Anaesthesia For Eye Surgery

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Anaesthesia for Eye-surgery

Dr.Shailendra.V.L.Specialist in AnaesthesiaAl Bukariya general hospitalSaudi Arabia.

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Introduction

Technological improvements Improved surgical techniquesImproved techniques in anaesthesia Better understanding of the

physiology

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Ophthalmic Surgery

Extra ocular surgery- strabismus correction

Intra ocular surgery- cataract with IOLMixed - drainage operations for glaucoma

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Anaesthesia requirements for ophthalmic surgery

Immobile eye Uncongested eye Intra ocular pressure:

- to minimize the danger of expulsion of intra ocular contents

Smooth recovery Avoidance of PONV

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Physiology of intra ocular pressure

INTRA-OCULAR PRESSURE DETERMINANTS:

Factors exerting outward pressure Factors exerting inward pressure

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Intra-ocular pressure

Aqueous humourVitreous humourBlood within the eyeScleral complianceExtra-ocular muscle tone

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Aqueous humour dynamics

Ultrafiltration of plasma by ciliary epithelium

Formation of A H in ciliary process

A H circulate around Iris via pupil

Anterior chamber

Canal of Schelmn

Trabecular spaces of Fontanadrains through

Episleral venous system

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Drugs acting on AH mechanics

production:Acetozolamide (carbonic anhydrase

inhibitor)Beta blockers

Improve drainage:Miotics (by contracting ciliary muscle)Mydriatics affects drainage

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Choroidal blood volume effecting AH mechanics

Systemic blood pressure: Choroidal capillaries auto-regulatory

function ↑ in Blood pressure causes transient ↑in IOP

Venous pressure: ↑in CVP causes acute ↑in IOP Coughing/ vomiting/ valsalva/ straining on

tube all ↑ IOP ↑PaCO2 causes ↑ IOP by choroidal

vasodilatation

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Vitreous Humour

Fine unstable gel consisting of water & fine supporting structure

Volume & pressure reduced by Mannitol which is a dehydrating agent & there by ↓ IOP

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Extra-ocular muscle tone

Tone controlled by the mid-brain

GA ↓ muscle tone & there by ↓ IOP

Gentle, constant pressure on the eye promotes aqueous humour flow & ↓ IOP

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Pharmacological modifications of IOP

Pre anaesthetic Medication:IV diazepam & midazolam ↓ IOPParental atropine has no effect on IOP

Intravenous anaesthetics:Only ketamine ↑ IOPAll other agents ↓ IOP

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Pharmacological modifications of IOP

Inhalational agents effect IOP by:Central action on mid-brainAlteration of aqueous humour↓ extra-ocular muscle tone

Dose dependent reduction in IOP

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Pharmacological modifications of IOP

Neuro-muscular blockers:Succinylcholine- ↑ IOP by 10 mmHg

by 1 minute & lasts for 10 minutes↑ IOP due to tonic action of drug on

Felderstruktur striated extra0ocular muscle

Laryngoscopy & Intubation: ↑ IOP

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Oculo-cardiac reflex

Trigemino-vagal reflexBradycardia, nodal rhythm, ectopic beats,

ventricular fibrillation, asystoleEyeball pressure, traction of extra-ocular

muscles, orbital haematoma, ocular trauma & eye pain, eyelid traction

Can occur even from enucleated orbit

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Oculo cardiac reflexAfferent pathway Efferent pathway

Short & long ciliary nerves Nucleus of vagus

Ciliary ganglion Cardiac branches

via ophthalmic division of trigeminal nerve Bradycardia

Trigeminal sensory nucleus

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Treatment of OCR

Ask surgeon to stop all the manipulations

Intravenous Atropine 15 micro grams / Kg or intravenous Glycopyrrolate 7.5 micro grams / Kg

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Systemic effects of ophthalmic medications

Eye drops are readily absorbed through hyperemic, incised conjunctiva causing systemic effects

Phenyleohrine(2.5%) cause hypertension, arrhythmia and headache

Adrenaline(2%) cause hypertension & arrhythmiasTimolol (B-blocker) causes bradycardia,

hypotension & exacerbation of asthmaPhospoline iodide is a lone acting anti-

cholinesterase used in glaucoma prolongs suxamethonium induced muscle relaxation

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Anaesthetic management of elective intra ocular surgery

Goals of general anaesthesia: Immobile eyeStable IOPMinimize bleedingAvoidance of Oculo-cardiac reflexSmooth inductionSmooth emergenceMinimal post-operative nausea & vomiting

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Common Ocular surgeries

Cataract surgeries Lid surgeries Conjuctival surgeries Strabismus surgeries Penetrating eye injuries Vitreous surgeries Retinal surgeries Laser surgeries

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Anaesthetic management of elective intra-ocular surgery

Pre-medication: use of anxiolytics Induction: Thiopentone + Suxamethonium Intubation: Smooth laryngoscopy & intubationMaintenance: O2 + N20 + Isoflurane/Halothane

IPPV with Non-depolarizing muscle relaxantReversal: Neostigmine + Atropine , extubate in

deeper planes

Problems encountered: Dark room

Face inaccessible

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Anaesthesia for perforating eye injury Problems: Full stomach patient

Perforated eye Plan: Preoxygenation Induction: Thiopentone + Atracurium

Sellick’s maneuver Smooth laryngoscopy & intubation

Controlled ventilation Smooth extubation

Use of Ondansetron to prevent PONV

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Anaesthesia for special ocular surgeries

Glaucoma:Anti-cholinesterase eye drops used in

treatment can potentiate effects of succinylcholine precipitating bradycardia & arrhythmias

To ↓ IOP 20% mannitol is used, hence it is better to catheterize these patients

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Anaesthesia for special ocular procedures

Retinal detachment surgery:Oculo-cardiac reflex commonly observedEssentially extra-ocular surgerySynthetic silicone strap used to produce

scleral indentation

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Anaesthesia for special ocular surgeries

Intra-vitreous gas injection:Intra-vitreous injection of inert gas of

low diffusibility such as Sulphar hexafluride (SF6) or Carbon octofluride (C3F6)

Gas is absorbed over 10 days and the bubble keeps the sclera intact

N20 must be avoided as the bubble size increases upto three times

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Anaesthesia for special ocular procedures

Vitrectomy:Closed intra-ocular procedureSurgeon controls IOP manometrically

by water tight infusion

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Ophthalmic procedures in children

Naso-lacrimal duct probing / syringingExamination under anaesthesiaIntra-ocular pressure measurementStrabismus correction

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Naso-lacrimal duct probing

Done to open up the ductTrachea to be intubated & throat packed

to prevent the fluid entering trachea

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Examination under GA

Very common procedureDone to examine in detail the eyesTotal intra-venous anaesthesia technique

should be used as the procedure is short

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IOP measurement in children

General anaesthesia with ketamine must be avoided as IOP will be raised with ketamine

General anaesthesia with non-depolarizing relaxants preferred

It is advisable to wait for 10 minutes to take measurements after intubation for the IOP to stabilize

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Strabismus surgery

Incidence of OCR very highCareful monitoring Should be anticipated and treated with

Atropine / GlycopyrrolateAvoidance of PONV by the use of

Ondansetrone

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