Hemostasis

Monitoring of heparin or direct or acting anticoagulant (DOAC) therapy is important to ensure appropriate dosing. Direct oral acting anticoagulants are newer drugs that target activated factor X (FXa) and can be given orally unlike heparin-based anticoagulants, which are injectable (subcutaneously or intravenously) The DOACs include rivoraxaban and apixaban, which have been evaluated in dogs, […]

Viscoelastic methods of clot detection are increasingly being used in veterinary medicine for diagnosis of these possible hemostatic states: normocoagulable, hypercoagulable, hypocoagulable, excessive fibrinolysis or reduced fibrinolysis (for reviews see Kol and Borjesson, 2010 and McMichael and Smith, 2011). However, there are some important limitations to the use of these techniques to diagnose hyper- or hypocoagulability, in

Physiologic inhibitors There are physiologic inhibitors for every stage of hemostasis. Some of these inhibitors are physical barriers, e.g. the endothelial cell acts as a physical obstruction between platelets and the matrix proteins that bind and activate them (von Willebrand factor and collagen) and between coagulation factors and their cofactors and substrate, specifically factor VII

Disseminated intravascular coagulation (DIC) is the abnormal (excessive) activation of hemostasis, with subsequent generation of excess thrombin and formation of microvascular thrombi (arterioles, venules, capillaries). As coagulation factors and platelets are consumed, inhibited or cleaved, hemorrhage can ensue. The disorder is not a simple syndrome, but is rather a continuum of hemostasis activation, beginning with

Most animals with hemostatic disorders present because of signs of excessive hemorrhage and diagnostic testing is most frequently performed in these patients. There are tests for each process of hemostasis (primary, secondary and fibrinolysis) as well as global tests of hemostasis that evaluate two or more of these hemostatic processes simultaneously, as well as the

The most commonly used (and available) tests for inhibitors are measurement of antithrombin and protein C activity. Tests for other inhibitors, such as alpha2-antiplasmin, protein Z, protein S, and heparin cofactor II, are either not available, have not been validated for use in animals or are used for research purposes by specific institutions. The presence of acquired

Tests for fibrinolysis involve evaluation of the fibrinolytic pathway. Unfortunately, measurement of many components of the fibrinolytic pathway, including plasminogen, tissue plasminogen activator, plasminogen activator inhibitor, have not been developed or validated in animals, or those that have, work poorly. Therefore, these tests are not offered routinely, which is a major shortcoming when evaluating animals

Fibrinogen concentration can be measured in three ways, the most accurate of which is clottable fibrinogen. Heat precipitation Heat precipitation is performed on anticoagulated samples (EDTA preferred). It is mostly used for determination of fibrinogen concentration as an indicator of inflammation in horses, ruminants and camelids and can be included on routine hemograms in horses.

Screening coagulation assays are the “bread and butter” of secondary hemostasis testing and consist of the prothrombin time (PT), activated partial thromboplastin time (APTT) and the thrombin clot time. The thrombin clot time can be modified to measure fibrinogen concentration. The activated coagulation time (ACT) is an in-house point-of-care test that provides some information on

von Willebrand factor is a large glycoprotein, composed of a series of protein polymers (multimers), which consist of repeating subunits linked by disulfide bonds. The number of subunits in each multimer varies, imparting a range of molecular weights to the multimers. The multimeric structure of vWf is important as the higher molecular weight multimers are