ABSTRACT
This chapter incorporates recommendations from an international consensus statement on the prevention and treatment of venous thromboembolism. Haemostasis is the response to stop bleeding following injury to a blood vessel. It involves simultaneous primary haemostasis due to vasoconstriction and adhesion of platelets, and secondary haemostasis by initiation of a coagulation cascade. Platelet microparticles appear when haemostasis is activated and with inflammation, malignancy, angiogenesis and immune reactions. Endothelial cells are normally anti-thrombotic due to negatively charged heparin-like glycosaminoglycans such as heparan sulphate and phospholipids, platelet and coagulation inhibitors and fibrinolysis activators. Endothelial trauma also causes exposed tissue to become pro-thrombotic due to secretion of platelet-activating agents and fibrinolysis inhibitors. Thrombin also activates thrombin activatable fibrinolysis inhibitor which protects the clot from fibrinolysis. Fibrinolysis is an enzymatic reaction that breaks down a fibrin clot to limit the extent of thrombosis. Plasmin activity is regulated to prevent widespread fibrinolysis by plasminogen activator inhibitor, a 2 antiplasmin, a 2 macroglobulin and thrombin-activatable fibrinolysis inhibitor.
