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ClINICS

ELSEVIER Smoll Animal ProcliceClin Smull AnímSAUNDERS

35 (2005)571-580

13C.üAnesthesia for Geriatric Patients

1Rachae1 E. Carpenter, DVM

a.*,

¡ Glenn R. Pettifer, DVM, DVScb,

t WiUiam J. Tranquilli, DVM, MSa

I"Depar/men/ol Ve/er/nary C/in/cal,Hedicine. Ulliversily 01 lI/il/ois.

1008 Wes/ Hazelll'ood Dril'e, Urbana,JL 6/802, USA

bDeparlment 01 Veúrinary Clin/cal Sciences, SciJool 01 Velerinary Afediclne,

LOIl/siano Slale Ulliversily. Batol/ ROllge. LA 70803, USA

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Veterinarians are seeing an increasing number of geriatric animals in theirdaily practice. Often, these patients need to be placed ui;\der generalanesthesia for dental care, surgical procedures, diagnostic procedures, or

treatment of chronic conditions, In 2002, ¡he pet populalion in the UnitedStates was estimaled at 100 milJion. Approximately 30% of lhose pets areexpected to be geriatric [11. Because there is wide species and breed várialionin life expeclancy, there is no one specific age that defines an animal as"geriatríc"; however, it is generalIy accepted that a geriatric animal is one

¡hat has rea<;hed 75% of its expected life span [2]. Because there little·

correlation between physiologic and chronologic age. each animal 11l1lst 51iH 'be evaluated as an individual. Many older animals remain remarkilbly fit,

whereas olhers seem lo age faster ¡han expected. Age itself is not a disease.but age-related changes and diseases do atiecl aneslhelic management.

Physiology of geriatric animals

Physiolol!ically. elderly animals cannot be consídered the same asyounger a d ~ l t s . Aging causes a progressive and irreversible decrease infunctíonal reserves of the major organ systems. leading lo altered r e ~ p o n s e s to stressors and anesthetic drugs. Such changes in organ syslem function arecovert until the palient is stressed by an illness. hospital stay. orgeneral

anesthetÍc procedure .

• Corresponding author.

E-mail aelel"ess: recrpntr@uiuc.edu (R.E. Carpenler).

0195-5616I 05i$ - see fronl matter © 2005 Elsevíer lnc. Al! rights reserved.

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572 CARPD;TER et .1

Cardiovascu[ar system

Geriatric animals have a decreased cardiac reserve compared with that 01'

younger animals. In the older animal, this often translates into a decreased

ability to respond appropriate ly to the changes brought about by anesthetic

drugs..Geriatric ilnimaIs have varying degrees oC myocardiaJ fiber atrophy,

which can affect rate and rhythm iC the conduction system is involvcd. The

aged heart also has increasing myocardial fibrosis and valvular fibrocalci

fication. As ventricular compliance decreases in the aging heart, relativelysmall changes in intravascular volume or venous capacitance become in

creasingly important determinants oC circulatory stability [3]. These changes 11

mean that whereas the geriatric animal is volume dependent, it is also",

volume -intole rant, beca use the decreased ventricular compliance is associ

ated with optimal hemodynamic Cunctioning within a narrow range oC end idiastolic volume and pressure: The maximal chronotropic response during ,

hysiologic stress decreases with age. Additionally, the response to

exogenousJy administered autonomic drugs i5 decreased. Younger adults ",can increase cardiac output primarily by increasing heart rate. In geriatric

animaJs, cardiac output is more dependent on increased stroke volume in

association with an increase in end-diastolic volume. For this reason,

volume depletion during lhe perioperative period i5 less well tolerated in

geriatric animáis than in younger animalsGeriatric animals are increasingly likely to experience degenerative

myocardial disease, usuallyin the form of chronic valvular disease. This

degenerative change has the potential to increase the likelihood oC rriyo

cardial hypoxia associated with the increased myocardial work and oxygen

consumption of inefficient pump ClInction [5].

