COMPARISON OF THE ANALGESIC EFFECTS OF INTRATHECAL CLONIDINE AND INTRATHECAL MORPHINE AFTER SPINAL-ANESTHESIA IN PATIENTS UNDERGOING TOTAL HIP-REPLACEMENT

We have studied the anaesthetic and analgesic properties of intratheca l clonidine and intrathecal morphine in patients undergoing total hip replacement under spinal anaesthesia. After routine spinal anaesthesia With 0.5% plain bupivacaine 2.75 ml, patients were allocated randomly to receive intrathecal clonidine, morphine or saline (control) as adj uvant to the bupivacaine. Postoperative analgesic effects were measure d by consumption of morphine via patient-controlled analgesia and visu al analogue pain scores. Both intrathecal clonidine and intrathecal mo rphine prolonged the time to first analgesia compared with saline (mea n 278 (SD 93.2) min, 498 (282.4) min and 54 (61.9) min, respectively) (P < 0.001). Total morphine consumption on the first night after opera tion was significantly less in the intrathecal morphine group. There w ere no differences between the clonidine and the control group. Intrat hecal, clonidine prolonged the duration of spinal analgesia, but was m arkedly inferior to the intrathecal morphine in providing subsequent p ostoperative analgesia.