INTRODUCTION: Although variability in vital parameters has been shown to predict outcomes; the role of change in shock index (Delta SI) as a predictive tool remains unknown.
METHODS: The NTDB (2011-2012) was abstracted for all patients 18-85 years of age and Injury Severity Score (ISS) >15 with complete data. Transferred patients and patients dead on arrival were excluded. Patient demographics, injury parameters were recorded, and SI in the field, SI in the emergency department (ED), and change in Shock Index (Delta SI = ED SI- Field SI) was calculated. Our outcome measure was mortality. Cox regression and Kaplan Meier analysis were performed.
RESULTS: A total of 95,088 patients were included and overall mortality rate was 11.9%. Patients with a positive Delta SI had a mortality rate of 13.3% compared with 9.6% mortality rate in patients who had an unchanged or negative Delta SI. After controlling for confounders, a Delta SI of >0.1 was found to be associated with an increased hazard of death (hazard ratio [95% CI] = 1.36 [1.29-1.45]) and mortality (16.6% vs. 9.5%, p < 0.001). Even in hemodynamically stable patients, a Delta SI >0.1 was associated with increased hazard of death (hazard ratio [95% CI] = 1.29 [1.20-1.39]).
CONCLUSION: Delta Shock index from field to hospital independently predicts higher mortality. It predicts higher mortality even in apparently hemodynamically stable patients with normal traditional vital signs and normal shock index. Delta shock index may serve as an adjunct to existing traditional vital signs for the identification of occult hypovolemic shock and higher risk of death in trauma patients.