Pulmonar)' system

Even mild or modera te respiratory depression associated with the

administration of sorne anesthetics can produce significant hypoxia and

hyperéarbia in the geriatric animal. This arises as a result of a decreasedCunctional reserve capacity in the aging lung. Aging is associated with

a decrease in chest wall compl iance beca use oC the loss oC intercostal and

diaphragmatic muscle mass. Vital capacity, total lung capacity, and

maximum breathing capacity also decrease. With a reduction or loss oC

lung elastin, pulmonary compliance is reduced (5]. Anatomic dead space hnd

functional residual capacity increase with age, as do closing volume, air

trapping, and ventilation-perfusion mismatch. Al! these changes tend to

lower Pao2 levels in older patients [6]. Pathologic events like pneumonia,

pulmonary edema, or pulmonary fibrosis exa cerba te these a ging proces ses.

Pulmonary aging serves to render a geriatric animal less tolerant oC even

transient hypoxia during the perianesthetic periodo

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Hepatíc system

The overall mass of the liver decreases with increasíng age, leading to

a decrease in overall hepatic function, including drug c1earance [3]. This

decrease in. hepatic function causes an inerease in the plasma half-life of

drugs dependent on hepatic excretion, metabolism, or conjugation. Other

important considerations in the geriatric patient incJude the potential Cor

hypoproteinemia, impaired clotting Cunctions, and hypoglycemia from

altered, hepatic Cunction (5].

Renal system

Normal aging can alter renal function in several ways. Renal blood flow

is decreased, making geriatric patients more suséeptible to renal Cailure

when exposed to renal ischemia. There is a decrease in the total number

oC functional glomeruli, and the glomerular filtration rate decreases. As

chariges in the renal tubules occur, there is an increase in the resistance oC

the distal renal tubules to antidiuretic honnone. This results in an impaired

ability to conserve sodium or concentrate urine, leading to a reduced ability

to correct fluid, electrolyte, and acid-base disturbances [6]. Overall, this may

make sorne geriatric animals much less tolerant of body water deficits or

excessive fluid administration. Additionally, the plasma half-Jife oC ananesthetic drug eliminated by renal excretion muy be prolonged, necessi·

tating a reduction in the dose when used in geriatric patients.

Aged patients are generally more susceptible to rena l Cailure after general

anesthesia. T,he effects oC anesthesia an d surgery can exacerba te preexisting

renal pathológic conditions (5]. General anesthesia typically reduces renal

blood ftow and glomerular filtration, whereas surgery may result in blood

loss, hypovolemia, and hypotension, which can Curther compromise renal

perfusion.

Celltral nerl'OllS system

Cerebral perfusion and oxygen consumption decline with increasing age

and may be related to an overalllossoC

brain mass that correlates with a lossof neurons rather than atrophy oC the supportive glial cells. Cereb rospinal

fluid volume inereases to maintain normal intracranial pressure in the Cace

oC this reduction in brain mass [6]. Anatomic and Cunctional redundancy

compensa tes Cor the loss oC cellular elements and neuronal intercbnnections;

thus, Cunction oC the central nervous system (CNS) is generally maintained

at levels close to those seen in young adults [3]. There are decreased amollnts

of neurotransmitters, such as dopamine, norepinephrine, tyrosine, and

serotonin, in the aging brain, and these substances may demonstrate

a reduced receptor affinity

Although not completely understood, one oC the overall results of these

changes is that geriatric animals have a decreased requirement for anesthetic

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57-1 CA RPE1'.rrER <1 a!

íagents. lt is well documented that minimum alvealar cancentratian (MAC)

decreases linearly with age, and requirements far local unesthetics, apioids.

benzadiazepines, and ather intraveno us dr ugs seem to be Iímilarly reduced [3,6,7J. \

Ireoperatiye asscssment

,Individual geriatric animals may reqúire different anesthetic pratocols.

As with any animal that is ta be anesthetized, a complete histary should be

taken, w¡ith particular attentian to previous and current medical prablems,

current. · medicatio ns, vitamins, and supplements. A thorough physical

examination and broad laboratory screening (ie, complete blood cell count

chemistry panel, urinalysis) afe essential in the assessment af the

functionalsti:ltus af d1fferent argan systems and in the identification af any

preexIsting problems. Careful auscultatianaf the heart shauld be perfarmed

in an attempt ta identify any underlying cardiac disease ar murmuro If

a cardiac murmur ar arrhythmia is detected, a cardiac workup (eg, chest

radiographs, echocardiagram, electrocardiogram [ECG]) may be perfarmed

to determine the cause af the murmur. Whenever possible, any significant

, abnormalities detected by physical examinatian or preoperative bload work

shauld be corrected befare the inductian of anesthesia.

