Maintenance of constant 95% neuromuscular blockade by adjustable infusion rates of pancuronium and atracurium.

In a double-blind study, 39 patients (ASA groups I-II,) were given either pancuronium or atracurium as an infusion during surgery. The drugs were given as an initial loading dose of 0.064 mg kg-1 or 0.30 mg kg-1, respectively, followed by an infusion, the rate of which was regulated to produce a constant 95% depression of the evoked twitch response throughout surgery. No significant difference in the number of corrections of the infusion rate per hour was found (4.6 v. 4.9). Mean infusion maintenance doses were 35 and 356 micrograms kg-1 h-1, respectively. The inter-individual variability of maintenance doses for the two drugs did not differ, the coefficients of variation being 0.32 and 0.24. On stopping the infusion, the patients given atracurium recovered to a 15% twitch faster than those given pancuronium. In addition neostigmine produced a quicker recovery in this group. Thus atracurium may be a more satisfactory drug for use by infusion.