Neuromuscular and haemodynamic effects of mivacurium in elderly and young adult patients

Abstract

We have studied the neuromuscular effects of mivacurium and changes in heart rate and arterial pressure in 40 elderly (aged 70 yr) and 20 young adult (aged 18-40yr) patients anaesthetized with thiopentone, fentanyl, nitrous oxide in oxygen and halothane. Neuromuscular block was monitored by train-of-four (TOF) stimulation of the ulnar nerve and recording of the force of contraction of the adductor pollicis muscle using a force displacement transducer and a neuromuscular function analyser (Myograph 2000, Biometer Ltd). Twenty elderly and 10 young adults received single closes of mivacurium 0.15 mg kg-1 and spontaneous recovery was recorded. The other 20 elderly and 10 adults received the same dose but an infusion was started at T1 (first response in TOF) of 10% and the block maintained at this level. Haemodynamic effects were studied after administration of mivacurium over 15 or 5 s in elderly (n=10 each) and over 5 s in adult (n=10) patients. Onset of maximum block occurred at a mean time of 122 (sd 32) and 125 (49) s in elderly and young adults, respectively. Recovery of T1 to 25% occurred in 22.0 (5.7) and 17.2 (4.4) min, and T1 to 90% in 32.8 (6.9) and 24.4 (5.8) min in elderly and adult subjects, respectively. Recovery of the TOF ratio to 0.7 occurred in 32.8 (7.1) and 26.0 (15.0) min in the elderly and young subjects, respectively (all P<0.05 between young and elderly). Mean mivacurium requirements by continuous infusion for maintenance of 90% block were 3.67 and 5.50 ng kg-1 min-1 in elderly and the young adults, respectively (P < 0.05). In the elderly, neuromuscular effects were prolonged by approximately 30% and infusion requirements reduced by 38%. Residual neuromuscular block was antagonized easily with edrophonium or neostigmine. Except for small changes in systolic arterial pressure, mivacurium exhibited good haemodynamic stability in both groups. Cutaneous flushing was observed in six elderly (1 5%) and six young adults (30%). © 1994 British Journal of Anaesthesia.