Hematocrit as a predictor of significant injury after penetrating trauma.

A study was undertaken to determine if there are differences in hematocrit (HCT) during the initial evaluation of patients with and without significant visceral intrathoracic or intraabdominal injury after penetrating trauma and, if so, the predictive value of this parameter. Sixty consecutive adults with potentially significant penetrating trauma who presented to an urban municipal trauma center during a 10-week period were studied. Diagnostic variables were recorded for all patients at risk for significant injury, defined as intrathoracic or intraabdominal injury requiring surgical intervention. Patients were ultimately grouped on the basis of operative findings or observation to discharge. Acquired variables included vital signs, initial HCT (HCT-0), HCT at 15 minutes (HCT-15), HCT at 30 minutes (HCT-30), and fluid administered. Twenty-one patients had significant injuries (INJ), and 39 did not (NO-INJ). INJ patients had lower HCT values than NO-INJ on presentation (35% +/- 6% and 41% +/- 5%, respectively). At presentation, a low HCT was predictive of significant injury, but a normal HCT did not preclude injury. The changes in HCT from arrival to 15 minutes, between INJ and NO-INJ patients, were similar (-1.5% +/- 3% and -0.6% +/- 3% respectively). Only when the decrease in HCT was > or =6.5% from presentation measurements was it predictive of injury. During the first 15 minutes a decrease in HCT of > or =6.5% had a positive predictive value and specificity of 1.0. The change in HCT between 15 and 30 minutes was less useful. There was a large difference between the amounts of fluid given to injured and uninjured patients, which may have been responsible for some of the differences in HCT between the two groups. These results show that HCT may have some diagnostic utility during the early management of penetrating trauma. Presentation with an HCT below normal, or an early decrease in HCT, is an indicator of potential injury. Although many patients with serious internal injuries do not manifest large decreases early after presentation, those who do have a high probability of internal injury. The lower the HCT, or the greater the decrease, the greater the probability that a significant injury exists.