Antithrombin III and trauma patients: factors that determine low levels.

A prospective (cohort) study was conducted to determine the incidence of low antithrombin III (AT III) levels and the association with selected clinical variables in adult trauma patients. One hundred sixty AT III levels were obtained on 50 consecutive trauma admissions to a community-based level I trauma center. Antithrombin III levels were drawn as soon after admission as possible and every other day thereafter. Thirty-one patients (62%) had at least one low AT III level (< 80%), whereas 15 concurrently drawn control levels were all > or = 90%. Low AT III levels were more common in patients with one or more of the following: base deficit less than -4 (39% vs. 0, p = 0.002); Injury Severity Score > 15 (48% vs. 16%, p = 0.04); and blood transfusion (32% vs. 5%, p = 0.04). All other variables (shock, surgical intervention, subcutaneous heparin, and sequential compression devices) were not statistically significant, although all six patients with shock had low levels. In conclusion, over 60% of adult trauma patients had low AT III levels at some time during hospitalization and these patients were clearly more severely injured. Further studies are required to determine if these patients are more susceptible to thromboembolic phenomena.