing in the recovery room,
and history of anemia confer moderate additional risk
for delayed breath-holding [26]. Intravenous caffeine
or theophylline may attenuate the likelihood of
postoperative apnea [27]. Ophthalmologists should
consider delaying ROP surgery until after 48 to
55 weeks postconceptual age when feasible. Alterna-
tively, examination and minor procedures on ex-
tremely premature patients may be performed bedside
in the NICU [28]. Preterm infants should be observed
after surgery with pulse oximetry and apnea monitor-
ing in an inpatient setting [29]. If the surgical venue is
a freestanding ophthalmic specialty center, arrange-
ments for a bed in an inpatient, monitored facility
as well as for a pediatric transport team must be
coordinated with sufficient time before the day of
surgery [30].
Patients may be brought to the operating room
for diagnostic or surgical interventions. Advances in
photography and ultrasonography now allow for
improved imaging of the eye’s posterior segment.
Cryotherapy, and more recently, laser photocoagula-
tion are common minimally invasive procedures.
Retinal detachment is managed with vitrectomy,
injection of intravitreal gas, and scleral buckle
surgery. General anesthesia with nitrous oxide should
be avoided if use of intravitreal gas is intended
[31,32].
Glaucoma
Congenital glaucoma is caused by aberrant de-
velopment of the trabecular mesh network with
obstruction of flow of aqueous humor. It may be
primary or secondary, infantile or juvenile. Infantile
glaucoma has onset within the first 3 years of life and
is commonly associated with elevated intraocular
pressure (IOP), enlargement of the eyes, and cloudy
corneas. Neonates have elastic, immature tissue that
stretches in response to increased pressure, so larger-
sized, buphthalmic ‘‘ox-like’’ eyes and are common,
while juvenile glaucoma patients do not have this
feature. The classic triad of symptoms for congenital
glaucoma includes tearing, photophobia, and blepha-
rospasm [33].
Corrective surgery to establish paths for aqueous
humor outflow include goniotomy, trabeculotomy,
and implantation of synthetic drainage devices. Aque-
ous humor production can be abated by destruction of
the ciliary body with laser in refractory cases. The
key to good outcome is prompt diagnosis because
early surgery is highly successful at curtailing prog-
ress of disease. On several occasions we have
operated on days-old neonates who have been diag-
nosed by astute parents and pediatricians. Because of
immaturity and inability to cooperate, older infants
and small children may not tolerate the initial diag-
nostic ophthalmoscopic examination and IOP mea-
surement, thus general anesthesia to accomplish a
meticulous eye assessment is warranted. Concomitant
congenital abnormalities such as craniofacial dysto-
ses, various chromosomal trisomies, and other
syndromes are not uncommon and may have sig-
nificant anesthesia implications [34,35]. After defini-
tive surgery, many pediatric patients return to the
operating room periodically for examination under
anesthesia until they are sufficiently mature to be
examined in an office setting.
Assessment of IOP is crucial to both diagnosis
and determination of response to treatment. Anes-
thetic intervention introduces variables that may taint
the accuracy of IOP measurements. Most anesthetics,
including inhalation and induction agents as well as
benzodiazepines and narcotics, lower ocular pressure
[36]. A number of etiologies, including depression of
central nervous system (CNS) activity, induction
of extraocular muscle tone relaxation, reduction of
aqueous humor production while enhancing aqueous
flow, and lowering of venous/arterial blood pressure
gayer & tutiven272
have been postulated. Recent studies have disputed
the traditional notion that ketamine raises IOP. Some
have found that pretreatment with benzodiazepines or
narcotics prevents change in eye pressure with
ketamine, while others have determined that ketamine
may actually decrease IOP [37,38]. Although non-
depolarizing neuromuscular blocking agents do not
increase IOP, succinylcholine may transiently do so
by as much as 10 mm Hg. Debate exists as to whether
or not pretreatment with a small dose of nondepo-
larizing agent ablates this effect [39].
Compression of the eye by an anesthesia face-
mask may lead to spuriously high IOP measurement
[40]. Laryngoscopy and intubation raise IOP through
sympathetic nervous system stimulation; however,
this may be attenuated by achieving a deep plane of
anesthesia before attempting airway manipulation
[41]. Supraglottic airway placement is not accom-
panied by significant increase of IOP and may have
comparable effect on pressure as use of a facemask
[42,43]. Both pediatric as well as glaucoma patients
experience less change in IOP with placement of a
laryngeal mask airway than with laryngoscopy and
intubation [44,45].
Because there are a number of confounding intra-
operative variables that may affect IOP, we believe that
it is important to achieve consistency of technique such
that the patient’s IOP is assessed under similar
conditions with each visit to the operating room [46].
Intraocular tumors
In adults, orbital tumors most commonly result
from secondary metastasis from other areas. The
major primary eye cancer is uveal tract melanoma. In
children, retinoblastoma is the predominant primary
eye neoplasm. It accounts for nearly 3% of all child-
hood cancers and, in the past, was the cause of almost
1% of all pediatric cancer deaths. Untreated, it is a
fatal disease; however, with therapy survival rates
exceed 90%. Retinoblastoma is caused by an abnor-
mality in a specific tumor suppressor gene. This
defect may occur spontaneously or be inherited. More
than half of the children of a parent with bilateral
retinoblastoma will develop ocular malignancy. Ini-
tial clinical diagnosis is made within the first 2 years
of age by observing leukocoria on gross examination
or via indirect ophthalmoscopy of the fundus [47,48].
Earlier detection and newer modalities of treat-
ment have led to improved survival and more
conservative approaches to retinoblastoma than the
traditional enucleation and external beam radiother-
apy [49]. Currently, enucleation is reserved for
patients with extensive disease or those who have
not responded to other therapeutic interventions. The
majority of patients, however, come to the operating
room for minimally invasive procedures. Often there
is no ‘‘surgery’’ on the day of surgery. Typical inter-
ventions are fundoscopic examination, photography,
ultrasound, laser, cryotherapy, and thermotherapy.
Owing to the need to document and follow progress/
regress of disease and provide therapy on a con-
tinuous basis, patients may return to the operating
room regularly over the course of their early child-
hood. The psychosocial aspect of care for both the
patient and parents should not be ignored. Small
children tend to begin fearing trips to the hospital and
develop ‘‘white coat’’ syndrome. Providing a relaxed
atmosphere with interesting toys along with age-
appropriate preoperative tours of the operating room
suite and videos for viewing at home can help belay
the onset of ‘‘blue scrubs’’ anxieties. Premedication
with benzodiazepines may also be beneficial [50,51].
Atraumatic, smooth induction of anesthesia reduces
the incidence of postoperative emotional conse-
quences by half [52]. Parental presence in the
operating room at the time of induction is somewhat
controversial. Although it has no impact on infant
distress during induction of anesthesia, it may allay a
small child’s anxiety and ease the experience [53]. On
the other hand, some children are not calmed by their
parents’ presence and staff and physicians may be
uncomfortable. Some parents are distressed by the
foreign environment. Each care team and institution
needs to develop its own suitable policy [54].
Preoperative labs are generally unnecessary for
children with retinoblastoma who return to the
operating room episodically for tailored, focused
interventions; however, a complete blood count may
be indicated for those who have received recent
chemotherapy. Inhalation induction of general anes-
thesia with maintenance of airway patency via a
facemask is typical. Access to the eye for the surgeon,
photographer, and ultrasonographer can be improved
with use of a mask such as a Rendell-Baker mask,
tailored to hug the bridge of the nose and taper away
from the eyes. If a brief procedure is anticipated,
assuming an otherwise healthy child without pro-
longed fasting, we often forgo intravenous cannula-
tion. If actual surgery is planned or if multiple
procedures are foreseen, an IV and supraglottic
airway such as an LMA are placed.
To avoid laryngospasm or the oculocardiac reflex,
particularly without an indwelling IV, sufficient depth
of anesthetic should be ensured before any manipu-
lation of the eye. Atropine, epinephrine, and succi-
nylcholine doses are calculated and drawn up before
anesthesia for pediatric ocular surgery 273
induction of anesthesia and are immediately available
for intramuscular injection should circumstances
require them. Materials for IV access are also placed
proximate to the patient. An indicator of insufficient
degree of anesthesia is the upward rolling of the eyes
in response to pressure on the eyelids by an eye
speculum. Normally, a natural protective reflex, this
so-called Bell’s phenomenon, causes the eye to gaze
cephalad when the lid begins to close. Since this
reflex is lost under deep general anesthesia and the
eyelids are open with the eye readily visible
throughout the procedure, ‘‘Belling’’ of the eye may
be a useful monitor of anesthetic depth [55,56].
Currently, there is debate as to whether bispectral
index data correlate with depth of anesthesia of
pediatric patients [57].
Sevoflurane is an ideal inhalation agent for
children undergoing examination under anesthesia
because of its favorable cardiovascular profile and
lack of respiratory irritation. One drawback, however,
is emergence delirium, most often encountered in
children younger than 6 years of age [58]. Post-
sevoflurane agitation occurs whether or not actual
surgery has occurred and is not caused by post-
operative pain [59]. It may, however, be related to a
child’s level of preoperative anxiety [60].
The child with retinoblastoma presenting for
examination under anesthesia is at enhanced risk of
post-sevoflurane agitation because his or her general
anesthetic primarily consists of high-dose sevoflurane
via facemask and little else. Some studies have found
that addition of midazolam, propofol, narcotics, or
nonsteroidal anti-inflammatory drugs (NSAIDS) to
the anesthetic regimen decreases the likelihood of
emergence delirium [58,61]. Preoperative narcotics
confer no advantage over midazolam, providing
further justification for our inclination to use oral
benzodiazepines before surgery [62]. Some consider
switching to an alternative inhalation agent after
induction. Fortunately, while acutely distressing to
patient and parents, there are no long-term behavioral
ramifications of sevoflurane-induced emergence
delirium [63].
Electroretinograms and visual evoked potentials
Electroretinography and visual evoked potentials
(VEPs) are used to assess the function of the visual–
cortical axis from the level of the photoreceptors to
the visual cortex. The examination is fairly brief and
noninvasive, requiring placement of a contact lens
electrode on each eye and subsequent exposure to
pulses of flashing light. For adults, this is an office
procedure. Infants and small children, however, often
will not tolerate the procedure and may require anes-
thesia. Traditionally, bulky electroretinogram (ERG)
equipment has been fixed in specialized lightproof
suites where patients’ retinal cells can be dark-
adapted before the examination. Older inhalational
anesthetics such as halothane and isoflurane, as well
as newer agents, sevoflurane and desflurane, are
known to decrease amplitude and prolong latency of
ERG/VEPs when given in high doses typically
needed for mask-induction of anesthesia, so their
use has been typically avoided for these studies
[64–67].While VEPs are exquisitely sensitive to inha-
lation agents, ERGs may be less so [68]. Methohexi-
tal, an ultrashort-acting barbiturate that has a rapid
recovery profile, provides effective sedation. It can be
administered rectally, obviating need for intravenous
access. Onset of effect occurs quickly with 15 to
30 mg/kg of a 10% solution [69]. Owing to potential
apnea of variable duration, post-procedure monitor-
ing is requisite [70]. Propofol may have less effect
upon the ERG than barbiturates and is associated
with a very rapid recovery, but requires cannulation
of a vein [71,72].
Although there are multiple techniques for seda-
tion of pediatric patients outside of the operating
room setting, customary use of rectally administered
barbiturate-based anesthesia for ERG/VEP examina-
tions evolved as a direct consequence of the need to
avoid inhalation agents for anesthesia of infants and
small children in an artificially darkened area remote
from the operating room [73]. Recently there have
been acute shortages of methohexital. The manufac-
ture of small portable ERG machines allow for dark-
adapted pediatric patients to undergo the examination
as scheduled cases in the operating room suite.
Strabismus
Strabismus is a misalignment disorder of extra-
ocular muscles characterized by amblyopia with or
without anisometropia. Surgery, including intramus-
cular placement of adjustable or semi-adjustable
sutures, resections, or direct injection of the par-
alytic botulinum toxin, often yields immediate
rectification of symptoms. Strabismus may be in-
herited, developmental, or acquired, and can have
associated comorbidities—particularly other neuro-
muscular disorders. Children with strabismus or pal-
pebral ptosis may be at increased risk for malignant
hyperthermia or harbor an undiagnosed cardiomy-
opathy, so a thorough preanesthesia examination is
warranted [74,75]. The incidence of malignant
gayer & tutiven274
hyperthermia, intraoperative hyperkalemic arrest, or
rhabdomyolysis has decreased with improved iden-
tification of highly susceptible patients, avoidance of
succinylcholine and other triggering agents, and use
of total intravenous anesthesia with nontriggering
anesthetics [76].
Usually elicited by traction on extraocular mus-
cles and their adnexa or by sudden pressure applied to
the eye or orbit, the oculocardiac reflex (OCR) is not
infrequently encountered in infants and children
having ophthalmic procedures under general anes-
thesia. It is fairly commonly experienced during
strabismus surgery. The stimulus is initially mediated
by the trigeminal nerve, with a vagal efferent re-
sponse that can produce abrupt changes in heart rate.
The cardiac response may be attenuated by a timely
prestimulus IV dose of anticholinergics, use of
sevoflurane instead of halothane, use of neuro-
muscular blocking drugs with vagolytic effects,
and gentle surgical handling of the extraocular
muscles [77]. Since the OCR displays tachyphy-
laxis, repeated stimuli are often accompanied by
attenuated responses—or extinguishment of symp-
toms. First response should be cessation of the
surgical stimulus, allowing the heart rate and rhythm
to return to baseline while simultaneously reassur-
ing adequate patient oxygenation, ventilation, and
depth of anesthesia. Mild hemodynamic instability
of brief duration may not require anticholinergics;
however, compromising bradycardia warrants the
use of atropine. Atropine, not glycopyrrolate or epi-
nephrine, is the appropriate initial agent for vagal-
induced symptomatic bradycardia [78]. Glycopyrrolate
may produce a similar cardiac effect with less pro-
arrhythmic consequences and is used prophylacti-
cally by some after induction of anesthesia, before
surgical stimulation [79].
Strabismus surgery is often accompanied with
postoperative nausea and vomiting (PONV). The
reported incidence of nausea and emesis ranges wide-
ly, no doubt because of differences in patient pop-
ulations as well as surgical and anesthetic techniques
[80]. The increased probability of PONV above
baseline may be a result of an oculo-gastric reflex
that is a vagally mediated response to surgical ma-
nipulation of extraocular muscles. Supporting this
notion, an association between the intraoperative
occurrence of another vagus nerve-mediated re-
sponse, the OCR, and PONV has been described
[81]. Following surgery, motion sickness because of
diplopia may also produce nausea and emesis.
While symptoms are usually self-limiting, serious
ramifications may occur. Delayed eating and drinking
may lead to dehydration, electrolyte imbalance, and
prolonged stay in the recovery room. Unanticipated
admission to an inpatient facility may be necessary.
PONV is distressing and its curtailment is valued
[82]. Avoidance of emesis and nausea after surgery is
a greater patient priority than prompt wakefulness,
rapid discharge from same-day surgery, cost, or even
pain itself [83].
Strategies to minimize PONV include adjustment
of the anesthetic plan as well as the use of anti-
emetics. Preoperative anxiety may contribute to
postoperative nausea/vomiting, so benzodiazepines
or clonidine may be beneficial [84,85]. Narcotics are
highly proemetic and newer agents such as remifen-
tanil may not confer advantage over fentanyl [86].
