Prolonged infusion of suxamethonium in infants and children

The neuromuscular blockade produced by a prolonged (greater than 90 min) continuous infusion of suxamethonium and measured with train-of-four stimulation was studied in 20 infants and 20 children during nitrous oxide and halothane in oxygen anaesthesia. The results were compared with a previous study in adults. Suxamethonium requirement was increased in infants and children. Mean peak infusion rates were 297 and 284 micrograms kg-1 min-1 in infants and children, compared with 134 micrograms kg-1 min-1 in adults. An initial tachyphylaxis was followed by bradyphylaxis, and the peak requirement occurred earlier in infants than in children and adults (40 v. 80-100 min). Phase II block developed during the tachyphylaxis. Recovery of neuromuscular activity commenced after stopping the infusion and was accelerated with neostigmine.