[The benefit of combining spinal morphine and intravenous buprenorphine for perioperative pain].

Concurrent administration of opioids with different affinity produces synergistic antinociceptive effect in rats. We tested the perioperative antinociceptive effects of the simultaneous double blind administration of morphine, a pure agonist and buprenorphine, a partial agonist, in 30 patients undergoing hysterectomy under general anesthesia. Pre- and post-operatively regimens consisted of random patient assignment to intrathecal 0.3 mg morphine plus intravenous saline (group 1), intravenous 0.09 mg buprenorphine plus intrathecal saline (group 2) or intrathecal morphine 0.3 mg plus intravenous buprenorphine 0.09 mg (group 3). Postoperative pain relief for group 3 consisted of supplementation of intravenous buprenorphine plus intrathecal saline. The immediate postoperative pain, sedation and anxiety levels (by numerical or categorical scores) were similar among all groups. The 12-hour pain and sedation scores were significantly (P < 0.05) lower in group 3 than in the other two groups. Buprenorphine-induced analgesia in group 3 lasted significantly (P < 0.05) longer than in group 2. Side effects in groups 2 and 3 were by 44% and 42% fewer than in group 1, respectively, with no withdrawal symptoms. Thus, concomitant administration of intrathecal morphine and low dose intravenous buprenorphine produces better and longer pain relief than intravenous buprenorphine alone in women after hysterectomy.