Bradycardia during antagonism of pancuronium-induced neuromuscular block.

Heart rate was compared in matched patients during antagonism of neuromuscular block induced by tubocurarine, pancuronium or alcuronium with neostigmine 0.03 mg kg-1 preceded by atropine 0.015 mg kg-1. The frequency of bradycardia was greater during antagonism of pancuronium compared with alcuronium. Although there was a difference between the group receiving pancuronium and that receiving tubocurarine, it was not statistically significant. The decrease in heart rate was more rapid and profound in the pancuronium group; seven of the 15 patients who received pancuronium required an additional dose of atropine as compared with only one patient who received tubocurarine. However, the difference in heart rate between those who received pancuronium and those receiving tubocurarine was short-lasting, whereas the heart rate of those who received alcuronium was higher than that in the other groups during the entire 60-min period of observation. The findings with pancuronium may be a result of its inhibitory effect on serum cholinesterase.