It is not clear whether mild hypothermia (34 ℃) enhances stress hormonal responses during surgery under general intravenous anesthesia. The purpose of this study was determine how mild hypothermia affects hemodymic and stress hormonal responses introperatively and during extubation in patients undergoing cerebral aneurysm surgery under general intravenous anesthesia.

Anesthesia was induced intravenously with thiopental sodium 5 mg/kg, succinylcholine 1 mg/kg, and maintained with 50% O2, 50% N2O, and propofol using a target controlled system; Diprifusor(R) (3-5 microgram/ml) and muscle relaxation were administered with intravenous vecuronium intermittently. For the normothermia and the hypothermia groups, body temperatures were maintained at 36.9±0.3℃ and 34.2±0.2 ℃, respectively, up to the recovery room. Hemodynamic changes were recorded continuously. Arterial blood gas analysis, glucose, hemoglobin, stress hormones comprising epinephrine, norepinephrine, ADH, ACTH and cortisol were measured at whilst awake, intraoperatively, and just after extubation.

Hemodynamic changes from the awake control state to postextubation were not significantly different between the normothermia and hypothermia groups. In the control awake state, all five hormonal concentrations were similar in the two groups. Intraoperatively and during extubation, all hormonal concentrations tended to be lower in the hypothermia group than in the normothermia group, except epinephrine during extubation. During the same period, all except ACTH decreased sufficiently to reach statistical significance (P < 0.05) versus the awake control state. But no significant differents were found between the two groups.

Our data suggest that intraoperative mild hypothermia dose not significantly affect hemodynamic changes or the plasma concentrations of stress hormones.