Maintenance of a normal to low intraocular pressure during ocular surgery is of critical importance. The prime considerations for anaesthetic management include adequate depth of anaesthesia, normal carbon dioxide and arterial oxygen tensions, stable cardiovascular status and avoidance of stimuli likely to raise central venous pressure. Non-depolarizing muscle relaxants are associated with a reduction in intraocular pressure. Metocurine, a non-depolarizing relaxant, formerly known as dimethyltubocurarine, has been recently reintroduced into clinical practice. Metocurine has been reported to be 1.8 times more potent than d-tubocurarine and has the clinically advantageous cardiovascular effects of stable heart rate and mean blood pressure with minimal associated histamine release. When combined with pancuronium, metocurine potentiates the neuromuscular blocking properties, so that small doses of both drugs in combination produce effective neuromuscular block. This study was designed to assess the suitability of metocurine 0.3 mg-kg-and metocurine 0.08 mg kg-plus pancuronium 0.02 mg kg-as muscle relaxants for ocular surgery. The results demonstrated that metocurine and metocurine-pancuronium combination in the above doses combined with sodium thiopentone 5 mg'kg -t produced ideal conditions for intubation of the trachea in 4.45 (---0.19 SE) minutes and 4.35 (-0.16 SE) minutes respectively. In both treatment groups intraocular pressure was reduced below control values and a pattern of intraocular pressure stability ideal for ocular surgery was obtained during the 10 minutes observation period. The delayed onset of sufficient paralysis for tracheal intubation -4.45 (---0.19 SE) minutes for metocurine and 4.35 (• SE) minutes for the combination -makes these techniques unsuitable for emergency ocular surgery because of the long interval when the airway is unprotected.KEY WORDS: EYE, intraocular pressure; NEUROMUSCULAR RELAXANTS, metocurine, pancuronium.THE PRIME considerations involved in the anaesthetic management of patients undergoing ocular surgery are a stationary eye, for safe surgical conditions; absence of coughing and vomiting during and after operation; avoidance of elevations in intraocular pressure, which can cause extrusion of globe contents; airway control and a stable cardiovascular system. The choice of muscle relaxant is of paramount importance. The ideal muscle relaxant for ocular surgery would be one that is potent, with a rapid onset, appropriate duration of action, and readily reversible. In addition, autonomic and cardiovascular side-effects should be minimal. Metocurine, a nondepolarizing neuromuscular blocking agent formerly known as dimethyltubocurarine,~ has been recently reintroduced into clinical practice. A trimethylated derivative of d-tubocurarine, metocurine has 1.8 times the potency of d-tubocurarine and in doses of 0.3 mg-kg -~ produces 96.1 per cent mean twitch depression within 4.8 ---0.6 (SEM) minutes, 2 allowing easy tracheal intubation. In such doses, metocunne offers the ...
