Pipecuronium-induced Neuromuscular Blockade during Nitrous Oxide-Fentanyl, Isoflurane, and Halothane Anesthesia in Adults and Children

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Abstract
To determine in adults and children the dose-response relationship and the duration of action of pipecuronium bromide during fentanyl-nitrous oxide (N2O), isoflurane, and halothane anesthesia, the authors studied 30 ASA Physical Status 1-2 adults (age: 16-55 yr) and 30 ASA Physical Status 1-2 children (age: 1.7-11.5 yr) during minor elective surgery. Patients were anesthetized with N2O/O2 (60:40) supplemented with either fentanyl (4 .mu.g/kg), or isoflurane (adults, 0.9%; children, 1.2%), or halothane (adults, 0.6%; children, 0.7%). Neuromuscular (NM) blockade was measured by electromyography. Incremental iv doses of pipecuronium were administered to determine the cumulative dose-response relationship of pipecuronium until a 95% twitch depression (ED95) had been obtained. In adults, ED50 was 31.7 .+-. 2.9 .mu.g/kg (mean .+-. SE) during fentanyl-N2O/O2, reduced by isoflurane (18.0 .+-. 4.8 .mu.g/kg, P < 0.05) but not by halothane (25.0 .+-. 2.6 .mu.g/kg, NS). ED95 was 59.4 .+-. 5.4 .mu.g/kg during fentanyl-N2O/O2, reduced by isoflurane (42.3 .+-. 2.5 .mu.g/kg, P < 0.05), but not by halothane (49.7 .+-. 3.1 .mu.g/kg, NS). In children, ED50 was 43.9 .+-. 4.7 .mu.g/kg during fentanyl-N2O/O2, reduced by isoflurane (23.1 .+-. 1.6 .mu.g/kg, P < 0.05), and halothane (33.2 .+-. 3.2 .mu.g/kg, P < 0.05). ED95 was 79.3 .+-. 9.8 .mu.g/kg during fentanyl-N2O/O2, and reduced by isoflurane (49.1 .+-. 3.1 .mu.g/kg, P < 0.05), but not by halothane (62.5 .+-. 7.3 .mu.g/kg, NS). Comparison between adults and children reveals no statistically significant differences, except for ED50 during fentanyl-N2O/O2 anesthesia which was increased in children. During fentanyl-N2O/O2 anesthesia, the time from the initial maximal blockade to 75% twitch height recovery (D75) was 78.0 .+-. 9.1 min in adults and 61.8 .+-. 7.8 min in chlidren (ND). D75 was not significantly changed during isoflurane and halothane anesthesia, neither in adults nor in children. The authors conclude that isoflurane but not halothane enhances the intensity of pipecuronium-induced NM blockade, both in adults and children. There is no significant difference in dose requirement for pipecuronium between children and adults. Finally, isoflurane and halothane do not change the duration of the pipecuronium-induced neuromuscular blockade neither in adults nor in children.