The interaction between doxacurium and halothane, isoflurane or alfent
anil has not been studied in children. Using the cumulative dose-respo
nse technique and electromyography, we determined ED(50) and ED(90) of
doxacurium during halothane (n = 9), isoflurane (n = 12) or alfentani
l (n = 9) based anaesthesia in children aged 2-10 years. Both isoflura
ne and halothane potentiated the effects of doxacurium compared to alf
entanil. The ED(50) for doxacurium/halothane was 23.9 mu g.kg(-1) comp
ared to 32.7 mu g.kg(-1) for doxacurium/alfentanil. The ED(90) for dox
acurium/isoflurane was 32.7 mu g.kg(-1) compared to 48.2 mu g.kg(-1) d
oxacurium/alfentanil (p < 0.05). There were no significant time course
differences between the groups. When equipotent doses of doxacurium w
ere used to provide muscle relaxation the duration of the neuromuscula
r block was similar in children who received aflentanil, halothane or
isoflurane supplementation of N2O/O-2 anaesthesia.