Obesity is linked to hypercoagulability with an increased risk of venous thromboembolic events (VTE) in the uninjured population. Therefore, we hypothesize that obesity (Body Mass Index (BMI) ≥30 kg/m) is associated with a hypercoagulable state postinjury characterized by increased clot strength and resistance to fibrinolysis.
Our prospective Trauma Activation Protocol database includes all trauma activations patients for whom a rapid thromboelastographic (TEG) is obtained within 60 minutes postinjury prior to any transfusions. The dataset was then stratified by BMI and subjects with BMI ≥ 30 kg/m were compared to those with BMI<30 kg/m). The following TEG measurements were obtained: activated clotting time (ACT), clot formation rate (angle), maximum clot strength (MA), and % clot lysis 30 min after MA (LY30, %). Fibrinolysis shutdown (SD) was defined as LY30 < 0.6% and hyperfibrinolysis (HF) as LY30 > 7.6%. Continuous variables are expressed as median (IQR).
Overall, 687 patients were included of whom 161 (23%) had BMI ≥ 30kg/m (BMI30). The BMI30 group was older, had a lower proportion of males and of blunt trauma, and were less severely injured. After adjustment for confounders, BMI30 was independently associated with lower odds of MA<55mm (OR 0.28; 95% CI 0.130.60) and of HF (OR 0.31; 95% CI 0.10- 0.97) and higher odds of SD (OR 1.82; 95% CI 1.09-3.05). No independent association was observed with angle<65 (OR 0.57 95% CI 0.30-1.05). While VTEs were more frequent among BMI30 patients (5.0 vs 3.3%), this did not reach significance after confounding adjustment (p=0.11).
Obesity was protective against diminished clot strength and hyperfibrinolysis, and obesity was associated with an increased risk of fibrinolytic shutdown in severely injured patients. These findings suggest a relative hypercoagulability. Although no difference in VTEs was noted in this study, these findings may explain the higher rate of VTEs reported in other studies.