PRIMING WITH ROCURONIUM ACCELERATES THE ONSET OF NEUROMUSCULAR BLOCKADE

Study Objective: To investigate the effects of priming recuronium on t he time course of neuromuscular blockade. Design: Prospective, control led, randomized clinical study. Setting: University teaching hospital. Patients: 42 ASA physical status I and II patients undergoing periphe ral surgery with general anesthesia. Interventions: Following a standa rdized propofol-fentanyl induction, patients in Group 1 (n = 21) recei ved a priming dose of recuronium 0.06 mg/kg followed two minutes later by an intubating dose of rocuronium 0.54 mg/kg. Patients in Group 2 ( n = 21) received a saline placebo injection followed two minutes later by rocuronium 0.6 mg/kg. Anesthesia was maintained with isoflurane an d nitrous oxide 60% in oxygen. Measurements and Main Results: Neuromus cular function was assessed at the wrist using mechanomyography with a single-twitch mode of stimulation at a frequency of 1 Hz until trache al intubation and at 0.1 Hz thereafter. The times from injection of th e intubating dose of rocuronium until 95% suppression of the twitch te nsion (onset time), recovery of twitch tension to 25% of control (clin ical duration of action), and the time from 25% to 75% spontaneous rec overy of twitch tension (recovery index) were recorded. The trachea wa s intubated at 95% depression of the twitch tension and the intubating conditions were graded using a 3-point scale. The onset times with pr iming rocuronium (34 +/- 6 s) were significantly shorter (p < 0.01) th an those without priming (59 +/- 14 s). The intubation conditions were similar in the two groups; however, the intubation times with priming were significantly shorter. The clinical duration of action and the r ecovery index did not differ significantly between the two groups. Con clusions: Priming rocuronium decreased the onset times and thus, the i ntubating times without increasing the clinical duration of action or recovery index. (C) 1996 by Elsevier Science Inc.