MoD 6 Thrombosis and Embolism Flashcards Preview

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Flashcards in MoD 6 Thrombosis and Embolism Deck (32):

What 4 things does successful haemostasis depend on?

Vessel wall
Coagulation system
Fibrinolytic system


What do blood vessels do upon injury?

Constrict to limit blood loss


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?

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
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