Pharmacodynamics of mivacurium in infants

A computerized infusion system was used to determine mivacuriuminfusion requirements to maintain 95% and 50% neuromuscularblock in 15 infants less than 1 yr of age. Neuromuscular blockwas measured by adductor pollicis EMG and anaesthesia maintainedwith 66% nitrous oxide in oxygen and alfentanil 50–100µg kg^–1 h^–1. Neuromuscular block was producedby repeated bolus doses of mivacurium 0.1 mg kg^–1; subsequentlythe target neuromuscular block was maintained by a closed loopinfusion. Dose potency of mivacurium was similar to that previouslypublished in children with a similar anaesthetic technique.Mean mivacurium requirement for 95% neuromuscular block was820 (SD 300) µg kg^–1 h^–1, which representedan hourly requirement of 6.6 (1.5) individual ED₉₅ doses. Infusionrequirement for 50% neuromuscular block was 320 (150) µgkg^–1 h^–1. These infusion rates were similar to thosein children. No side effects of mivacurium were noticed.