Spinal anaesthesia with adjunctive intrathecal morphine versus continuous lumbar plexus blockade: a randomised comparison for analgesia after hip replacement.

Following elective total hip replacement, both continuous lumbar plexus blockade and spinal anaesthesia (with adjunctive intrathecal morphine) have shown early outcome benefits over opioid analgesia and single-injection nerve block. However, the two techniques have not been compared in a prospective randomised manner. Our study examined 50 patients undergoing elective hip joint replacement who were randomised to receive spinal anaesthesia (with adjunctive intrathecal morphine 0.1 mg) or patient-controlled continuous lumbar plexus blockade. All surgery was conducted under general anaesthesia. Measured outcomes included numerically rated postoperative pain, supplemental opioid consumption and indices of mobilisation together with complications. Results show that block placement time was marginally shorter for the spinal group (5 versus 7 minutes, P=0.01). The primary outcome, worst pain on movement/mobilisation during the first 24 hours, was not statistically significantly different between groups. Patients in the lumbar plexus group were given more intraoperative opioid and rescue morphine in the post-anaesthesia care unit (median = 4 versus 0 mg, P <0.001), with correspondingly higher pain scores (median 5/10 versus 0/10, P <0.001). Pain scores during the subsequent 24 hours were similar between groups, but more patients in the spinal group were given rescue morphine (5 versus 0, P=0.02). Physiotherapy mobilisation indices appeared similar between groups. More spinal group patients reported pruritus (12 versus 5, P=0.01), but antiemetic requirements, episodes of disorientation, arterial oxygen desaturation and falls were all similar between groups. Postoperative symptoms suggestive of neurological irritation or injury did not differ between groups. We found that following elective hip joint replacement, compared to continuous lumbar plexus blockade, spinal anaesthesia incorporating adjunctive intrathecal morphine did not result in a statistically significant difference in worst pain on movement/mobilisation during the first 24 hours, although it was associated with better analgesia in the post-anaesthesia care unit. Subsequently, however, these patients appeared to require more rescue morphine and more of them reported pruritus.