Dose-response curves for suxamethonium in neonates, infants and children

Single dose-response curves were determined for suxamethonium in neonates, infants and children during thiopentone-fentanyl-nitrous oxide anaesthesia. During onset of neuromuscular block, suxamethonium produced an increase in muscle tone which was greatest in neonates and infants. The dose-response curves for the three groups were parallel. The effective doses producing 90% depression of twitch height were significantly greater in neonates and infants compared with children (517 and 608 v. 352 micrograms kg-1). These values were greater than those obtained in a comparable study in adults. In view of their higher ED values compared with adults and a marked individual variability in response to small doses of suxamethonium, we recommend an intubating dose of 3 mg kg-1 for neonates and infants and 2 mg kg-1 for children. These doses are 50-100% greater than those previously recommended for paediatric patients.