Different priming techniques, including mivacurium, accelerate the onset of rocuronium

Different priming sequences of equipotent doses of rocuronium and mivacurium on the onset of maximum neuromuscular block and intubating conditions were compared with those obtained after succinylcholine. During thiopentone-fentanylnitrous oxide anaesthesia, 70 patients were randomly assigned into seven groups. Group I received mivacurium 0.15 mg.kg-1 as a single bolus dose. Group II received a priming dose of mivacurium 0.015 mg.kg-1 followed three minutes later by mivacurium 0.135 mg.kg-1. Group III received rocuronium 0.6 mg.kg-1 as a single bolus dose, and Group IV received an initial dose of rocuronium 0.06 mg.kg-1 followed by rocuronium 0.54 mg.kg-1. Group V received a priming dose of mivacurium 0.015 mg.kg-1 followed by rocuronium 0.54 mg.kg-1. Group VI received an initial dose of rocuronium 0.06 mg.kg-1 followed by mivacurium 0.135 mg.kg-1. Group VII received succinylcholine 1.0 mg.kg-1. Groups I, III, and VII received a placebo injection before the administration of the neuromuscular blocking drug. Additional thiopentone 2 mg.kg-1 iv was given 30 sec before intubation. Onset times (mean (95% confidence interval)) after priming a rocuronium block with either rocuronium (73 (57-90) sec) or mivacurium (58 (47-69) sec) were similar to those after succinylcholine (54 (40-68) sec), and were shorter (P < 0.01) than that observed in other groups. Intubating conditions were not different between the groups. The duration of neuromuscular block was shortest with succinylcholine. It is concluded that priming a rocuronium block with either mivacurium or rocuronium resulted in a neuromuscular block comparable to that of succinylcholine in both the onset of action and intubating conditions.