Hemostasis

Hemostatic disorders usually manifest as excessive hemorrhage in animals, however certain hemostatic disorders, such as disseminated intravascular coagulation (DIC), are characterized by thrombosis more than hemorrhage, particularly in horses and cats. Historical details and signalment are important when evaluating an animal with a suspected hemostatic disorder. Recurrent clinical signs, particularly in a young animal, are […]

Tests for hemostasis generally fall under the categories of primary and secondary hemostasis, fibrinolysis and testing for inhibitors. We have also provided a diagnostic algorithm for test interpretation and a table summaries of thrombocytopenia mechanisms and interpretation of coagulation screening assays. Further information is available on all coagulation tests offered by the Animal Health Diagnostic Center’s Comparative

Introduction Definition: Fibrinolysis involves the dissolution of the fibrin clot by the protease, plasmin and takes place in solid phase, i.e. on the surface of cells and fibrin. Constituents: The fibrin clot, tissue-type plasminogen activator (tPA), contact pathway factors (FXII, prekallikrein, high molecular weight kininogen [HMWK]) and plasminogen. Note that there is also urokinase-type plasminogen activator, but

Conceptually, it is useful to separate hemostasis into three processes, primary and secondary hemostasis, and fibrinolysis. However, all processes are activated simultaneously (to varying degrees), and do not occur sequentially, in vivo. Also, hemostasis does not proceed in the fluid phase. It is restricted to cell surfaces (primarily platelets, endothelial cells and fibroblasts, but also

The most important aspect of diagnosis of hemostatic disorders is the collection and submission of an optimal sample for testing. Unlike many other clinical pathologic tests, coagulation assays are unforgiving with respect to poor sample collection and handling. Many causes of prolonged clotting times or decreased factor concentrations are artifactual, due to poor sample collection

Introduction Definition: Secondary hemostasis is defined as the formation of insoluble, cross-linked fibrin by activated coagulation factors, specifically thrombin. Fibrin stabilizes the primary platelet plug, particularly in larger blood vessels where the platelet plug is insufficient alone to stop hemorrhage. Synonym: Coagulation Constituents: These consist of cells, enzymatic and non-enzymatic coagulation factors, protein substrates, calcium

Introduction Definition: Primary hemostasis is defined as the formation of the primary platelet plug. This serves to plug off small injuries especially in microvessels (< 100 μm) in mucosal tissues (respiratory, gastrointestinal, genitourinary tracts). Platelets are not only involved in platelet plug formation but are also crucial for formation of fibrin (secondary hemostasis). Activated platelets

Hemostasis is a complex physiological process involving cells (platelets, especially but also fibroblasts), and soluble (coagulation factors and inhibitors) and insoluble proteins (extracellular matrix proteins). The hemostatic system is usually activated upon injury to the blood vessels, which disrupts endothelial cells exposing thrombogenic (or procoagulant) substances in the extravascular space.  Once activated, the hemostatic system