Neuromuscular and cardiovascular effects of atracurium during nitrous oxide-fentanyl and nitrous oxide-isoflurane anaesthesia.

The neuromuscular and cardiovascular effects of atracurium were compared during nitrous oxide-isoflurane and nitrous oxide-fentanyl anaesthesia in healthy surgical patients. The dose-response curve was shifted significantly to the left during nitrous oxide-isoflurane anaesthesia (ED50 0.068 mg kg-1) as compared with nitrous oxide-fentanyl anaesthesia (ED50 0.083 mg kg-1). For equipotent doses, the time course of neuromuscular effects (onset and duration) was not appreciably different between the nitrous oxide-isoflurane group and the nitrous oxide-fentanyl group. Minimal cardiovascular effects were observed from atracurium in doses up to 0.5 mg kg-1. Using comparisons from earlier studies, atracurium was approximately one-quarter as potent as pancuronium and vecuronium (Org NC 45). The onset time (time from injection to peak effect) for subparalytic doses of atracurium was approximately 6.5 min and is comparable to the onset time for equipotent doses of pancuronium and vecuronium. The duration of neuromuscular effects of atracurium (time from injection to 95% recovery) was approximately 20 min for subparalytic doses and is the same as that of vecuronium and one-third to one-half that of pancuronium. It is concluded that the peak effect of atracurium is enhanced more by nitrous oxide-isoflurane than by nitrous oxide-fentanyl anaesthesia, but for equipotent doses the time-course is the same.