MoD 6 Thrombosis and Embolism Flashcards
What do blood vessels do upon injury?
Constrict to limit blood loss
What 4 things does successful haemostasis depend on?
Vessel wall
Platelets
Coagulation system
Fibrinolytic system
What do platelets do upon injury?
Adhere to damaged vessel wall and each other
Form platelet plug
What clotting factor do both the extrinsic and intrinsic pathway activate?
Factor 10
What does factor 10 activate and what does the product do?
Cleaves prothrombin to thrombin which converts fibrinogen to fibrin and activates factor 13 which cross links the fibrin
Which factors does thrombin exert positive feedback on?
Five, eight and eleven
What are some thrombin inhibitors?
Anti-thrombin iii
Alpha 1 antitrypsin
Alpha 2 macroglobulin
Protein C/S
Inherited deficiencies in which thrombin inhibitors cause thrombophilia and thrombosis?
Anti thrombin iii
Protein C/S
What is fibrinolysis?
Breakdown of fibrin by plasmin
What is fibrinolytic therapy and when is it used?
Clot/ thrombus busters e.g streptokinase which activates plasminogen.
Very drastic only used in serious situations e.g coronary artery occlusion or thrombus cutting off circulation to a limb
What is thrombosis?
Formation of a solid mass of blood within the circulatory system during life
What is Virchow’s triad?
Changes in blood flow- stagnation, turbulence
Changes in vessel wall- atheroma, injury, inflammation
Changes in blood components- smokers, pregnancy
These are what causes thrombus to form
What are the differences between arterial thrombi and venous thrombi?
Arterial- pale, granular, lines of zahn, lower cell content
Venous- deep red, soft, gelatinous, higher cell content
What are the effects of arterial thrombosis?
Ischaemia, infarction
Depends on site and collateral circulation
What are the effects of venous thrombosis?
Congestion, oedema, ischaemia ( if tissue pressure die to oedema> arterial pressure), infarction
What are the outcomes of thrombosis?
Lysis- complete dissolution of thrombus. Fibrinolytic system active, blood flow re-established. Most likely with small thrombus
Propagation- progressive spread of thrombus (distally in arteries, proximally in veins)
Organisation- reparative process with in growth of fibroblasts and capillaries. Lumen remains obstructed
Recanalisation- blood flow re-established usually incompletely as a channel formed by organising thrombus
Embolism- part of thrombus breaks off, travels through blood stream and lodges at distant site e.g coronary artery causing MI
What is an embolism?
Blockage of blood vessel by a solid, liquid or gas at a site distant from its origin
Most emboli are thrombo-emboli, what are some other types?
Air Amniotic fluid Nitrogen (bends) Medical equipment Tumour cells
Where will thrombi from systemic veins cause embolism?
Will cause pulmonary embolism in lungs as won’t get stick in large veins near heart, next place where small artery where can get stuck is, is lungs
Where will thrombi from heart cause embolism?
Renal, mesenteric and other arteries
Where will thrombi from atheromatous carotid arteries cause embolism?
Brain (stroke)
Where will thrombi from atheromatous abdominal aorta cause embolism?
Arteries of legs
What are the consequences of pulmonary embolisms?
Massive- over 60% reduction in blood flow. Rapidly fatal
Major- medium sized vessels blocked. Shortness of breath, cough, blood stained sputum
Minor- small peripheral pulmonary arteries. Asymptomatic or minor shortness of breath
Recurrent PEs cause pulmonary hypertension
What can cause deep vein thrombosis?
Immobility/ bed rest Post-operative Pregnancy and post partum Oral contraceptives Severe burns Cardiac failure Disseminated cancer
How is DVT treated?
Intravenous heparin- anticoagulant, co factor for anti thrombin 3
Oral warfarin- interferes with synthesis of Vit K dependent clotting factors, slow effect
What causes fat embolism?
Fractures of long bones
Lacerations of adipose tissue
Gives rash, shortness of breath, confusion
How do cerebral embolisms occur?
Atrial fibrillation causes stasis which causes thrombus
In left heart can go to brain and cause stroke or TIA
What is an iatrogenic embolism?
Embolism due to medical treatment e.g air embolism from an injection
What is a nitrogen embolism?
Nitrogen bubbles form in blood with rapid decompression
The bends
What is disseminated intravascular coagulation (DIC)?
Pathological activation of coagulation mechanisms that occurs in response to a variety of diseases
Small clots form throughout body, disrupting normal coagulation as they use up all the clotting factors causing abnormal bleeding from the skin
Triggers: infection, trauma, liver disease, obstetric complications
What is haemophilia?
Type A- factor 8 deficiency
Type B-factor 9 deficiency
X linked recessive so more common in boys
Varying severity, due to nonsense point mutation
Haemorrhage into major joints, synovial hypertrophy, pain
Muscle bleeding causes pressure and necrosis of nerves (painful)
Can haemorrhage into retroperitoneum or urinary tract
Treated with self administer factor replacement therapy
What is thrombocytopenia?
Platelet count way below reference range Due to: failure of platelet production Increase in platelet destruction Sequestering of platelets Usually accompanied by bone marrow disfunction e.g anaemia, leukaemia If due to sequestering could be DIC
