Intraoperative use of methadone improves control of postoperative pain in morbidly obese patients: a randomized controlled study.

Objectives: Surgical patients still commonly experience postoperative pain. With the increasing prevalence of obesity, there is a growing demand for surgical procedures by this population. Intraoperative use of methadone has not been well assessed in this population.

Materials and methods: Patients with a body mass index of 35 kg/m2 or more undergoing bariatric surgery were randomly assigned to receive either fentanyl (group F) or methadone (group M) in anesthesia induction and maintenance. The primary outcome was morphine consumption during the first 24 hours after surgery through a patient-controlled analgesia device. Secondary outcomes were pain scores at rest and while coughing, opioid related side effects, and patient satisfaction. The patients were also evaluated 3 months after surgery for the presence of pain, dysesthesia, or paresthesia at surgical site.

Results: Postoperative morphine consumption was significantly higher for patients receiving fentanyl than methadone during the postoperative period at 2 hours (mean difference [MD] 6.4 mg; 95% CI 3.1-9.6; P <0.001), 2-6 hours (MD 11.4 mg; 95% CI 6.5-16.2; P <0.001), 6-24 hours (MD 10.4 mg; 95% CI 5.0-15.7; P <0.001), and 24-48 hours (MD 14.5 mg; 95% CI 3.9-25.1; P =0.01). Patients from group F had higher pain scores until 24 hours postoperatively, higher incidence of nausea and vomiting, lower satisfaction, and more evoked pain at surgical scar at the 3-month postoperative evaluation than group M.

Conclusion: Intraoperative methadone can safely lower postoperative opioid consumption and improve postoperative pain scores compared with fentanyl in morbidly obese patients.