Distribution and performance of shock index to predict postpartum hemorrhage after vaginal delivery

The shock index (SI) – heart rate (.min-1) divided by systolic blood pressure (mmHg) – has emerged as a promising tool to predict postpartum hemorrhage (PPH) after delivery but has been poorly assessed in the general population of parturients. This study aimed to describe the distribution of SI during the two first hours after vaginal delivery, and to evaluate the performances of SI measured at 15 and at 30 minutes in predicting the occurrence of PPH. Data came from a multicenter, randomized controlled trial aimed to compare prophylactic administration of tranexamic acid versus placebo in addition to prophylactic oxytocin for the prevention of PPH in women with a singleton live fetus ≥ 35 weeks, born vaginally (TRAAP trial). SI was systematically measured at 0, 15, 30, 45, 60 and 120 minutes after delivery. We selected the measurement at 15 and at 30 minutes as predictors for PPH. Primary and secondary outcomes were respectively quantitative blood loss ≥ 1000 mL (QBL≥1000) and provider-assessed clinically significant PPH (cPPH). For each outcome, we calculated the area under the receiver operating characteristic curve (AUROC) values of each predictor. For each analysis, women who already met the PPH-related outcome to be predicted before the SI measurement were excluded to take into account the temporal sequence between predictors and outcomes. Among the source population of 3891 women, the prevalence of QBL≥1000 and cPPH was respectively 2.7% (104/3839) and 9.1% (354/3891). The distributions of SI at 15 and at 30 minutes after delivery were similar with median value of 0.73 and 97th percentile of 1.11 for both (Table 1). The AUROC values of SI measured at 15 minutes to predict QBL≥1000 and cPPH were respectively 0.66 (95% confidence interval (95%CI) 0.60-0.73) and 0.56 (95%CI 0.52-0.60) (Table 2). The AUROC values of SI measured at 30 minutes to predict QBL≥1000 and cPPH were respectively 0.68 (95%CI 0.61-0.75) and 0.49 (95%CI 0.43-0.55) (Table 2). SI measured at 15 and at 30 minutes after vaginal delivery was a poor predictor of QBL≥1000 and of cPPH.View Large Image Figure ViewerDownload Hi-res image Download (PPT)