Identifying Life-Threatening Shock in the Older Injured Patient: An Analysis of the National Trauma Data Bank

Abstract

Reliance on traditional vital signs (TVS), particularly in older patients, to identify life-threatening shock after injury may be unreliable. Shock index (SI), defined as heart rate divided by systolic blood pressure (SBP), may be a better indicator of early shock after injury than TVS. Multiplying age by SI (age x SI) may be better in older injured patients. We hypothesized that age x SI would be a better predictor of 48-hour mortality in old patients (age, >55 years) compared with TVS, whereas for young patients (age, <or=55 years), SI would be a better predictor than TVS. Version 8.1 of the National Trauma Data Bank was queried for incidents of blunt, non-neurologic injury occurring during 2007, to patients aged 18 to 81 years. Areas under the receiver operating characteristic curves (AUC) were compared for TVS, SI, and age x SI in young and old patients for predicting 48-hour mortality. A total of 189,574 incidents were identified. Overall 48-hour mortality was 1.18%. For young patients, there was no difference between SBP (AUC, 0.654) and SI (AUC, 0.655) for predicting 48-hour mortality. For old patients, age x SI (AUC, 0.693) was a better predictor of 48-hour mortality compared with heart rate (AUC, 0.626; p < 0.0001), SBP (AUC, 0.657; p < 0.0002), or SI (AUC, 0.684; p < 0.008). TVS are inadequate predictors of shock after non-neurologic blunt injury. Using SI in the young and age x SI in old to identify patients at risk for early mortality after blunt injury could result in earlier definitive treatment.