Intrathecal hydromorphone added to hyperbaric bupivacaine for postoperative pain relief after knee arthroscopic surgery: a prospective, randomised, controlled trial.

BACKGROUND AND OBJECTIVE: Adding opioid to spinal anaesthetic provides additional analgesia during the postoperative period. The purpose of this study was to determine the dose of intrathecal hydromorphone necessary to achieve postoperative pain relief after arthroscopic knee surgery. METHODS: In a prospective, double-blinded parallel, placebo-controlled manner, 60 patients who were undergoing unilateral knee arthroscopy randomly received unilateral spinal anaesthesia with 0.5% hyperbaric bupivacaine 6 mg combined with 0.0, 2.5, 5.0 or 10.0 µg per 0.05 ml hydromorphone. Fifteen patients were assigned to receive each dose. The visual analogue pain scores (VAPSs) were measured at 30 min and 2, 4, 6, 12 and 24 h postoperatively, and the side-effects of hydromorphone were recorded. RESULTS: The postoperative VAPSs at 4, 6 and 12 h for the 5 and 10 µg hydromorphone groups were significantly decreased, compared to the control group. The 2.5 µg hydromorphone group had lower VAPS only at 4 and 6 h postoperatively. Nausea was significantly increased in the 10 µg hydromorphone group (46.6%). CONCLUSION: The analgesic effects of 5 and 10 µg intrathecal hydromorphone provided satisfactory pain relief for 12 h postoperatively and nausea increased significantly in a dose-dependent manner.