13. Thrombosis, embolism, DIC Flashcards
Define thrombus
A mass that is formed by the constituents of the coagulation system within blood vessels or heart. Composed mostly of numerous platelets and red blood cells trapped in a mesh of an insoluble protein called fibrin.
What do endothelial cells posses?
Anti-thrombotic qualities
-synthesise prostacyclin and nitric oxide which cause vasodilation and inhibit platlet aggregation
What happens when endothelial cells are activated?
Secrete or express prothrombotic substances
What do platelets do when they become active?
When activated they become sticky by increasing the expression of cell surface receptors
What is the coagulation cascade?
Complex interaction of proteins resulting in the formation of an insoluble protein called fibrin
Where are the precursor forms of fibrin synthesised?
In the liver
What is the intrinsic coagulation cascade?
Activation requires local damage to the endothelial surface of a blood vessel
What is the extrinsic pathway of the coagulation cascade?
Activation requires tissue injury
Starts from blood vessel injury and release of tissue factor
Describe the morphology of a thrombus?
Successive deposition of platelets and fibrin
Appears as alternating bands (lines of zahn)
Where does a thrombosis occur?
Any vascular system, arterial in the heart, venous
What are the three predisposing situations known as and what are they?
Virchows Triad
Changes in the intimal surface of the vessels
Changes in the pattern of blood flow
Changes in the blood constituents
What are the risk factors of virchows triad?
Immobilisation Bed rest Surgery Obesity Hyper-coagulable blood Pregnancy
What are the risk factors of DVT?
Immobilisation Bed rest Surgery Obesity Hyper-coagulable blood Pregnancy
What is used to reduce and remove risk factors?
Elastic stockings
Early mobilisation
Anti-coagualtion
Whats is an arterial thrombosis?
Sudden onset of a severe impairment of organ function such as “stroke” or “heart attack”
What is a venous thrombosis?
Swelling blood clot in the lower limbs tissue
Swollen red and tender
What is an embolism?
A mass of material that can move in the vascular system and become lodged in some vessel and blocks it lumen
What do pulmonary embolisms lead to?
Venous thrombosis in deep leg veins
What is the most common type of embolism?
Thromboembolism
What are the sources of arterial emboli?
Carotid artery Mural thrombus - left atrium Endocartitis in aortic and mitral valves Mural thrombus - left atrium Aortic atherosclerosis
What are common sites of infarction as a consequence of arterial emboli?
Brain Retina Heart (LV) Spleen Kidney Small intestine Lower leg
Why are plumonary embolisms the most common?
Most arrest at the first vascualar bed they meet (lungs)
What are the effects of a pulmonary embolism?
May by small and not notice
Organise and cause minor reduction in lung function
Numerous emboli can cause marked reduction in lung function over time
Medium emboli can cause acute resp and cardiac problems
Large emboli can cause sudden death
What is Disseminated Intravascular Coagualtion
Usually a life threatening condition, causes include sepsis, obstetric complication or malignancy.
Multiple thrombi throughout organs which consumes clotting factors and there is subsequently simultaneous bleeding
