OCULAR ANESTHESIA

ANANT VIR JAIN

THE PURPOSE OF ANESTHESIA IS TO SAFELY PROVIDE COMFORT FOR THE PATIENT WHILE OPTIMIZING THE CONDITION FOR SURGEON

SELECTION OF ANESTHESIA

A number of factors influence the choice ofanesthesia:

The anticipated complexity and duration of the surgical procedure. The patient's medical status (e.g., the presence of cardiopulmonary disease or coagulopathy). The patient's emotional status and ability to cooperate. The surgeon's skill and preference. The anesthesiologist's skill and preference.

TYPESRetrobulbarPeribulbarparabulbarTopicalTopical with intracameralFacialGeneral

LOCAL ANESTHESIA AGENTS Xylocaine 2%Xylocaine 2% with adrenaline 1:200000Xylocaine 4%Bupivacaine .5%Hyaluronidase 25 to 75 I.U. /ml

RELEVANT ORBITAL ANATOMY

Orbital rim is usually 35mm vertically and 40 mm horizontally in diameterDepth from infra orbital rim to orbital foramen is 42 to 54mm

RETROBULBAR ANESTHESIA injection of local anesthetic into the muscle cone in the retrobulbar space An effective retrobulbar block results in ocular akinesia, anesthesia of the ocular surface, and internal ophthalmoplegia of the iris sphincter and ciliary muscle

TECHNIQUEUse a sharp or dull l.5-inch., 25-gauge needle with a 5-rnl syringeLength of needle should ideally be less than 33mmInstill topical proparacaine in the upper and lower conjunctival fornices (optional)Palpate the inferior orbital margin at its outer one third and clean the skin in this area with an alcohol swabdirect the patient to gaze primary gaze, Which keeps the optic nerve out of the needle's path

Introduce the needle along the inferior orbital rim at the junction of its outer one-third and inner two-thirdsThe needle should be parallel to the orbital floor for approximately the first 1 cm of its insertion, then directed medially toward the orbital apex as it is advanced posteriorlyAs the muscle cone is entered, resistance can frequently be felt if the Atkinson needle (dull) is used

Aspirate with the plunger, if no blood is seen in the syringe, perform a slow deliberate injection of the anesthetic agent (3 to 4 ml) with infiltration along the track of the needle as it is withdrawnInject slowly 1 ml / 10 second Immediately after withdrawing the needle, close the lids and apply pressure to the eye with the flat of the hand over a gauze square. Maintain pres- sure for approximately 60 secondsIf considerable proptosis exists or the globe feels firm, apply additional pressure, but for no longer than 60 seconds at a timeRetract the lids manually and examine the eye for signs of retrobulbar hemorrhage

COMPLICATIONSChemosisSub conjunctival haemorrhageRetrobulbar haemorrhageGlobe perforationIntrathecal injectionstrabismus

Peribulbar

the injection of anesthesia is "deliberately" extra-conical, introduced about 15 years ago to reduce the incidence of complications associated with the intra-conical injection usually produces good anesthesia but bulbar akinesia is usually incomplete except when considerable volumes of anesthetic are injected

techniqueinjection of 7-10 mI of anesthetic split into two administrations the first inferotemporal injection ( 4-5 mI) differs from the Retrobulbar because the needle is not angled and it is not moved centrally once the bulbar equator has been exceeded

The second injection is performed in a superonasal position (4-5 mI) more proximally on the edge of the superior rectus muscle As the considerable volume of anesthetic used, it is necessary to perform adequate ocular pressure to obtain the adequate conditions of intraocular tension Complications same as retrobulbar but less frequency

PARABULBAR (SUB TENON)Sub Tenonian space extends from the limbus to sub-dural space of the optic nerve An anesthetic solution injected in the sub- Tenonian space spreads along the eye- bulb, in the retrobulbar space as far as the optic nerve, eyelids and extra ocular muscles The sub- Tenonian injection produces good anes- thesia of the iris and the anterior segment, and akinesia is proportional to the volume of the anesthetic injected

TECHNIQUEThe conjunctiva and the Tenon capsule are opened 2- 3 mm from the limbus with Vannas or Westcott scissors, following appropriate cauterization the injection is normally performed in the supero-nasal quadrant Greenbaum polyethylene cannula with a flat edge facing downwards is introduced in to the sub- Tenonian space until the base of the cannula closes the opening forming a fold in the. conjunctiva

Once the cannula has been positioned, 1-1.5 mI of solution is injected under sufficient pressure to diffuse the anesthetic posteriorly. The anesthetic effect is immediate whereas akinesia appears later (4-5 min) It does not create a significant rise in the IOPComplications are chemosis and sub conjunctival haemorrhage

TOPICALAdvantages

• Absence of potential complications associated with the orbital block:

• Retrobulbar hemorrhage• Perforation of the bulb• Retinal vascular occlusion• Diplopia• Ptosis• Systemic complications

• Immediate functional recovery• No anxiety from the injection• Persistence of blinking• Greater safety during systemic therapy / pathology

(anticoagulants)• Limited allergic reactions• Saving in terms of time and cost

• Disadvantages• more challenging owing to saccadic eye movements

during surgery • Maximum anxiety to the patient• Eye motility• Relatively contra-indicated in complicated cases

(narrow pupil) and in patients affected by deafness or dementia

TECHNIQUESterile, preservative-free topical anesthesia such as methylparaben-free 0.75% bupivacaine hydrochloride or 4 to 2% xylocaine should be used Every attempt should be made to avoid applying the drop directly onto the cornea, as this can result in epithelial toxicity Applica- tion of the topical anesthetic in a circurn-limbal pattern anesthetizes the long ciliary nerves while protecting the corneaintravenous sedation can be a useful adjunct to topical or intra- cameral anesthesiaOne percent preservative free xylocaine is an excellent adjunct to topical anesthesia A 0.25- to 0.50-ml bolus may be injected into the AC

FACIAL BLOCKSVan Lint's technique• The needle is inserted 1cm posterior to the junction point between the

inferior and lateral orbit rim and penetrates as far as the periostium 1 mI of anesthetic is injected

• The needle is then directed towards the lower eyelid and 1 mI of anesthetic is injected deep in the orbicular muscle

• The needle is then re-direct~d towards the upper eyelid and another 1 mI of local anesthetic is injected

O'Brien's technique• The needle is introduced 1 cm anterior to the tragus until it comes into

contact with the periostium of the mandibular condyle that is easily identified when the patient opens and closes his mouth

• 2-4 mI of anesthetic agent is introduced as the needle is withdrawn

Atkinson's technique• The branches of the facial nerve are blocked on the zymgomatic arc by

injecting 5-10 mI of anesthetic agent• The technique is not frequently used because of the high number of

failures

Nadbath and Rehman technique• The block of facial nerve is achieved with the injection of local anesthesia

where the main trunk of the nerve emerges from the stylomastoideal foramen• The injection site is located between the mastoid process and the posterior

edge of the mandibular branch• A short needle (12-16 mm) is used and between 2-4 mI of anesthetic agent is

injected• Associated with the highest risk of serious complications as rapid-onset

dysphagia, accumulation of secretions, laringo-spasm and distressed respiration because of ipsilateral paralysis of the IX, X and XI cranial nerves

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