'.Premedication .

Preanesthetic sedatian reduces stress in anxious patients and decreuses

the amollnt of anesthet.ics needed far induction and maintenance of

anesthesia .The chaice of premedication depends on the geríatric animal's

conditian, any concurrent disease pracesses, current medicatians.

and the particular requirements ror sedation and analgesia that are dictated

by the intended procedure (suggested sedatives and preanesthetics are

presented in Table

A1/1 ic/lOlinergics

Antkholinergics (eg, atrapine, glycapyrrolate)' shauld . not be lIsed

indiscriminately in the geriatric patient . Patients with preexisting cardiac

disease may na t tolerate the increase in myacardial oxygen demand and

work resulting fram a marked increase in heart rate. Sinlls tachycardia may

preCipitate acute myacardial failure [5J. In mast cases, it is probably best to

treat bradycardia as needed with judicious use af antichalinergic drugs an

u case-by-case basis. Alter natively ; cx;!-agonist-mediated reducti ons in heart

rate can be t reated by titrati ng the reversal agent,. atipamezole, ta achieve

lhe desired reversal af brady cardia .· Althaugh sarne clinicians recamm end

that ct2-agonists be given in cambination with anticholinergics [8J, others

would suggest that this practice may result in a patent ially undesir able

ANESTHESIA 575

Table 1

Suggested drug doses (mg, kg) of anesthelic drugs in geriatric small animal,

Drug Cat

Anticholinergics

Atropine 0.01-0.02 1M. IV 0.01-0.02 1M. IVGlycopyrrolate 0.005-0.01 1M. IV 0.005-0.01 1M, IV:

Sedatives and/or tranquilizers

Acepromazine 0.01-0.05 1M, se , IV 0.01-0.05 1M, se . IVDiazepam 0.2-0.4 IV 0.2-0.4 IVMedetomidine 0.002-0.004 1M 0.006--0.008 1M !Midazolam 0.1-0.3 1M, IV 0.1-0.3 1M, SC: IV

Opioíds

Buprenorphine 0.005-0.01 IM,'Se, IV 0.005-0.01 1M, SC, IV, POButorphanol 0.2-0.4 1M, se , IV 0,2-0.4 1M, SC, IV

Hydromorphone 0.1-0.2 1M, se , IV 0.1-0.2 1M, se , IVMorphine 0.05-1 1M, se 0.002-0.1 1M. se

Oxymorphone 0.1-0.2 1M, se , IV 0.05-0.1 1M, se , IVlnduction'

Etomidate 0.5-1.5 IV 0.5-1.5 IVKetamine and/or valium 3-510.2-0.4 IV 3-5/0.2-0.4 I\i .Propofol <HiIV 4-6 IVThi(Jpental 2-6 IV 2-6 IV

Abbrl.'l'Í(lIiolls: 1M, intramuscular: IV, intravenous; PO, by mouth; se , subcutaneous.

, Al! recommended doses should be litraled slowly to elfect.

increase in myocardial work and possible arrhythmias [9]. Because of the

potential far development of serious side effects, ct2-agonists should be

reserved for use in cardiovascularly healthy geriatric animals.•

Opioids

Opiaids aften pravide adequate sedatian in geriatric animals. with the

udded benefit of providing analgesia. p-Aganists (OPragonists;marphine,

hydromarphane, and axymarphone) provide the greatest sedatian but may

also cause the greatest cardiovascular and respiratory depression. Morphine

(and other ~ l / O P r a g a n i s t s ) has the potential lo induce vagally mediatedbradycardia, which muy be prevented with an anticholinergic if needed [IOJ.

Lowering the heart rate can reduce myocardial axygen demand and

cansumptian and muy actually be desirable in sorne aged patients. Partíal

agonists (eg, buprenarphine) and aganist-antaganists (eg, butorphanal)

provide only mild ta madera e analgesia and sedation but alsa cause míni

mal cardiavascular and respiratory depressian. These agents may be quite

useful in the geriatric animal, where concern far cardiapulmonary instability

is present but mild sedatian and analgesia are desired for the pracedure.

