Impairment of the antagonism of vecuronium-induced paralysis and intra-operative disopyramide administration.

A 63-year-old male was admitted to hospital for a cholecystectomy, vagotomy and gastro-enterostomy. Muscle paralysis was induced with 70 micrograms/kg vecuronium, followed by increments of 20 micrograms/kg when the initial twitch height returned to 25% of control. The patient received 3 doses of 10 mg disopyramide intravenously, on account of supraventricular ectopic beats, followed by an infusion of 25 mg/hour. Paralysis was reversed using 0.75 mg atropine and 2.5 mg neostigmine once the twitch height had returned spontaneously to 25% of its initial value. Fifteen minutes later, twitch height had returned to control value and the train-of-four was above 85%, but the responses to tetanic stimulation at 100 Hz and 50 Hz remained severely depressed (10% and 45%, respectively). The patient's trachea was extubated after 20 minutes, but residual fade was still observed. This impairment of neuromuscular transmission, detected only with high frequency stimulation, was present with a measured concomitant plasma level of disopyramide of 5.1 micrograms/ml.