Shock index: an effective predictor of outcome in postpartum haemorrhage?

ObjectivesTo compare the predictive value of the shock index (SI) with conventional vital signs in postpartum haemorrhage (PPH), and to establish alert' thresholds for use in low-resource settings. DesignRetrospective cohort study. SettingUK tertiary centre. PopulationWomen with PPH 1500ml (n=233). MethodsSystolic blood pressure (BP), diastolic BP, mean arterial pressure, pulse pressure, heart rate (HR) and SI (HR/systolicBP) were measured within the first hour following PPH. Values measured at the time of highest SI were selected for analysis. The area under the receiver operating characteristic curve (AUROC) for each parameter, used to predict admission to an intensive care unit and other adverse outcomes, was calculated. Sensitivity, specificity and negative/positive predictive values determined thresholds of the best predictor. Main outcome measuresIntensive care unit (ICU) admission, blood transfusion4iu, haemoglobin level<7g/dl, and invasive surgical procedures. ResultsShock index has the highest AUROC to predict ICU admissions (0.75 for SI [95%CI 0.63-0.87] compared with 0.64 [95%CI 0.44-0.83] for systolicBP). SI compared favourably for other outcomes: SI0.9 had 100% sensitivity (95%CI 73.5-100) and 43.4% specificity (95%CI 36.8-50.3), and SI1.7 had 25.0% sensitivity (95%CI 5.5-57.2) and 97.7% specificity (CI94.8-99.3), for predicting ICU admission. ConclusionsShock index compared favourably with conventional vital signs in predicting ICU admission and other outcomes in PPH, even after adjusting for confounding; SI<0.9 provides reassurance, whereas SI1.7 indicates a need for urgent attention. In low-resource settings this simple parameter could improve outcomes. It was not possible to adjust for resuscitative measures administered following vital sign measurement that may have influenced the outcome.