Tral1quilizers and sedatil'es

Even though geríatric animals may be calmer than their yaunger

coun terparts, il may still be quite valuable ta include a tranquilizer in lhe

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576 CARPENTER « al

anesthetic protocol to reduce the stress associated with hospitalization,

treatment, anesthesia, and surgery. The benzodiazepines (eg, diazepam, !midazolam) are reversible and produce little to no cardiovascular or i

.respiratory depression, making\ them appropriate for many geriatric

'1

animals. Although benzodiazepinecinduced sedatíon can be unreliable inl1

younger unimals, this is less of ti concern in geriatric animals. Ir needed, tjbenzodiazepines can be combined with other premedicants, such as opioids,

to achieve the desired level or sedation. In addition, benzodiazepines like 1diazepam or midazolam can be combined with ketamine for the induction of

anesthes.ia in selected geriatric animals. In h e ~ t l t h y geríatríc unimals, low doses of acepromnzine may be a suítable

choice for premedication. Acepromazine produces general CNS depression :1....and sedation without analgesia. Nevertheless, it has a perípheral vaso

dilating effect that can cause significant hypotension, which contríbutes to

the development of hypothermia in geriatric animals. When acepromazíne is

combined wit h the opio d analgesics, remarkably low doses of the .,

tranquilizer cun be used to muximize sedation and minimize the unwanted

side effects.

The Ctrugonists may be considered for sedatíon and premedication in ih e ~ \ l t h y geriatric ani mals beca use ¡hey are reversible and thus are not t

dependent on hepatic or renal c1earance for recovery. A recent study showedthat sale effective sedatíon could be performed in geriatric cancer patients

undergoing daily radiatíon, therapy using a combinatíon of low-dose

medetomidine, butorphanol, and glycopyrrolate [11]. Although these

nnimals were an older (average of 8.9 years for dogs and 10.8 years for

cats) and had a variety of age-related díseases, they were an ídentified as

being in good cardiopulmonary health before drug administration. The C(r

agonists can cause serious side effects, such as bradycardia, atrioventricular, conduction block, increased p ~ r i p h e r u l vascular resístance, and hyperten,.

síon, making appropriate patient selection a must, especially when consid

ering use in a geriutric populatíon.

Anesthctk induction

Anesthetic induction may be accomplished using injectable anesthelics or

by m:tsk ddivery of inhalant anesthetics if necessary. Because many

injectable nnesthetics demonstrate altered pharmacokinetics and pharma

codynamics, decreased plasma protein binding, and decreased hepatic and

renal metabolism and excretion in geriatric animals, the use of these drugs

should be undertaken cautiously.

Barbitllrates

Barbiturates are highly protein bound and depend on redistribution and

hepatíc metabolism for terminatíon of activity. As such, they should be used

At'ESTrlESIA 577

cautiollsly in geriatric animals. Decreased protein binding and hypoprotei

nemia may lead to enhanced drug elfects in geriatric animals [3,10]. To

minimize the potential for a relative overdose, the lowest possible dose that

produces the desired etTect should be used. Barbiturates can cause significant

cardiovascular and respíratory depression, and their use should be reserved

for the healthy geriatric animal.

Dissociatil;e anesthetic agents

The N-methyl-o-aspartate (NMDA) antagonist ketamine may be used ror

the induction of anesthesia in geriatríc animals. Ketamine 'may improve

cardiovascular function through stimulation of the sympathetic nervous

system [12,13]; however, this may not always be desirable in the geriatric

animal. NMDA antagonists may increáse heart rate, causing a marked

increase in myocardial oxygen demand and consumption that may not be

well lolerated by a'nímals with preexisting cardiovascular disease. Because

ketamine causes muscle stiffness and rigidity, it is typically combined with

a benzodiazepine to ameliorate this undesirable side effect. The effects of

ketamine may be prolonged in patients with failing h ~ p a t i c and renal

systems, necessitating the administrati on of decreased doses in these animals.

