ANESTHESIA FOR OPHTHALMIC SURGERY

Dr Md Ferdous IslamCMH,Dhaka

INTRODUCTION

Anesthesia for EYE surgery presents many unique challenges.

In addition to possessing technical expertise, the anesthesiologist must have detailed knowledge of ocular anatomy, physiology, and pharmacology.

Ocular anatomy Physiology of intraocular pressure and

effect of anesthetic drug on it, Systemic effects of ophthalmic drugs Technique of anaesthesia: advantage

and limitations Pre op evaluation General anaesthesia Complications Specific considerations for eye

surgeries

Challenges for the anaesthesiologist are

Akinesia Analgesia Minimal Bleeding Awareness of drug interactions Regulation of intraocular pressure Prevention of the oculocardiac

reflex Management of oculocardiac reflex Control of intraocular gas

expansion Smooth emergence

TECHNIQUES OF ANAESTHESIA GENERAL ANESTHESIA

LOCAL ANESTHESIA

a. Topical anesthesia

b. Infiltration anesthesia

Retrobulbar block

Peribulbar block

Sub Tenon block

Sub conjunctival block

c. Nerve block

d. Intra cameral

AGENTS

Adjuvants:Inj.Adrenaline( 1 in 100000) It reduces systemic absorption by local

vasoconstriction.It also reduces chance of bleeding, prolongs the duration of action. It is contraindicated in HTN and Heart diseases.

Inj Hyaluronidase It enhances diffusion of agents through tissue by

breaking down extracellular matrix. It is used 15 unints/ ml of anesthetic solution

GA Vs LA The choice is made on the basis of

the duration of the surgery, the relative risks and benefits of

each technique for the patient, patient preference.

Indication of GA In children EUA Probbing of NLD Surgeries Cataract Glaucoma Enucleation in Retinoblastoma Injury Repair Squint DCR

In adults Repair of perforating injury Mentally retarded pt Non co operative Pt Too nervous and apprehensive pt Eneucleation, evisceration,

Exenteratin surgery Major Occuloplastic surgery Surgeon’s preference

General versus Local AnesthesiaGeneral

Anesthesia:

Patient refusal

Children / movemen

t disorders

Major / lengthy

procedures

Inability to lie still /

flat

Local Anesthesi

a:

No Physio-logical distur-bance , PONV

Economic, Day care

Regional Anesthesi

a:

Good akinesia

and anaesth

esia

Minimal effect on IOP

Minimal equipm

ent require

d

Topical Anesthesi

a:

no risk of hemorrhag

e, brainstem

anesthesia, optic nerve damage or

globe perforation

LIMITATIONS…General Anesthesia:

Eye surgery necessitates

positioning the anesthesiologist away from the

patient’s airway

Patients at extremes of age

Pediatric patients : associated congenital

disorders (eg: rubella syndrome, Down syndrome).Co-morbidity in

elderly: esp. Diabetes,

hypertension and coronary artery

diseaseOphthalmic

drugs

Local Anesthesia:

Complications , Allergy to drug

Skill of anaesthetist

Shortness of breath on

lying down, chronic cough

Parkinson’s disease

Eye Trauma

Topical Anesthesia:

lack of eye

akinesis

treatment of

uncomplicated

cataracts only

PREOPERATIVE EVALUATION Eye surgery patients are a high-risk

group Age diabetes, hypertension, and

atherosclerosis informed consent of the patient.

HISTORY

Allergies and drug sensitivities A current list of medications Patient factors incl dementia,

deafness, language difficulty, restless legs syndrome, obstructive sleep apnea, tremors, dizziness, and claustrophobia.

PHYSICAL EXAMINATIONS Check for signs of major cardiac or

pulmonary decompensation.

Particular attention should be paid to positioning issues, such as severe scoliosis or orthopnea, Tremor.

CARDIOVASCULAR EVALUATION The AHA and American College of

Cardiology published guidelines for perioperative cardiovascular evaluation for noncardiac surgery.

Ophthalmic procedures such as cataract extraction are specifically identified as low-risk procedures.

HYPERTENSION

Severe hypertension may lead to perioperative complications.

It would be prudent to reschedule elective procedures in patients with sustained stage 3 hypertension until after 2 weeks of antihypertensive therapy.

PULMONARY CONSIDERATIONS

Preoperative risk reduction strategies

incl cessation of cigarette smoking, treatment of airflow obstruction administration of antibiotics for

respiratory infections. Patients should be assessed for sleep

apnea. Intravenous sedation is often contraindicated in these patients.

ENDOCRINE CONSIDERATIONS Severe hyperglycemia and

hypoglycemia should be avoided. A FBS should be checked

preoperatively. Insulin therapy should be used, if

needed, to maintain blood glucose at 150 to 250 mg/dL.

