[Use of vecuronium and atracurium in continuous infusion. A comparative study using electromyography and...

Vecuronium and atracurium, muscle relaxant agents of intermediate action, were administered in continuous infusion to 175 patients undergoing prolonged surgical operations with the purpose of achieving serum concentrations inducing maintained blocking of neuromuscular function. We used a 0.08 mg/kg or 0.5 mg/kg bolus intubation dose followed by a continuous infusion of vecuronium (72 patients) or atracurium (103 patients) 10 minutes after, at the necessary pace to maintain inhibition of neuromuscular transmission over 90%. Monitoring of relaxation was done by means of four supramaximal stimuli trains which were repeated every 20 seconds and applied to the cubital nerve. Composite electromyogram (electromyography) and thumb acceleration (mechanomyography-accelerometry) were simultaneously recorded. Infusion was interrupted 15 minutes before ending the operation; reversion occurred spontaneously in 143 patients and 32 patients had to be reversed with neostigmine. Beginning of action, total duration of infusion, infusion speed, and 25-75 spontaneous and after decurarization recovery index were measured. Initial dose allowed an easy tracheal intubation and the constant relaxation achieved with 0.068 mg/kg/h and 0.46 mg/kg/h infusion of vecuronium and atracurium was adequate for all operations. Spontaneous recovery is often adequate at the end of operations in carefully monitored patients. Both monitoring methods are useful for clinical evaluation of neuromuscular transmission.