Differential effects of myoneural blocking drugs on neuromuscular transmission in infants

Equipotent, paralysing doses of pancuronium and tubocurarine were administered to 40 patients, aged from 1 day to 12 months, during nitrous oxide, oxygen and fentanyl anaesthesia. Neuromuscular activity was measured during onset and recovery from paralysis using train-of-four stimulation. At the same depression of the first stimulus of the train, the train-of-four ratio was decreased more during recovery than during onset with each drug and more with tubocurarine than with pancuronium. These results are qualitatively similar to those found in adults, but the decrease in train-of-four ratio was less in infants. Thus, it is concluded that prejunctional neuromuscular activity, recognized as fade in response to train-of-four stimulation, can be detected after administration of pancuronium or tubocurarine to infants, but that it is less marked than in adults.