METABOLIC CHANGES DURING RECOVERY IN NORMOTHERMIC VERSUS HYPOTHERMIC PATIENTS UNDERGOING SURGERY AND RECEIVING GENERAL-ANESTHESIA AND EPIDURAL LOCAL-ANESTHETIC AGENTS

Background: Mild hypothermia is accompanied by metabolic changes. Epid ural local anesthetic agents attenuate the surgical stress response, b ut it is not known whether they modulate thermal stress. Methods: Thir ty patients undergoing colorectal surgery, performed by one surgical t eam, received epidural 0.5% bupivacaine to achieve T3-S5 sensory block . They were then assigned randomly to two groups of 15 patients each. The control or unwarmed group was left to cool during surgery, whereas active warming was used in the warmed group. General anesthesia was i nduced by thiopentone, vecuronium, fentanyl, nitrous oxide in oxygen, and enflurane. At the end of surgery, both groups received epidural 0. 25% bupivacaine to maintain a T5-L3 sensory block. Aural canal (core) and skin surface (15 sites) temperatures; oxygen consumption; pain vis ual analogue score; and concentrations of epinephrine, norepinephrine, glucose, cortisol, lactate, and free fatty acids in plasma were measu red before epidural blockade, 30 min after epidural blockade, at the e nd of surgery, and for 4 h after surgery. Patients and those measuring the outcomes were unaware of group allocation. Results: Core and mean skin temperatures decreased significantly in the control group (P < 0 .001) but not in the warmed group. Catecholamine concentrations in pla sma decreased significantly after epidural block, and although concent ration of epinephrine in plasma increased from baseline sharply in the control group at the end of surgery (P = 0.004), it decreased in the warmed group (P = 0.007). During recovery, there was no difference bet ween the two groups for norepinephrine concentrations in plasma, body weight-adjusted oxygen consumption, pain visual analogue score, and me tabolites. Conclusions: The postoperative metabolic changes obtained w ith epidural block were similar except for an attenuated concentration of epinephrine in normothermic patients compared with those who were mildly hypothermic.