Variation in postoperative analgesic requirements in the morbidly obese following gastric bypass surgery

Patient-controlled analgesia is a relatively new method of administering intravenous narcotics for postoperative pain relief. The technique involves the self-administration of a given analgesic in a bolus dose with the aid of a timed infusion and sequencing device. Ten morbidity obese patients undergoing elective gastric bypass surgery were treated in a prospective, unblinded, pilot project to evaluate the efficacy of patient-controlled analgesia. Analgesic therapy was satisfactory in all patients. The mean total dose of morphine sulfate administered during the first 36 hours postoperatively was 66 mg, an average of 1.7 mg/hr. There was a tenfold variation (17.5-175 mg) in the 36 hr total dose. The total dose was not related to body surface area, age, sex, dose per injection, or anesthetic agent. The large variation in individual narcotic analgesic requirements could be a major factor in the suboptimal management of postoperative pain with conventional dosing. Patient-controlled analgesia may circumvent these problems.