To evaluate muscle relaxant onset times and tracheal intubating conditions, 60 children (ASA physical status I or II) aged 18 to 72 mo were randomly assigned to receive a bolus of either rocuronium 0.6 mg/kg, vecuronium 0.1 mg/kg, or atracurium 0.5 mg/kg. After induction of anesthesia with etomidate 0.2-0.4 mg/kg and fentanyl 1-3 mg/kg, lungs were ventilated with 50% nitrous oxide in oxygen via a face mask. The evoked electromyogram of the adductor pollicis to a train-of-four stimulation every 20 s was monitored. After administration of the muscle relaxant, endotracheal intubation was attempted every 30 s, beginning 30 s after drug administration, until intubation could be achieved with good or excellent conditions. Rocuronium produced acceptable intubating conditions significantly faster (all tracheas intubated within 60 s) compared with vecuronium (120 s) and atracurium (180 s). The quality of intubating conditions at the time of completed intubation was rated significantly better with rocuronium than with vecuronium or atracurium. However, onset to 95% block at the adductor pollicis muscle was not significantly different after rocuronium (92 +/- 46.9 s), vecuronium (112 +/- 33.3 s), or atracurium (134 +/- 57.1 s), and mean neuromuscular block achieved at the point of successful intubation was not complete in all groups. We conclude that clinically acceptable intubating conditions are produced more rapidly with rocuronium than with atracurium or vecuronium.

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126.3±61.0 s). Clinical duration with rocuronium was In order to compare the neuromuscular effects fol-22.8±5.31 min and thus significantly shorter than that lowing rocuronium 0.6 mg kg −1 and atracurium 0.5 mg of atracurium, which was 31.5±6.01 min. A statkg −1 30 children aged from 18 to 67 months were istically significant difference between rocuronium studied under the same anaesthetic conditions. After and atracurium also had been found for recovery of induction of anaesthesia with etomidate and fentanyl, T 1 to 50%, 75% and 90% as well as for the time neuromuscular blockade was monitored by recording taken to a TOF ratio of 70%. The recovery index for rocuronium and atracurium was not significantly difthe electromyographic response of the adductor polferent with 9.2±3.43 min and 10.9±2.65 min, relicis muscle to a supramaximal train-of-four (TOF) spectively. Thus, rocuronium may be more stimulation of the ulnar nerve at 2 Hz for 2 s at 20-s advantageous than atracurium for short-lasting surintervals. Intubation was performed when more than gical procedures in young children. 90% muscle relaxation was achieved, thereafter anaesthesia was maintained with 70% nitrous oxide in Keywords: anaesthesia, paediatric; monitoring, oxygen and isoflurane 0.5% end-tidal. Mean onset of neuromuscular blockade, neuromuscular relaxants, rocuronium, atracurium. action was significantly faster following rocuronium compared with other age groups [1,2,3], whereas atra-