[Antithrombotics: backgrounds with haemostasis and antithrombotic therapy]

The clinical guidelines on antithrombotics, published by the Dutch Institute of Expertise for Oral Healthcare, give advice on policy to be followed in cases of dental procedures involving bleeding. The guidelines allow room for professional assessment of bleeding risks, for which background knowledge about haemostasis, thrombosis and antithrombotic processes is necessary. Normal haemostasis can be divided in several steps: vasoconstriction, primary haemostasis by aggregation of thrombocytes, and secondary haemostasis by the formation of fibrin out of coagulation factors. In the case of thrombosis, a blood clot forms inside a blood vessel, causing obstruction of blood flow to the underlying tissue. Various antithrombotics are prescribed for the prevention and treatment of thrombosis. Thrombocyte aggregation inhibitors only have an effect on primary haemostasis. Vitamin K antagonists influence secondary haemostasis by lowering the production of several coagulation factors. The direct oral anticoagulants have an immediate effect on an activated coagulation factor, and are currently prescribed in large quantities [in the Netherlands]. Low-molecular-weight heparin also inhibits activated coagulation factors, but is not used for long-term antithrombotic therapy since it is administrated subcutaneously.