Performance of Shock Index as a predictor of severe postpartum hemorrhage following cesarean section under spinal anesthesia: a retrospective cohort study.

Background: An early diagnosis of a postpartum hemorrhage (PPH) can be challenging. The Shock Index (SI), the ratio of heart rate to systolic blood pressure, appears to be a useful indicator for the early diagnosis of severe PPH after vaginal delivery. Our primary aim was to evaluate if the SI has a predictive value for severe PPH following cesarean section (C-section) under spinal anesthesia (SA) and its best predictive threshold.

Methods: Retrospective single-center trial including women scheduled for C-section under SA with prevention of maternal hypotension by phenylephrine, and complicated by PPH between 2019 and 2021. Women were divided into two groups: non-severe PPH (blood loss <1000 mL) versus severe PPH (blood loss ≥1000 mL). SI was calculated and compared between the groups at four different time points: T0: prior to C-section; T1: at incision; T2: 15 minutes from start of PPH; T3: end of PPH management. Using receiver operating characteristic curve, we calculated the area under the curve (AUC) and the best diagnostic threshold (sensitivity and specificity) for predicting severe PPH.

Results: Overall, 129 patients were included, 26 (20.2%) with severe PPH. Median SI was significantly higher at T2 in the severe PPH group (1.14 (1.10-1.25) versus 1.0 (0.85-1.10), P<0.001), but not at other times of management. An SI value of ≥1.17 was the best threshold with an AUC of 0.81 (95% CI 0.72 to 0.90), a sensitivity of 0.42 and a specificity of 0.88.

Conclusions: SI may be an early indicator of severe PPH during C-section under SA.