Pharmacodynamics of mivacurium in children, using a computer-controlled infusion

A computerized infusion system was used to determine requirement for a mivacurium infusion to maintain a 95% and a 50% neuromuscular block in 21 children aged 1-15 yr. Neuromuscular block was measured by adductor pollicis EMG and anaesthesia maintained with 66% nitrous oxide in oxygen and alfentanil 50-100 micrograms kg-1 h-1. The targeted neuromuscular block was reached within mean 5 (SD 3) min from initiation of an infusion. Mivacurium requirement for 95% neuromuscular block was 950 (350) micrograms kg-1 h-1, which represented an hourly requirement of 6.8 (1.6) individual ED95 doses. Infusion requirement for 50% neuromuscular block averaged 350 (150) micrograms kg-1 h-1. There was a significant negative correlation between infusion rate and age of a patient. Great individual variation of the infusion rate makes a computerized infusion an easy method to achieve and maintain a desired level of neuromuscular block. No side effects of mivacurium were noticed.