The onset time of rocuronium is slowed by esmolol and accelerated by ephedrine.

Abstract

Administration of ephedrine prior to rocuronium decreases the onset time of neuromuscular blockade from rocuronium by 26%. This effect was attributed to a increased cardiac output. If so, beta adrenergic-blocking drugs, which decrease cardiac output, should prolong the onset time of rocuronium. In a double-blind study, 60 patients were randomly assigned to three groups (n = 20) to receive either 70 microg. kg(-1) of ephedrine, 0.5 mg. kg(-1) esmolol or placebo, 30 s before induction of anesthesia. Onset time of rocuronium was defined as the time from the end of its injection to disappearance of all four twitches of the train-of-four. The onset time of rocuronium was significantly shorter after ephedrine (22%) and longer after esmolol (26%), as compared to placebo. No differences were observed among the three groups with regard to heart rate, systolic, diastolic or mean blood pressure. We concluded that a dose of 0.5 mg. kg(-1) of esmolol significantly prolongs the onset time of rocuronium with minimal hemodynamic changes.