ANTICOAGULATION Perioperative management of

anticoagulants against possible hemorrhagic complications. That depends on the following:     The degree of anticoagulation.    The hemorrhagic potential of the surgical

procedure as in orbital and oculoplastic surgery; of intermediate probability in vitreoretinal, glaucoma, and corneal transplant surgery; least likely in cataract surgery.

INVESTIGATIONS

ECG: New chest pain, decreased exercise tolerance, palpitations, near-syncope, fatigue, or dyspnea. Tachycardia, bradycardia, or irregular pulse on examination.

Serum electrolytes: H/O severe vomiting or diarrhea, poor oral intake, changes in diuretic management, or arrhythmia.

Critical results: Na less than 120 mEq/L or greater than 158 mEq/L.

K less than 2.8 mEq/L or greater than 6.2 mEq/L.   

INVESTIGATIONS Urea nitrogen: renal decompensation.

Critical result: Greater than 104 mg/dL.    RBS: Polydipsia, polyuria, or weight loss.

Critical results: Less than 46 mg/dL or greater than 484 mg/dL.   

Hematocrit/hemoglobin: History of bleeding, poor oral intake, fatigue, decreased exercise tolerance, or tachycardia. Critical results: Hematocrit less than 18% or greater than 61%. Hemoglobin less than 6.6 mg/dL or greater than 19.9 mg/dL

GENERAL ANESTHESIA

PREMEDICATION

An effective antiemetic should be used

to decrease PONV. eg- Ondansetron

Opioids are avoided as they contribute

to PONV.

Benzodiazepines are given.

GENERAL ANESTHESIA

Intravenous agents: Propofol , Thiopental and Etomidate.

Coughing during intubation: avoided by a deep level of anesthesia and profound paralysis.

The IOP response: to laryngoscopy and endotracheal intubation can be blunted.

LMA: can also be used. Less changes in IOP.

AIRWAY MANAGEMENT maintenance of spontaneous

respiration via a facemask should be used, as intubation will raise the intraocular pressure.

Examination under anaesthesia (EUA)-spontaneous respiration through a reinforced laryngeal mask airway (LMA)

GENERAL ANESTHESIA

RELAXATION- A nondepolarising muscle relaxant is

used instead of succinylcholine because the latter increases intraocular pressure.

However, the rise in IOP is small by succinylcholine than the fall caused by intravenous induction agent, and also considering risk of aspiration succinylcholine can be used in an emergency case.

USE OF NITROUS OXIDE The use of nitrous oxide in eye surgery

is limited by two factors. Increase the risk of PONV, and in

ophthalmic procedures there is a high incidence of PONV

Secondly, nitrous oxide diffuses from the blood into gas filled spaces in the body.

It should be avoided in vitreoretinal detachment surgery where intraocular gas bubbles of sulphur hexachloride or perfluropropane are introduced into the eye to tamponade detached surfaces.

GENERAL ANESTHESIA

EXTUBATION & EMERGENCE A smooth emergence from general

anesthesia Deep level of anesthesia. Intravenous lidocaine (1.5 mg/kg)

prior to extubation. Severe postoperative pain is

unusual.

The effect of anesthetic agents on intraocular pressure (lOP).

Topical anesthesia

Relieve pain and itching caused by conditions such as sunburn or other minor burns, insect bites, minor cuts and scratches.

Fluorescence dye examination for corneal ulcer.

Gonioscopy Corneal scrapping for bacteriological study Paracentesis Perform a contact /applanation tonometry. Cataract, pterygium and glaucoma surgery Removal of small foreign objects from the

uppermost layer of the cornea or conjunctiva.

Retrobulbar Block A long needle is introduced at junction

of middle third and lateral third of inferior orbital margin and then directed backwards and medially towards the apex of the orbit.

Effects are Anaesthesia, akinesia, Hypotony

proptosis

65

Peribulbar Blocks• At superior and inferior parts of

peripheral space of orbit.• The superior injection.• The Inferior Inj• An Intermittent Pr. • Advantages

66

Sub-Tenon’s Block

• Sensory block• Short-ciliary nerves

pass through Tenon’s capsule to globe

• Akinesia• Direct blockade of ant.

nerve fibres as they enter extra-ocular muscles 68

FACIAL NERVE BLOCK

Blocked at several points after exiting from the base of the skull from the stylomastoid foram

Van Lint block A needle is introduced about 1 cm below and behind the lareral canthus. About 4ml sol along the supero lateral and inferolateral orbital margin in a V shape manner.

O'Brien’s procedure About 4 ml sol is infiltrated at the neck of the mandible just infront of the tragus.

