SHOCK INDEX AS A MARKER FOR SIGNIFICANT INJURY IN TRAUMA PATIENTS

Objective: To determine whether the shock index (SI), defined as the r atio of heart rate (HR) to systolic blood pressure (SEP), is a useful marker for significant injury in trauma patients, Methods: A retrospec tive database analysis was used to relate the SI to the clinical measu res: death within 24 hours, injury severity score (ISS) greater than o r equal to 16, intensive care unit (ICU) stay greater than or equal to 1 day, and amount of blood transfused (BT) greater than or equal to 2 units, Consecutive trauma patients seen at one level I trauma center over a 24-month period were reviewed; excluded were patients not requi ring trauma team consultation, or those with either incomplete records , severe head injury (Glasgow Coma Scale score less than or equal to 8 ), or age <14 years, The SI was calculated from ED admission vital sig ns, Receiver operating characteristic (ROC) curves were used to find t he value of the SI that maximized the sum of sensitivity and specifici ty for predicting each measure, separately; a separate analysis was do ne to determine the optimal SI threshold for predicting any of the sev erity measures, Results: 1,101 cases met study criteria, The optimal S I values (by ROC analysis) for predicting the severity measures were: 1.10 for death <24 hours, 0.71 for ISS greater than or equal to 16, 0. 77 for ICU greater than or equal to 1 day, and 0.85 for BT greater tha n or equal to 2 units, The optimal SI value (by ROC analysis) for any of the above measures was 0.83; use of this SI cutoff provided a sensi tivity of 37% (95% CI 32-42%), a specificity of 83% (95% CI 80-87%), a nd a negative predictive value of 58% (95% CI 54-61%) for any measure. This SI threshold predicted between 24% fewer cases and 4% more cases of poor outcome than did the optimal thresholds HR and SEP, respectiv ely. Conclusion: The optimal SI threshold performed similarly to the o ptimal threshold HR or SEP for prediction of injury severity.