Conflicting reports regarding nitrous oxide exist.
Higher oxygen concentrations allay PONV in adults
after gastrointestinal (GI) surgery, however, increased
FI O2 has not been found to have similar effect in
pediatric and adult strabismus patients [87,88].
Anticholinesterases used for reversal of neuromus-
cular blocking agents promote nausea, so preintuba-
tion use of an ultrashort neuromuscular blocking
agent that does not require reversal, such as miva-
curonium, is warranted [89]. Supraglottic airways
obviate the need for paralysis altogether. Propofol
may reduce the incidence of nausea and vomiting, but
is associated with the oculo-cardiac reflex and
bradydysrythmias [90,91]. Peribulbar or sub-Tenon’s
block before emergence from general anesthesia
lessens PONV [92,93]. Nonpharmacologic tech-
niques such as acupressure may be helpful [94].
Postoperatively, premature inducement to eat and
drink should be avoided [95].
Antiemetics can be administered during surgery or
once symptoms arise after emergence. Since strabis-
mus surgery is, in and of itself, a notable independent
risk factor for PONV in children, prophylactic admin-
istration of antiemetics is warranted [84]. Surgery in
excess of 30 minutes, as well as a family history of
PONV confer additional risk and further justify
intraoperative antiemetics [96]. Additionally, in this
setting, prophylactic antiemetics may be more cost-
effective than symptomatic treatment of nausea and
vomiting [97].
PONV after strabismus surgery has been studied
with all classes of antiemetics, including butyrophe-
nones, benzamides, histamine and muscarinic receptor
antagonists, steroids, and serotonin 5-HT3 receptor
antagonists [98,99]. Use of combinations of anti-
emetics with differing mechanisms of action may be
more effective for those eye muscle surgery patients
at highest risk of PONV. One such combination
includes droperidol, a 5-HT3 receptor agonist, or ste-
roid. Droperidol has a marked anti-nausea effect
anesthesia for pediatric ocular surgery 275
while the serotonin receptor antagonists are better
suppressers of vomiting than nausea, and dexametha-
sone has a prolonged duration of action [98].
Traumatic eye injuries
Traumatic eye injuries are relatively common with
small children and adolescents. Reparative surgery
occurs more frequently in community-based facilities
than trauma centers [100]. Open eye injuries are
either ruptures from blunt objects or lacerations from
sharp projectiles. Lacerating injuries may be pene-
trating, with single full-thickness lesions, or perforat-
ing, with entrance and exit wounds. An intraocular
foreign body may also be present. Anesthesia strate-
gies for management of open-globe patients are de-
scribed elsewhere in this text. In the otherwise healthy,
normovolemic, fasted child, a gentle inhalation-based
induction may be considered since squeezing of the
eyelids owing to attempted IVaccess can cause IOP to
exceed 70 mm Hg, potentially precipitating extrusion
of globe contents [101]. Although general anesthesia
remains conventional, anesthesia for select patients
with open globe injuries can be accomplished with
regional anesthesia [102,103]. In the pediatric
population, with the possible exception of older
more-mature teenagers, general anesthesia is most
appropriate. Nonetheless, an eye block before con-
clusion of surgery provides effective postoperative
analgesia for the child having repair of a traumatic
eye injury under general anesthesia. Emergence from
anesthesia is more quiescent, with less PONV than
encountered with opiates, and the child is less likely
to rub or squeeze an eye that has been rendered
insensate with local anesthetics [104]. Appropriate
dosing can be achieved with proportionally smaller
volumes and lower concentrations of local anes-
thetic. Alternatively, intravenous, but perhaps not
topical, ketorolac as well as oral or rectal acetami-
nophen may also attenuate postoperative pain with-
out enhancing the potential for PONV [105–107].
Summary
The intent of this article was to shed light on
important issues in pediatric ophthalmic anesthesia
within the constraints of the space allotted. A timely
and detailed history and physical examination com-
plimented with indicated diagnostic tests generally
ensures a safe anesthetic course. Preterm and ex-
premature infants as well as syndromic children un-
dergoing eye surgery require proper institutional
support, and may also need postoperative trans-
portation from the ophthalmology specialty center
to a pediatric intensive care unit for further monitor-
ing. Anesthesia implications for particular ophthalmic
pathologies including retinopathy of prematurity,
glaucoma, retinoblastoma, strabismus, and traumatic
eye injuries were discussed. We reviewed peri-
operative considerations including the preoperative
examination, evaluation of comorbidities and syn-
dromes, preoperative labs, premedication, separation
anxiety, systemic effects of ophthalmic medications,
emergence delirium, the increasing use of supra-
glottic airways, IOP, OCR, PONV, and pain manage-
ment strategies including intraoperative eye block.
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Ophthalmol Clin N
Succinylcholine and the Open Eye
Elie Joseph Chidiac, MDa,b,T, Alex Oleg Raiskin, MDa
aDepartment of Anesthesiology, Wayne State University School of Medicine, Anesthesiology Education Office,
Room 2901, 2-Hudson, 3990 John R., Detroit, MI 48201, USAbKresge Eye Institute, 4717 St. Antoine, Detroit, MI 48201, USA
The use of succinylcholine in ocular trauma is
controversial. This article reviews the determinants
of intraocular pressure (IOP), the effects of succinyl-
choline on IOP, and the advantages and disadvantages
of alternatives to succinylcholine, including regional
anesthesia for open globe injuries. We review various
methods to attenuate the effect of succinylcholine on
IOP, if it is to be used. Finally, we suggest an algo-
rithm for airway management of patients with pene-
trating eye injuries, highlighting circumstances where
succinylcholine may be the safest muscle relaxant.
Intraocular pressure
Normal IOP is 10 to 22 mm Hg, with diurnal
variations (ie, 2 to 3 mmHg higher in the daytime) and
positional changes (ie, 1 to 6 mm Hg higher if su-
pine).It is physiologically determined by aqueous hu-
mor dynamics, changes in choroidal blood volume,
central venous pressure, and extraocular muscle tone
[1]. The most important determinant of IOP is the
balance between production and elimination of aque-
ous humor, maintaining an average volume of 250mL.
Aqueous humor is formed in the ciliary process from
capillaries by diffusion, filtration, and active secretion
[2]. It flows through the posterior chamber, around the
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.015
T Corresponding author. Department of Anesthesiology,
Wayne State University School of Medicine, Anesthesiology
Education Office, Room 2901, 2-Hudson, 3990 John R.,
Detroit, MI 48201.
E-mail address: [email protected]
(E.J. Chidiac).
iris, and into the anterior chamber. It is eliminated
through the spaces of Fontana and Schlemm’s canal
at the iridocorneal angle, where it flows into the
episcleral venous system. Any increase in venous
pressure (eg, cough, strain, head-down position) will
increase IOP. Additionally, any decrease in cross-
sectional area of the spaces of Fontana (eg, mydriatic
drugs) will increase IOP.
The choroid is a meshwork of arterial anasto-
moses in the posterior chamber. Autoregulation of
choroidal blood flow keeps IOP stable [3]. However,
this process is slow, so that sudden increases in sys-
temic blood pressure or central venous pressure
(coughing, bucking) will cause a transient increase
in choroidal blood volume and thus IOP. Addition-
ally, there is a linear relationship between choroidal
blood volume and hyper- and hypoventilation, so that
an increase in carbon dioxide tension will raise IOP.
A sudden drop in IOP to atmospheric pressure (open
eye) can cause rupture of choroidal vessels.
Extraocular muscles (EOM) have a unique mor-
phologic structure that enables rapid and precise
control with resistance to fatigue. Whereas skeletal
muscles have a single nerve axon connected to an
endplate at the mid-belly of each fiber, EOM are
both singly innervated and multiply innervated. With
firing of synapses, the action potential of multiply
innervated fibers is not an all-or-none phenomenon;
instead, there are tonic focal contractions and the
force generated is directly proportional to the mem-
brane depolarization [4]. This may explain differ-
ences in the response of EOM to succinylcholine; in
the EOM of cats, multiply innervated fibers are more
sensitive to succinylcholine than singly innervated fi-
bers [5].
Am 19 (2006) 279 – 285
reserved.
ophthalmology.theclinics.com
chidiac & raiskin280
Succinylcholine and IOP
When first introduced, succinylcholine was seen
as an ideal muscle relaxant [6]. Soon thereafter, it was
reported that succinylcholine increased IOP [7] and
with personal communications from surgeons, con-
cerns were raised regarding possible vitreous extru-
sion [8]. Others studied intraocular physiology and
described loss of vitreous after succinylcholine ad-
ministration under light anesthesia, suggesting that
the use of succinylcholine in intraocular surgeries
was ‘‘hazardous’’ [9]. Anesthesiologists at the Wills
Eye Hospital in Philadelphia performed a retrospec-
tive review of 100 of 228 open eye trauma cases from
1982. Of those 100 cases, 81 had general anesthesia:
11 had an inhalational induction (all were children)
and 70 had an intravenous induction. Of those 70,
there were 63 who received succinylcholine, at 60 to
160 mg. Based on the description of the eye on the
operative report and in the preoperative progress
notes, there was no extrusion of vitreous in any of the
cases where succinylcholine had been used. They
added that they had no anecdotal reports of loss of
ocular content using succinylcholine for eye injury
patients in more than 10 years at their institution [10].
This article generated two Letters to the Editor, one
with a case report of extrusion of vitreous necessitat-
ing an enucleation [11] and the other from the
anesthesiologists at the Massachusetts Eye and Ear
Infirmary in Boston, MA, citing more than 10 years
of using succinylcholine at induction in open globe
injuries without vitreous expulsion [12].
IOP increases within 1 minute and peaks at an
increase of 9 mm Hg within 6 minutes after suc-
cinylcholine administration [13]. The exact mecha-
nism of this increase is unknown. Some feel that tonic
contractions of the extraocular muscles may explain
this IOP increase. However, in a feline model of an-
terior and posterior ocular trauma, there was no ex-
trusion of ocular contents after succinylcholine. The
only effect was forward displacement of the lens and
iris [13]. In a study of 15 patients undergoing elective
enucleation, succinylcholine was given after all the
extraocular muscles to the diseased eye had been
detached. There was no difference in IOP increase
between the detached and intact eyes [14]. It is now
thought that succinylcholine-induced IOP increase is
a vascular event, with choroidal vascular dilatation or
a decrease in drainage secondary to elevated central
venous pressure, temporarily inhibiting the flow of
aqueous humor through the canal of Schlemm [15].
Therefore, it is clear that succinylcholine raises
IOP. However, at induction of general anesthesia
there are many activities that raise IOP with a much
larger increase than that with succinylcholine, includ-
ing crying, Valsalva, forceful blinking, and rubbing
of the eyes [16] as well as coughing or bucking during
poor intubating technique [1]. Therefore, the increase
in IOP owing to succinylcholine may be inconse-
quential if optimal intubating conditions are not pro-
vided [17].
Nondepolarizing muscle relaxants
There are many nondepolarizing muscle relaxants
that can be used to facilitate rapid-sequence induction
for open eye injuries. In general, onset time is slower
than succinylcholine. Various methods have been
proposed to speed this onset: priming, administering
the neuromuscular agent before the induction agent,
and using high-dose regimens.
The priming principle suggests that a small dose
of a nondepolarizing muscle relaxant be given 3 min-
utes before rapid sequence induction, when the induc-
tion agent and the rest of the nondepolarizing drug
are given. This runs the risk of partial paralysis from
the priming dose itself as well as the risk of loss of
airway control [18].
Some have proposed administering the neuro-
muscular agent before the induction agent. With that
technique, the concern is a poorly timed disconnec-
tion at the site of the intravenous catheter and a longer
interval between induction and intubation [19].
Some have proposed using high-dose regimens
of nondepolarizing muscle relaxant. High doses of
vecuronium, 0.2 to 0.3 mg/kg, can provide good in-
tubating conditions in 90 seconds [20]. Rocuronium
0.6 mg/kg can be a good substitute for rapid se-
quence induction and intubation [21,22]. When
comparing succinylcholine 1.5 mg/kg versus rocu-
ronium 0.6 mg/kg, the intubating conditions were
excellent after 60 seconds and the IOP rise with
succinylcholine was 21.6 mm Hg as opposed to
13.3 mm Hg with rocuronium [23]. However, others
have suggested that as much as 0.9 to 1.2 mg/kg of
rocuronium is needed to provide equivalent intubat-
ing conditions to succinylcholine, at the expense of
prolonged duration of action [24–26].
Therefore, despite various methods to optimize
their use, nondepolarizing muscle relaxants can result
in nonideal intubating conditions at 60 seconds, a
delay in intubation, a prolonged effect, increases in
intraocular pressure from mask application, and a
longer time with an unprotected airway. Some feel
that depolarizing agents will always be faster be-
cause, compared with succinylcholine molecules,
more receptors have to be occupied by nondepolariz-
succinylcholine & the open eye 281
ing muscle relaxant molecules to produce an equiv-
alent degree of paralysis [27].
Regional anesthesia for open globe injuries
Regional anesthesia can be a safe, albeit non-
routine anesthesia technique for repair of open eye
injuries. It is a reasonable alternative for the manage-
ment of trauma patients where general anesthesia
may expose patients to excessive risk for complica-
tions, or for patients with less traumatic globe injuries
that pose a lower threat of loss of the eye.
There are many techniques for ocular conduction
anesthesia: cannula-based sub-Tenon block tech-
niques, topical anesthesia, intracameral injection,
and peribulbar and retrobulbar anesthesia. Selection
of the appropriate anesthesia technique should con-
sider many factors that pertain to the patient, surgery,
surgeon, anesthesia provider, and operative venue.
The risks of all ocular block techniques are inversely
proportional to education and experience. This is af-
firmed by several reports of complications by in-
adequately trained personnel [28–31].
Regional anesthesia has traditionally been consid-
ered contraindicated in patients with penetrating eye
injuries because of the concerns with potential extru-
sion of intraocular contents from the force generated
by local anesthetics, from needle instrumentation of
the orbit, from squeezing of the eyelids because of
pain on injection, or from a potential hemorrhage
after injection. Nonetheless, there are some anecdotal
case reports of successful use of ophthalmic blocks in
this setting [32,33].
There is a spectrum of eye injuries based on type
(defined by the mechanism of the injury), grade
(based on visual acuity), pupillary defect, and zone of
injury [34]. This spectrum has been validated in a
subsequent study, with a prognostic correlation be-
tween initial evaluation and eventual visual out-
come [35].
Regional anesthesia can be a reasonable alter-
native to general anesthesia for selected patients with
open globe injuries. Two retrospective studies inves-
tigated clinical features and visual acuity outcomes
associated with regional anesthesia versus general
anesthesia for open globe injuries in adult reparable
eyes. With a total of 458 patients with open globe
injuries, those who underwent surgery without gen-
eral anesthesia were more likely to have an intra-
ocular foreign body, better presenting visual acuity,
more anterior wound location, shorter wound length,
and dehiscence of previous surgical wound, and were
less likely to have a pupillary defect. There were no
anesthesia-related complications. The general anes-
thesia groups had longer operating times. Change
in visual acuity between the presenting and final
examinations was similar in the general anesthesia
and regional anesthesia groups [36,37]. A similar
prospective study showed that patients with small
anterior penetrating globe injuries may be operated
with a combined peri- and retrobulbar anesthetic,
with operative conditions as good as those with gen-
eral anesthesia [38].
