Comparison of the effects of extradural clonidine with those of morphine on postoperative pain, stress responses, cardiopulmonary function and motor and sensory block

Abstract

We have examined the effects of extradural clonidine 150 μg or morphine 4 mg on postoperative pain, stress responses, cardiopulmonary function and motor and sensory block in a double-blind, randomized study in 20 patients undergoing hysterectomy with general anaesthesia. Observations were made for 6h after each patient's first request for analgesia. Clonidine provided greater pain relief than morphine only for the first 2 h of observation (P < 0.001). Plasma cortisol concentrations decreased to a greater extent (P < 0.05) with morphine, while plasma glucose concentration increased by a similar extent in both groups. After clonidine, mean arterial pressure decreased from 100 (SEM 3) mm Hg to 70 (3) mm Hg (P < 0.05), but there was no change after morphine. There were no significant changes in heart rate, pulmonary function (FEV1), motor function or sensory analgesia to touch, temperature and pinprick in both groups. Additional systemic opioids were required by five and six patients in the clonidine and morphine groups, respectively. © 1989 Oxford University Press.