1. Eye surgery Requirements for eye surgery: 1.Akinesia of the eye 2.Intense analgesia 3.Minimal bleeding (avoid HT or movement of eye) 4.Management of oculo-cardiac reflex 5.Control of intra-ocular pressure (IOP) 6.Beware of drug interactions 7.Smooth recovery with no PONV

2. Oculo-cardiac reflex Occurs with pulling of eye muscles/pressure on eye ballOccurs with pulling of eye muscles/pressure on eye ball Afferent = N V (V1), efferent = N X → bradycardiaAfferent = N V (V1), efferent = N X → bradycardia Most common in children for strabismus repair, but can occur during any ophthalmic procedureMost common in children for strabismus repair, but can occur during any ophthalmic procedure Management:Management: 1. Ask surgeon to stop pulling on muscles 1. Ask surgeon to stop pulling on muscles 2. Confirm adequate depth of anaesthesia 2. Confirm adequate depth of anaesthesia 3. Administer atropine (0.02 mg/kg) if bradycardia persists 3. Administer atropine (0.02 mg/kg) if bradycardia persists 4. The reflex eventually fatigues itself with repeated pulling 4. The reflex eventually fatigues itself with repeated pulling and release of eye muscles and release of eye muscles

3. Control of intra-ocular pressure Eye cavity = hollow sphere with a rigid wall. If contents ↑→ IOP ↑→ extrusion of ocular contents through open surgical/trauma woundEye cavity = hollow sphere with a rigid wall. If contents ↑→ IOP ↑→ extrusion of ocular contents through open surgical/trauma wound Anaesthesia can → ↑ IOP due toAnaesthesia can → ↑ IOP due to 1. laryngoscopy/ intubation (HT), 1. laryngoscopy/ intubation (HT), 2. airway obstruction, coughing, ↑ CVP, Trendelenburg 2. airway obstruction, coughing, ↑ CVP, Trendelenburg position (↓ venous drainage) position (↓ venous drainage) 3. ↑ PaCO2 (vasodilatation →↑ eye blood flow 3. ↑ PaCO2 (vasodilatation →↑ eye blood flow 4. Drugs: Ketamine, suxamethonium →↑ IOP 4. Drugs: Ketamine, suxamethonium →↑ IOP Other anaesthetic drugs (opioids, induction agents, muscle relaxants do not ↑ IOP and are thus save Other anaesthetic drugs (opioids, induction agents, muscle relaxants do not ↑ IOP and are thus save

4. Drug interactions Ecothiopate is a pseudocholinesterase (pCE) inhibitor used to ↓ IOP but it can prolong the action of suxamethonium (which is broken down by pCE)Ecothiopate is a pseudocholinesterase (pCE) inhibitor used to ↓ IOP but it can prolong the action of suxamethonium (which is broken down by pCE) Timolol is a β-blocker used in the eye to ↓ IOP but can cause bradycardia, asthma etcTimolol is a β-blocker used in the eye to ↓ IOP but can cause bradycardia, asthma etc

5. Strabismus surgery Oculo-cardiac reflex = commonOculo-cardiac reflex = common ↑ incidence of malignant hyperthermia (temperature monitoring = NB)↑ incidence of malignant hyperthermia (temperature monitoring = NB) ↑ incidence of PONV (consider prophylactic anti-emetics)↑ incidence of PONV (consider prophylactic anti-emetics)

6. The open eye Emergency, thus can not wait for pt to be NPOEmergency, thus can not wait for pt to be NPO Do rapid sequence induction (trauma delays gastric emptying)Do rapid sequence induction (trauma delays gastric emptying) Avoid KetamineAvoid Ketamine Consider suxamethonium (although ↑ IOP), because it is given with IV induction agent and opioid which both decrease IOP. Suxamethonium provide excellent intubation conditions and thus prevents ↑ IOP due to coughing etc.Consider suxamethonium (although ↑ IOP), because it is given with IV induction agent and opioid which both decrease IOP. Suxamethonium provide excellent intubation conditions and thus prevents ↑ IOP due to coughing etc. Avoid all factors that ↑ IOP (see above)Avoid all factors that ↑ IOP (see above)