RESUMEN
BACKGROUND: Epidural analgesia may cause maternal hypotension and changes in the fetal heart rate. The implications of such side effects on the course of labor and delivery are incompletely understood. OBJECTIVE: This study aimed to assess whether the occurrence of maternal or fetal side effects associated with labor epidural analgesia increased the risk for cesarean delivery. STUDY DESIGN: This was a cohort study of all women who underwent epidural analgesia during labor for the period October 1, 2020 to December 31, 2020. Excluded were cases of multiples, fetal death, noncephalic presentation, and gestational age at birth <37.0 weeks. Maternal vital signs and fetal heart rate tracings for the 1 hour before and 1 hour after epidural analgesia was administered were reviewed. The occurrence of maternal hypotension, defined as a continuous variable and dichotomized into a decrease in maternal systolic blood pressure to <90 mm Hg or a drop in systolic blood pressure by >20% below the last value before epidural analgesia was administered, was related to changes in the fetal heart rate category. The principal outcome was cesarean delivery rate; binary logistic regression analysis was used to control for confounders, and mediation model analysis was used to quantify the extent to which significant variables participated in the causation pathway to cesarean delivery (SPSS version 28 was used for the analyses). RESULTS: A total of 439 women met the study criteria. Significant adverse reactions owing to epidural occurred in 184 of 439 women (41.9%) and included severe maternal hypotension in 159 of 439 participants (36.2%) and worsening fetal heart rate category in 50 of 439 participants (11.4%). The logistic regression analysis revealed that cervical dilation at epidural (P=.03), the duration of labor after epidural (P<.001), and worsening fetal heart rate category within 60 minutes of epidural administration (P=.01) were independently associated with recourse to cesarean delivery. The mediation analysis showed that both cervical dilatation at epidural administration and worsening fetal heart rate category had significant direct and indirect effects in the pathway to cesarean delivery. CONCLUSION: Worsening fetal heart rate category related to labor epidural independently increased the risk for cesarean delivery.
RESUMEN
BACKGROUND: In scheduled cesarean deliveries, the rate of decrease in the umbilical artery pH is related to the severity of maternal hypotension and the interval from spinal placement to delivery. Base excess values have greater use than umbilical artery pH values to time the duration of fetal acidemia because they demonstrate a linear rather than logarithmic correlation with the degree of acidosis. OBJECTIVE: This study aimed to evaluate the rate of decline in the fetal base excess in scheduled cesarean deliveries that were converted to emergency cesarean delivery owing to fetal bradycardia following spinal anesthesia. STUDY DESIGN: All cases of scheduled cesarean deliveries in gestations at >34 weeks' gestation under spinal anesthesia that were converted to emergency cesarean deliveries owing to fetal bradycardia in the period May 2019 to May 2021 were reviewed. Included were those with (1) a preoperative reactive nonstress test and (2) fetal acidemia (umbilical artery pH <7.20). Excluded were those with anesthesia other than spinal and a birthweight below the 10th percentile for gestational age. Time intervals between the completion of spinal anesthesia and delivery were calculated and related to umbilical cord gas analytes. RESULTS: From a cohort of 1064 scheduled cesarean deliveries, 7 fulfilled the study criteria yielding 8 neonates. Mean ± standard error of the mean interval of spinal anesthesia to delivery was 15.0±1.9 minutes, and the decrease in mean blood pressure after spinal anesthesia was 39.1±3.0 mm Hg. Umbilical artery base excess ranged from -5.2 to -16.6 mmol/L (median, -8.0). Based on published normative data of prelabor fetal umbilical artery base excess (-2±0.6 mmol/L), the mean rate of base excess decrease was 0.38±0.25 mmol/minute. CONCLUSION: The rate of decrease in base excess when scheduled cesarean deliveries are converted to emergency cesarean deliveries owing to fetal bradycardia related to spinal anesthesia (1 mmol/2.6 min) matches the estimated rate of loss of base excess (1 mmol/2-3 minutes) reported in cases of severe bradycardia or sentinel events during labor.