Topical anesthesia has been used for an open
globe injury in a situation where cardiopulmonary
disease prevented the use of general anesthesia and
the extensive extrusion of eye contents made peri-
and retrobulbar blocks contraindicated [39]. A pro-
spective study of 10 open globe injuries repaired
under topical anesthesia showed that, for less severe
eye injuries, surgeons have adequate operative con-
ditions (slight difficulty in 9, moderate difficulty in
1 case) and most patients have minimal pain and
discomfort [40].
Blunting the effect of succinylcholine on IOP
Various methods have been used to attenuate the
effects of succinylcholine on IOP. They include self-
taming and pretreatment with lidocaine, narcotics,
nifedipine, nondepolarizing muscle relaxants, nitro-
glycerin, and propranolol.
Self-taming is a technique where a small dose
of succinylcholine is initially given, before rapid-
sequence induction. This has been found to be inef-
fective in reducing the rise in IOP and can, by itself,
cause an increase in IOP [41,42].
Pretreatment with lidocaine partially blunts the
IOP increase from succinycholine and blunts the
further increase from intubation [43].
Pretreatment with narcotics decreases the IOP rise
from succinylcholine. After fentanyl or alfentanil, IOP
increased significantly following suxamethonium, but
mean IOP remained significantly less than control
values. Tracheal intubation caused a further significant
increase in IOP, and both opioids reduced, but did not
abolish the hemodynamic responses to tracheal intu-
bation [44]. The IOP rise from succinylcholine can be
obtunded with remifentanil [45,46], sufentanil [47],
and alfentanil [48]. This decrease may be related to the
effects of opioids on systemic vascular resistance [49].
Pretreatment with nifedipine can blunt the IOP
increase from succinylcholine: the IOP increased
7.82 mm Hg in the placebo group and 0.15 mm Hg
chidiac & raiskin282
in those who received 10 mg sublingual nifedi-
pine [50].
Pretreatment with a small defasciculating dose of
nondepolarizing muscle relaxant has shown mixed
results. Some have suggested that mivacurium at-
tenuates the IOP increase from succinylcholine [51].
D-tubocurarine has been shown to be beneficial by
some authors [52], while others have shown no sig-
nificant difference between the IOP increase after
succinylcholine alone or after succinylcholine when
given 3 minutes after d-tubocurarine [53–55].
Pretreatment with nitroglycerin will cause signifi-
cantly less increases in IOP after succinylcholine and
after tracheal intubation [56].
Pretreatment with propranolol has been shown to
prevent significant increases in IOP after succinyl-
choline, but there was significant cardiovascular
depression [57].
The practice at the Kresge Eye Institute
At our institution, we feel that succinylcholine
may be used to facilitate endotracheal intubation
during rapid sequence induction, despite its effects
on IOP, because it allows intubation within 30 to
60 seconds. Its short half-life also allows fast recov-
ery of muscle power if the airway conditions are
difficult. In a ‘‘full stomach-open eye injury’’ situa-
tion, with the need for a rapid-sequence induction
with avoidance of IOP increase, there is a balancing
act: preventing aspiration and preventing IOP in-
crease. When succinylcholine is chosen, we use vari-
ous medications to blunt its effect on IOP, such as
opioids, lidocaine, nifedipine, and defasciculating
doses of nondepolarizing drugs.
Is this an easy airway?
YES NO
Short- orintermediate-
actingnondepolarizing
musclerelaxants.
Is the eye viable?
YES NO
Fiberopticlaryngoscopy
Succinylcholine(after pre-treatments)
Fig. 1. Intubation algorithm for open eye injuries.
After approval by our Institutional Review Board,
we retrospectively reviewed all open globe surgeries
performed at the Kresge Eye Institute in a 24-month
period. There were 59 cases and all were adults re-
ceiving general endotracheal anesthesia. One was a
planned fiberoptic intubation because of facial inju-
ries. Eight were judged to be possibly difficult intu-
bations (see algorithm, Fig. 1) and therefore received
succinylcholine. Five of them were indeed difficult
intubations, requiring more than one attempt (one of
these five patients required fiberoptic intubation). In
all 59 cases, comparing ophthalmologists’ comments
in the preoperative assessment and after induction,
similar to the process used by Libonati et al [10],
there were no increases in vitreous loss, no lens or
uvea extrusion, and no excessive intraocular bleeding
causing further extrusion.
A proposed algorithm
We feel that two questions need to be asked before
the decision about the use or the avoidance of suc-
cinylcholine in open globe surgeries: Is this an easy
airway? and Is the eye viable? (see Fig. 1).
If the airway assessment shows that intubation
should be easy, then regardless of the patient’s aspi-
ration risk and regardless of the viability of the eye,
we feel that succinylcholine can be avoided and re-
placed with the currently available short- or inter-
mediate-acting nondepolarizing muscle relaxants.
If the airway assessment, using whatever tools the
anesthesiologist prefers, shows that this could be a
difficult intubation, regardless of the patient’s aspira-
tion risk, then a second question becomes important:
Is the eye viable? In that setting, the anesthetic in-
duction plan may need to change.
If, during the preoperative ophthalmologic exami-
nation, it is felt that the eye is not salvageable, and
the surgery is to assess the damage and create a cos-
metic closure, we prefer to use fiberoptic laryn-
goscopy. This, we realize, may increase intraocular
pressure (gagging from local anesthetic spray, retch-
ing from local anesthetic nebulized breathing treat-
ments, bucking from transtracheal injection,
hypercarbia from sedation), but this increase should
be similar to that from blinking, crying, or rubbing
the eye.
If the ophthalmologist feels that the eye is via-
ble, then we prefer using succinylcholine over any
other modality. In this setting, we start with other
drugs that attenuate the intraocular pressure effect
of succinylcholine.
succinylcholine & the open eye 283
Summary
There is still no real case report of extrusion. The
witnessed extrusions of the 1950s and 1980s spoke
of ‘‘light anesthesia.’’ Although it is inevitable that the
use of succinylcholine will decline with the availabil-
ity of new drugs [58], the currently available shorter-
acting nondepolarizing muscle relaxants have yet to
replace the fast onset and short duration profile of
succinylcholine [59]. A new ideal replacement must
work as fast as succinylcholine, wear off as quickly as
succinylcholine, and not cause an IOP increase.
Choosing or avoiding succinylcholine is a matter
of balance of risk. To control IOP at induction, there
must be adequate dosing of drugs and adequate
timing to coincide with the three potent stimuli: the
administration of succinylcholine, the laryngoscopy,
and the endotracheal intubation. We know that
succinylcholine increases IOP, but this increase can
be attenuated with various pretreatments, is less than
the increases seen with inadequate paralysis at the
time of laryngoscopy and intubation, and is unim-
portant when weighed against the risk of loss of
the airway. Therefore, we feel that in the situation
of ‘‘difficult airway, eye viable,’’ one should
use succinylcholine.
Acknowledgments
Many thanks to Dr. Steven Gayer, Associate
Professor of Anesthesiology and Ophthalmology at
the University of Miami and Director of Anesthesia
Services at the Bascom Palmer Eye Institute, for his
advice and guidance, particularly in the area of re-
gional anesthesia for open eye injuries.
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Ophthalmol Clin N
Management of a Blind Painful Eye
Shannath L. Merbs, MD, PhD
Wilmer Eye Institute, 600 North Wolfe Street, Maumenee 505, Baltimore, MD 21287, USA
Ophthalmologists are often asked to treat patients
who have eye pain from a variety of ocular diseases.
Topical steroids, cycloplegics, ocular hypotensives,
and bandage contact lenses can be effective in many
cases. However, when the pain is intractable and the
eye has very poor vision and is disfigured, surgical
removal of the eye has traditionally been the
definitive treatment of choice. In several situations,
an alternative to enucleation is warranted, and in-
jection of a neurolytic substance can often induce
long-lasting anesthesia for a blind painful eye.
One of the most common causes of a blind pain-
ful eye is trauma [1,2], but many other ocular condi-
tions, such as retinal detachment, chronic open-angle
glaucoma, phthisis, intraocular inflammation, and
corneal decompensation can lead to loss of vision
and pain.
A blind eye can be associated with several types
of pain or discomfort. Most common is an aching or
sharp pain of the eye or orbit, but the pain may also
be referred to the forehead or temple. Photophobia
of the contralateral eye is not uncommon, even in
patients who have lost all sight in the affected eye [2].
Retrobulbar injection
Ethyl alcohol
Retrobulbar alcohol injections have been used as
an alternative to enucleation since the early 1900s to
treat blind painful eyes. Retrobulbar injections may
be preferred in cases where the blind painful eye is
cosmetically normal and not disfigured, as is often
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.010
E-mail address: [email protected]
the case in refractory, or end-stage glaucoma [3,4].
Patients, who cannot proceed with enucleation for
medical reasons or who are reluctant to proceed with
enucleation for psychological, cultural, or religious
reasons, can be temporarily relieved of their eye pain
by a retrobulbar alcohol injection in about 85% of
cases for at least 1 month [4]. However, the discom-
fort often returns an average of 6 months after injec-
tion [3,4]. The pain is believed to recur because the
alcohol, that infiltrates the area surrounding the sen-
sory nerve fibers, damages but does not destroy the
nerve fibers. After a few months, the peripheral por-
tion of the nerve fibers regenerate and the pain recurs.
Typically, 1 mL of 95% ethyl alcohol is injected
after a standard retrobulbar block (see later discus-
sion). Immediately after a retrobulbar alcohol injec-
tion, the patient may experience a sharp pain in the
orbit or a dull occipital headache [4]. This discom-
fort can last for several minutes. Other transient com-
plications include eyelid swelling, ptosis, chemosis of
the conjunctiva, slight proptosis of the globe, and
temporary paralysis of one or more extraocular
muscles. In general, these complications last for a
few days to two months [4,5]. Neurotrophic kera-
titis is a rare complication of retrobulbar alcohol in-
jection [4].
Phenol
Chemical neurolysis by phenol is frequently used
by disciplines other than ophthalmology to provide
relief of pain and spasticity. Phenol has several
advantages over alcohol, including a less painful
injection and a more rapid onset [6]. In the treatment
of blind painful eyes, the effectiveness of phenol
(80%) is similar to alcohol, although the duration
may be longer (mean 15 months) [7]. Using the stan-
Am 19 (2006) 287 – 292
reserved.
ophthalmology.theclinics.com
merbs288
dard technique described below, injection of local
anesthetic is followed by 1.5 mL of a 1:15 (6.7%)
aqueous phenol solution [7]. Complications, which
include ptosis, ophthalmopelgia, and neurotrophic
keratitis, are also similar to retrobulbar alcohol and
typically resolve after a few weeks [7].
Chlorpromazine
Chlorpromazine is another chemical that has been
injected into the retrobulbar space to treat blind pain-
ful eyes [8]. The effectiveness of phenol for elimi-
nating pain with one injection (80%–83%) is similar
to retrobulbar alcohol and phenol [8,9]. Like phenol,
the duration of pain control after a retrobulbar in-
jection of chlorpromazine can exceed that of alcohol
and normally lasts more than a year. Mild to moder-
ate chemosis, lid edema, and ptosis can occur but
usually resolve within a few weeks [9]. Typically,
1 mL of 25 mg/mL chlorpromazine is injected after
retrobulbar anesthesia.
Technique
Retrobulbar injection of neurolytic agents, espe-
cially alcohol, is painful. To minimize discomfort, the
injection is preceded by a retrobulbar block which is
administered using standard technique [4]. The
patient is asked to look up and nasally. A 3.5-cm,
22-gauge needle is inserted into the lateral third of the
lower lid just above the rim of the orbit. The needle is
passed through Tenon’s capsule between the lateral
and inferior rectus muscles into the muscle cone. The
plunger of the syringe is withdrawn slightly to insure
that the needle has not entered a blood vessel. An
initial injection of 1-2 cc of 2% lidocaine is given into
the retrobulbar space. The syringe is removed, and
the needle is held in place with a clamp. A second
syringe, containing 1–1.5 mL of either 95% ethanol,
6.7% aqueous phenol, or 25 mg/mL chlorpromazine,
is attached to the needle, and the solution is injected
into the orbit. A patch is applied.
A variation on the injection technique uses
95% ethanol and 2% lidocaine in the same syringe
[10]. Because the specific gravity of ethanol is less
than lidocaine, ethanol drawn first into a syringe
remains above the lidocaine if the syringe is held
perpendicular to the floor while the lidocaine is
drawn into the syringe slowly to avoid turbulence and
inadvertent mixture. Use of a single syringe sim-
plifies the procedure. Alternatively, two syringes can
be attached to the same retrobulbar needle with a
three-way stopcock.
Intravitreal injection
Phthisis bulbi is a progressive process in which
intraocular fibrosis leads to ciliochoroidal detach-
ment, hypotony, and a blind painful eye. In one report,
intravitreal corticosteroid injection into a phthisical
eye alleviated pain for at least 2 months [11], and this
treatment may be a viable alternative to retrobulbar
alcohol injection. The corticosteroid also appeared to
reduce ocular inflammation, with decreased conjunc-
tival congestion after injection [11]. After standard
retrobulbar anesthesia, 0.3 mL (12 mg) of triamcino-
lone acetonide (40 mg/mL) is injected intravitreally
and the eye is patched. Most patients reported pain
relief within 24 hours [11].
Cyclodestruction
Cyclodestruction destroys a portion of the ciliary
body and reduces aqueous production which de-
creases intraocular pressure. This form of therapy can
be used to relieve pain in patients who have a blind
hypertensive eye. Cyclodestruction by transcleral
cryotherapy effectively reduces intraocular pressure
and pain, but this technique is usually reserved for
cases of end-stage glaucoma because of an increased
risk of complications such as visual loss and phthisis
bulbi [12]. Cyclophotocoagulation by diode laser is
more commonly used and also effectively provides
pain relief in blind hypertensive eyes and results
in fewer complications [12,13]. Under retrobulbar
or peribulbar anesthesia, a quartz fiberoptic probe
(600 mm diameter) is used to apply the diode laser
over the ciliary body. One-half to three-quarters of
the ciliary body is treated with 20–40 applications
of 1.5–2 seconds duration. Complications of cyclo-
destruction include post-operative uveitis and hyphema,
and persistent hypotony [12,13].
Enucleation
One of the leading causes of enucleation, or re-
moval of the eye from the orbit, is a blind painful
eye [1,14]. When topical medications or retrobulbar
injections fail to control the pain, enucleation can
usually provide complete pain relief within 3 months
[15]. Painful, and severely traumatized or phthisical
blind eyes are usually best treated by enucleation
or evisceration (see later discussion). The decision
to recommend enucleation must take into account a
patient’s psychological state and general medical
condition, the etiology of the pain, the cosmesis of
blind painful eye management 289
the eye, and the potential for complications. Patients
who have blind painful eyes that are disfigured from
trauma, may more readily agree to enucleation [2].
Enucleation provides pain relief for over 90% of
patients [2]. Some patients experience phantom
eye pain or visual hallucinations after enucleation
[16,17].
Technique
Standard enucleation techniques are detailed in a
number of oculoplastic surgical textbooks [18–21].
Enucleation is usually performed under general anes-
thesia [18–20], although it can be performed with
a retrobulbar or peribulbar block [22–24]. After an
eyelid retractor is placed, a 360� conjunctival peri-
tomy is performed around the corneoscleral limbus.
