Intravenous Methadone versus Intrathecal Morphine as Part of an Enhanced Recovery After Cardiac Surgery Protocol on Postoperative Pain and Outcomes: A Retrospective Cohort Study

Abstract

ObjectiveEvaluate the effect of intravenous (IV) methadone versus intrathecal morphine (ITM) within an Enhanced Recovery After Cardiac Surgery (ERACS) pathway on postoperative pain and outcomes (length of hospital stay, postoperative complications) after cardiac surgery. DesignRetrospective cohort study. SettingTwo tertiary academic medical institutions within the same health system. ParticipantsEligible 289 adult patients undergoing elective cardiac surgery with an enhanced recovery pathway from January 2020 through July 2021. InterventionsPatients were administered ITM (0.25mg) or IV methadone (0.1mg/kg) if ITM was contraindicated. All patients were enrolled in an ERACS pathway utilizing current Enhanced Recovery After Surgery society guidelines. Measurements and Main ResultsPrimary outcome measures included postoperative pain scores and opioid consumption measured as oral morphine equivalents (OMEs). We analyzed patient demographics, procedural factors, intraoperative medications, and outcomes. Adjusted linear mixed models were fit to analyze associations between intervention and pain outcomes. ITM was associated with decrease in pain scores on postoperative day 0 after adjusting for clinical variables (average marginal effect, 95% confidence interval; 0.49 (0.002, 0.977), p=0.049). No difference in opioid consumption could be demonstrated between groups after adjusting for postoperative day and other variables of interest. ConclusionsITM when compared to IV methadone was associated with decrease in pain scores without any difference in opioid consumption after elective cardiac surgery. Methadone can be considered as a safe and effective alternative to ITM for ERACS protocols. Future large prospective studies are needed to validate this finding and further improve analgesia and safety.