Cardinal Health

Preventing Venous Thromboembolism: A Healthcare Professional Guide to Intervention 5 What is VTE? When a clot develops and persists in a deep vein it is a deep vein thrombosis (DVT). A thrombus that breaks away from a vein wall and floats freely in the blood stream is an embolus. An embolus that travels via the venous system to the vessel that carries blood from the heart to the lungs (pulmonary artery) is called a pulmonary embolism (PE). A PE is a very serious and potentially fatal complication. DVTs also have long term complications. These are known as post thrombotic syndrome and may include chronic pain, swelling and or ulceration of the skin. Clot Formation. A blood clot is a coagulation of red and white blood cells, platelets and clotting factors localised within an insoluble fibrin network. • The haemostatic systemmaintains the balance between coagulation and lysis with three processes: - clot formation - anticoagulation - fibrinolysis • When a blood vessel is injured, it constricts to minimise blood loss. • Then, platelets adhere to the exposed sub endothelium and release substances that attract additional platelets, creating a feedback cycle that continues to adhere and attract platelets. • Circulating fibrinogen binds to the platelets and forms a soft plug composed of platelets and fibrin. This initial response of soft plug formation is followed by a cascade of events activating clotting factors that interact to further activate the coagulation cascade. • Fibrinogen is converted to fibrin resulting in a stable clot made up of fibrin, platelets and red blood cells. If the process of clot formation continues unchecked by anticoagulation and fibrinolysis, it can cause thrombosis. Where Do Clots Form? • In DVT a blood clot forms in the deep veins of the peripheries, most commonly in the legs, including the popliteal vein (behind the knee), femoral vein (of the thigh), and iliac veins of the pelvis. • PE generally arise from proximal thromboses 1 . • Femoral DVTs are responsible for 75% of fatal PE 2 . Proximal Distal 49% 49% OF THROMBI OCCUR IN THE VEINS OF THE THIGH AND POPLITEAL SPACE WITHOUT CALF INVOLVEMENT 1 Maternity - Where Do Clots Form? • When DVT occurs during pregnancy, it is more likely to be proximal, massive, and in the left lower extremity 3 . • Up to 90% of DVTs in pregnant women occur in the left leg, most are ileo-femoral 4 . • Pulmonary emboli generally arise from proximal thrombosis 1 . Proximal Distal 71% 71% OF DVTS IN MATERNITY PATIENTS WERE PROXIMAL WITH NO CALF INVOLVEMENT 4