Adding intrathecal morphine to unilateral spinal anesthesia results in better pain relief following knee arthroscopy.

Purpose: Intrathecal morphine is administered to provide profound and prolonged analgesia, and to treat acute postoperative pain. We compared the effectiveness of hyperbaric bupivacaine alone and in combination with morphine for unilateral spinal anesthesia in patients undergoing knee arthroscopy.

Methods: Sixty patients were randomly allocated to two groups to receive either 1.2 ml (6 mg) of 0.5% hyperbaric bupivacaine (group B; n = 30) or 1.2 ml of 0.5% hyperbaric bupivacaine containing 0.16 mg of morphine (group BM; n = 30). Spinal block was assessed by pinprick and a modified Bromage scale and compared between the operated and nonoperated sides. Visual analog scale (VAS) values, duration of analgesia, and total analgesic requirement of patients were recorded.

Results: Patients in group BM had significantly lower VAS values on movement at 30 min and at 2, 4, 6, and 12 h postoperatively (P < 0.05 and P < 0.001, P < 0.001, P < 0.001, and P < 0.05, respectively). The total analgesic requirement in the first 24 h after surgery was significantly higher in group B (P < 0.001). Patients in group BM had a significantly longer duration of analgesia in the first 24 h postoperatively (P < 0.001). Motor blockade of the operated limb in group BM was similar to that in group B (P > 0.05), and motor blockade of the nonoperated limb in group BM was also similar to that in group B (P > 0.05).

Conclusion: We conclude that unilateral spinal anesthesia with hyperbaric bupivacaine plus 0.16 mg morphine is preferable to hyperbaric bupivacaine alone with respect to analgesic requirement, duration of analgesia, and VAS values.