[Mechanomyographic and electromyographic studies of endotracheal intubation with 2 different rocuronium dosages]

Rocuronium is a new, intermediate-acting, nondepolarizing relaxant with rapid onset of action leading to both good and very good intubation conditions. It was the aim of our study to investigate the onset of action, the intubation conditions and the course of relaxation using two different dosage regimes. Thirty consenting ASA 1 and 2 patients received either 0.6 mg/kg (2 x ED 95; group 1) or 0.06 mg/kg as priming dose followed by an intubating dose of 0.24 mg/kg rocuronium (group 2) four min later. Anaesthesia was induced with propofol (2 mg/kg) and alfentanil (0.02 mg/kg) and maintained with nitrous oxide/oxygen and propofol (6 to 8 mg/kg/h). Neuromuscular function was monitored mechanomyographically and electromyographically with TOF stimulation at the wrist every 10 seconds. Intubation conditions were determined using a semiquantitative score system, and times to 90% block (intubation time), maximum block (onset time) and recovery from neuromuscular blockade to 25%, 50%, 75% and 90% were calculated and comparisons were made between the corresponding results of the two groups. The intubation dose of 2 x ED 95 (group 1) was followed by a significantly shorter intubation time (39.1 +/- 9.6 sec.) than in group 2 with priming and an intubation dose of 0.24 mg/kg (50.7 +/- 11.0 sec). The intubation conditions showed no differences. In both groups they were good or very good. The clinical duration of action was significantly longer in group 1 (28.4 +/- 8.0 min) than in group 2 (14.8 +/- 2.5 min). It can be concluded that rocuronium which has shorter intubation times than atracurium and vecuronium is very useful for endotracheal intubation in both dosage regimes in long and very long lasting operations. Using the "priming principle" the patient has to be carefully controlled during priming time.