A comparative study of the dose-response and time course of action of rocuronium and vecuronium in anesthetized adult patients

Abstract

Study objectives: (1) To compare the dose-response relations of rocuronium and vecuronium in healthy adult patients anesthetized with nitrous oxide-oxygen-fentanyl-thiopental; and (2) to evaluate the time-course of action of two drugs following equipotent doses.

Design: Prospective, randomized, clinical comparison.

Setting: Operating room, Plastic Surgery Hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College.

Patients: 60 ASA physical status I patients, aged 17-51 years, scheduled for elective plastic surgery.

Interventions: All patients were randomly assigned to either the rocuronium or vecuronium group. General anesthesia was induced with thiopental 4 to 6 mg/kg and fentanyl 2 to 4 micrograms/kg intravenously (i.v.), and maintained with 60% nitrous oxide (N2O) in oxygen. Further increments of thiopental or fentanyl were given as required. The dose-response relations of rocuronium and vecuronium were determined by the cumulative dose-response technique.

Measurements and main results: Neuromuscular function was assessed mechanomyographically with train-of-four (TOF) stimulation at the wrist every 12 seconds. The percentage depression of first twitch (T1) was used as the study parameter. The cumulative dose-response curve of vecuronium was shifted to the left in a parallel fashion compared with that of rocuronium. As assessed by linear regression, the potency ratio of vecuronium: rocuronium was 1:7.2. There were significant differences in the ED50, ED90, and ED95 between the two drugs. After i.v. administration of equipotent doses of both drugs (2 x ED90), the duration of peak effect, clinical duration, recovery index, and total duration were not significantly different between the two drugs.

Conclusions: Compared with vecuronium, rocuronium is a low-potency, nondepolarizing relaxant, and its neuromuscular blocking potency is approximately 15% that of vecuronium in adult patients anesthetized with N2O and fentanyl. Following equipotent doses, the time-course of recovery for rocuronium is similar to that of vecuronium.