Neuromuscular Effect of Pipecuronium Bromide in Infants and Children during Nitrous Oxide-Alfentanil Anesthesia

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Abstract
To determine in infants and children the neuromuscular effect of pipecuronium during alfentanil-N2O/O2 anesthesia, the authors studied 32 ASA Physical Status 1 and 2 pediatric patients undergoing minor elective surgery, divided into three groups according to their age: group 1 included 12 infants, 1.9 .+-. 0.2 months old (mean .+-. SE; range, 20 days to 3 months), weighing 5.2 .+-. 0.3 kg; group 2, 10 infants, 6.1 .+-. 0.9 months old (range, 3-11 months), 6.9 .+-. 0.4 kg; and group 3, 10 children 5.6 .+-. 0.9 yr old (range 2-9 yr), 19.6 .+-. 2.2 kg. Neuromuscular blockade at the ulnar nerve-adductor pollicis muscle was measured by electromyography. Incremental iv doses of pipecuronium were given (one 20 .mu.g/kg first dose, followed by 10 .mu.g/kg increments) to reach a 95 .+-. 2% twitch depression (ED95). In children ED50 and ED95 of pipecuronium were 45.0 .+-. 5.8 .mu.g/kg (mean .+-. SE) and 70.5 .+-. 9.3 .mu.g/kg, respectively. In 3- to 12-month-old infants ED50 and ED95 were 25.8 .+-. 1.5 .mu.g/kg and 48.7 .+-. 3.5 .mu.g/kg, respectively, and both significantly (P < 0.05) less than those in children. In 0- to 3-month-old infants ED50 and ED95 were 23.7 .+-. 1.7 .mu.g/kg and 46.5 .+-. 2.9 .mu.g/kg, respectively, and also significantly (P < 0.05) less than those measured in children. Time from maximal initial neuromuscular blockade to 75% recovery was 64.5 .+-. 8.8 min in children and significantly shorter (P < 0.05) in the two infant groups (0- to 3-month-old: 38.7 .+-. 5.7 min, 3- to 12-month old: 43.8 .+-. 5.3 min, respectively). In conclusion, this study demonstrates that the neuromuscular potency of pipecuronium is increased in both groups of infants compared with that in children older than 2 yr. Furthermore, whereas pipecuronium is a long-acting neuromuscular blocking agent in children (similar to what has been reported in adults), it has only an intermediate duration of action in infants.