Impact of Neuraxial Preservative-Free Morphine in Vaginal Delivery on Opiate Consumption and Recovery: A Randomized Control Trial

BACKGROUND: Neuraxial opioids are commonly used after cesarean delivery (CD). However, they are not commonly used after vaginal delivery (VD) though some studies have suggested they may be beneficial from a pain perspective. However, they did not evaluate other potential benefits including patient satisfaction, impact on postpartum depression and breastfeeding (BF) success, or side effects such as pruritus. METHODS: Parturients who delivered vaginally with epidural analgesia were randomized to receive either 2 mg of preservative-free morphine (4 mL) or saline (4 mL) via the epidural catheter within 1 hour of VD. Routine analgesics were unchanged and included q 6-hour dosing of acetaminophen 975 mg orally and ketorolac 30 mg intravenous (IV). Hydromorphone 2 mg or oxycodone 10 mg were offered for breakthrough pain. Our primary outcome was opiate consumption in the first 24 hours after drug administration. Secondary outcomes included pain scores at 24 hours and 1 week postpartum as well as opiate consumption up to 1 week postpartum. Additional end points such as obstetric quality of recovery score (OBS-QOR10) breast feeding success, and an Edinburgh Postnatal Depression Score (EPDS) were also obtained. RESULTS: Data were analyzed for 157 parturients, 80 in the morphine group and 77 in the saline group. No difference was observed in the EDPS score predelivery or intention to BF. We found a statistically significant difference in the use of opioids in the first 24 hours, 3.8% (95% confidence interval [CI], 0.9%-11.3%) vs 14.3% (7.7%-24.5%) in the morphine and saline groups, respectively; and in total opioid dose, median (interquartile range, IQR [range]) of morphine milligram equivalent vs 0 (0-0 [0-47.5]) vs 0 (0-0 [0-72]), P =.023, in the morphine and saline groups, respectively. Verbal pain scores (0-10) at 24 hours were lower in the morphine group (median (IQR [range): 2.0 (1-4 [0-10]) vs 3.0 (1.5-5.0 [0-10]), P =.043. There was a greater incidence of pruritus in the morphine group versus saline group, 37.5% (95% CI, 27.1%-49.1%) vs 18.2% (95% CI, 10.6%-29.0%), P =.008. We did not find any differences in the OBS-QOR10, BF success, or EPDS at 6 weeks PP (P <.05). CONCLUSIONS: A single epidural dose of 2 mg preservative-free morphine after VD was effective at decreasing pain and opioid use at 24 hours after VD but came at the cost of increased pruritus. We did not detect any differences in BF, recovery scores, or PPD. Future studies should focus on elucidating the role of neuraxial preservative-free morphine after VD.