Etomidate

Etomidate is a sedative-hypnotic agent with a rapid onsel of action and

rapid recovery. At doses normall y used to produce general anesthesía, .

etomidat e mainlains cardiovascu lar stabílity, making it a good choice for the

induction of arlesthesia in animals with c1inically significanl cardiac disease

[10]. Debililated or seduted patients normally have a smooth anesthetic

induction when etomidate is titrat ed intravenousl y to eft'ect. Exciled animals

may exhibit undesirable side en'ects: such as retching, myoclonus, an d apn ea,

during induction.

Illhahmt illduction

lnhaled aneslhetics may be used for the induction of anesthesia in

otherwise sedated or debilitated patients. There are many caveats to the use

of inhaled anesthetics for induclion. These indude the associnted severe

physiologic stress of protracted induction in the anímals and unwanted

environmental pollution and exposure of personnel to waste anesthetic gases.

An excessive depth of anesthesia can be ttttuined rapidly during the induction

of anesthesia with inhalant anesthetics, and animals must be c10sely moni

tored and assessed to prevent overdose.

PropaloIPropofol is a good choice for use in most geriatric patients because it is

rapidly c1eared from the body by many different routes. Recovery is

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578 CARPENTER <t .1

gene rally rapid in dogs, even afte r repeate d doses, and metabolism is not 1ependen! on the function of a single organ system. Propofol can induce

significant respiratory and cardiovascular depression and should be titrated I•,.to achieve the desired effect Premedication decreases the amount of

propofol needed and helps to minimize side effects. Propofol has beenshown to cause increased Heinz body produ ction in cats when used for dailyinduction and maintenance (for an average of 6 days) and should thus be

used with caution in this species if daily anesthesia is needed [14].

1Anesthetic maintenance

Inhalant anesthetics are the agents of choice for anesthetic maintenancein geriatric. animals, particularly for procedures lasting longer than lOto

15 m j n ! ! t e s ~ Halothane, isofiurane, and sevofiurane may be used with successin geriatric animals as long as c10se attentíon is paid to the monitoringof anesthetic depth and cardiopulmonary function during the anestheticperiodo

Halothane

Halothane has been the cornerstone of anesthetic practice in veterinarymedicine for many years, and·many geriatric animals have been successfullyanesthetized using halothane. With the newer inhalants available, however,il is generally held that the use of halothane should be reserved for healthyanimals and avoided jn higher risk animals. Halothane. causes significantdose-related cardiovascular depression that may ~ o t be well tolerated inolder patients. Heart rate, contractility, and cardiac output are significantlydecreased in a dose-dependent manner [10]. Halothane can also causeprofound hypotension beca use of vasodilation and direct depression of thevasomotor center. Halothane is also known to sensitize the myocardium tocatecholamines; thus, it should be avoided in patients with the potentíal fordysrhythmias. Hepatitis has been reported in human patients after exposure

to halothane; thus, chronic liver dysfunction.should probably be considereda Jelative contraindication to its use.

Isojfurane

Compared with halothane, isoflurane better maintains cardiac output inanesthetized animals [10]. In addition, it does not sensitize the heart tocatecholamines to the same degree as halothane. Because isoflurane has thepotential to cause significant hypotensjon due to a direct effect on

vasomotor tone, the lowest concentration necessary to achíeve the desíredlevel of anesthesia should be administered. Overall, there are fewer contraindications to the use of ísoflurane in geriatric animals than to the use of

halothane.

AII:ESTHESI.-\ 579

Sel'ojfurclIle

Sevoflurane is a newer inhaled anesthetic that produces extremely rapídinduction and recovery. Se voflurane is les s pungent than isoflurane, makingit a better choice during the induction of anesthesia with an inhaledanesthetic. Faster induetion and recovery, coupled with the inereasedacceptance of sevoflurane's o dor, reduces the stress ofinhalant induction and

minimizes delay in achieving airway control with endotracheal intubation.Generally speaking, this makes sevoflurane preferable to isoflurane when theinduction of anesthesia is performed wíth an inhaled anesthetic [15].

Monitoring and support

Geriatric animals are less tolerant of a busy hospital environment and arelikely to beco me more stressed t han younge r animals when taken o ut of

tbeir normal daily routine. Every effort to make their hospitalization stressfree should be made.

