548 Use of ketamine infusion in post cesarean pain management in patients with opioid use disorder

Abstract

Low dose post-operative IV ketamine infusions successfully improve pain and decrease opioid usage in non-obstetric populations. In this study, we have examined the effect of low dose IV ketamine in post-cesarean section women with opioid use disorder (OUD). We performed a single center retrospective cohort study of women >18 years old receiving medication assisted treatment (MAT) for OUD who underwent cesarean delivery between June 1, 2019-September 1, 2020. Women were stratified based on whether or not they received ketamine infusion for pain control and outcomes were assessed over the first 48 hours postpartum. The primary outcome was opioid consumption in the first 24 hours postpartum; the secondary outcome was pain scores during this period. Outcomes were compared between subgroups using chi square or the Fisher exact test, and t tests or Mann Whitney U tests, as appropriate. Significance was accepted at P<.05 44 subjects met inclusion criteria, with 22 receiving and 22 not receiving ketamine infusion. Overall, 43/44 (97.7%) were white; 33/44 (75%) were taking buprenorphine, and 11/44 (25%) were taking methadone. All characteristics were similar between subgroups, except for a higher rate of tobacco use among those not receiving ketamine [12 (54.5%) vs 8 (36.4%), P=0.03]. The mean (SD) duration of ketamine infusion was 23.8 (12.4) hours. Opioid consumption in the first 24 hours post-op was decreased in the ketamine group compared to the non-ketamine group (median [interquartile range], 30 [7.6-46.2] vs. 45.5 [18.7-60] morphine milli-equivalents, p=0.08), but did not reach statistical significance. Mean pain scores, measured on a numerical rating scale, did not differ between groups 5.4 (1.8) and 5.0 (1.6), respectively. No major maternal or fetal adverse events were recorded. Low dose ketamine infusion shows promise for use in women receiving MAT for OUD to reduce the dose of opioid analgesia required in the first 24 hours following cesarean delivery. Larger, prospective studies are needed.