Clinical Effects of Low-Dose Esketamine During Emergency Conversion From Labor Epidural Analgesia to Category I Cesarean Section: A Randomized Controlled Trial of Maternal Hemodynamics, Analgesia, Sedation, and Neonatal Outcomes

Background: Emergency conversion from labor epidural analgesia to Category I cesarean section leaves little time for epidural top-up to produce a surgical block. We examined whether low-dose intravenous esketamine could provide short-term bridging analgesia and sedation while maintaining maternal hemodynamics, oxygenation, and early neonatal safety. Methods: In this randomized study, parturients requiring Category I cesarean section after labor epidural analgesia received either esketamine 0.15 mg/kg or normal saline 1 min before skin incision, together with epidural alkalinized lidocaine. The primary outcome was the longitudinal change in maternal systolic blood pressure during the 20-min observation window. Secondary outcomes included heart rate, SpO2, intraoperative pain, surgeon satisfaction with muscle relaxation, Ramsay sedation score, and neonatal Apgar scores. We analyzed repeated continuous outcomes with linear mixed-effects models and repeated binary outcomes with generalized estimating equations. The single post-administration Ramsay outcome was analyzed using logistic regression. Apgar scores were summarized descriptively using medians, interquartile ranges, and counts.Results: We analyzed 55 parturients, 31 in the esketamine group and 24 in the normal saline group. Esketamine did not meaningfully alter the systolic blood pressure trajectory. Heart rate and SpO2 showed broadly similar patterns between groups, with no signal of esketamine-related respiratory deterioration. The esketamine group had lower odds of intraoperative pain at 5, 15, and 20 min and a higher probability of target Ramsay sedation. Surgeon satisfaction with muscle relaxation showed no clear between-group difference. Apgar scores remained high in both groups. Conclusion: Low-dose intravenous esketamine 0.15 mg/kg may be a practical bridging adjunct during emergency conversion from labor epidural analgesia to Category I cesarean section. It improved early pain control and target sedation without a clear adverse signal in systolic blood pressure, heart rate, oxygenation, or early Apgar scores. Trial Registration: Chinese Clinical Trial Registry, ChiCTR2600121948; retrospectively registered.