Correlation Between Shock Index and Mortality in the Prehospital and Level 1 Rural Trauma Center Emergency Department Settings

Abstract

Background: The shock index is a valid tool used to detect impending circulatory collapse in the pre-hospital setting. As validation of the shock index requires high sample sizes, the majority of retrospective studies have been performed at urban level 1 trauma centers. We hypothesized that the shock index would accurately predict mortality in a rural level 1 trauma center. Objective - Determine if the shock index continues to be a reliable predictive value in trauma patients for morbidity and mortality.  Setting - This retrospective study was performed at a state-designated level 1 trauma center in Johnson City, Tennessee. Patients were excluded from the study if they were under the age of 18, not immediately transported to the trauma center or if insufficient data was available. The shock index was calculated as heart rate/systolic blood pressure. Both the prehospital and emergency department shock indexes were calculated, with the emergency department vital signs being the first upon arrival. Patients were divided into three categories: SI ≤ 0.7, 0.71-0.89, and ≥ 0.9. We assessed the relationship between SI, blood product usage, and outcome variables using Pearson correlation coefficients and logistic regression. Chi-square analysis was used to show the difference in mortality between the groups. Results - A higher shock index score after arrival to the emergency department experienced longer hospital, intensive care unit, and mechanical ventilation days, injury severity scores, packed red blood cells, plasma, platelets, and total blood product usage. Mortality was higher in the groups with an SI of ≥ 0.9 at the scene and arrival to the emergency department.  Conclusion - Patients with a shock index > 0.71-0.89 in both prehospital and emergency departments had higher mortality rates and need for transfusion. The shock index continues to be a reliable predictive value in trauma patients for morbidity and mortality.