Pancuronium requirements during hypothermic cardiopulmonary bypass in man

Eight patients were studied to determine the changes in pancuronium requirements during hypothermic cardiopulmonary bypass. They were anaesthetised with fentanyl as the principal agent, ventilated with oxygen and the neuromuscular junction was monitored using train-of-four stimulation. After a bolus dose of pancuronium an infusion was used to maintain the first twitch of the train-of-four at 5-15 per cent of control. Before bypass the mean pancuronium infusion rate was 0.52 (SD 0.16) micrograms/kg/min. There was a small, brief increase in requirement with the initiation of bypass to 0.62 (SD 0.38) micrograms/kg/min, which was followed by a decrease of more than 80 per cent during hypothermia to 0.08 (SD 0.03) micrograms/kg/min. Rewarming was associated with a rapid increase in requirement to 0.64 (SD 0.17) micrograms/kg/min, which decreased to 0.33 (SD 0.23) micrograms/kg/min when normothermia was re-established.