Admission shock indices and lactate for mortality risk stratification in non-traumatic hypotensive patients

Early risk assessment is challenging in emergency department (ED) patients with non-traumatic hypotension. This study investigated whether admission shock index (SI), modified shock index (MSI), lactate, and exploratory lactate-based combined indices could discriminate 28-day mortality in this population.

This prospective, single-center observational study included adults presenting to the ED with non-traumatic hypotension, defined as systolic blood pressure < 90 mmHg at initial assessment. SI, MSI, lactate, lactate-shock index (LSI = lactate × SI), and lactate-modified shock index (LMSI = lactate × MSI) were evaluated. The primary outcome was all-cause 28-day mortality. Secondary outcomes were mechanical ventilation requirement and vasoactive drug requirement. Discriminatory performance was assessed using receiver operating characteristic curve analysis, and pairwise AUC comparisons were performed using DeLong's test.

Among 157 patients, 54 (34.4%) died within 28 days. SI, MSI, lactate, LSI, and LMSI were all significantly higher in non-survivors. The area under the curve values for 28-day mortality were 0.771 for SI, 0.748 for MSI, 0.741 for lactate, 0.800 for LSI, and 0.796 for LMSI. Mortality increased stepwise across SI-lactate risk groups, from 3.1% when both markers were normal to 54.9% when both were elevated. A similar gradient was observed for MSI-lactate groups, with mortality rising from 10.5% to 56.9%.

In non-traumatic hypotensive ED patients, admission SI, MSI, and lactate were associated with 28-day mortality. Lactate-based combined indices and combined risk groups may provide additional information for early risk stratification, although LSI and LMSI should be considered exploratory and require external validation.