Time-course of action and intubating conditions with rocuronium bromide under propofol-alfentanil anaesthesia

Thirty ASA I and II patients received either an intubating dose of 0.6 mg kg-1 rocuronium (2 x ED95, group 1) or 0.06 mg kg-1 as a priming dose followed by an intubating dose of 0.24 mg kg-1 rocuronium (group 2) 4 min later. Anaesthesia was induced with propofol (2.0 mg kg-1) and alfentanil (0.02 mg kg-1) and maintained with nitrous oxide/oxygen and propofol (6.0 mg kg-1 h-1). Neuromuscular function was monitored mechanomyographically and electromyographically with train-of-four (TOF) stimulation at the wrist every 10 s. The following parameters were measured and compared between the two groups: time to 90% block (intubation time), time to maximum block (onset time), and the times for T1 (25%, 75% and 90%) and TOF > 70%. In group 1 the intubation time was significantly shorter (40 +/- 10 s) than in group 2 (51 +/- 11 s). Intubating conditions were good or excellent in both groups. The clinical duration of action was 28 +/- 8 min in group 1 and 15 +/- 3 min in group 2, respectively. Mechanomyography showed a significantly faster development of neuromuscular block than electromyography. The comparison of mechanomyographically and electromyographically measured recovery times did not show any differences. In 60% of the patients a priming dose of 0.06 mg kg-1 was followed by a considerable decrease in neuromuscular function.