Geriatric animals may have sorne degree of arthritis or muscle wasting,making it harder for them to líe down comfortably on a cage or run floor. If

possible, their cages should be well bedded with soft matefÍals (eg, padded

beds, orthopedic foam) to ensure thejr comfort whíle hospitalized. Additionally, they ma y be less flexible t han y ounger anjrrials, and care should be

taken when their legs are secured during surgery so that they are not pulledtoo tight, potentíally causing soreness in the postoperative periodo

Because geriatric animals have decreased thermoregulatory capacity,every effort sl\ould be made during the perianesthetic period to keep themwarm with warmed fluids, circulating water blankets, and foreed air warmers.Hypothermia increases the incidence of arrhythmias, leads to a catabolíc stateand delayed healing, adversely affects immune function, leads to hypoxía andmetabolic acidosis, and prolongs the effects of anesthetic agents·[16]. Whenthe body attempts to rewarm itself after surgery by shivering, thefe is a 200%to 300% increase in oxygen consumption thal may lead lo increasedmyocardial work and ischemia or systemic hypoxia in the postoperativeperiodo This may be especially relevant in the geriatric animal with significantloss in functional cardiopulmonary reserve. It is easier to maintain a corebody temperature in animals while they are anesthetized and vasodilated than

to try to rew arm them externall y as the effects of anesthetic drugs are wearing. off and they become more vasoconstricted duríng the recoveryperiod.

As discussed previously, geriatric anímals are less tolerant of v.olumeoverload than juvenile or míddle-aged animals. Aggressive fluid therapymay result in excessive intravascular and extravascular volume, leading tocongestive heart failure and pulmonary edema in geriatric animals that areunable to excrete a salt and water load efficiently [6]. The goal for fluidtherapy in aged animals should be the correction of any specific deficits nndthe maintenance of adequate tissue perfusion and oxygen delivery.

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!580 e l RPf:-lTER el al

) 1ummary ;1

Choosing lhe best anesthetic agents for each geriatric animal does not in ¡itse1f cnsure a successful outcome. Aggressive, careful, vigilant monitoringduring the anesthetic and recovery periods is required to detect and correct talterations in h6meostasis thac may develop during the perianestheticperiodo With appropriate preoperative screening, ínformed choice and jjudicíous dosing of anesthetics, and careful monitoring and supportive care, tthe risk of anesthesia in geriatric animals can be greatly reduced.

I '.1References

(1] Wise JK. Healhcott BL, Gonzulez M L Results oflhe AVMA survey on compunion animal ownership in US pel-owning households. J Am Vet Med Assoc 2002;221:1572-3. I2) Ooldston" RT. Introduction and overview of geriatrics. In: Ooldston RT. Hoskins JD, editors. Oerialries and geronloloú of Ihe dog and cat. Philadelphia: WB Saunders; 1995. p.I-IO.

(31 Muravchiek S. Anesthesia for Ihe elderly. In: MiI1er RD, edilor. Aneslhesia. 51h edilion. Philad.:lphia: Churehill Uvingslone; 2000. p. 214G-56.

(4J Thurmon JC. Tranquilli WJ. Benson OJ. Aneslhesia for special palienls: neonalal and 1erialric palÍ!!nts. In: Thurmon JC, Tranquilli Wl . Benson OJ, edilors. Lumb and Jones' velerinary aneslhesia. 3rd edilion. Baltimore: Williams & Wilkins: 1996. p. 844-8.

(5) Puddleford RR. Aneslhesia. In: Ooldslon RT, Hoskins JD. edilors. Oerinlrics and geronlology uf lhe dog ¡md e:Il·. Philadelphia: WB Saunders: 1995. p. 363-77.

[6J Pettiler O R. Orubb TC. Aneslhesia ror seleeted palienls and procedures: neonalul and geríulríc palients. In: Thurmon Je. Tranquilli WJ. Orimm KA. edilors. Lumb ,¡nd Jon.:s· velerinary unesthesiu. 4th edilion. Ballimore: Williams & Wilkins; in press.

[71 Eger El. An<!slhelic uptnke and aelion. Baltimore: WilIiums & Wilkins; 1974. p. 1-25.[8J Orimm KA, Thurmon lC. Olson \VA. el 111. The ph"rrnaeodynamics 01' Ihiopenlal.

m.:delomidine. bUlorphanol and atropine in beagle dogs. J V ~ I Pharmacol Ther 1998;2: 133-7.