Tenon’s capsule is opened in all 4 quadrants between
the rectus muscles with blunt dissection. Each rectus
muscle is isolated, secured with a locking suture, and
severed from the globe at its insertion. The superior
oblique tendon is isolated and divided. The muscular
insertion of the inferior rectus muscle is clamped or
cauterized to minimize bleeding and then divided.
Remaining fibrous attachments to the globe are di-
vided. The optic nerve is clamped behind the eye
and enucleation scissors are used to cut the optic
nerve between the clamp and the back of the eye.
Alternatively, a snare can be used to isolate and cut
the optic nerve. Hemostasis is achieved with digital
pressure for several minutes.
In most cases, the orbital volume lost by removing
the eye is replaced with an alloplastic orbital implant.
Many implant materials have been advocated in the
past, but integrated implants that allow for fibrovas-
cular tissue ingrowth into the inorganic material are
currently favored. Two of the most commonly used
materials are hydroxyapatite and high-density porous
polyethylene [25–27]. The hydroxyapatite implant is
usually wrapped in a material such as donor sclera,
pericardium, or synthetic mesh to decrease the rate
of extrusion of the implant and to facilitate the at-
tachment of the extraocular muscles to the implant
[28–30]]. The porous polyethylene implant, in con-
trast to hydroxyapatite, is less expensive and does not
require wrapping because of its smoother surface.
Greater malleability of the porous polyethylene im-
plant makes it possible to suture the extraocular
muscles directly to the implant [26].
Because of the fibrovascular ingrowth into an
integrated implant, a titanium peg can be placed into
the implant, which couples to the posterior surface of
the prosthesis for increased motility of the prosthesis.
Placement of the peg is usually performed at least
6 months after enucleation to allow for sufficient
vascularization of the implant. Although motility peg
placement can improve patient satisfaction after
enucleation [31], a significant proportion of patients
suffer from minor, peg-associated complications [32].
Therefore, most surgeons in the United States choose
not to place a motility peg [27].
After the orbital implant material has been se-
lected and the implant has been placed into the
muscle cone [33], the rectus muscles are sutured
to the implant, to the wrapping material, or to one
another anterior to the implant. Tenon’s capsule is
closed, with care not to incarcerate conjunctiva in the
closure. The conjunctiva is closed in a separate layer
to avoid conjunctival cyst formation. A conformer is
placed to occupy the fornices while the wound is
healing, and this is replaced by an ocular prosthesis in
about 6 weeks.
Enucleation can result in significant immediate
postoperative pain that requires outpatient oral
narcotics or inpatient analgesia [34,35]. Inadequate
postoperative pain relief can result in crying and
restlessness, which leads to hematoma formation, in-
creased pain, delayed wound healing, and prolonged
recovery. To reduce acute postoperative pain and
bleeding, 3–5 mL of a long-acting anesthetic with
epinephrine can be injected into the retrobulbar space
at the end of the surgical procedure. However, the
relief is only temporary. As an alternative, or in
combination with oral narcotics, an orbital catheter
can be placed for repeated delivery of a local anes-
thetic on an outpatient basis [36,37]. Although the
death of a patient who had a connective tissue ab-
normality has been attributed to the use of a par-
ticularly long indwelling orbital catheter [38], in
general, these catheters safely provide superior post-
operative pain control and allow a patient to recover
in a comfortable environment surrounded by a fa-
miliar support structure [37].
Perioperative complications of enucleation in-
clude orbital hemorrhage and edema, orbital infec-
tion, and conformer extrusion. These risks can be
minimized by preoperatively discontinuing antico-
agulants, leaving the clamp around the optic nerve
for several minutes after transaction of the optic
nerve, and administering systemic and topical anti-
biotics for 7 days postoperatively. A temporary su-
ture tarsorrhaphy can aid in the retention of the
conformer in cases of more severe postoperative
edema. Other complications, including implant migra-
tion, exposure, and extrusion, can be minimized by
the use of an integrated implant. Long-term compli-
cations after enucleation affecting cosmesis and fit-
ting of the ocular prosthesis include ptosis, lower
merbs290
eyelid retraction, superior sulcus deformity, and rela-
tive enophthalmos of the prosthesis because of re-
duced orbital volume [39].
Evisceration
Evisceration is the complete removal of the con-
tents of the eye while the scleral shell attached to
the extraocular muscles remains intact. Evisceration
is another surgical procedure that can effectively
eliminate intractable ocular pain [15]. When com-
pared with enucleation, evisceration is a simpler pro-
cedure, recovery is faster, and there is less trauma
to the orbital tissues [40]. This leads to superior
cosmesis and prosthesis movement because of the
preservation of the muscular attachments to the sclera
and their relationship to the orbital implant [41–43].
Evisceration, because it removes only a portion of the
eye, may be more acceptable to patients who are
having difficulty psychologically with enucleation. In
the pre-antibiotic era, evisceration was the treatment
of choice for a blind painful eye in the setting of
endophthalmitis, because it minimized the chance of
orbit and central nervous system contamination with
infectious organisms [44]. Many surgeons still prefer
evisceration in the setting of endophthalmitis.
Although evisceration has many advantages over
enucleation, significant controversy surrounds the
evisceration procedure because of the very small risk
of sympathetic ophthalmia. Sympathetic ophthalmia
is a bilateral granulomatous panuveitis that occurs
after penetrating ocular surgery or injury that involves
the uvea of one eye. The exact pathogenesis of sym-
pathetic ophthalmia is unknown, but it is thought
that the ocular penetration may release a uveal an-
tigen that stimulates an immunologic response [45].
Although an increased risk of sympathetic ophthal-
mia theoretically exists after evisceration because of
the inability to completely remove the uveal tissue
from the sclera [41,43,44,46], the true incidence of
sympathetic ophthalmia after evisceration is
unknown [44,47]. Even though anecdotal reports of
sympathetic ophthalmia exist in the older literature,
many surgeons believe that evisceration is a safe
and effective procedure with little risk of sympa-
thetic ophthalmia and better cosmesis and motility
[27,47,48].
A disadvantage of evisceration when compared
with enucleation is increased pain in the immediate
postoperative period [41,44,49]. However, eviscera-
tion ultimately results in pain relief equivalent to that
of enucleation; most patients achieve pain relief
within 6 weeks and the rest within 15 months [15].
Evisceration can unsuspectingly disseminate an intra-
ocular tumor, and therefore, when evisceration is
being considered, ophthalmic ultrasound should be
performed to eliminate the possibility of intraocular
malignancy [50].
Technique
Like enucleation, the surgical technique of evis-
ceration is well described in textbooks [21,51]. The
technique usually involves removing the cornea if it
is thin or severely traumatized. Also, some patients
may complain of postoperative corneal sensitivity if
the cornea is left intact [43]. After a 360� conjunctivalperitomy, the conjunctiva and Tenon’s capsule are
undermined for several millimeters, the anterior
chamber is entered at the limbus, and the cornea is
removed with scissors. Anterior relaxing incisions are
made in the sclera to facilitate entry of a larger
implant into the scleral cavity. An evisceration spoon
is used to remove the intraocular contents from the
sclera. The interior surface of the scleral shell is
wiped with absolute alcohol to remove any residual
uveal pigment and then rinsed with saline. The sites
of the four vortex veins and the optic nerve head
should be cauterized to minimize bleeding. Poste-
rior meridional and equatorial sclerotomies make it
possible to place an 18- or 20-mm implant and still
maintain effective closure without tension [52]. It is
important to avoid incising the sclera through a rectus
muscle insertion when performing the sclerotomies
to minimize the chance for intraoperative hemor-
rhage. After placement of a non-porous or porous
implant, the scleral edges are overlapped and secured
with mattress sutures. It is usually necessary to trim
the scleral corners to avoid redundancy and allow for
a smooth closure. Interrupted absorbable sutures are
used to close Tenon’s capsule and the conjunctiva is
closed by using a running absorbable suture. In cases
of endophthalmitis, placement of an orbital implant
is usually performed as a secondary procedure after
evisceration, to minimize the risk of implant infection
[19,21], although some believe it is safe to place the
implant during the primary procedure [53].
Complications after evisceration with an implant
are similar to enucleation: possible implant exposure,
infection, or extrusion as well as periorbital changes
such as superior sulcus defect [54].
Summary
Debilitating ocular pain poses a significant chal-
lenge to the ophthalmologist. Enucleation or eviscera-
blind painful eye management 291
tion of a blind painful eye is usually recommended
because of its ability to permanently eliminate the
eye pain. However, many people are uncomfortable
psychologically with removal of their eye, however
painful, and other patients are not good surgical can-
didates. For both of these situations, retrobulbar
injection provides an excellent alternative for tempo-
rary pain relief.
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Ophthalmol Clin N
Complications of Anesthesia for Ocular Surgery
Marc Goldberg, MDT
Wills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA
Ophthalmic anesthesia is unique because ophthal-
mic surgery itself rarely causes unanticipated hemo-
dynamic instability. Unlike more invasive surgery,
intravascular fluid shifts, blood loss, and changes
in cardiac, respiratory, hepatic, and renal function are
almost never caused by the surgical procedure. Com-
plications of anesthetic management stand alone;
patients are subject to every known complication of
anesthesia, magnified at times by ophthalmologic
or patient demographic factors, but not caused by
those factors. Ocular anesthesia complications can be
divided into three categories: complications of moni-
tored anesthesia care (MAC), complications of gen-
eral anesthesia, and a small set of complications
unique to ophthalmic surgery.
Systematic study of anesthesia complications be-
gan in 1984 when the American Society of Anesthe-
siologists (ASA) initiated a review of closed medical
malpractice claims, the ASA Closed Claims Project.
Malpractice insurers voluntarily reported details of
5,475 claims against anesthesiologists that were
finally adjudicated between 1970 and 1999 [1]. It
was quickly evident that respiratory misadventures,
particularly inability to ventilate patients by mask
or intubate patients’ tracheas, were the cause of the
worst outcomes and highest dollar payouts for mal-
practice claims. Analysis of the types of claims al-
lowed classification by root causes and prompted
specific anesthesia practice guidelines that have
significantly improved patient safety and reduced
the number of claims and their severity (Fig. 1) [2].
Malpractice costs for anesthesiologists have reflected
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NJ 08077.
E-mail address: [email protected]
this emphasis on safety. Average cost for malpractice
insurance for anesthesiologists is $21,000 per year,
less than 20 years ago in constant dollars [3].
The Closed Claims Project allowed analysis of
clusters of complications, showing systemic issues
or common root causes and suggesting methods of
prevention not evident via analysis of any one par-
ticular claim. Closed claims results show that the
frequency of hypoxic episodes resulting in brain
death or damage has decreased, although these claim
payouts are still in the hundreds of thousands of
dollars [4]. As Cheney [4] noted, in the 1970 to 1979
period, 41% of closed claims were for death and 15%
were for brain damage. By 1990 to 1994, only 22%
of closed claims were for death and only 9% were for
brain damage. This correlates with the universal in-
troduction of pulse oximetry and capnometry in first-
world countries. At the other end of the frequency/
payout spectrum, dental damage during airway
manipulation is now the most frequent minor claim.
Warner found an incidence of dental injury in 1 in
2,805 patients who had endotracheal intubation [5].
The mean repair cost was $782, with a range of $88
to $8,200. Closed claims analysis is used in this
article to elaborate the complications of MAC and
general anesthesia.
Complications of monitored anesthesia care
Postoperative nausea and vomiting
The most frequent complication of MAC is post-
operative nausea or vomiting (PONV). Awide variety
of afferent pathways, including vagal, sympathetic,
and vestibular nerves, activated by visceral distention
or traction, activate the chemoreceptor trigger zone
Am 19 (2006) 293 – 307
reserved.
ophthalmology.theclinics.com
Fig. 1. American Society of Anesthesiologists Difficult Airway Algorithm. As a practice parameter and standard of care, the
difficult airway algorithm provides guidance for management of suspected and unsuspected airways. The conceptualization
behind its adoption has significantly decreased anesthesia morbidity and mortality from hypoxia. (Adapted from American
Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the
difficult airway. A report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway.
Anesthesiology 1993;78(3):597–602.)
goldberg294
Fig. 2. Cumulative risk of PONV. Risk factors include female gender, nonsmoking, history of motion sickness or PONV, and the
use of postoperative narcotics. (Data from Apfel CC, Laara E, Koivuranta M. A simplified risk score for predicting post-
operative nausea and vomiting: conclusions from cross-validations between two centers. Anesthesiology 1999;91:693–700.)
complications of anesthesia for ocular surgery 295
(CTZ), located on the floor of the fourth ventricle.
Higher cortical pathways triggered by pain, hypoxia,
increased intracranial pressure, and odors also acti-
vate the CTZ. All narcotics act directly on the CTZ to
cause PONV, but reversal of narcotic action by nal-
oxone may paradoxically increase PONV because of
the resulting increased perception of pain.
Different studies estimate the incidence of PONV
to be between 10% and 80%. Risk factors include
female gender, particularly in premenopausal women,
nonsmoking, use of narcotics and nitrous oxide, a
past history of PONV or motion sickness, younger
age, and gynecologic and certain ophthalmic surger-
ies. Apfel and colleagues [6] developed a risk score
for prediction of PONV, demonstrating that the risks
were cumulative (Fig. 2).
PONV is the complication most feared by
patients. In addition to patient discomfort, PONV
contributes to increased nursing costs, delays in post-
operative discharge from the operative facility, and
readmissions to hospital. Prevention of PONV is
more effective than treatment, but antiemetics have
independent adverse side effects and increase the cost
of surgery. Identification of at-risk patients allows
targeting of prophylactic treatment. Prophylaxis is
more cost-effective for the high-risk pediatric patient
having strabismus surgery than for the elderly patient
having cataract removal. Narcotic treatment, a major
trigger of PONV, should be avoided whenever pos-
sible for ocular patients.
Thousands of papers in the anesthesiology litera-
ture have assessed different antiemetic regimens, with
no clear consensus as to which regimen is most ef-
fective. Avoidance of triggering agents, particularly
narcotics and nitrous oxide, has been shown in mul-
tiple studies to decrease the incidence of PONV.
Some studies find a benefit to high inspired oxygen
concentrations; other studies do not [7,8]. Acetamino-
phen and ketorolac may substitute for narcotics for
relief of postoperative pain. Nonnarcotic analgesics
are more effective if administered before the onset
of surgical stimulation. The modern use of propofol,
which itself has an antiemetic effect, and midazolam
for sedation has decreased the incidence of PONV
compared with barbiturates and diazepam [9].
The most common agents used prophylactically
or for treatment of PONV are the antiserotonin drugs
ondansetron, dolasetron, and granisetron. These drugs
have no effect on dopaminergic, cholinergic, adren-
ergic, or histaminic receptors and have a remarkably
low incidence of adverse side effects. Ondansetron
may be associated with headaches (9%), and dolase-
tron may cause symptomatic electrocardiographic
changes, including increases in PR and QRS intervals
[10,11]. Depending on type of surgery and patient
population considered, 5-HT3 receptor blockers have
been found to significantly decrease the incidence
of PONVor to decrease it no more than supplemental
oxygen [12,13].
