Utility of the shock index in predicting mortality in traumatically injured patients.

Background: Currently, specific triage criteria, such as blood pressure, respiratory status, Glasgow Coma Scale, and mechanism of injury are used to categorize trauma patients and prioritize emergency department (ED) and trauma team responses. It has been demonstrated in previous literature that an abnormal shock index (SI = heart rate [HR]/systolic blood pressure, >0.9) portends a worse outcome in critically ill patients. Our study looked to evaluate the SI calculated in the field, on arrival to the ED, and the change between field and ED values as a simple and early marker to predict mortality in traumatically injured patients.

Methods: A retrospective chart review of the trauma registry of an urban level I trauma center. Analysis of 2,445 patients admitted over 5 years with records in the trauma registry of which 1,166 also had data for the field SI. An increase in SI from the field to the ED was defined as any increase in SI regardless of the level of the magnitude of change.

Results: Twenty-two percent of patients reviewed had an ED SI >0.9, with a mortality rate of 15.9% compared with 6.3% in patients with a normal ED SI. An increase in SI between the field and ED signaled a mortality rate of 9.3% versus 5.7% for patients with decreasing or unchanged SI. Patients with an increase in SI of >or=0.3 had a mortality rate of 27.6% versus 5.8% for patients with change in SI of <0.3.

Conclusion: Trauma patients with SI >0.9 have higher mortality rates. An increase in SI from the field to the ED may predict higher mortality. The SI may be a valuable addition to other ED triage criteria currently used to activate trauma team responses.