An analysis of shock index as a correlate for outcomes in trauma by age group

Shock index as the ratio of heart rate to systolic blood pressure is a simple triage tool that correlates well with various outcomes in trauma patients. Concern has been raised regarding the accuracy of shock index in older patients. We sought to investigate the effects of age on the accuracy of shock index.

This is a retrospective review of data from a level I trauma center. Shock index was calculated for 16,269 patients, and they were stratified into age groups by decade. The correlation between prehospital shock index for each of the age groups and for several outcome variables were evaluated by Pearson correlation coefficients. Logistic regression was used to evaluate an increase in shock index during transit and its relationship with mortality.

All correlation values for patients between 16 and 60 years of age were positive (P < .05). In patients who are older than 80 years, none of the correlations with the outcome variables were statistically significant. In patients older than 60 years, an increased shock index during transit correlated with an increase in mortality rates.

As expected, prehospital shock index alone has diminishing accuracy for patients older than 60 years of age and should be interpreted cautiously by trauma triage personnel. Shock index alone in patients younger than 60, and its increase during transit in patients older than 60, can be used as a valuable tool for the prehospital triage of trauma patients when determining the need for transport to a trauma center, preparation of resources, or activation of the trauma team.