Viscoelastic hemostatic assays in trauma-induced coagulopathy: Precision transfusion, fibrinolytic phenotyping, and future directions.

Trauma-induced coagulopathy (TIC) is a rapidly evolving hemostatic disorder that develops early after severe injury and remains a major determinant of hemorrhagic mortality and thrombotic complications. Conventional coagulation tests provide limited information on the dynamic interactions among coagulation factors, platelets, fibrinogen, and fibrinolysis, often delaying targeted intervention. Viscoelastic hemostatic assays (VHAs), thromboelastography and rotational thromboelastometry, offer real-time whole-blood assessment of clot initiation, propagation, strength, and lysis. This narrative review synthesizes evidence on TIC pathophysiology, emphasizing shock-induced endotheliopathy, activated protein C signaling, platelet dysfunction, and the fibrinolytic spectrum. VHA-guided transfusion is examined against fixed-ratio protocols and low-titer group O whole blood. Equal attention is given to the boundaries of these assays. Because VHAs are static, low-shear tests performed without a vascular surface, they do not interrogate platelet adhesion and cannot detect the receptor shedding characteristic of exhausted platelet syndrome; a normal clot strength with an adequate platelet count may therefore coexist with impaired platelet plug formation. Initiation parameters are sensitive to acidosis, hypothermia, and endogenous heparinoids independently of factor concentration, and conventional assays cannot distinguish pathologic fibrinolytic shutdown from hypo-fibrinolysis. Two constraints limit generalizability of published thresholds. Parameters are not interchangeable between manufacturers or between device generations, so thresholds cannot be transferred, a limitation that also constrains meta-analysis. Reference values differ systematically by sex and age, and current trauma thresholds derive from predominantly male cohorts. Emerging approaches include provocative tissue plasminogen activator-challenged testing, dielectric coagulometry, and flow-based microfluidic assays that interrogate adhesion under shear.