Intraoperative methadone administration and postoperative pain control: a systematic review and meta-analysis

Postoperative pain is not adequately managed in greater than 40% of surgical patients and is a high priority for perioperative research. In this meta-analysis, we examined studies comparing postoperative opioid consumption and pain scores in surgical patients who received methadone by any route vs those who received another opioid by any route. Studies were identified from PubMed, Cochrane, Web of Science, EMBASE, and Scopus from January 1966 to November 2018. Pooled odds ratios were calculated for a primary outcome of postoperative opioid consumption and secondary outcomes of time-to-extubation, time-to-first postoperative analgesia request, satisfaction, hospital length-of-stay, and complications. Postoperative pain scores were assessed qualitatively. Ten studies (617 patients) were included. Postoperative opioid consumption at 24 hours was lower in the methadone group vs control (mean difference = -15.22 mg oral morphine equivalents, 95% confidence interval -27.05 to -3.38; P = 0.01). Patients in the methadone group generally reported lower postoperative pain scores in 7 of 10 studies. Meta-analysis revealed greater satisfaction scores with analgesia in the methadone group vs control (0-100 visual analog scale; mean difference = 7.16, 95% confidence interval 2.30-12.01; P = 0.004). There was no difference in time-to-extubation, time-to-first analgesia request, hospital length-of-stay, or complications (nausea, sedation, respiratory depression, and hypoxemia). The results demonstrate that surgical patients who received intraoperative methadone had lower postoperative opioid consumption, generally reported lower pain scores and experienced better satisfaction with analgesia. However, these advantages need to be weighed carefully against dangerous risks with perioperative methadone, specifically respiratory depression and arrhythmia. Future studies should explore logistics, safety, and cost effectiveness.