Dose-response and time-course of the effect of rocuronium bromide during sevoflurane anaesthesia

To evaluate the influence of sevoflurane on the dose-response relationship and on the time-course of the effect of rocuronium, 60 adult patients undergoing elective plastic surgery were randomly allocated to either the control or the sevoflurane group. Anaesthesia was maintained with 60% nitrous oxide in oxygen and thiopentone in the control group and with 60% nitrous oxide in oxygen and an end-tidal concentration of 1.75% sevoflurane in the sevoflurane group. Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12s and the percentage depression of the first twitch of the train-of-four was used as the study parameter. The dose-response relationship of rocuronium in the two groups was determined by the cumulative dose-response technique. The dose-response curve of rocuronium in the sevoflurane group was shifted to the left compared to the control group, indicating a potentiation of rocuronium-induced neuromuscular block. The effective doses of rocuronium required to produce 50%, 90% and 95% twitch depression in the sevoflurane group were decreased by 30.5%, 26.7% and 25.2%, respectively, compared to the control group. Following the administration of a total dose of rocuronium of 400 micrograms.kg-1, the duration of action of, and the recovery from, rocuronium were both significantly prolonged by sevoflurane. There were significant differences in the duration of peak effect, clinical duration, recovery index and the total duration of action between the control and the sevoflurane groups.