The effect of spinal hypotension and anesthesia-to-delivery time interval on neonatal outcomes in planned cesarean delivery

Background Maternal hypotension after spinal anesthesia, and time from anesthesia to delivery, are potentially modifiable risk factors for neonatal acidosis. Objective This study aimed to examine the relationship between the time from spinal anesthesia to delivery and spinal hypotension in planned cesarean deliveries and their effect on neonatal outcome, primarily neonatal acidosis. Study Design We performed a retrospective analysis of women with singleton pregnancy undergoing spinal anesthesia for planned cesarean delivery between 37 0/7 and 41 6/7 weeks’ gestation using electronic medical records. The occurrence of spinal hypotension and anesthesia-to-incision and incision-to-delivery intervals (minutes) were the primarily studied variables. In addition, spinal hypotension index was developed to account for the duration and magnitude of maternal hypotension. The 90th percentile for the spinal hypotension index defined the sustained spinal hypotension group. The primary outcome was neonatal acidosis (pH of ≤7.1 or base deficit of ≥12.0). The odds ratios were calculated using univariate and multivariate logistic regression models. The multivariate analysis included sporadic spinal hypotension or sustained spinal hypotension, use of vasopressor treatment, and anesthesia-to-incision and incision-to-delivery intervals. Results We included 3150 women in the study. Notably, 43.4% experienced at least 1 event of spinal hypotension (sporadic) and 14.8% experienced sustained spinal hypotension. Neonatal acidosis occurred in 3.4% cases of sporadic spinal hypotension (odds ratio, 1.83; 95% confidence interval, 2.27–2.87) and in 5.8% cases of sustained hypotension (odds ratio, 3.00; 95% confidence interval, 1.87–4.80). Both anesthesia-to-incision and incision-to-delivery intervals were significantly associated with neonatal acidosis as follows: at 90th percentile cutoff, the odds ratios for neonatal acidosis were 3.82 (95% confidence interval, 2.03–7.19) and 2.94 (95% confidence interval, 1.70–5.10), respectively. The use of ephedrine (odds ratio, 2.42; 95% confidence interval, 1.35–4.32) but not phenylephrine (odds ratio, 0.76; 95% confidence interval, 0.34–1.72) treatment was also associated with more cases of neonatal acidosis. The woman’s age, gestational age, neonatal birthweight, fetal presentation, and the number of previous cesarean deliveries were not associated with neonatal acidosis. In multivariate analysis, anesthesia-to-incision and incision-to-delivery intervals, use of vasopressor treatment, and sustained spinal hypotension were independently associated with neonatal acidosis. After adjustment, the risk for neonatal acidosis did not increase in women who experienced sporadic spinal hypotension only. Neither neonatal acidosis nor the primary research variables were associated with neonatal complications such as transient tachypnea of the newborn, respiratory distress, or admission to the neonatal unit. Conclusion Neonatal acidosis in planned cesarean delivery was common. However, serious perinatal consequences were rare. The adverse effects of sustained spinal hypotension and prolonged anesthesia-to-incision and incision-to-delivery intervals on neonatal acid-base balance were additive. This supports the adoption of prevention strategies for spinal hypotension, which is widely evidenced based on the obstetrical anesthesia literature, but still not universally used. Whether the reduction in intraoperative time intervals would benefit the neonate should be determined by future prospective studies.