Post-Cesarean Delivery Analgesic Outcomes in Patients Maintained on Methadone and Buprenorphine: A Retrospective Investigation.

ABSTRACT

BACKGROUND: Despite the increasing prevalence of opioid use disorder (OUD) in pregnant women, there are limited studies on their anesthesia care and analgesic outcomes after cesarean delivery (CD). METHODS: Patients with OUD on either buprenorphine or methadone maintenance therapy who underwent CD at our institution from 2011 to 2018 were identified. Anesthetic details and analgesic outcomes, including daily opioid consumption and pain scores, were compared between patients maintained on buprenorphine and methadone. Analgesic outcomes were also evaluated according to anesthetic type (neuraxial or general anesthesia) and daily buprenorphine/methadone dose to determine if these factors impacted pain after delivery. RESULTS: A total of 146 patients were included (buprenorphine n=99 (67.8%), methadone n=47 (32.2%)). Among all patients 74% had spinal/CSE, 15% epidural, and 11% general anesthesia. Anesthesia types were similar among buprenorphine and methadone patients. For spinal anesthetics, intrathecal fentanyl (median 15 µg) and morphine (median 100 µg) were commonly given (97.2% and 96.3%, respectively), and dosed similarly between groups. Among epidural anesthetics, epidural morphine (median 2 mg) was commonly administered (90.9%), while fentanyl (median 100 µg) was less common (54.5%). Buprenorphine and methadone groups consumed similar amounts of oxycodone equivalents per 24 hours of hospitalization (80.6 vs 76.3 mg; p=0.694) and had similar peak pain scores (8.3 vs 8.0; p=0.518). Daily methadone dose correlated weakly with opioid consumption (R=0.3; p=0.03), although buprenorphine dose did not correlate with opioid consumption or pain scores. General anesthesia correlated with greater oxycodone consumption in the first 24 hours (median 156.1 vs 91.7 mg; p=0.004) and greater IV PCA use (63% vs 7%; p<0.001) compared to neuraxial anesthesia. CONCLUSION: Patients on buprenorphine and methadone had similar high opioid consumption and pain scores after CD. The anesthetic details and analgesic outcomes reported in this investigation may serve as a useful reference for future prospective investigations and aid in the clinical care of these patients.