Anesthesiology
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Biography Historical Article
ASA Award: Francis F. Foldes. American Society of Anesthesiology.
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Randomized Controlled Trial Comparative Study Clinical Trial
The thermoregulatory threshold in humans during nitrous oxide-fentanyl anesthesia.
Narcotics and nitrous oxide (N2O) inhibit thermoregulatory responses in animals. The extent to which N2O/fentanyl anesthesia lowers the thermoregulatory threshold in humans was tested by measuring peripheral cutaneous vasoconstriction using skin-surface temperature gradients (forearm temperature-fingertip temperature) and the laser Doppler perfusion index. Fifteen unpremedicated patients were anesthetized with N2O (70%) and fentanyl (10 micrograms/kg iv bolus followed by 4 micrograms.kg-1.h-1 infusion) during elective, donor nephrectomy. ⋯ Four hypothermic patients developed a passive thermal steady state without becoming sufficiently cold to trigger vasoconstriction. Thus, active thermoregulation occurs during N2O/fentanyl anesthesia but does not occur until core temperatures are approximately 2.5 degrees C lower than normal. The thermoregulatory threshold during N2O/fentanyl anesthesia is similar to that previously determined during halothane (34.4 +/- 0.2 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)