The corticosteroid dexamethasone has prophylac-
tic PONV and antiemetic effects, demonstrated in
many studies. Bhatia and colleagues [14] found a
much lower incidence of PONV in pediatric strabis-
mus patients prophylactically treated with dexametha-
sone 0.25mg/kg (P = .001) between 0 and 24 hours
after surgery than in the control group. Fifty-one
percent of children who received dexamethasone had
no PONV compared with only 15% of children in the
Box 1. General anesthesia complications
Airway difficultiesCardiac compromise and arrestRespiratory depression and aspirationUnexpected awareness during anesthesiaFailure to regain consciousnessComplications of monitoringPeripheral nerve damageAllergic reactionsHepatic and renal compromiseEquipment malfunctions, mechanical
misadventures, and syringe swapMortalityDental damageAirway management
goldberg296
control group. Hyperglycemia and impaired wound
healing were not seen.
Droperidol, a centrally acting butyrophenone, is
extremely effective in low doses for PONV prophy-
laxis and treatment by itself and in combination with
other drugs [15]. After several incidents of prolonged
QT intervals leading to the ventricular dysrhythmia
torsades de pointes, the American Food and Drug
Administration issued a ‘‘black box’’ warning against
the use of droperidol for PONV. A review of the
cases, particularly considering the many millions of
previous uses of droperidol for PONV, suggests that
the warning was unnecessary [16].
Metaclopramide acts on central domaminergic re-
ceptors and has long been used as an adjunct, rather
than as a primary anti-PONV drug. By itself, it has
little efficacy and probably has no role in nonrescue
PONV treatment [17,18]. Extrapyramidal side effects,
although rare, are extremely disturbing.
PONV is the most common complaint after MAC
anesthesia. Adequate (pre-) treatment of pain with
nonnarcotic analgesics and avoidance of narcotics
whenever possible, and prophylactic pretreatment of
high-risk patients with use of serotonin antagonists
and dexamethasone, are the most reliable means to
avoid PONV.
Oversedation and undersedation
Another frequent complication of MAC for oph-
thalmic surgery is over- or undersedation of patients.
Adequate topical or nerve block anesthesia is critical
to use of MAC because using intravenous sedatives
(propofol, midazolam, narcotics) to compensate for
inadequate local anesthetic will result in oversedation
and airway obstruction. Careful attention to the pa-
tient’s level of consciousness and comfort is critical
to avoid the extremes of either patient discomfort or
hypoxia and respiratory compromise during surgery.
During ocular surgery, the anesthesia provider has
impaired access to the patient’s airway and less abil-
ity to assess patient response because the patient’s
head position is oriented away from the anesthetist.
There is an unfortunate tendency to be less ‘‘in
contact’’ with the patient and to lower the level of
vigilance; MAC is sometimes considered less of an
anesthetic than general anesthesia. The same level of
vigilance is required for MAC as for general anes-
thesia. For certain patients, MAC is more difficult
to provide than general anesthesia. Though the use
of the pulse oximeter has decreased the incidence
of unrecognized hypoxia, electronic monitoring
should not substitute for visual and tactile contact
with the patient.
Inadvertent local anesthetic injection
Intravascular and subarachnoid injection of local
anesthetic agents is an infrequent but serious com-
plication of MAC [19]. Undoubtedly an under-
reported complication, unexpected subarachnoid
local anesthetic injection has decreased with replace-
ment of retrobulbar blocks by topical, peribulbar, or
subtenon’s injection of local anesthetic. Newer topi-
calization techniques have also decreased the inci-
dence of accidental intraorbital injection of local
anesthetics. Intravenous injection of ophthalmic
volumes of local anesthetics (eg, 5 to 10 mL of
bupivicaine or carbocaine 0.5%) may cause transient
CNS effects but rarely cause cardiovascular collapse,
as would larger volumes of local anesthetics. Intra-
arterial injection of these volumes of local anesthetics
may cause a grand-mal seizure or respiratory arrest.
Although the incidence of intravascular and sub-
arachnoid local anesthetic injection has decreased,
anesthesia providers must be ready immediately to
secure the patient’s airway and to administer ad-
vanced cardiac life support if needed.
Complications of general anesthesia
Ophthalmic anesthesia is subject to all of the po-
tential complications of general anesthesia even
though the level of surgical stimulation and fluid
shifts are smaller than for other operations. A list of
general anesthesia complications appears in Box 1.
As noted, skillful airway management is critical to
avoid hypoxia upon induction of anesthesia. Evalua-
tion begins with the history of previous anesthetics,
particularly whether patients have been told that their
complications of anesthesia for ocular surgery 297
tracheas are difficult to intubate. After difficulty in
either ventilating by mask or intubating, the anes-
thesiologist must inform the patient or family of the
difficulty. This is best done via a letter that explains
the problems encountered and how the airway was
ultimately established (or not). Patients with known
difficult airways should be advised to share such a
letter with future anesthesiologists and to consider ob-
taining a MedicAlert bracelet for difficult intubation.
The anesthesiologist observes the airway, looking
for the visibility of the epiglottis, tonsil pillars, uvula,
and soft palate as the airway class advances from 0 to
4, as described by Mallampati [20]. A class 0 airway,
wherein the epiglottis itself is visible, should present
little intubation difficulty. A class 4 airway, with a
large tongue, small oral opening, protruding teeth,
and only hard palate visible, correlates with 84%
sensitivity and 71% specificity for inadequate view
on laryngoscopy [21]. The anesthesiologist’s goal is
to detect potentially difficult airways before induction
of general anesthesia, however, Mallampati classi-
fication and other screening systems imperfectly
predict intubating difficulty [22]. Morbid obesity,
pregnancy, cervical spine disease, thyroid nodules,
Down’s syndrome, and congenital or acquired tra-
cheal stenosis may also increase the potential for air-
way management problems. Patients with anticipated
difficult intubations, or a history of difficult intuba-
tion, may require awake (sedated) fiberoptic intuba-
tion to prevent loss of the airway and inability to
ventilate the lungs. Laryngeal mask airways (LMA)
are commonly used either to avoid endotracheal intu-
bation or as rescue airways after difficult intubation
or ventilation. LMAs can provide an airway seal up to
20 cmH20 pressure, giving some assurance against
aspiration. However, many anesthesiologists are
reluctant to rely on LMAs for positive pressure ven-
tilation in paralyzed patients because of the risk of
regurgitation of stomach contents and pulmonary as-
piration. If an ophthalmology patient needs paralysis
or the guarantee of minimal eye movement, and has a
difficult airway, the anesthesiologist may prefer to
secure the airway via awake fiberoptic intubation—
an intervention considerably more invasive than
many ocular surgeries. The ASA Difficult Airway
Algorithm (see Fig. 1) gives best practice parameters
for the anticipated and unanticipated difficult airway.
Peterson recently reviewed ASA closed claims
data for difficult airway management between 1985
and 1999 [23]. Since promulgation of the ASA
difficult airway algorithm, the likelihood of death or
brain damage for an airway claim during induction
decreased almost 50%, whereas the odds of death
or brain damage during the other phases of the
anesthetic remained the same. The fear that practice
guidelines may be used legally against physicians did
not materialize. The airway algorithm was used in
only 8% of claims to defend the care given; it was
cited in only 3% of claims to criticize the care given.
A related airway compromise at the end of the
general anesthetic may result in life-threatening pul-
monary edema. Obstruction of the airway, most
commonly by laryngospasm, may result in markedly
negative intrapleural pressures (up to �100 cmH20)
and draws transcapillary fluid into the alveoli. Risk
factors include young age, male gender, sleep apnea,
hypertrophied adenoids or tonsils, hypoxia, and
hyperadrenergic states. If early airway obstruction
during emergence is suspected, mechanical airway
opening (oral airways) or administration of small
amounts of succinylcholine (5 to 10 mg) may relieve
obstruction or laryngospasm and prevent develop-
ment of negative-pressure pulmonary edema. If these
measures fail, most patients require reintubation,
positive-pressure ventilation, and postincident moni-
toring. Episodes resolve quickly without diuresis and
without permanent sequellae, unlike other causes of
postoperative pulmonary edema, such as aspiration
pneumonia, acute respiratory distress syndrome, co-
existing cardiac anomalies or myocardial infarction,
and anaphylaxis.
Aspiration of gastric contents
Passive or active aspiration of gastric contents can
cause aspiration pneumonia, which has a high rate
of morbidity and mortality. Traditional practice has
called for an 8-hour fast before elective surgical
procedures for adults. Recent studies have indicated
that a total fast can decrease gastric pH and make
aspiration-induced pulmonary damage worse. Fasting
guidelines for children reflect this change [24]. Chil-
dren under 6 months of age should have a 2-hour
clear-liquid fast before elective surgery. Children be-
tween 6 and 36 months should fast for 3 hours; older
children should fast for 8 hours. Formula and breast
milk are considered solids and should occasion a
4-hour fast. Particulate aspiration is probably more
harmful than acid aspiration.
Patients at risk for aspiration include those who
require emergency surgeries, morbidly obese or preg-
nant patients, and diabetics with gastric motility dis-
orders. These patients are always considered to have
‘‘full stomachs.’’ Patients with difficult airways are
also at risk due to gastric gas insufflation during air-
way manipulation.
Table 1
American Society of Anesthesiologists Physical Status
Classification
ASA
class Description
I Healthy patient
II Mild systemic diseases—no functional limitation
III Severe systemic disease—definite functional
limitation
IV Severe systemic disease that is a constant threat
to life
V Moribund patient unlikely to survive 24 hours
with or without surgery
VI Organ donor
goldberg298
Warner and colleagues [25] found the incidence
of aspiration in general anesthetics was 1 in 3,216;
aspiration was 4.3 times more likely during emer-
gency surgery. Most (64%) of patients who aspirated
did not develop coughing, wheezing, or decreased
arterial oxygen saturation within 2 hours of aspira-
tion. This patient group did not develop respiratory
sequellae. One half of the remaining patients needed
respiratory support for longer than 6 hours after
aspiration, and 5% of these patients died of respira-
tory insufficiency.
Prophylaxis against aspiration includes delaying
emergency surgery if possible, administration of non-
particulate antacids, use of cricoid pressure to prevent
regurgitation during endotracheal intubation, and
postintubation emptying of gastric contents by way
of a nasogastric tube.
Cardiac complications
All of the currently used potent inhalation anes-
thetics (isoflurane, sevoflurane, and desflurane) have
negative inotropic effects and may affect heart
rhythm and atrial-ventricular conduction.Cardiac con-
cerns for young patients are primarily avoidance of
severe bradycardia or asystole from the occulocardiac
reflex and recognition of rare congenital or acquired
valvular or cardiac structural anomalies, such as atrial
or ventricular septal defects. Elderly patients present
issues of myocardial ischemia, cardiomyopathy, and
valvular stenosis or insufficiency.
The preanesthetic history includes a functional
assessment of the patient’s cardiac status using a
standardized guideline, such as the American College
of Cardiology/American Heart Association scale of
cardiac risk factors, including exercise capability,
recent history of myocardial infarction, dysrhythmias,
congestive heart failure, and presence of a pacemaker
or automatic implanted defibrillator [26]. These
assessment systems are used to determine the extent
of preoperative cardiac function investigation needed
to reduce risk of intraoperative or postoperative myo-
cardial ischemia. Patients with multiple risk factors
who have not had a reasonable cardiologic evaluation
may require consultation, a stress test or echocardio-
gram, or, rarely, cardiac catheterization before elec-
tive ophthalmic surgery.
The incidence of myocardial infarction or ische-
mia after ocular surgery is small. McCannel and col-
leagues [27] followed 418 patients for 4 weeks who
had received general anesthesia for vitreoretinal or
ocular oncologic surgery. The incidence of myocar-
dial infarction was 0.24% (one case). However, the
average American Society of Anesthesiology physi-
cal status of his patients was 2.1; elderly patients
frequently have multiple medical conditions and a
physical status of III or IV, indicating greater like-
lihood of postoperative complications (Table 1). Mor-
tality and morbidity estimation based on ASA
physical status must be qualified by the limited inva-
siveness of ocular surgery.
General anesthesia permits alleviation of anxiety
and pain with provision of high levels of arterial
oxygenation and decreased myocardial demand for
oxygen (from the negative inotropic effect of inhaled
anesthetics). For patients and procedures not amena-
ble to local anesthesia, general anesthesia is safe as
long as the patient’s cardiac risk factors are assessed
and optimized, symptoms and signs of ischemia are
monitored and recognized, and airway obstruction
and hypoxia throughout the perianesthetic period are
avoided. Anesthesia personnel should be prepared
to provide initial treatment of myocardial ischemia
and should be advance cardiac life-support certified
(or its equivalent) to treat dysrhythmias during or af-
ter surgery.
Awareness during anesthesia
Unintended patient consciousness during general
anesthesia has received increased recognition in the
past 10 years [28]. The ASA Closed Claims Project
disclosed 79 (1.9%) of 4,183 claims were for intra-
operative awareness [29]. Estimates of awareness
during anesthesia with use of neuromuscular blocking
drugs (NMBs) are as high as 1 in 556 general anes-
thetics [30]. Potent inhalation anesthetics generally
provide amnesia at 20% of the dose required to pre-
vent movement upon surgical stimulation. Anesthetic
adjuncts, such as midazolam, have excellent amnesic
complications of anesthesia for ocular surgery 299
properties in small doses. However, patient variation,
use of NMBs, and lack of definitive clinical signs of
awareness make it difficult to detect. During general
anesthesia with an LMA, spontaneous ventilation and
avoidance of NMBs require deep enough levels of
anesthesia to prevent movement so that conscious-
ness rarely occurs. Patient paralysis may mask
inadequate anesthesia. Emergency (eg, trauma, Cae-
sarian section) and cardiac surgery patients, who
receive more NMB than inhalation agent, are more at
risk of awareness than ocular patients.
Patientsmay remember a combination of conscious-
ness, conversations, or pain during general anesthesia.
Self-doubt, anger, nightmares, and fear of future op-
erations may result, as a form of posttraumatic stress
syndrome [31]. Treatment involves frank discussion
with the patient acknowledging that awareness has
occurred. Fear of legally admitting liability should not
dissuade the anesthesiologist from discussing the
problem with the patient. The best legal defense against
a claim for awareness during anesthesia is that the
anesthesiologist has informed a patient of the risk be-
fore the operation; (2) talked to her after the surgery
about her experience; and (3) provided her with an
explanation or an apology [32].
Some of the increased concern about awareness
during general anesthesia may coincide with the in-
troduction of a monitor that purports to detect it [33].
The BIS monitor uses a proprietary algorithm to pro-
cess an electroencephalographic signal. It produces
an absolute number from 0 (isoelectric EEG) to 100
(fully awake); awareness and recall supposedly do
not occur when the BIS score is between 50 and 60.
O’Connor and colleagues [34] performed a power
analysis to determine the cost of preventing aware-
ness using BIS monitoring. If the incidence of aware-
ness is 1 in 20,000, the cost to detect one case is
$400,000; if the incidence is 1 in 100, the cost to
detect one case is $2,000. Because there are reported
cases of awareness using BIS monitoring, O’Connor
[35] concludes that BIS monitoring is not cost-
effective for prevention of awareness.
The ASA is currently in heated discussion about
adopting some type of EEG monitoring to detect and
prevent intraoperative awareness. Until BIS or some
equivalent monitor becomes a standard of care by
way of a practice guideline, its use is at the discretion
of the individual anesthesiologist. Ophthalmologic
patients are rarely at high risk for awareness. Judi-
cious use of NMBs and administration of low doses
of potent inhalation agents along with pre- and
postoperative patient consultation is the most cost-
effective way to prevent the consequences of aware-
ness during general anesthesia.
