Fibrinolysis and Antifibrinolytics

The balance between hemostasis and fibrinolysis can be lost in various situations, due to ineffective fibrinolysis in the setting of thrombosis or excessive fibrinolytic activity contributing to hemorrhage. Key players in the fibrinolytic system include plasminogen activators and inhibitors, plasmin and its precursor plasminogen. Disorders of fibrinolysis are challenging to diagnose due to limited availability of appropriate tests. D-dimer measurement is widely available, but does not allow evaluation of the balance between pro- and antifibrinolytic factors and hence cannot identify hypo- or hyperfibrinolysis. Individual assays of fibrinolytic proteins may be available at reference laboratories but currently, viscoelastic coagulation tests offer the best way to identify hypo- or hyperfibrinolysis at the point of care. When hyperfibrinolysis is identified or highly suspected, antifibrinolytic agents such as epsilon-aminocaproic acid and tranexamic acid can be used therapeutically. Although experience with these agents in veterinary medicine is limited, recent studies suggest they may be safe and effective in specific veterinary patient populations. Therapeutic thrombolysis is uncommonly performed in veterinary medicine, but involves administration of supraphysiological doses of tissue plasminogen activator to initiate fibrinolysis. This procedure carries significant risks of hemorrhage and reperfusion injury, but may be life-saving in selected cases.