Muscular relaxation with atracurium, vecuronium and duador under balanced anaesthesia

The neuromuscular effects of three new nondepolarizing neuromuscular blocking drugs, atracurium, vecuronium and Duador, were investigated in surgical patients under balanced anaesthesia. (The numbers of patients in each study are given in the tables.) There were no significant differences in the neuromuscular effects of the three agents. None showed any cumulation after repeated administration of maintenance doses. Muscular relaxation for upper abdominal surgery was adequate as long as the isometric twitch tension (P) was no more than 25% of control. Conditions for tracheal intubation were satisfactory within less than 3 min after the start of injection. Spontaneous recovery of P to 90-95% of control, after the last dose of neuromuscular blocker was the fastest with vecuronium (35.8 +/- 2.4 min) and about the same with atracurium (54.3 +/- 2.4 min) and Duador (54.2 +/- 4.7 min). The T4/T1 ratio at the time of greater than 90% recovery of P was 0.44, 0.52 and 0.56 with vecuronium, Duador and atracurium, respectively, indicating the need for the reversal of the residual neuromuscular block. This could be accomplished within 2 min by the i.v. injection of edrophonium 0.5 mg kg-1, preceded by atropine 0.01 mg kg-1. No side-effects were observed with vecuronium. Atracurium caused mild to moderate histamine release in four of 50 patients included in this study, all of whom received an initial dose of 0.5 mg kg-1. The initial dose of Duador caused a 16.7% increase in heart rate. The findings indicate that the three new muscle relaxants merit further clinical trial. In our opinion, until the results of such studies become available, atracurium should not be used in patients with a history of allergic diathesis and Duador in those in whom increased heart rate may be harmful.