Failure to regain consciousness after general
anesthesia
Unanticipated failure to regain consciousness after
general anesthesia is fortunately a rare complication.
The most common reason is probably anesthetic
overdose. This is usually as a result of inadvertently
continuing to administer inhalation anesthetics by
failing to turn off the vaporizer, overuse of narcotics
or NMBs, or syringe swap (eg, giving an NMB in-
stead of a NMB reversal agent). Use of capnometry
with analysis of inhalation agents is useful to detect
their accidental continued administration. Peripheral
nerve monitoring (‘‘twitch monitoring’’) allows as-
sessment of the degree of neuromuscular blockade
and the effectiveness of NMB reversal drugs. Recog-
nizing the potential for reactive hypertension and
tachycardia, naloxone, physostigmine, and flumazenil
may be used to reverse sedation from, respectively,
narcotics, centrally acting anticholinergic agents
(scopolamine and rarely ophthalmic atropine), and
benzodiazepines. Hyperventilation, used to quickly
eliminate inhalation anesthetics, frequently decreases
arterial carbon dioxide levels below the level required
(PaCO2 of 45 mmHg). This eliminates the sponta-
neous hypercarbic ventilatory drive needed to acti-
vate the respiratory centers. Respiratory drive is also
blunted by small residual doses of inhalation anes-
thetics. Because the patient (hopefully) lacks a hyp-
oxic ventilatory drive, relative hypocarbia leaves the
patient apneic until carbon dioxide levels rise with
metabolism. Hypocarbic apnea combined with mini-
mal stimulation and use of ocular local anesthetics
can make the patient appear unresponsive for 10 to
20 minutes after cessation of a general anesthetic.
After unexpected unresponsiveness persists and
anesthetic overdose has been eliminated as a cause,
less frequent and more serious causes must be con-
sidered. Metabolic causes of persistent unconscious-
ness include hypoglycemia, particularly in diabetic
patients, hyperglycemia and hyperosmolar syn-
dromes, hepatic and renal dysfunction, electrolyte
imbalance (particularly hyponatremia), hypothermia
and hyperthermia, and acidosis. Intraoperative neuro-
logic injury may occur from hypoxemia or cerebral
hypoxia and hypoperfusion, intracranial hemorrhage,
and cerebral embolism. Though some operations are
associated with cerebral impairment (heart surgery
with cardiopulmonary bypass, major joint replace-
ment), ocular surgery normally lacks this association.
Failure to regain consciousness after general anes-
thesia requires maintenance of oxygenation and
ventilation with mechanical ventilatory support; veri-
fication of arterial oxygen, carbon dioxide, pH, elec-
goldberg300
trolyte, glucose, and serum osmolarity levels; and, if
not tested preoperatively, determination of hepatic
and renal function. CT or MRI scans may detect intra-
cranial hemorrhage, mass lesions, or anoxic enceph-
alopathy. If due to anesthetic overdose of some kind,
patients will regain consciousness to some de-
gree within hours of anesthetic cessation. If uncon-
sciousness persists longer, neurologic or neurosurgical
consultation should be obtained.
Monitoring complications
Ophthalmic patients frequently have significant co-
morbidity, including coronary artery disease, chronic
obstructive pulmonary disease, diabetes, and cerebral,
renal, or hepatic insufficiency. Use of electrocardio-
gram, noninvasive blood pressure, capnometry, pulse
oximetry, and temperature during general anesthesia is
the standard of care [36]. Complications from these
monitors are extremely rare.
Invasive monitors, such as peripheral arterial,
central venous, and pulmonary artery catheters, have
a significantly higher risk of complications, including
vessel thrombosis, arterial dissection, ventricular dys-
rhythmias, and infection [37]. A more subtle com-
plication of invasive monitoring is lack of usefulness
or misinterpretation of the information provided [38].
Considering the risks of invasive hemodynamic
monitoring and its marginal benefits to the ocular
patient who does not undergo massively stimulating
surgery or suffer large fluid shifts, few of these pa-
tients need invasive monitoring for purely ocular sur-
gery. The patient whose preoperative evaluation
suggests a need for invasive monitoring is probably
not in optimal medical condition for elective surgery.
Peripheral nerve damage
Peripheral nerve damage is a surprisingly fre-
quent complication after general anesthesia. The ASA
Closed Claims study reviewed 670 claims for pe-
ripheral nerve damage (16% of 4,183 claims); most
claims associated with general anesthesia were for
injury to the ulnar nerve [39]. Warner and colleagues
[40] found a rate of development of unilateral (91%)
or bilateral (9%) ulnar neuropathy in 1 in 2,729 pa-
tients undergoing general anesthesia at the Mayo
Clinic. Predisposing factors include male gender, thin
or obese body habitus, and preexisting neuropathy
and diabetes. Although proper padding and patient
positioning during general anesthesia are critical to
preventing ulnar nerve injury, postoperative deficits
may still occur despite these precautions. Neurop-
athies may not become manifest until days after
surgery; the anesthesiologist will only discover them
if the patient complains to the surgeon [41]. The
ultimate outcome is not good; only 53% of Warner’s
patients regained complete motor function and sen-
sation a year after anesthesia and surgery [40]. Be-
cause good anesthesia practice (proper positioning
and padding) does not reliably prevent postanesthetic
neuropathy development, it may be useful to include
this complication when obtaining informed consent
for general anesthesia.
Allergic reactions during general anesthesia
Most intravenous anesthetic agents have been re-
ported to cause allergic reactions. However, reactions
range from the expected (nausea from narcotics,
reddish facial flushing from atropine) to the catas-
trophic (anaphylactic/anaphylactoid), requiring car-
diopulmonary resuscitation. Preoperative evaluation
involves careful questioning of the circumstances of a
reaction to medication. For example, patients com-
monly claim to be allergic to local anesthetics, but
true anaphylaxis is exceedingly rare, even reportable
[42]. Much more likely, the circumstances will reveal
an expected cerebral reaction to rapid injection of
local anesthetic or cardiovascular reaction to rapid
injection of adjuvant epinephrine (eg, during den-
tal injections).
Anaphylactic reactions are immune mediated;
some previous exposure to a related antigen is neces-
sary for antibody formation and reaction to occur.
Anaphylactoid reactions are not immune related and
may occur on first exposure to a triggering agent.
Like most emergencies in anesthesia, recognition and
immediate treatment is more important than definitive
diagnosis of which agent has caused the reaction and
why [43,44].
Anaphylactic reactions under general anesthesia
produce any of the following symptoms and signs:
wheezing, hypoxia, increased peak airway pressures,
acute pulmonary edema, bronchospasm, tachycardia,
dysrhythmia, severe hypotension or cardiovascular
collapse, urticaria, or periorbital and perioral edema
[45]. Treatment requires removal of the triggering
agent if identified and discontinuation of anesthetic
agents, early use of epinephrine and corticosteroids,
fluid resuscitation, protection of the airway by way of
endotracheal intubation, administration of 100%
oxygen, and rapid termination of the surgical proce-
dure. Even in the operating room context with instant
observation, full monitoring and resuscitative mea-
complications of anesthesia for ocular surgery 301
sures available, severe outcomes, such as cardiac
arrest, renal failure, coma, persistent vegetative state,
hemiplegia, or other neurologic sequellae, may re-
sult [46].
A recent French study reviewed 789 episodes of
anaphylactic reactions during anesthesia. Most (58%)
were caused by NMBs, particularly the newer non-
depolarizing NMB rocuronium, with the rest caused
by latex (17%), antibiotics (15%), and other various
medications (10%) [47]. Rocuronium and succinyl-
choline were the NMBs most likely to cause these
reactions; after allergy testing, cross-reactivity be-
tween NMBs was observed in 75% of cases [47].
Although the French study may have overestimated
the incidence of anaphylaxis as a result of their
method of skin testing, American and Norwegian
studies also found NMBs to be the most common
cause of perioperative anaphylactic reactions [48,49].
Inhalation agents do not cause anaphylactic reac-
tions. The only instance of allergic reaction to inhala-
tion anesthetics is rare, reportable cases of hepatitis
after repeated exposure. Sufficient doubt has been
cast on the existence of ‘‘halothane hepatitis’’ to con-
sider it an exceedingly rare reaction [50]. However,
prolonged exposure to inhalation anesthetics that pro-
duce trifluroacetyl (halothane, isoflurane, and des-
flurane) results in antibodies to the molecule in
anesthesia personnel [51]. Inhalation agent related
hepatitis remains a diagnosis of exclusion.
Renal and hepatic complications of general
anesthesia
Various metabolites of inhalation anesthetics have
been theorized to cause renal function impairment.
Fluoride ion from halothane, isoflurane, and sevo-
flurane can be measured, after long exposure, in
micron concentrations associated with nephrotoxicity
in animals [52]. However, Kharasch and colleagues
[53] measured serum creatinine, blood urea nitrogen,
creatinine clearance, urinary protein, and glucose
excretion for 24 and 72 hours after 9 hour mean
exposure to sevoflurane and isoflurane and found no
evidence of renal function impairment. Sevoflurane
metabolism under particular conditions (low fresh gas
flows, particularly desiccated carbon dioxide absor-
bent) produces a haloalkane called ‘‘compound A,’’
which causes nephrotoxicity in rats [54]. Kharasch
[53] and others who have reviewed this issue have
concluded that the incidence of renal function
abnormalities produced by sevoflurane must be ex-
ceedingly small given the large number of sevoflur-
ane anesthetics given since its introduction [55]. For
ophthalmic patients with compromised renal function
(eg, diabetics), sevoflurane may be used safely as
long as systemic hypotension and low fresh gas flows
(allowing washout of any compound A generated)
are avoided.
All potent inhalation anesthetics undergo hepatic
metabolism. Up to 15% to 20% of halothane is
metabolized, but the newer inhalation agents, sevo-
flurane and desflurane, undergo only 0.5% to 1%
metabolism [56]. There are case reports of fulminant
postoperative liver damage associated with all cur-
rently used inhalation anesthetics [57–59]. Proving a
causal association between hepatic dysfunction and
either a single or repeated exposure to an inhalation
anesthetic is exceptionally difficult. Patients who
present with hepatic dysfunction after anesthesia
most often have other comorbidities or surgeries that
predispose them to hepatic damage. Many studies
have closely measured hepatic function and found
minimal alterations after anesthesia. For example,
Suttner and colleagues [60] found that though
hepatocyte oxygenation levels slightly decreased dur-
ing general anesthesia with desflurane and sevoflur-
ane, overall hepatic function was unchanged.
Various mechanisms have been proposed for he-
patic injury after general anesthesia. Concurrent viral
hepatitis may be unmasked by the stress of surgery
and anesthesia, and most likely accounts for most
anesthesia-related hepatic dysfunction. Oxidative and
reductive metabolism of inhalation anesthetics results
in compounds hepatotoxic in some species (rats, cats)
but not others (dogs, mice) [61]. Metabolites of halo-
thane have been found to bind to liver proteins and
act as haptenes to produce hepatocyte-specific anti-
bodies, which in certain families and patient popu-
lations reliably cause postexposure hepatitis [62].
Risk factors for inhalation agent-related hepatitis
include obesity, middle age, female gender, and
Mexican-American ethnicity. Obesity allows extended
duration of storage and slow release and further
metabolism of lipid-soluble agents. Repeated ex-
posure, except in patients previously suspected of
inhalation-related hepatitis, does not predispose to
hepatic dysfunction.
The entire subject of inhalation-related hepatic
dysfunction has been compared with ‘‘a sea of mys-
tery, with some islands of knowledge, but generally
pervaded by clouds of speculation, misinformation,
and ignorance’’ [63]. The diagnosis of postinhalation
agent hepatitis is a diagnosis of exclusion, and cases
are rare enough to be reportable. Proper attention to
preexisting liver function via history and laboratory
examination, avoidance of (repeated) exposure in the
face of a family history of anesthesia-related hepatitis,
goldberg302
and avoidance of liver hypoxia and hypoperfusion
should make postocular surgery hepatitis an ex-
tremely rare complication of general anesthesia.
Equipment malfunctions and mechanical
misadventures
Anesthesia gas delivery systems and monitors
are highly reliable but are subject to human error
(common) and mechanical or electronic failure (rare)
[64]. The standard of care is that anesthesia machine
and monitor readiness are checked extensively at the
beginning of the day and briefly before each sub-
sequent case against a US Food and Drug Adminis-
tration functionality checklist, much as a commercial
airline pilot goes through a checklist before takeoff
[65]. Unfortunately, compliance with the checklist
requirement has been less than optimal. Armstrong-
Brown and colleagues [66] reported that academic
attending anesthesiologists checked, on average, only
10 of 20 items on a standardized checklist. Intensive
training may improve machine checkout performance
[67]. Simulations with intentionally created machine
faults have also been disappointing. In a machine
with five intentional faults, 7% of anesthesiologists
found no faults and only 3% found all five faults. The
average number found was 2.2 faults [68]. Anesthesi-
ologists have reported some incredible human errors
(eg, complete anesthesia circuit obstruction due to
failure to remove shrink-wrap from carbon dioxide
absorber canisters) [69]. However, candor in report-
ing mechanical problems has led to improvements in
safety. For example, now carbon dioxide canisters
are packaged in corrugated plastic, which cannot
be ignored.
Modern anesthesia machines do not allow admin-
istration of hypoxic gas mixtures; ophthalmic office
practices should ensure that they do not use older
machines without this failsafe. Devices to indepen-
dently measure inspired oxygen concentration are par-
ticularly important in isolated or office facilities.
Anesthesia machines also have alarms that detect low
oxygen supply pressure, to alert to the need to switch
to new oxygen supply tanks or emergency oxygen
tanks mounted on the machine.
Initial and continuous measurement of end-tidal
carbon dioxide during general anesthesia is a firm
standard of care [70]. If a functioning capnometer is
not available, general anesthesia should not be pro-
vided. Introduction of capnometry has eliminated
otherwise undetected esophageal intubation, which
was previously a major source of anesthetic morbid-
ity and mortality, particularly in obese patients with
difficult airways and distant breath sounds. Analysis
of inspired and exhaled inhalation anesthetics, now
commonly and economically available on capnome-
ters, assists in not only decreasing unexpected
awareness during anesthesia but also in facilitating
anesthesia emergence.
An exhaustive list of equipment-related problems
with general anesthesia cannot be repeated here. En-
tire monographs have been dedicated to mechanical
misadventures in anesthesiology (including an amus-
ing photograph of a large ‘H’ oxygen cylinder’s mis-
sile trajectory when its yoke was broken and it flew
out of an operating room onto the sidewalk below)
and understanding anesthesia equipment [71,72].
New equipment malfunctions are reported continu-
ously and corrective actions are taken accordingly.
Compliance with machine checkout procedures, scru-
pulous adherence to monitoring standards, and avoid-
ance of personnel fatigue will increase detection and
prevention of mechanical problems with general
anesthesia [73].
Another common source of human error frequent
enough to mention is syringe swap [74]. Anesthesia
drugs are drawn from vials into labeled syringes in
advance of usage. Care must be taken to avoid mis-
taking look-alike vials or labels. Meticulous identifi-
cation of syringes immediately before injection can
prevent mistakes such as giving more NMB or nar-
cotic when an NMB reversal agent is intended. Mod-
ern inhalation vaporizers are agent specific and have
a key-lock system to prevent accidental introduction
of incorrect agents. Unfortunately, anesthesia person-
nel can be resourceful at bypassing safety systems.
