COMPARISON OF MIVACURIUM AND SUXAMETHONIUM ADMINISTERED BY BOLUS AND INFUSION

Mivacurium chloride is a new, short-acting non-depolarizing neuromuscular blocking agent presently undergoing clinical evaluation. The neuromuscular effects of mivacurium and suxamethonium given by bolus and infusion were compared in adult patients during nitrous oxide-oxygen-oploid anaesthesia. Neuromuscular block was monitored by recording the compound electromyogram of the adductor pollicis muscle resulting from supramaximal train-of-four stimuli applied to the ulnar nerve. Time to onset of complete block and recovery to T<inf>5</inf> were significantly shorter for suxamethonium than for mivacurium (1.0 (0.1) v. 2.5 (0.3) min and 6.4 (0.7) v. 17.5 (1.8) min; mean (SEM)). Conditions for tracheal intubation were similar in the two groups although intubation was performed 0.75–1.3 min later following mivacurium. The infusion rate required to maintain neuromuscular block was 88.6 (10.4) μg kg−1 min−1 for suxamethonium and 7.8 (1.2) μg kg−1 min−1 for mivacurium. There was a significant negative correlation between recovery to T<inf>5</inf> and infusion rate for mivacurium and for suxamethonium. It was equally easy to titrate the in fusion rate to the desired degree of block in each group. The recovery index (T<inf>25</inf>–T<inf>75</inf>) after the infusion stopped was similar in patients who received mivacurium and those who received suxamethonium.