Naloxone infusion and post-hysterectomy morphine consumption: a double-blind, placebo-controlled study.

BACKGROUND: The evidence that an infusion of a low dose of naloxone reduces post-operative pain and opioid analgesic consumption is somewhat conflicting. Thus, the aim of the present study was to investigate the effect of an ultra-low dose of naloxone on patient-controlled morphine analgesia.

METHODS: Ninety patients, 35-55 years old, scheduled for total abdominal hysterectomy, were enrolled in this prospective, randomized, double-blind and placebo-controlled study. Post-operatively, they received either saline (n = 45) or naloxone (n = 45) for 24 h. A standard general anesthesia was administered in both groups. In the recovery room, patients received morphine by a patient-controlled analgesia device. An ultra-low dose of naloxone was infused intravenously at 0.25 μg/kg/h for 24 h in the intervention group. Saline was infused in the control group. Following the surgery, morphine consumption, numeric rating score for pain intensity, nausea and vomiting, pruritus, and requests for antiemetic were recorded at baseline, 30 min, 1, 4, 8,16, 20, and 24 h following their discharge from recovery.

RESULTS: Naloxone reduced morphine consumption over the first 24 post-operative hours significantly compared with the controls (saline) {19.5 [standard deviation (SD) 3.4] mg vs. 27.5 [SD 5.9] mg; P < 0.001}. The incidence and severity of nausea and vomiting was significantly reduced in the naloxone group. The incidence of pruritus and the pain scores at rest and activity were not significantly different.

CONCLUSION: Following hysterectomy, an ultra-low dose of naloxone infusion proved to reduce morphine consumption as well as the incidence and severity of opioid-induced nausea and vomiting.