MIVACURIUM CHLORIDE IN INFANTS AND CHILDREN

Mivacurium has been little studied in infants and children without a v olatile anaesthetic agent. We analysed onset time and maximal neuromus cular response after mivacurium 0.1 mg/kg, and the infusion requiremen t of mivacurium to maintain a 50, 90, or 95% neuromuscular block in 76 infants and children under N2O-O-2-alfentanil anaesthesia. Furthermor e, we assessed the time course of potentiation of 1 MAC end-tidal halo thane or isoflurane on the infusion requirement of mivacurium. Neuromu scular response was recorded by adductor pollicis electromyogram. The onset time of mivacurium was shorter in infants than in children (2.1/-0.6 and 3.2+/-0.9 min (mean+/-SD); P=0.0001). The dose potency of mi vacurium did not depend on the age of a paediatric patient. The estima ted ED(95) of mivacurium was 136+/-46 mu g/kg. The mivacurium requirem ent to maintain a 50, 90, or 95% neuromuscular block averaged 340, 730 , and 900 mu g/kg/h, respectively. Halothane and isoflurane decreased this hourly requirement by 35 and 70%, respectively. The decrease in t he mivacurium infusion require ment was fastest in the youngest childr en. In conclusion, mivacurium is easy ro administer as bolus doses or continuous infusion in paediatric patients because its potency is simi lar in all patients from 1 month to 15 years of age. Halothane and iso flurane produce their maximal potentiation of neuromuscular block only after 30-60 min of administration. This potentiation is similar in ma gnitude in all patients, but takes place fastest in the youngest child ren.