The influence of hypothermia (surface cooling) on the time-course of action and on the pharmacokinetics of rocuronium in humans

Hypothermia prolongs the time-course of action of non-depolarizing neuromuscular blocking agents. The mechanism, however, is unknown. We studied the influence of hypothermia (by surface cooling, nasopharyngeal temperature less than or equal to 31 degrees C) on the time-course of action and on the pharmacokinetics of rocuronium in humans. Nineteen neurosurgical patients were divided into hypothermic and normothermic groups. Hypothermia (30.4 +/- 0.8 degrees C (mean +/- SD)) increased the duration of action, temperature dependently, and delayed the recovery. Hypothermia reduced the plasma clearance significantly (2.17 +/- 0.62 vs. 4.26 +/- 0.50 mL kg(-1) min(-1), P = 0.004), did not change the volume of distribution (224 +/- 64 vs. 232 +/- 60 mL kg(-1) min(-1), P = 1.0), and prolonged the mean residence time (108 +/- 39 vs. 56 +/- 19 mL kg(-1) min(-1), P = 0.01). We conclude that hypothermia prolongs the duration of action of rocuronium and delays spontaneous recovery and that altered pharmacokinetics, such as a decreased clearance, play an important role in this