[9] Ku Je. Fu" SM. Mandsagcr RE. EITecIs ofpreemplive ¡ l I r o p i n ~ udminislr¡llion on incidcnce01' medctomidine-induccd bradycardia in dogs. J Am Vel Med Asso.: 200 I 218:52-8.

[101 Sloelting RK. Phannucology ¡¡nd physiology in aneslhelie praclice. 3rd edilion.Philadelphm: Lippincott. Williums & Wilkins; 1999. p. 36-157.

(IIJ Orimm JB. deLorimier LP. Orimm KA. Medetomidine-bulorphanol-glycopyrrolatesed,llion f ~ r radiution therapy: un eight-year sludy [abstraet]. In: Proceedings of IheVClerinary Midwes[ Aneslhesia ¡¡nd Analgesia Conference. Columbus: The Ohio SlaleUniv.:rsity; 2004. p. 18.

[12] Kohrs R. Durieux ME. Kel¡¡mine: leaehing un old drug new Iricks. Aneslh Analg 1998;87:1 1 ~ 6 - 9 3 .

(13) Wright M. Phurmaeologic elfects 01' hlamine and Íls use in velerinury medicine. J Am VdIvléd Ass,.; 19\16:209:967-8.

[14/ Al1dress JL. Day TK. Day D. Etlecls of eonsecutive duy unesthesi . un feline red blo od cells.Vel Surg 1995;24:277-82.

(15] Johnson RA. Striler E, Snwyer DC. el al. Comparison of isofiurane wilh sevoflurane forunesthesia induction und recovery in adull dogs. Am J V ~ t Res 1998;59:478-81.

¡(6J Kaplan RF. Hypothermiaihyperlherrnia. In: Gravenstein N. editor. Manual of complications during aneslhesia. New York: lB Lippincott; 1991. p. 121-50.

VETERINARY

ClINICS

ELSEVIER Smoll Animal ProdiceVél Clin Small AnimSAUNDERS

35 (2005) 581-596

Early Detection of Renal.Danlage and Disease in Dogs and Cats

Gregory F. Grauer, DVM, MS Deparlmenl 01 Clinical Sciellt:es. College 01 Ve¡erinary ¡'\;fedicille, JJ JB jl¡Josier Hall.

Kansas Slate UnÍ\'ersily. Man/wl/an, KS 66506, USA

Renal damage and disease can be caused by acute or chronic insults to

the kidney. The terms renal disease ana rellal damage are used to denote theprésence of renal lesions; however, the tenns imply nothing about renalfunction or the cause, distríbution. or severily of the renal lesions. Acute

renal damage (ARD) orlen results from ischemic or toxic insults and uSl.lallyaffects the tubular portion of the nephron. In contrast, chronic renal disease(CRD) can be caused by diseases andjor disorders that affect any portion 01'

the nephron, including its blood supply and supporting interstitium. Earlydetection of AR D facilitates appropriate Íntervention tbat can arrest or at

least attenuate tubular cell damage and the development of established acu terenal failure (ÁRF). Similarly, early detection of CROo before lhe onset orrenal azotemih and chronic renal failure (CRF), shou)d facilitate appropri

ate intervention that stabi¡¡zes renal function or at least slows its progressivedecline.

Acute renal dllmage nnd acute renal faHure

In many cases, ARO lending to ARF inadvertently develops in the. hospital setting in conjunction \Vith diagnostic or therapeutic procedures.

For example, AR O may result from decreased renal perfusion associatedwith aneslhesia ¡¡nd surgery or with the use of vasodilators and nonsteroidulanti-inflammatory drugs (NSAIDs). Similarly, ¡¡elite tubular damngt:frequently occurs in patients treated with potential nephrotoxicants. slIchas gentamicin. amphotericin, und cisplalin. Ischemic and nephrotoxic insultsusually involve Ihe most metabolically active p ortions of the nephron (ie. (he

proximal convoluted tubule and the thick ascending limb 01' Henle). This

E-mail atltlress: ggntuer@ksu.edu 

0!95-5616/05/S· see fronl maller © 2005 Elsevier lne. Al! ríghts reserved. doi: 10.1 016/j.cvsm.2004.12.0 13 ,·elsmall.lhl!d¡n¡cs.t:mn