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 mu g.kg(-1) of ephedrine, 0.5 mg.kg(-1) esmolol
or placebo, 30 s before induction of anesthesia. Onset time of rocuronium w
as defined as the time from the end of its injection to disappearance of al
l four twitches of the train-of-four. The onset time of rocuronium was sign
ificantly shorter after ephedrine (22%) and longer after esmolol (26%), as
compared to placebo. No differences were observed among the three groups wi
th regard to heart rate, systolic, diastolic or mean blood pressure. We con
cluded that a dose of 0.5 mg.kg(-1) of esmolol significantly prolongs the o
nset time of rocuronium with minimal hemodynamic changes.