Redefining Fibrinolytic Insufficiency in Sepsis-Associated DIC.

Sepsis disrupts the physiological balance between coagulation and fibrinolysis, resulting in a state in which fibrin formation exceeds fibrin removal and drives microvascular thrombosis, organ failure, and mortality. Although an early burst of endothelial tissue-type plasminogen activator (t-PA) may transiently increase plasmin generation, this phase is rapidly eclipsed by sustained upregulation of plasminogen activator inhibitor-1 (PAI-1), dysregulated activation of thrombin-activatable fibrinolysis inhibitor, depletion of endogenous anticoagulants, and progressive endotheliopathy. Beyond inhibitor excess, emerging evidence indicates that a quantitative defect in plasminogen is a central contributor to fibrinolytic insufficiency. Neutrophil extracellular traps (NETs) contain elastase, which cleaves plasminogen into inactive fragments, reducing functional plasminogen availability and impairing fibrin-bound plasmin generation. When functional plasminogen falls below rate-limiting levels, fibrin surfaces cannot efficiently support plasmin formation, resulting in persistent microvascular fibrin deposition despite elevated D-dimer concentrations. This NET-plasminogen axis links immunothrombosis to the "fibrinolytic insufficiency phenotype observed in sepsis-induced coagulopathy and overt disseminated intravascular coagulation (DIC)." Clinically, hypofibrinolysis is characterized by high D-dimers, elevated PAI-1, reduced plasmin generation, and low fibrinolytic activity on viscoelastic testing. Multimodal assessment integrating biomarker panels and viscoelastic assays, including t-PA- or urokinase-challenged protocols, may improve risk stratification. Therapeutic strategies largely targeted coagulation; however, persistent hypofibrinolysis limits their effectiveness. Translational data demonstrate that plasminogen supplementation restores functional plasminogen levels and normalizes plasmin generation in septic patients and in experimental DIC, providing proof of concept for fibrinolysis-directed therapy. Future progress requires standardized definitions, functional fibrinolytic phenotyping, and phenotype-guided clinical trials to restore the coagulo-fibrinolytic balance in sepsis.