Major trauma is an independent risk factor for developing venous thromboembolism (VTE). While increases in thrombin generation and/or procoagulant microparticles (MP), have been detected in other patient groups at higher risk for VTE, such as cancer or coronary artery disease, this association has yet to be documented in trauma patients. This pilot study was designed to characterize and quantify thrombin generation and plasma MP in individuals early after traumatic injury.
Blood was collected in the trauma bay from 52 blunt injured patients (case) and 19 non-injured outpatients (controls) and processed to platelet poor plasma for 1) isolation of MP for identification and quantification by flow cytometry; and 2) in vitro thrombin generation as measured by calibrated automatic thrombography (CAT). Data collected are expressed as either mean ± standard deviation or median with interquartile range.
Among cases, 39 men and 13 women (age = 40 ± 17), the injury severity score was 13 ± 11, INR 1.0 ± 0.1, PTT 25 ± 3 (sec), and platelet count 238 ± 62 (thousands). The numbers of total (cell-type not specified) procoagulant MP, as measured by Annexin V staining, were increased compared to non-trauma controls (541 ± 139/μl and 155 ± 148/μl, respectively, p<0.001). There was no significant difference in the amount of thrombin generated in trauma patients compared to controls; however, peak thrombin was correlated to injury severity, (Spearman correlation coefficient R= 0.35, p=0.02).
Patients with blunt trauma have greater numbers of circulating procoagulant MP and increased in vitro thrombin generation. Future studies, to characterize the cell-specific profiles of MP and changes in thrombin generation kinetics post-traumatic injury will determine whether they contribute to the hypercoagulable state observed after injury.