Definition

Disseminated intravascular coagulation (DIC) is a coagulation disorder characterized by ongoing activation of the coagulation cascade in response to a clinical or systemic event. Organ damage and death are the result of widespread microvascular bleeding and thrombosis.

Pathophysiology

The diagnosis of DIC is usually secondary to a systemic illness or insult. Coagulation activation ranges from mild thrombocytopenia and prolongation of clotting times to acute DIC characterized by extensive bleeding and thrombosis. During overactive coagulation, the available platelets and coagulation factors are consumed. This consumption along with fibrinolysis exhausts the hemostatic balance. Rarely is the primary cause a coagulation deficiency or dysfunction.

Several factors play an important role in the pathogenesis of DIC, including the propagation of thrombin, alteration in anticoagulant activity, impaired functioning of the fibrinolytic system, and the release of cytokines. Tissue factor release is considered to play the most important role in the development of a hyperthrombinemia in DIC. Mediators such as antithrombin and tissue factor pathway inhibitor that normally inhibit coagulation are altered. Reasons for this impairment include septicemia, liver impairment, capillary leakage, and the release of endotoxins and proinflammatory cytokines. The initial increased fibrinolytic activity is followed by the release of plasminogen activator inhibitor type 1 (PAI-1), which in turn impairs fibrinolysis and leads to accelerated thrombus formation in DIC. And, lastly, activated protein C mediates the release of inflammatory cytokines such as TNF and ILs from endothelial cells. Complement activation and kinin generation increase the coagulation response, leading to subsequent vascular occlusion.