Epidural naloxone reduces intestinal hypomotility but not analgesia of epidural morphine

Purpose: Epidural morphine is associated with decreased bowel motility and increased transit time, Low doses of intravenous naloxone reduce morphine-induced pruritus without reversing analgesia, but the effect of epidural naloxone on bowel motility has not been studied. Therefore we evaluated bowel motility and analgesia when naloxone was co-administered with morphine into the epidural space. Methods: Forty-three patients having combined thoracic epidural and general anesthesia for subtotal gastrectomy were randomly assigned to one of two study groups. All received a bolus dose of 3 mg epidural morphine at the beginning of surgery, followed by a continuous epidural infusion containing 3 mg morphine in 100 mi bupivacaine 0.125% with either no naloxone (control group, n = 18) or a calculated dose of 0.208 mug.kg(-1).hr(-1) of naloxone (experimental group, n = 25) for 48 hr. We measured the time to the first postoperative passage of flatus and feces to evaluate the restoration of bowel function, and visual analog scales (VAS) for pain during rest and movement. Scores were assessed at 2, 4, 8, 16, 24, 36 and 48 hr postoperatively. Results: The experimental group had a shorter time to the first postoperative passage of flatus (51.9 +/- 16.6 hr vs 87.0 +/- 19.5 hr, P < 0.001) and feces (95.3 +/- 25.0 hr vs 132.9 +/- 29.4 hr, P < 0.001). No differences were found in either resting or active VAS between the two groups. Conclusion: Epidural naloxone reduces epidural morphine-induced intestinal hypomotility without reversing its analgesic effects.