Shock index and delta-shock index are superior to existing maternal early warning criteria to identify postpartum hemorrhage and need for intervention.

Objective: To determine whether shock index (SI) is superior to traditional vital signs in predicting postpartum hemorrhage and need for intervention.

Methods: Retrospective case-control study in an academic tertiary-care county hospital. Forty-one consecutive postpartum hemorrhage (PPH) cases and 41 controls were frequency-matched by mode of delivery and maternal weight. We measured four criteria: heart rate, systolic blood pressure (SBP), SI (HR/SBP), and delta-SI (peak SI - baseline SI). Using received operating characteristic curves, we compared the discrimination performance of each criterion to predict PPH, transfusion, and surgical intervention, and identified thresholds with the strongest classification.

Results: SI ≤1.1 can be normal in peripartum. Peak SI and delta-SI were generally superior to heart rate (HR) and SBP in predicting PPH, transfusion, and surgical intervention. SI ≥1.143 and SI ≥1.412 were strong initial and "critical" thresholds. Delta-SI was the strongest classifier overall; both SI and delta-SI remain sensitive and specific when adjusted for potential confounders.

Conclusions: SI and delta-SI appear to be superior to HR and SBP in predicting PPH and need for intervention. Utility of delta-SI should be prospectively explored.