Postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia.

STUDY OBJECTIVE To evaluate the postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia. DESIGN Prospective, randomized clinical trial. SETTING Operating room and postanesthesia care unit of a university hospital. PATIENTS 74 healthy, ASA status I, II, and III patients (average age 58 yrs) undergoing elective colon surgery. INTERVENTIONS Patients were randomly assigned to be kept normothermic or approximately 2.5 degrees C hypothermic during surgery. Anesthesia was maintained with isoflurane, nitrous oxide, and fentanyl. Postoperatively, surgical pain was treated with patient-controlled analgesia (PCA) opioid. MEASUREMENTS AND MAIN RESULTS An observer blinded to group assignment and core temperatures evaluated shivering, thermal comfort, surgical pain, heart rates (HRs), and blood pressures (BPs) during the first six postoperative hours. Morphometric characteristics, oxygen saturation, fluid balance, PCA-administered opioid, and visual analog pain scores were comparable in the two groups. Hypothermic patients felt uncomfortably cold during recovery, and their postoperative core temperatures remained significantly less than in the normothermic patients for more than four hours. Peripheral vasoconstriction and shivering were common in the hypothermic patients but rare in those kept normothermic. HRs and BPs were comparable in the two groups. CONCLUSIONS These data confirm that the effects of intraoperative hypothermia on postoperative HR and BP are modest in relatively young, generally healthy patients. In contrast, intraoperative hypothermia caused substantial postoperative thermal discomfort, and full recovery from hypothermia required many hours. Delayed return to care normothermia apparently resulted largely from postoperative thermoregulatory impairment.