The hypothermic action of epidural and subarachnoid morphine in parturients

Sublingual body temperatures were measured before and at 0.5, 1, 2, 3, 4, 8, 12, and 24 hours after administration of epidural or subarachnoid morphine in four groups of patients (n = 15 in each group) undergoing cesarean delivery with regional anesthesia. All patients were acutely hydrated with 1200 ml warmed lactated Ringer's solution. Group 1 received 5 mg epidural morphine; Group 2, 5 ml epidural saline; Group 3, 0.5 mg subarachnoid morphine, and Group 4, 0.5 ml subarachnoid saline. The results were expressed as means +/- SEM and analyzed using analysis of variance at p less than 0.05. Body temperature decreased significantly in all the four groups after anesthesia. The maximum decreases in Groups 1, 2, 3, and 4, respectively, were 0.95 +/- 0.1, 0.9 +/- 0.1, 1.4 +/- 0.2, and 0.8 +/- 0.13 degrees C and occurred at 0.5, 1, 2, and 1 hour, respectively. The decrease was greater in the subarachnoid morphine group than in the other groups (p less than 0.03). At any of the measurement periods, the temperatures in the two epidural groups did not differ from each other. However, the temperature in the subarachnoid morphine group remained significantly lower than the corresponding temperature in the control group for up to 24 hours. It is concluded that subarachnoid morphine intensifies the hypothermic action of spinal anesthesia in parturients.