Malignant hyperthermia
Malignant hyperthermia (MH) deserves mention
in a compendium of general anesthesia complications
because it has received attention disproportionate to
its incidence and is not likely to be encountered by an
ophthalmologist not specializing in pediatrics. MH is
an autosomal-dominant variable-penetrance genetic
defect of calcium reuptake. The incidence is reported
to be 1 in 15,000 children and may be more common
in pediatric strabismus patients [75]. The adult inci-
dence is less than 1 in 50,000 anesthetics. Succinyl-
choline and inhalation anesthetic agents trigger MH
and result in skeletal muscle hypermetabolism.
Before capnometry, the first indication of MH sus-
ceptibility was often high body temperature, para-
doxical masseter muscle rigidity, or oliguria and
myoglobinuria. By the time these signs appeared,
survival from an untreated episode was less than
complications of anesthesia for ocular surgery 303
30%. Routine use of capnometry allows early de-
tection of MH episodes, as the first sign of an episode
is hypercapnia despite seemingly adequate minute
ventilation. A Web site (www.mhaus.org) and an
expert-assisted hotline (United States and Canada,
1-800-644-9737, outside North America, 0011 315
464 7079), as well as a registry of known patients in
North America, is maintained by theMalignant Hyper-
thermia Association of the United States (MHAUS).
Family history of high temperature or fatality after
anesthesia is suggestive of susceptibility, but non-
diagnostic. Although several animal models, human
blood tests, and DNA mapping have been studied,
definitive diagnosis of MH is still made either after
a well-documented episode or by way of muscle bi-
opsy with in-vitro characteristic reactivity to trigger-
ing agents. Patients with a suggestive family history
need not undergo muscle biopsy; a nontriggering
anesthetic with propofol, midazolam, fentanyl, and a
nondepolarizing NMB can be safely given [76].
The skeletal muscle relaxant dantrolene is a spe-
cific inhibitor of MH-induced hypermetabolism.
Although expensive, it is a standard of care that dan-
trolene be readily available wherever inhalation anes-
thesia is provided. If geographically feasible, several
facilities may share parts of the supply of dantrolene
to decrease the per-facility cost.
Anesthetic mortality
Older patients often fear general anesthesia. Be-
fore modern monitoring techniques and anesthetic
agents, mortality from general anesthesia was as high
as 1 in 1,216 anesthetics [77]. By 1989, Eichhorn
[78] was able to report a mortality rate solely at-
tributable to general anesthesia of 1 in 200,000. The
reduction in mortality closely followed introduction
of standardized monitoring protocols despite some
caviling about the introduction of mandatory moni-
toring standards without double blind study verifica-
tion of efficacy [36,79].
The American Society of Anesthesiologists devel-
oped a clinical classification of patient preoperative
physical status in 1941, and although attempts have
been made to supplant it, it remains in use today (see
Table 1). Anesthetic mortality is roughly correlated
with physical status. Wolters found a mortality rate of
0.1% for ASA physical status I patients and 18% for
ASA physical status IV patients [80]. Type of surgery
(major vascular) and emergency surgery also increase
anesthetic mortality. Patient tolerance of critical in-
cidents (‘‘near misses’’) decreases as ASA physical
status increases.
Whether a particular type of anesthetic (MAC
versus general, or one agent versus another) can
prospectively affect mortality has been an extremely
controversial subject. Thousands of studies and meta-
analyses have not provided a clear answer. In the
ocular surgery setting, the common-sense thought
that general anesthesia is a more invasive intervention
than MAC is often, but not always, correct. MAC
anesthesia affects cardiovascular and respiratory
function less than general anesthesia and usually pro-
vides faster return to preoperative functionality. How-
ever, patients with extreme anxiety, claustrophobia,
chronic obstructive pulmonary disease, motion dis-
orders, compromised airways, and those who need
long (greater than 1.5 hours) surgery may have less
physiological stress with general anesthesia than with
MAC. General anesthesia with a secure airway, lack
of tachycardia and hypertension, and an immobile
surgical field is less stressful (for everyone) than ‘‘big
MAC’’ anesthesia with sedation, resulting in airway
obstruction and patient head or body movement.
Choice of MAC versus general anesthesia depends in
part on the patient’s ASA physical classification but
also on type and duration of surgical procedure and
patient, anesthesiologist, and surgeon emotional
characteristics. Perioperative mortality is influenced
more by skill in selection and administration of the
anesthetic than by choice of MAC versus general
anesthesia or the particular agent chosen.
Dental damage
Damage to teeth during either anesthetic induction
or emergence is one of the most frequent but minor
complications of general anesthesia [81]. As major
morbidities and mortalities decrease, the incidence of
dental claims in the ASA Closed Claims database has
increased; dental injuries may account for as many as
33% of anesthesia-related malpractice claims [82].
Warner and colleagues [5] found an incidence of
dental injuries requiring repair or extraction in 1 in
4,537 general anesthetics. Risk factors include poor
dentition, preexisting crowns or caps, and various
indices of difficult intubation. The level of resident
training did not affect the likelihood of dental in-
jury [83].
Anesthesia complications specific to the eye and
ocular surgery
Several ophthalmic complications of general anes-
thesia should not be of concern during ocular surgery.
goldberg304
Corneal abrasions account for 3% of ASA closed
claims; these cause pain, but permanent corneal dam-
age is rare. Malpractice payouts are low, and the
median payout is $3,000 [84]. Despite ophthalmo-
logic control of the surgical area, anesthesiologists
should be careful to prevent corneal abrasions of the
nonoperative eye.
Catastrophic visual loss after nonophthalmologic
surgery is rare. Ischemic optic neuropathy and reti-
nal arterial or venous occlusion are the most likely
mechanisms of injury [85]. Predisposing factors in-
clude preexisting hypertension, diabetes, sickle cell
anemia, renal failure, gastrointestinal ulcer, narrow-
angle glaucoma, vascular occlusive disease, cardiac
disease, arteriosclerosis, polycythemia vera, and col-
lagen vascular disorders. Precipitating factors for
ischemic optic neuropathy include prolonged hypo-
tension, anemia, surgery trauma, gastrointestinal
bleeding, hemorrhage, shock, prone position, direct
pressure on the globe, and long operative times.
Prone and Trendelenburg positions and increased in-
tracranial pressure are additional risk factors. Unex-
pected vision loss in the nonoperative eye after ocular
surgery is extremely rare.
Certain specific complications of general anes-
thesia occur during ocular surgery. Thirty percent of
ASA closed claims for ocular injury were due to
unexpected patient movement during ocular surgery;
blindness resulted in every case [84]. Inadequate
muscle relaxation by NMBs during inadequately
deep general anesthesia, or coughing from endotra-
cheal intubation, may cause retinal detachment,
corneal laceration, lens subluxation, or expulsion of
intraocular contents during corneal grafting. Preven-
tion requires use of neuromuscular blockade moni-
toring, assurance of adequate levels of anesthesia, and
acceptance of delayed NMB reversal upon com-
pletion of surgery as the price of assuring unexpected
movement during surgery.
The hoary debate about the effect of succinylcho-
line on intraocular pressure during ruptured globe
surgery has been obviated by use of nondepolarizing
NMBs [86]. Increased intraocular pressure from
succinylcholine may be associated with small corneal
lacerations or globe puncture wounds that have main-
tained overall globe integrity. If the globe is ruptured
or the laceration is large enough that the intraocular
pressure is near 0 mmHg, succinylcholine will not
increase the intraocular pressure. Use of a large dose
of nondepolarizing NMB provides emergency muscle
relaxation for intubation quickly compared with
succinylcholine [87].
A rare but avoidable complication of general
anesthesia after retinal surgery is blindness caused by
nitrous oxide-induced expansion of perflurocarbon or
sulfur hexafluoride bubbles. Nitrous oxide will dif-
fuse into gas-filled spaces faster than nitrogen; oxy-
gen or ophthalmic gases diffuse out and cause retinal
ischemia. Yang and colleagues [88] first reported a
case of blindness after nonocular general anesthesia
in 2002, and seven cases have been reported since
then. Patients who have retinal surgery with use of
intraocular gas bubbles should wear warning brace-
lets until the bubble has likely dissipated. The anes-
thesia history should disclose recent ocular surgery
for past retinal surgery or current retinal surgery, and
nitrous oxide is easily avoided.
Summary
Complications of MAC and general anesthesia are
increasingly rare, and severe morbidity and mortality
have decreased as techniques for prevention and
treatment have become widespread. Ocular anesthe-
sia involves population subsets (geriatric, pediatric,
vascular, and diabetic) that have known propensities
to have certain complications, and ophthalmic sur-
gery requires certain routine precautions to avoid
the most common complications. Vigilance in patient
evaluation, equipment and drug preparation, and
monitoring during surgery, despite production pres-
sure of modern anesthetic practice, is the best way to
prevent avoidable anesthesia complications [89].
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Ophthalmol Clin N
Economic Evaluation of Different Systems for Cataract
Surgery and Anesthesia
Kevin D. Frick, PhD
Johns Hopkins Bloomberg School of Public Health, Department of Health Policy and Management,
Health Services Research and Development Center, 624 North Broadway, Room 606, Baltimore, MD 21205, USA
Economic evaluation is an increasingly important
component of health and medical care policy making
although it continues to be met with some resistance—
in part because of misgivings about the methods that
are used [1,2]. Many fields of medical care services
and public health have extensive economic evalua-
tion literature. In ophthalmology, the literature is
less well developed and there is an ongoing dis-
cussion of the most appropriate methods [3–5]. This
article (1) outlines different types of economic eval-
uations providing examples on their potential use
in ophthalmic care decision making, (2) reviews
three articles in the brief recent literature on the
cost-effectiveness of ophthalmic anesthesia and cata-
ract surgery in the United States with a focus on
explaining methods that were used, and (3) dis-
cusses ways in which research in this area might be
moved forward.
Types of economic evaluations
High-quality economic evaluations provide a
logically consistent and methodologically rigorous
way of describing the costs associated with a
condition or comparing costs of a treatment to effects
of the treatment. Evaluations include information on
costs, clinical effectiveness measures, quality of life,
or other aspects of the value that individuals place on
care and the effects of care.
0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights
doi:10.1016/j.ohc.2006.02.013
This work was supported by the National Eye Institute’s
grant no. 5R01EY012045.
E-mail address: [email protected]
In most evaluations, all spending is given equal
weight in the cost analysis and the clinical and quality
of life changes for all patients are given equal weight
in the assessment of effectiveness [6]. Treating
everyone equally is fair, but it does not capture other
values that may be of interest. For example, there is
no explicit consideration of whether the treatment is
more likely to be administered to those of higher or
lower socioeconomic status. An intervention may be
aimed at one socioeconomic group so that the results
will obviously be interpreted with a focus on a
specific socioeconomic group, or subgroup analyses
may be conducted to help policy makers understand
the effects on different groups. However, general
cost-effectiveness analysis of a treatment affecting
multiple socioeconomic groups does not dictate or
even use relative values for different individuals. All
analyses must be interpreted with an understanding of
how the analysis treats different individuals and
whether this is consistent with the values of the
policy maker or the affected population.
The following six types of economic evaluations
are discussed in this section [6–8].
� Cost of illness/burden of disease� Cost minimization� Cost consequence� Cost effectiveness� Cost utility� Cost benefit
The types of studies are listed in order of in-
creasing ability to provide policy makers with infor-
mation that can be directly used to set policy. The
Am 19 (2006) 309 – 315
reserved.
ophthalmology.theclinics.com
frick310
reasons that the studies at the bottom of the list pro-
vide information that can be used more directly will
become clear as each is described. Along with each
definition, the use of the type of study for health de-
cisions about cataract surgery or ophthalmic anes-
thesia will be illustrated.
Cost of illness and burden of disease studies pro-
vide the least information for policy makers as both
types of studies only describe the costs experienced
and do not compare costs with effects. Cost of ill-
ness studies can take either an incidence cost ap-
proach or a prevalence cost approach [9]. Incidence
costs are lifetime costs associated with a new case of
the condition being studied. Prevalence costs are all
costs of treating everyone with the condition in a
given year. We will refer to cost of illness studies
taking an incidence cost approach as cost of illness
studies and those that take a prevalence approach
as burden of disease studies.
To illustrate the implications of these definitions,
consider studies related to cataract surgery. A cost of
illness study focusing on cataracts will enumerate
the expected lifetime costs of an incident case of cat-
aract. In contrast, a cataract burden of disease study
will enumerate the amount of money that is spent
to treat all cataract patients in a year. This includes
treatment for both cases prevalent at the start of the
year and cases incident during a year.
If cataract prevention were the objective, a cost
of illness study would provide information on the
lifetime costs that could be avoided by preventing a
cataract. If cataract surgery for an individual who is
otherwise legally blind were the objective, a cost of
illness study focusing on blindness would provide
information on the lifetime costs that could be
avoided by a successful surgery. In neither case does
the cost of illness alone provide an economic reason
for prioritizing cataract surgery. In both cases the cost
of illness that could be avoided must be compared
with the cost of treatment to make an economic
recommendation. Burden of disease provides infor-
mation on the impact of a condition on the economy
in a year but can only be used to describe the total
costs that can be avoided if all cases of the condition
are eliminated. This type of study is useful for
directing the public’s attention to the importance of a
condition but is not particularly useful in making
policy recommendations.
Cost minimization studies can be used to facilitate
policy recommendations when two interventions or
treatments have similar effects. Similar effects could
mean literally the same effect. However, similar
effects could also mean two treatments for which
the effects are not statistically different. Finally, two
treatments might both meet a threshold criterion, and
the policy maker may not be concerned with the
degree to which the effects exceed the threshold.
Healthy People 2010 provides an example of thresh-
olds of interest [10], although many of the vision
care objectives are developmental and the only ob-
jective for cataract is to reduce visual impairment as
a result of a cataract. If each of two interventions
reduced visual impairment and a policy maker was
not interested in the magnitude of reduction, then
the two alternatives could be compared to determine
which has the lower costs. Cost minimization based
on two alternatives meeting a threshold would be
more useful if the objective were stated in the form
of ‘‘reduce the proportion of the population with
visual impairment due to cataract to less than 1% of
the population aged 65 or older.’’
Another important aspect of cost minimization
analyses is an understanding of the perspective from
which costs are being considered. The perspective
refers to whose costs are considered. The objective
may be to minimize costs to the government, costs to
a private insurer, costs to the patient, or costs to all of
society. A single intervention may not minimize costs
from all perspectives.
Cost consequence studies are useful when there
are multiple impacts of a treatment or intervention but
it is difficult or impossible to find a suitable summary
measure for the outcomes. This type of analysis may
be more palatable to a policy maker; in spite of the
lack of a summary measure, the outcomes are more
transparent as the policy maker does not need to
understand how dollar values are placed on clinical
outcomes or how quality adjusted life years are
calculated [7]. This type of analysis is not likely to
be necessary for ophthalmology interventions or
treatments. Ophthalmology care is usually aimed at
avoiding or overcoming visual impairment or blind-
ness—and cases of these conditions are often the
primary outcomes of interest. These can affect quality
of life and mortality, which can also be considered in
cost outcome studies.
When cost consequence studies are performed,
they are less directly informative than cost minimi-
zation studies. Cost minimization studies can be used
to make a clear case for one intervention based on
having a lower cost when multiple interventions have
similar effects. In contrast, cost consequence studies
essentially provide a list of pros and cons. The policy
maker must then make a comparison of the pros and
cons in a relatively unstructured way.
