(1111) Spinal-induced hypotension and time from spinal-to-delivery in scheduled cesarean deliveries: the association with neonatal acidosis

In a cohort of scheduled cesarean delivery (CD) with universal exposure to prophylactic vasopressors, we sought to: 1) ascertain the effect of sustained hypotension (SHP) on neonatal acidosis and adverse perinatal outcomes and, 2) examine differences in spinal-to-delivery (S-D) time in those with and without neonatal acidosis.

Study Design:

We conducted a retrospective cohort study of all scheduled CD at a quaternary center (Jan 2019 to Dec 2021). Non-anomalous singletons who had a scheduled CD under spinal anesthesia at ≥ 37 wks were included. Subjects with missing cord gases were excluded. Hypotension was defined as a systolic blood pressure < 100 mmHg (SYS-BP100) and/or a 20% drop from baseline (SYS-BP20). A hypotension index was generated to account for both magnitude and duration of hypotension. SHP was defined as a hypotension index > 95^th percentile (for SYS-BP100) and/or > 90^th percentile (for SYS-BP20) for the cohort. Primary outcome was neonatal acidosis (umbilical artery pH ≤ 7.10 or base excess ≤ -12). Secondary outcomes were composite neonatal (CNAO) and maternal (CMAO) adverse outcomes. Multivariable Poisson regression models with robust error variance were used and crude and adjusted relative risk with 95% confidence intervals were calculated. 

Results:

Of the 816 scheduled CD, 332 (41%) met eligibility criteria. SHP after spinal occurred in 41 (12%) cases. Maternal characteristics were similar between those with and without SHP, except for number of prior CD (p=0.007) and rate of GHTN/ preeclampsia (p=0.004; Table 1). Neonatal acidosis was more common in those with SHP compared to those without (aRR 3.96, 95% CI 1.21-12.98). There were no significant differences in the CNAO and CMAO by SHP status (Table 2). There was also no significant difference in time from S-D in those with and without acidosis (p=0.571).

Conclusion:

Despite universal exposure to prophylactic vasopressors, those with SHP were at increased risk for neonatal acidosis.  Maternal and neonatal adverse outcomes by SHP status, however, were similar. In addition, time from S-D was similar by neonatal acidosis status.