Electromyographic assessment of neuromuscular blockade induced by atracurium.

The effects of atracurium besylate 0.3 mg kg-1 or 0.6 mg kg-1 on neuromuscular function were assessed by electromyography in 11 normal subjects, using successive trains of four supramaximal stimuli. After the induction of anaesthesia, the relation between the reduction in the amplitude of the compound muscle action potential and decrement was studied during the onset and recovery of nondepolarizing blockade. During induction, the decrease in the amplitude of the initial compound muscle action potential was usually greater than decrement, and resembled the pattern observed with pancuronium. In contrast, during recovery from myoneural blockade, decrement was invariably greater than the reduction in the amplitude of the action potential. It was considered that these effects were consistent with the action of atracurium on more than one group of receptors at the neuromuscular junction. The effects of atracurium were rapidly antagonized by neostigmine, and supplementary doses of the drug showed no evidence of cumulation.