The analgesic effect of morphine on postoperative pain in diabetic patients

Background: Many clinical and experimental studies have suggested that diabetes or hyperglycemia alter opioid responsiveness. However, little information is available on the effects of diabetes mellitus on opioid requirements in the postoperative period. Methods: Sixty-four patients scheduled for elective, total abdominal hysterectomy were included into this prospective study to evaluate the effect of diabetes mellitus on morphine requirement in the postoperative period. A loading dose of morphine (50 mug kg(-1)) was administered in the perioperative period. Postoperative analgesia consisted of intravenous morphine-PCA. No analgesic other than morphine was allowed during the study. In cases of inadequate analgesia intravenous 1 mg of morphine was given as a rescue analgesic. Cumulative morphine consumption, pain scores and morphine-related adverse effects were recorded. Results: A total of 60 patients were evaluated: Group D, 30; and Group ND, 30. Patients in Group D received more morphine than those in Group ND (54.12 +/- 25.09 and 42.66 +/- 20.67, respectively). The difference in cumulative morphine consumption was higher in the first hour (P = 0.037) in diabetic patients and they required significantly more morphine in the last 24 h (P = 0.015). Postoperative pain scores were higher in the diabetic group. More patients in the diabetic group required rescue medication (26 vs. 19) and felt nauseous (25 vs. 14; P = 0.003). Conclusion: The findings of the study appear to support experimental and clinical impressions that the analgesic effect of morphine is attenuated in hyperglycemic conditions. Therefore, larger doses of morphine may be administered to diabetic patients for effective postoperative analgesia.