Application of the Shock Index to the prediction of need for hemostasis intervention.

Introduction: The traditional method to identify hemorrhage after trauma has been vital signs-based. More recent attempts have used mathematical prediction models, but these are limited by the need for additional data including a Focused Assessment with Sonography for Trauma exam, or an arterial blood gas. Shock Index (SI) is the mathematical relationship of the heart rate divided by the systolic blood pressure; the cutoff of >0.9 has been associated with bleeding.

Methods: A total of 4292 trauma patients were identified in database over an 11 year period. Inclusion criteria included age >16 years and initial presentation to our trauma center. Patients were excluded for incomplete data, traumatic brain injury, or transfer leaving 4277 patients for analysis. Patients were further subdivided by age, and by mechanism of injury (blunt versus penetrating). Finally, patients were divided into bleeding versus nonbleeding, and the SI formula was applied to their initial hospital vital signs.

Results: Across our dataset, using the standard SI cutoff of >0.9 as the threshold for bleeding, the sensitivity is 54.5%, with a specificity of 93.6%. In the geriatric subanalysis, there was no difference for sensitivity between the age groups, but SI is more specific in the older patients. There was no difference in sensitivity using SI in blunt versus penetrating. Lowering the SI to ≥0.8 increases the sensitivity to 76.1%, with a specificity of 87.4%.

Conclusion: SI, at a lowered threshold of ≥0.8, can be used to identify trauma patients that will require intervention for hemostasis.