COMPARISON OF THE NEUROMUSCULAR BLOCK INDUCED BY MIVACURIUM, SUXAMETHONIUM OR ATRACURIUM DURING NITROUS OXIDE-FENTANYL ANAESTHESIA

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Abstract
We compared the neuromuscular and cardiovascular changes following administration of mivacurium 0.15, 0.20 and 0.25 mg kg−1, suxamethonium 1.0 mg kg−1 or atracurium 0.5 mg kg−1 i.v. in 41 (ASA physical status I or II) patients during nitrous oxide—fentanyl anaesthesia. Mean onset times for total ablation of twitch response for mivacurium 0.15, 0.20 and 0.25 mg kg−1, were 2.5, 2.4 and 2.7 min, respectively, similar to that for atracurium (2.5 min), but longer than for suxamethonium (1.1 min) (P < 0.05). Mean times from administration of drug until twitch response recovered to 10% of control were shorter for each dose of mivacurium (15.6, 18.0 and 20.6 min, respectively) than for atracurium (40.0 min) and longer than for suxamethonium (7.7 min) (P < 0.05). Mean infusion rate required to maintain twitch response at 5±4% control was 6.7 μg kg−1 min−1 for mivacurium and 6.3 μg kg−1 min−1 for atracurium. Following neostigmine 0.045 mg kg−1, mean times for twitch tension to recover from 10% to 90% of control were similar for mivacurium (9.7 min) and atracurium (10.5 min). Transient decreases in mean arterial pressure (> 20%) were observed in seven of 15 patients who received the two higher doses of mivacurium.