Vital Signs and Estimated Blood Loss in Patients with Major Trauma: Testing the Validity of the ATLS Classification of Hypovolemic Shock

The Advanced Trauma Life Support (ATLS) classification of shock is a widely accepted and utilized tool to assess the severity of trauma, direct treatment, and predict morbidity and mortality. This retrospective case review from England and Wales sought to validate the classification of shock based on physiological parameters taught in ATLS. The authors reviewed all blunt and penetrating traumas included in the Trauma Audit and Research Network database between 1989 and 2007. Patients were included if they were older than 16 years and admitted to the hospital for more than 3 days, admitted to an intensive care unit, or died within 93 days of injury. Patients were excluded if they were over 65 years of age with isolated orthopedic injuries, or of any age with isolated limb injuries. Included patients had an estimation of blood loss based on mechanism of injury (e.g., pelvic fractures correspond with 23% blood loss by volume), and based on this, were then assigned an ATLS shock classification. The patients’ actual vital signs were then compared to ATLS predictions. The principal findings were that as estimated blood loss increased, heart rate (HR) was seen to increase and systolic blood pressure (SBP) to decrease as predicted by ATLS, but not to the same magnitude. For example, in Class 4, where ATLS predicts a HR > 140 beats/min, a maximal HR of only 114 was seen. Furthermore, there was significant overlap between patients in the different groups. No statistical difference was noted with an increasing respiratory rate nor decreased Glasgow Coma Scale (GCS) score with increasing shock classification, although shock class 4 was associated with GCS ≤ 8 in 25% of patients. A significant limitation in this analysis was that the amount of intravenous fluids administered was recorded in only 5.3% of patients, and the subsequent effect on the recorded patient's vitals could therefore not be quantified in the vast majority. Nevertheless, the authors concluded that the ATLS guidelines, although correct in their assertion that vital signs do trend with increasing blood loss, need to be adjusted so as to avoid underestimating the severity of injury.