General anaesthesia for ophthalmic surgery

Local anaesthesia for eye surgery is increasingly popular, but there will always be a need for general anaesthesia. Patients may refuse local anaesthesia, may be unable to keep still or lie flat for the duration of surgery or lack the mental facility to cooperate whilst awake. Young children and those with allergy to local anaesthetic also need general anaesthesia. Careful patient preparation is important before surgery. Glycaemic control in patients with diabetes, adjustments to warfarin or aspirin dosing, thromboembolic prophylaxis and preoperative fasting need to be considered. Eye surgery alone is rarely a true emergency, and surgery can usually wait until the patient’s stomach is empty. Eye pathology requiring surgery is a feature of many medical conditions and syndromes. Many patients are elderly with ischaemic heart disease, hypertension, chronic obstructive pulmonary disease and renal impairment, which must be assessed before general anaesthesia. Systemic effects of ophthalmic medications, such as hypokalaemia caused by acetazolamide should be considered. A wide range of general anaesthetic techniques are suitable for eye surgery, but certain key points are relevant to specific operations. These include the oculo-cardiac reflex in strabismus and retinal surgery, the use of intraocular gas bubbles in vitreo-retinal operations, controlled hypotension in lacrimal, orbital and other oculoplastic procedures, and the high incidence of nausea after strabismus surgery. Total intravenous anaesthesia (TIVA) fulfils many of the requirements for the ideal anaesthetic technique for ophthalmic surgery. Blood pressure, heart rate and intraocular pressure are lowered. It is rapidly titratable and recovery is fast. Postoperative nausea is reduced and TIVA works well in patients with renal and hepatic disease. Remifentanil infusion allows nitrous oxide to be avoided and top-up doses of muscle relaxants to be minimized during ventilation. For most ophthalmic surgery, postoperative pain is mild and non-steroidal anti-inflammatory drugs work well. Intraoperative sub-Tenon’s local anaesthetic is useful.