The time-course of action and recovery of rocuronium 0.3 mg center dot kg(-1) in infants and children during halothane anaesthesia measured with acceleromyography

This study compares the time-course of action of neuromuscular paralysis af ter 0.3 mg.kg(-1) of rocuronium during nitrous oxide-halothane anaesthesia in children of three different age groups. With appropriate approval and in formed consent from the parents, 51 children, ASA I-II, scheduled for elect ive surgery requiring muscle relaxation, were studied. The children were as signed to three groups according to age: group 1, 0-6 months; group 2, 6-24 months; and group 3, > 24 months of age. Induction of anaesthesia and trac heal intubation were performed under halothane anaesthesia. Acceleromyograp hy of the thumb was recorded after supramaximal transcutaneous ulnar nerve stimulation using train-of-four (TOF) stimulation. Rocuronium 0.3 mg.kg(-2) was given as a rapid i.v. bolus prior to surgical incision. The onset time (time to max effect) and the maximal depth of the block, the time to recov ery of the first twitch (T1) to 25% and 75% of its baseline, the recovery i ndex (RI), and the time to recovery of the TOF ratio to 70% after the end o f injection of rocuronium were all measured. The mean (SD) age of the child ren in groups 1, 2, and 3 was 3.1 (1.6), 12.6 (3.7), and 63 (46) months, re spectively. The onset time of rocuronium was 47 (12), 83 (42) and 94 (12) s , respectively, in groups 1, 2, and 3 (P < 0.05 group 1 vs. 2 and 3). One h undred percent block was achieved in 18/19 patients in group 1, 12/14 in gr oup 2 and 6/18 in group 3. The times to 25% and 75% recovery of T1 and the time for recovery of the TOF ratio to 70% were all significantly longer in groups 1 and 2 compared to group 3. Group 1 and 2 showed no significant dif ferences in recovery times. The RI was significantly prolonged in group 1 v ersus 3. The authors conclude that rocuronium 0.3 mg.kg(-1) during halothan e anaesthesia causes more neuromuscular depression and has a longer duratio n of action in infants than in children older than 2 years.