Abstract: Objective To explore the effect of epidural labor analgesia duration on the outcomes of different anesthetic approaches for conversion to cesarean section. Methods We retrospectively collected the clinical data of pregnant women undergoing conversion from epidural labor analgesia to cesarean section at Sichuan Maternal and Child Health Hospital and Jinjiang District Maternal and Child Health Care Hospital between July, 2019 and June, 2020. For cesarean section, the women received epidural anesthesia when the epidural catheter was maintained in correct position with effective analgesia, spinal anesthesia at the discretion of the anesthesiologists, or general anesthesia in cases requiring immediate cesarean section or following failure of epidural anesthesia or spinal anesthesia. Receiver-operating characteristic curve analysis was performed to determine the cutoff value of the analgesia duration using Youden index. The women were divided into two groups according to the cut off value for analyzing the relative risk using cross tabulations. Results A total of 820 pregnant women undergoing conversion to cesarean section were enrolled in this analysis, including 615 (75.0%) in epidural anesthesia group, 186 (22.7%) in spinal anesthesia group, and 19 (2.3% ) in general anesthesia group; none of the women experienced failure of epidural or spinal anesthesia. The mean anesthesia duration was 8.2±4.7 h in epidural anesthesia, 10.6±5.1 h in spinal anesthesia group, and 6.7 ± 5.2 h in general anesthesia group. Multivariate logistic regression analysis showed that prolongation of analgesia duration by 1 h (OR=1.094, 95% CI: 1.057-1.132, P<0.001) and an increase of cervical orifice by 1 cm (OR=1.066, 95% CI: 1.011-1.124, P=0.017) were independent risk factors for epidural analgesia failure. The cutoff value of analgesia duration was 9.5 h, and beyond that duration the relative risk of receiving spinal anesthesia was 1.204 (95% CI: 1.103-2.341, P<0.001). Conclusion Prolonged epidural labor analgesia increases the risk of failure of epidural analgesia for conversion to epidural anesthesia. In cases with an analgesia duration over 9.5 h, spinal anesthesia is recommended if immediate cesarean section is not required.

Key words: epidural labor analgesia; analgesia duration; cesarean section; anesthesia method