The result of a cost-effectiveness analysis is the
amount of money spent per clinical outcome. In
the context of cataract, the simplest clinical outcome
economic evaluation 311
is cases of visual impairment prevented. Obviously,
there could be more specific measures of visual
acuity or visual function as well. The key is that there
is a clear primary outcome. These studies are useful
when making a decision about a new treatment or
intervention used for a specific condition or to avoid
a specific clinical outcome.
If there were an improvement in cataract surgical
technique, a cost-effectiveness study could address
the following question: using the new surgery rather
than the old, how much extra money is spent and how
many more cases of visual impairment are avoided?
Taking the ratio of these two figures, the result can be
expressed as the extra cost per extra case of visual
impairment avoided. A limitation with this type of
study is that there is no explicit way to compare cost-
effectiveness analyses done for different conditions or
treatments. For example, there is no explicit way to
determine whether spending $2000 to avoid a case of
visual impairment is worth more or less than
spending $10,000 to avoid a stroke. This limitation
may not be severe, as health policy makers rarely
make decisions on whether to treat visual impairment
or stroke but most often seem to make decisions on
the best way to treat a particular condition.
Cost-utility analyses use a standard outcome that
summarizes multiple types of morbidity and mortal-
ity. This summary measure is referred to as a quality
adjusted life year. Ophthalmology patients can gain
quality adjusted life years by increasing their quality
of life (by maintaining visual functional) during the
years they would have been alive anyway or by ex-
tending the length of their lives. The final result in cost
utility analyses is not the extra dollars spent per extra
case of visual impairment avoided, but the extra
dollars spent per extra quality adjusted life year gained.
The use of cost-utility results requires policy
makers to decide whether it is worth spending a cer-
tain amount of money to gain a quality adjusted life
year (QALY). The advantage over cost-effectiveness
is that only a single figure is needed, because the
theory underlying cost-utility analysis suggests that
the reason for improvements in QALYs should not
affect the value of the QALYs.
Cost-benefit analyses require the analyst to ex-
press the benefits in dollars. Some effects of changes
in health at the individual or population level are
difficult to express in monetary terms and can only
appear alongside the main result in a cost-benefit
analysis. The primary result is the calculation of the
difference between the dollar value of benefits and the
costs, and the primary criterion for implementation is
that the net benefit is positive, that is, benefits are
larger than costs. Thus, the policy interpretation is
much more direct with cost-benefit analyses than
with other cost outcome analyses.
A simple cost-benefit analysis from the limited
perspective of an insurer would ask whether there is a
business case for a new treatment, or ‘‘Does care
under a new treatment regimen cost less than an older
treatment regimen?’’ From a broader societal per-
spective, there could be an interest in the amount of
productivity gained by patients, the amount of de-
creased informal care provided by family and friends,
and other results of morbidity and mortality that
can be expressed in monetary terms.
From a payer’s perspective, a new development in
ophthalmic anesthesia could lead to higher costs in
the operating room but lower total costs including
recovery time. From society’s perspective, a cost-
benefit analysis focusing on cataract surgery could
define all economic changes related to cataract sur-
gery and ask whether the dollar value of the ben-
eficial changes is higher than the dollar value of the
changes that increase costs.
Cataract surgery and anesthesia
One recent study used a decision analytic model
to evaluate different anesthesia management strat-
egies [11]. This article demonstrates many methods
common to economic evaluations. These methods in-
clude modeling, the need for transparent parameters,
preference elicitation, sensitivity analysis, and appro-
priate incremental analysis.
Decision trees and modeling
Reeves and colleagues [11] used a decision tree to
model the costs and effects of six anesthesia manage-
ment strategies. A decision tree represents a sequence
of decisions, random events, and outcomes. The out-
comes usually include costs and either clinical or
quality of life outcomes. The tree allows for the cal-
culation of the probability of each outcome that is
used to define expected costs and expected outcomes.
The costs and clinical or quality of life outcomes are
compared to determine which alternative yields the
most preferred combination of costs and outcomes or
which alternative yields the best outcome but is not
excessively costly per unit of outcome. The authors
provide a useful and understandable description of
decision trees.
Many economic evaluations rely on models be-
cause randomized trials would be unethical, or cost
prohibitive, or require too much time relative to the
time frame for policy making. In some cases, a model
frick312
can be used as a precursor to a randomized trial.
Models can be simple, for example, a screening
model in which individuals are true positive, true nega-
tive, false positive, or false negative and the results
do not vary once a patient is in one of these groups.
Alternatively, models can be complex with multiple
levels of random events necessary to represent events
like annual diabetic retinopathy screenings over time.
Transparent model parameters
A key feature of the article by Reeves and
colleagues [11] is a table that lists all the parame-
ters in the model including probabilities of events,
the costs associated with the choice of anesthesia
management methods and the consequences of the
methods, and the preferences for each method. The
combination of a figure showing the decision tree and
a table showing the parameters in the tree helps to
make the model that is being used transparent so that
readers can evaluate validity of the model. At one
level of validation, a model must include appropriate
outcomes that are linked to choices and random
events in ways that make clinical sense. A model can
also be externally validated if there is an outside data
source that includes longitudinal data on individuals
who begin at a point at which they would enter the
model. The observed probability of various outcomes
can then be compared with the results obtained when
individuals are modeled to assess how well the model
predicts the distribution of outcomes.
The table in the Reeves and coworkers’ article
[11] not only lists the parameters but also the sources
of data for the parameters. In general, there are
multiple sources of data for nearly every model-based
cost-effectiveness or decision analysis—past reports
of randomized trials, administrative claims data,
Medicare reimbursement rates for prices, average
wholesale prices, survey data, and expert panel data.
Expert panel data are generally the least preferred and
should be used sparingly, but these data are some-
times the only data available. In this study, only the
three probabilities of converting between types of
anesthesia and preferences for management strategies
were provided by the expert panel.
Obtaining probabilities from an expert panel is
less problematic than obtaining preferences. Stein
[12] suggests that providers have a different percep-
tion of the utility of various treatments and health
conditions than their patients have. The standard
recommendation for preference measurement is that a
cost-effectiveness or decision analysis should use
preferences of a cross-section of individuals from
society at large [6]. Societal preferences are thought
to be best to use when allocating societal resources.
However, at least some authors focus on patient
preferences [3]. Societal preferences can be difficult
to obtain if the condition or treatment has not been
studied before and if the condition or treatment is
difficult to describe to a group of respondents who
have not experienced the condition.
Preference elicitation
The research [11] used a visual analog scale ap-
proach for preference elicitation. This is the least cog-
nitively demanding and least preferred method from
a theoretical perspective, although for an assessment
of the preferences for a temporary condition like
anesthesia management rather than a chronic condi-
tion like blindness, it was completely appropriate. The
visual analog scale approach to preference elicita-
tion has two important limitations. First, given the
historical definition of health utility measures, they
are supposed to reflect tradeoffs and forced choices
between alternatives [6]. The visual analog scale does
not do this. Second, the visual analog scale described
in the article used anchor points representing the ideal
experience and the worst experience imaginable. Not
everyone imagines the same worst experience. The
scale used in most preference elicitation methods that
involve a specific tradeoff is anchored by perfect
health and death.
Given the limitations of visual analog scale
methods generally and the relatively narrow topic
for which preferences were measured in this study,
the preference scale can only be used to compare
anesthesia management methods for cataract surgery.
Preferences measured in this study lack comparability
with preferences assessed in other studies. Compara-
bility across studies is a goal of cost-utility analyses.
Other preference elicitation measures include the
time tradeoff and standard gamble [6]. These methods
force respondents to make a choice between an al-
ternative involving living the remainder of one’s life
in a less than optimal health state and a second al-
ternative involving either living in perfect health a
shorter amount of time for certain or a probability of
perfect health or immediate death. These are more
cognitively demanding and many respondents refuse
to make this type of tradeoff, but they are based more
clearly in economic theory. There is not a single
preference value for blindness. One study found a
value of 0.70 for monocular blindness and 0.35 for
binocular blindness [13]. A second study demon-
strated that among a legally blind sample there is a
wide range of utilities that patients report for their
own condition: those with no light perception have the
economic evaluation 313
lowest utility; those with light perception have higher
utility; and those with visual acuity of 20/200-20/400
in the better seeing eye have the highest utility [14].
The utility weight for blindness in a community
sample was 0.75 [15].
Sensitivity analysis
Sensitivity analysis is a term for assessing changes
in the cost-effectiveness results with changes in the
values of parameters—particularly those that are
assumed. Reeves and colleagues [11] conduct sensi-
tivity analysis by varying one parameter or two para-
meters at a time. While this type of analysis indicates
whether the results change when a parameter
changes, this type of analysis does not give a clear
indication of the likelihood of a change in the quali-
tative nature of the cost-effectiveness results. State of
the art analyses at present use probabilistic sensitivity
analyses in which parameters are drawn repeatedly
from distributions and the results are reevaluated with
each draw to describe the probability of the quali-
tative cost-effectiveness results holding.
Incremental analysis
Finally, the authors performed a proper incremen-
tal analysis. Sometimes authors simply ask how much
it would cost per QALYor improved clinical outcome
under each alternative. A true incremental analysis
considers all the alternatives (six in this case) simul-
taneously. The alternatives are arranged in order by
cost. Alternatives that are equally expensive but pro-
duce less positive outcome and alternatives that pro-
duce a similar positive outcome but cost more are
eliminated from consideration. Among those that re-
main, the extra cost per extra unit of outcome is
assessed as the policy choice changes from the least
expensive to the most expensive alterative that
has not been eliminated. This allows the policy
maker to ask repeatedly, ‘‘How much would more
of the outcome cost?’’ Based on economic criteria
alone, resources should be allocated to the alterna-
tive with the maximum positive outcome for which
the policy maker is willing to pay the cost per im-
proved outcome.
Conclusion
The authors concluded that alternatives including
topical anesthesia yielded a lower utility at approxi-
mately the same costs as alternatives without topi-
cal anesthesia. Among the three alternatives without
topical anesthesia, having an anesthesiologist on call
cost only a small amount more than not having
an anesthesiologist available but that the preference
for the on-call scenario was much higher. In con-
trast, while having an anesthesiologist present in-
creased the preference weight relative to having an
anesthesiologist on call, the cost was over six times
higher per patient.
Cataract surgery
Two relatively recent US studies characterize the
cost-effectiveness of cataract surgery separately in
the first eye and the second eye [16,17]. Both used
similar methods that will be described together.
Modeling and parameters
Similar to the work by Reeves and colleagues
[11], both articles used modeling. An article on care
for age-related macular degeneration patients still
used a model but built more directly on a randomized
trial [18]. The decisions modeled in the two articles
on cataract surgery were ‘‘surgery in the first eye or
not’’ and ‘‘surgery in the second eye or in one eye
only.’’ In each model, the decision on surgery is
followed by the possibility of one of four compli-
cations within the first 4 months. One of the com-
plications (retinal detachment) is given a single
preference value and each of the other three com-
plications will result in one of two outcomes. A key
implication of the model is that the preference weight
improvement is the same no matter how old the
patient is. When there are no complications, a gain of
0.15 units on a scale that ranges from 0 to 1 for
surgery in the first eye is assumed to apply for the
remainder of the person’s life. A gain of 0.11 units on
the same scale is assumed to apply for the remainder
of the person’s life after surgery in the second eye.
The gains in utility from improved vision may di-
minish over time as a patient experiences other co-
morbidities that limit utility.
Present value
In the article analyzing the management of
anesthesia, the analysis included preferences for the
management strategy during the short surgery rather
than for the chronic health state being addressed. In
the cost-effectiveness analyses related to cataract
surgery, the time period to which the preference
applies is the remainder of the patient’s life. For most
patients, the life expectancy is more than 1 year. The
analysis applies relative weights to benefits and costs
frick314
that occur in the future in comparison with those that
occur immediately. This is the process of calculating
a present value or discounting.
Under the standard approach the relative weight
for future events is smaller than for immediate events.
For costs, the reasoning is straightforward. If a patient
will need to spend $100 for eye care next year, the
patient could put less than $100 in the bank now, earn
interest, and have the $100 next year. This generalizes
so that the present value of any dollars used a year
from now is lower than number of dollars considered.
Health benefits are treated the same—so a year with
better vision that happens in the future is worth less
than the current year with better vision. A commonly
recommended discount rate is 3% [6,19]. This
implies that the value of events that occur 1 year
later is 97% of the value this year. One year later, the
value is 97% of the 97%. This continues indefinitely
and the value of a future benefit 24 years in the future
is approximately one half of the value of the same
benefit that occurs today. This can make the lifetime
value of a health improvement considerably smaller
than the 1-year gain multiplied by the remaining life
expectancy. The authors of the two articles [16,17] use
a 3% discount rate and it diminishes the QALYs gained
from 1.78 without discounting to 1.25 in present va-
lue terms—in effect decreasing the gains by one third.
Sensitivity analyses
Both articles [16,17] used one-way sensitivity ana-
lyses and analyses that changed all utility values si-
multaneously. The reason for changing all utility
values simultaneously is not entirely clear. The effect
of changing all values simultaneously is essentially
that the differences in utilities will increase or
decrease by the percentage of increase or decrease.
The differences are critical to incremental cost-
effectiveness analysis. By way of example, increasing
the utility of both no surgery and no complications by
10% would change the utilities from 0.71 and 0.86
(a difference of 0.15) [16] to 0.78 and 0.95 (a differ-
ence of 0.17). The increase in the difference is
approximately 10%. One difficulty with a scale that is
bounded at 1 is that increasing the utility of some of
the states by a substantial amount makes the health
state appear to be much less negative or much less
worse than a perfectly healthy status.
Conclusions
Both studies demonstrate that cataract surgery
costs a small amount for each QALY gained in the
analysis using all the base assumptions and in all
sensitivity analyses. A key consideration is the
interpretation of ‘‘a small amount per quality adjusted
life year gained.’’ In the United States, a threshold
of $50,000 per QALY gained is often used to separate
treatments and interventions that are deemed to be
relatively cost-effective from those that are not. How-
ever, there is not complete agreement on the appro-
priate threshold value [20].
Future of economic evaluation in ophthalmic
anesthesia and cataract studies
If economic studies continue to gain traction in
health care priority setting, the number of economic
evaluations of anesthesia management practices
associated with ophthalmology procedures and eco-
nomic evaluations of the procedures themselves is
likely to grow. Economic evaluation can be an im-
portant input to policy making and treatment recom-
mendations but should never be the only input. The
studies reviewed are instructive; they provide a tem-
plate and set a high standard for future studies. Addi-
tional assessment of patients’ and the general public’s
preferences for health states associated with vision
problems and the incidence costs of visual impair-
ment will make future studies more informative.
Following methods recommendations, particularly
making models and their parameters transparent will
increase future studies’ impact.
Summary
This article (1) outlines different types of eco-
nomic evaluations, (2) reviews three recent articles on
the cost-effectiveness of ophthalmic anesthesia and
cataract surgery, and (3) discusses ways in which
research in this area might be moved forward. Cost-
utility analyses using decision trees, societal pref-
erences, and probabilistic sensitivity analyses would
represent the state-of-the-art in all respects. The three
articles reviewed do not meet all three criteria. Read-
ing, interpreting, and conducting such analyses in
the future will be facilitated by understanding
methods recommendations.
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