Background: 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 [BMI30]) is associated with a hypercoagulable state postinjury characterized by increased clot strength and resistance to fibrinolysis.
Methods: Our prospective Trauma Activation Protocol database includes all trauma activations patients for whom a rapid thrombelastography is obtained within 60 minutes postinjury prior to any transfusions. The data set was then stratified by BMI and subjects with BMI30 were compared with those with BMI less than 30 kg/m). The following thrombelastography measurements were obtained: activated clotting time, clot formation rate (angle), maximum clot strength (MA), and % clot lysis 30 minutes after MA (LY30, %). Fibrinolysis shutdown (SD) was defined as LY30 < 0.6% and hyperfibrinolysis (HF) as LY30 greater than 7.6%. Continuous variables are expressed as median (interquartile range).
Results: Overall, 687 patients were included of whom 161 (23%) had BMI30. The BMI30 group was older, had a lower proportion of males and of blunt trauma, and was less severely injured. After adjustment for confounders, BMI30 was independently associated with lower odds of MA less than 55 mm (odds ratio [OR], 0.28; 95% confidence interval [CI], 0.13-0.60) 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 less than 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).
Conclusion: Obesity was protective against diminished clot strength and hyperfibrinolysis, and obesity was associated with an increased risk of fibrinolytic SD 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.
Level of evidence: Prognostic and Epidemiological, level III.