Priming with nondepolarizing relaxants for rapid tracheal intubation: a double-blind evaluation

Results of a series of controlled, randomized, double-blind trials investigating intubation conditions with priming sequences of nondepolarizing relaxants are reported. In Phase I of the study the groups received: Group A, tubocurarine (DTC) 3 mg + succinylcholine 1.5 mg.kg-1, Group B, atracurium 0.05 mg.kg-1 + 0.35 mg.kg-1, Group C, vecuronium, 0.01 mg.kg-1 + 0.07 mg.kg-1; in Phase II: Group D, no relaxant, Group E, DTC 0.05 mg.kg-1 + vecuronium 0.07 mg.kg-1, Group F, vecuronium 0.01 mg.kg-1 + vecuronium 0.12 mg.kg-1; in Phase III, Group G, DTC 3 mg + succinylcholine 1.5 mg.kg-1, Group H, vecuronium 0.01 mg.kg-1 + 0.09 mg.kg-1, Group I vecuronium 0.1 mg.kg-1 as a single bolus. Intubation conditions were assessed at 60 seconds. A seven-minute priming interval was used in Phase I and II and a four-minute interval was used in Phase III. Priming produced significantly better intubating conditions than an equivalent single bolus; however, intubating conditions with priming did not appear to match the uniformly excellent conditions produced by succinylcholine. The data suggest that a four-minute priming interval is as effective as a seven-minute interval. The results of this study differed substantially from previous unblinded studies; therefore, it is suggested that a randomized, double-blind design with simultaneous succinylcholine controls be considered a prerequisite for future studies of intubation conditions.