Time course of potentiation of mivacurium by halothane and isoflurane in children

We studied 40 children, aged 1-15 yr, to analyse the time course ofpotentiation of mivacurium produced by halothane and isoflurane. A steadyinfusion requirement of mivacurium to maintain 90% neuromuscular block wasestablished during thiopentone-alfentanil-nitrous oxide- oxygenanaesthesia. Patients were then allocated randomly to receive 1 MACend-tidal concentration of either halothane (group Hal) or isoflurane(group Iso) while neuromuscular block was maintained at 90%. Both volatileagents decreased the infusion requirements of mivacurium in an exponentialmanner in that maximal potentiation occurred only after 30-80 min. Maximalreduction in infusion rate (32% in group Hal and 70% in group Iso; P <0.0001) did not depend on the age of the child but became establishedsooner the younger the child in the case of isoflurane (P = 0.002).