Intraoperative Intravenous Methadone and Ketamine Combination versus Intravenous Morphine and Ketamine Combination for Post-Operative Analgesia in Patients Undergoing Lower Extremity Fracture Surgery

Background: Pain management for lower extremity fracture surgeries can be challenging. The purpose of this study is to determine whether the use of ketamine and methadone are more effective than ketamine and morphine to reduce postoperative pain and morphine requirements in patients undergoing lower extremity fracture surgery. Materials and Methods: Seventy-five patients 18-65 years of age, ASA class I-III, were enrolled in this study, which scheduled for elective lower extremity orthopedic surgery involving fracture of femur or tibia were recruited for the study. Thirty-eight randomized to the Methadone group and 37 randomized into the Morphine group. Participants were randomized to either one of the two groups: methadone (2ug/kg fentanyl, 0.2 mg/kg ketamine and 0.2 mg/kg methadone IV) versus control (2 ug/kg fentanyl, 0.2mg/kg ketamine and 0.2 mg/kg morphine IV). The primary outcome was total morphine equivalent (MEQ) during the first 24 and 48 hours after surgery. Secondary outcomes included postoperative pain scores in PACU, at 24 and 48 hours, as well as postoperative nausea and vomiting (PONV). Results: There was no difference in intraoperative consumption of fentanyl between the Methadone group 360mcg and Morphine group 344mcg. In the first 24 hours postoperatively, the Methadone group consumed less MEQ compared with the Morphine group (36.1 mg vs 54.8 mg, p=0.0072), showed lower pain scores than the Morphine group (p=0.0146), and experienced more nausea and vomiting than the Morphine group. There were no differences in sedation in both groups. Conclusion: The intraoperative use of intravenous methadone significantly reduced post-operative opioid requirement in patients undergoing lower extremity fracture surgery. The results also demonstrated the methadone group had a higher rate of PONV.