Disopyramide Vecuronium

A 65-year-old woman, who had had normal preoperative serum electrolytes and a normal QT interval with sinus rhythm, received hydroxyzine and atropine premedication followed by thiopental and vecuronium for anesthetic induction. Endotracheal intubation was difficult and precipitated atrial fibrillation, which was refractory to disopyramide 100 mg. Anesthesia was then maintained with sevoflurane 2% and nitrous oxide 50%. Ten minutes later ventricular tachycardia ensued, refractory to intravenous lidocaine, disopyramide, and magnesium. DC cardioversion resulted in a change to a supraventricular tachycardia, which then deteriorated to torsade de pointes. External cardiac massage and further DC cardioversion were initially unsuccessful, but the cardiac rhythm reverted to atrial fibrillation 10 minutes after the sevoflurane was switched off. Two weeks later she had her operation under combined epidural and general anesthesia, with no changes in cardiac rhythm. 

Baurain M, Barvais L, d Hollander A, Hennart D. Impairment of the antagonism of vecuronium-induced paralysis and intra-operative disopyramide administration. Anaesthesia 1989 44(l) 34-6. 

Disopyramide has also been associated with impairment of neostigmine antagonism of vecuronium-induced neuromuscular blockade (45). 

A 63-year-old man was given vecuronium 70 pg/kg followed by increments of 20 pg/kg, and three intravenous doses of disopjramide 10 mg for supraventricular extra beats, followed by an infusion of 25 mg/hour. Paralysis was reversed using atropine 0.75 mg and neostigmine 2.5 mg. The twitch height returned to normal and the train-of-four was above 85%, but the responses to tetanic stimulation at 100 and 50 Hz remained severely depressed (10 and 45% respectively). The plasma concentration of disopyramide was 5.1 pg/ml. 

An isolated case report su ests that disopyramide may oppose the effects of neostigmine used to reverse neuromuscular blockade with vecuronium. 

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