ABSTRACT
BACKGROUND: Following activation, platelets release small vesicles called platelet-derived microparticles (PMPs). PMPs accelerate thrombin generation and thus clot formation at sites of injury by exposing the procoagulant membrane phospholipid phosphatidylserine (PS). The role of PMPs in coagulopathy and hemorrhage following trauma remains elusive. We hypothesized that low levels of PS-positive PMPs (PS + PMPs) would be associated with impaired clot formation. METHODS: This is a prospective observational study of 210 trauma patients admitted directly to a Level 1 trauma center. Plasma levels of PS + PMPs were determined by flow cytometry. Coagulation status was assessed by rotational thrombelastometry, and impaired clot formation was defined by an α angle less than 63 degrees using the tissue factor-based EXTEM reagent. Transfusion requirement was assessed by number of units of red blood cells (RBCs) transfused within 24 hours of admission; platelet aggregation capacity was evaluated by the Multiplate assay; and injury severity was determined by the Injury Severity Score (ISS). RESULTS: The median ISS was 17, and blood samples were obtained after a median of 65 minutes following injury. Significantly lower levels of PS + PMPs were found in patients with impaired clot formation (p < 0.001). A low level of PS + PMPs was associated with a higher number of RBCs transfused during the initial 24 hours after admission (p < 0.03) when corrected for risk factors, for example, platelet count, hemoglobin level, and ISS. Platelet aggregation and PS + PMPs did not correlate significantly. CONCLUSION: Low levels of PMPs were associated with impaired clot formation in trauma patients at admission and also with the number of RBC transfusions. This suggests that PMPs may play an important and not previously investigated role in trauma-induced coagulopathy. LEVEL OF EVIDENCE: Prognostic study, level III.
ABSTRACT
It remains to be debated whether traumatic brain injury (TBI) induces a different coagulopathy than does non-TBI. This study investigated traditional coagulation tests, biomarkers of coagulopathy, and endothelial damage in trauma patients with and without TBI. Blood from 80 adult trauma patients was sampled (median of 68 min [IQR 48-88] post-injury) upon admission to our trauma center. Plasma/serum were retrospectively analyzed for biomarkers reflecting sympathoadrenal activation (adrenaline, noradrenaline), coagulation activation/inhibition and fibrinolysis (protein C, activated protein C, tissue factor pathway inhibitor, antithrombin, prothrombin fragment 1+2, thrombin/antithrombin complex, von Willebrand factor, factor XIII, d-dimer, tissue-type plasminogen activator, plasminogen activator inhibitor-1), immunology (interleukin [IL]6), endothelial cell/glycocalyx damage (soluble thrombomodulin, syndecan-1), and vasculogenesis (angiopoietin-1, -2). Patients were stratified according to: (1) isolated severe head/neck injuries (Abbreviated injury score [AIS]-head/neck ≥ 3, AIS-other<3) (isoTBI); (2) severe head/neck and extracranial injuries (AIS-head/neck ≥ 3, AIS-other>3) (sTBI+other); and (3) injuries without significant head/neck injuries (AIS-head/neck<3, including all AIS-other scores) (non-TBI). Twenty-three patients presented with isoTBI, 15 with sTBI+other and 42 with non-TBI. Acute coagulopathy of trauma shock, defined as activated partial thromboplastin time (APTT) and/or international normalized ratio (INR)>35 sec and>1.2, was found in 13%, 47%, and 5%, respectively (p=0.000). sTBI+other had significantly higher plasma levels of adrenaline, noradrenaline, annexin V, d-dimer, IL-6, syndecan-1, soluble thrombomodulin, and reduced protein C and factor XIII levels (all p<0.05). No significant biomarker differences were found between isoTBI and non-TBI patients. Injury severity scale (ISS) rather than the presence or absence of head/neck injuries determined the hemostatic and biomarker response to the injury. The coagulopathy identified thus reflected the severity of injury rather than its localization.