Other Nerve Block Intratrochlear nerve block Supraorbital nerve block Lacrimal nerve block Infraorbital and Zygomatic nerve

block

Intra Cameral Anaesthesia

Injecting 1% Lidocaine inj into ant chamber by side port incision or paracentsis.

Anaesthetises Iris and the Ciliary Body

Reduces pain and IOP The drug must be washed

properly

COMPLICATIONS

COMPLICATIONS OF REGIONAL ANAESTHESIA

Retrobulbar hemorrhage

CRAO

Stimulation of OC reflex

Puncture of posterior globe

IV injection of LA brainstem anesthesia - (delayed

onset LOC and resp. depression)

Optic nerve trauma.

RETROBULBAR HAEMORRHAGE

Venous hemorrhages - spread slower

Arterial hemorrhages - rapid and taut orbital swelling with marked proptosis.

incidence-1% to 3%. Clinical suspicion: stained

conjunctiva and a proptotic globe

RETROBULBAR HAEMORRHAGEMANAGEMENT Determine IOP OphthalmoscopyTREATMENT reduce orbital compartment

pressure, thereby IOP Osmotic diuretics Lateral canthotomy Orbital decompression

OCULOCARDIAC REFLEX

The Oculocardiac Reflex(OCR) is manifested by Bradycardia Ectopics Nodal rhythm Atrioventricular block Cardiac arrest

OCULOCARDIAC REFLEX

Caused By: Traction on the extraocular muscles

(medial rectus) Ocular manipulation Manual pressure on the globe

The OCR is seen during: Eye muscle surgery Detached retina repair Enucleation

OCULOCARDIAC REFLEX Factors contributing to the

incidence of the oculocardiac reflex: Preoperative anxiety

Hypoxia

Increased vagal tone owing to age

OCULOCARDIAC REFLEX

Management stop stimulation by the surgeon

before the arrhythmia progresses to sinus arrest

Atropine (0.01 mg/kg IV) local injection of lidocaine near the

eye muscleEnsure depth of general anesthesia normocapnia surgical manipulation is gentle.

OCULORESPIRATORY REFLEX may cause shallow breathing,

reduced respiratory rate and even full respiratory arrest.

Trigemino vagal reflex- connection exists between the trigeminal sensory nucleus and the pneumotactic centre in the pons and medullary respiratory centre.

Commonly seen in strabismus surgery

OCULOEMETIC REFLEX

It is likely responsible for the high

incidence of vomiting after squint surgery (60-90%).

Trigemino-vagal reflex with traction on the extraocular muscles stimulating the afferent arc.

Antiemetics may reduce the incidence, a regional block technique provides the best prophylaxis

Disturbances of swallowing and respiratory difficulties

Horner's syndrome permanent facial nerve paralysis-

longer needles and hyaluronidase use of a single injection of a large

volume of LA

BRAINSTEM ANAESTHESIA Amaurosis

Gaze Palsy (Ductional Defects),

Apnea Shivering Tachycardia and

Hypertension Dysphagia Loss Of

Consciousness Cardiac Arrest

BRAINSTEM ANAESTHESIA The onset of symptoms -delayed 2

to 40 minutes after injection.

Management: Early and prompt treatment 100% oxygen maintenance of vital signs tracheal intubation and controlled

ventilation

OCULAR PENETRATION AND PERFORATION most common in the myopic,

elongated globes. Myopics with staphyloma. associated with the use of large,

dull needles. a sensation of "poking through

”during the placement of the needle.

sudden appearance of hypotony, vitreous hemorrhage or a diminished red reflex

OCULAR PENETRATION AND PERFORATION Diagnosis -Indirect fundoscopy

The most common sequelae- Retinal detachment

Appropriate retinal surgery-to prevent the loss of vision.

COMPLICATIONS ASSOCIATED WITH GENERAL ANAESTHESIA

PONV

Increase in IOP-extrusion of intraocular contents

Intraocular gas expansion

Pulmonary embolism

POST OPERATIVE NAUSEA AND VOMITING Most common complication

associated with outpatiet The incidence in patients

undergoing strabismus surgery -85%.

MANAGEMENT Metoclopromide i.v (10 mg) 5HT3 antagonists Dexamethasone i.v

Pulmonary Embolus

chief cause of postoperative ophthalmic surgery death

particularly a problem with long procedures (retinal and oculoplastic surgery) in the elderly.

from a leg deep venous thrombosis

Pneumatic leg compression devices

INTRAOCULAR GAS EXPANSION Intravitreal air/SF6 injection: to

flatten a detached retina and allow anatomically correct healing

Nitrous oxide:expansion of air bubble and rise in IOP

Prevention: discontinue nitrous 15-20 mins prior to injection

Ref

American Academy of Ophthalmology Alexander J.E. Foss,Essential Ophthalmic Surgery