Utility of shock index for predicting severity of postpartum haemorrhage: A systematic review and meta-analysis

Postpartum haemorrhage (PPH) is a leading cause of maternal mortality globally. Shock index (SI), a simple measure of heart rate to systolic blood pressure ratio, has been proposed as a tool to predict severe PPH, but its efficacy varies across different settings. This study aims to assess diagnostic accuracy of SI for severe PPH.

Comprehensive database searches of EMBASE, CINAHL, PubMed, and MEDLINE Cochrane library was done for studies reporting data on SI in patients with PPH from inception of each database until March 2024. Data on sensitivity, specificity, likelihood ratios, diagnostic odds ratio (OR), and area under the receiver operating characteristic curve (AUC) were extracted. Subgroup analyses were performed based on the income group of the countries and the criteria used to define severe PPH.

Twenty studies were included. Pooled sensitivity and specificity of SI for predicting severe PPH were 76% (95% confidence interval (CI): 67%-83%) and 78% (95% CI: 68%-85%), respectively; diagnostic OR was 11 (95% CI: 5-24), and the AUC was 0.84 (95% CI: 0.80-0.87). Subgroup analysis revealed higher diagnostic accuracy of SI in lower/upper middle-income countries compared to high-income countries. Studies using blood transfusion as a criterion for severe PPH showed higher predictive sensitivity and specificity of the shock compared to studies using quantitative blood loss.

Shock index demonstrates moderate effectiveness in predicting severe PPH and can be a valuable tool in emergency obstetric care, particularly when used as part of a multi-parameter diagnostic approach. Future research should focus on refining its use across different clinical settings.