MOD 5.1 - Haemostasis and Thrombosis Flashcards Preview

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Flashcards in MOD 5.1 - Haemostasis and Thrombosis Deck (38):

What is haemostasis?

The process that stops bleeding


What are the depending factors of haemostasis?

- Vessel wall

- Platelets

- Coagulation System

- Fibrinolytic System


How do blood vessels contribute to haemostasis?

- Constrict

- Decreases blood volume so limits loss


How do platelets contribute to haemostasis?

- Stick to each other and to the walls of the vessels

- Forms a platelet plug


How does the coagulation system contribute to haemostasis?

- Inactive components become activated in a cascade

- Thrombin converts fibrinogen to fibrin for clotting


What is fibrinolysis?

- Breakdown of fibrin i.e. clots

- Done by plasmin


How is the coagulation system regulated?

- Thrombin positively feedbacks on factors 5, 8 and 11 (so increased Thrombin = increase in specific factors)

- Thrombin is inhibited by:

- Antithrombin 3
- Alpha 1 anti trypsin
- Protein C/S


What is used in fibrinolytic therapy and what does this achieve?

When in fibrinolytic therapy used?

- Streptokinase, activates plasminogen to be convertedto plasmin

- Serious cases e.g. coronary artery occlusion


What do hereditary deficiencies in antithrombin 3 or protein C/S cause?

- Thrombophilia (blood is more likely to form clots which increases chance of a DVT)

- Thrombosis


What is thrombosis?

The formation of a solid mass of blood within the circulatory system during life


What are the predisposing factors to thrombosis? (Virchow's Triad)

1) Changes in blood flow (stagnation/turbulence)

2) Changes in blood vessel walls (trauma, atheroma, inflammation)

3) Changes in blood components (Post op, post partum, smoking = increase in coagulation factors)


Describe an arterial thrombus (4)

- Pale
- Granular
- Lines of Zahn (alternating lines of platelets mixed with fibrin)
- Lower cell content


Describe a venous thrombus (4)

- Deep red
- Soft
- Gelatinous
- Higher cell content


What are the differences between a thrombus and a clot?

Clot =
- Physiological/normal
- Outside of blood vessels

Thrombus =
- Pathological/not normal
- In blood vessels


What are the arterial effects of thrombosis? (2)

- Ischaemia
- Infarction

(depends on site and collateral circulation)


What are the venous effects of thrombosis (4)

- Congestion
- Oedema
- Ischaemia (tissue pressure due to oedema > arterial pressure)
- Infarction


What are the outcomes of thrombosis? (5)

- Resolution/lysis
- Recanalisation
- Embolism
- Organisation
- Propagation


Describe resolution/lysis of a thrombus

- Complete breakdown of the thrombus

- Re-establishment of blood flow


Describe recanalisation of a thrombus

- Channels form through the thrombus

- Results in partial re-establishment of flow


Describe embolism of a thrombus

- Part of the thrombus breaks off

- Blocks a different site


Describe organisation of a thrombus

- Reparative process

- Ingrowth of fibroblasts and capillaries

- Still obstructs lumen


Describe propagation of a thrombus

- Thrombus gets bigger in direction of blood flow

- Arteries = Distal
- Veins = Proximal


What is an embolism?

The blockage of a blood vessel by a solid, liquid or gas at a site that is distant from its origin


If 90% of emboli are thrombo-emboli, what makes up the other 10%?

- Air
- Nitrogen
- Amniotic Fluid
- Medical equipment
- Tumour cells
- Fat e.g. from a long bone fracture


What is the passage of an embolism from the heart?

- Via aorta

- Renal, mesenteric or any other arteries


What is the passage of an embolism from systemic veins?

- To lungs via the right heart

- Don't get stuck in large veins near heart


What is the passage of an embolism from atheromatous carotid arteries?

- To the brain (cause of a stroke)


What is the passage of an embolism from atheromatous abdominal arteries?

- To the arteries of the legs


What are the 4 types of pulmonary embolism?

- Massive PE (more than 60% reduction in blood flow = death)

- Major PE (medium vessels blocked = shortness of breath, coughing bloody sputum)

- Minor PE (small peripheral arteries blocked = no symptoms/minor shortness of breath

- Recurrent PE (pulmonary hypertension)


What are some of the causes of deep vein thrombosis? (4)

- Immobility

- Post-op

- Post partum

- Oral contraceptives


How are DVTs treated?

- Intravenous heparin (co factor for anti-thrombin 3)

- Oral Warfarin (interferes with vit K dependent clotting factors)


How is a cerebral embolism caused?

- Atrial fibrillation --> Stagnation of blood --> Thrombus

- Transient ischaemic attack/stroke if from left heart to brain


How is a Iatrogenic embolism caused?

Embolism due to medical treatment e.g. air from an injection


How is a nitrogen embolism caused?

Nitrogen bubble form in blood after rapid decompression e.g. the bends in divers


What is disseminated intravascular coagulation?

- Activation of coagulation mechanisms due to disease

- Small clots form throughout body and use up all clotting factors = abnormal coagulation


What is haemophilia?

- X-linked recessive disorder due to a nonsense point mutation

- Type A = deficiency in factor 8
- Type B = deficiency in factor 9


What can haemophilia cause?

- Haemorrhage into major joints
- Synovial hypertrophy
- Pain


What is thrombocytopenia? What can cause this?

- Platelet count is below reference range

- Platelets not produced OR;
- Too many platelets destroyed OR;
- Sequestering of platelets (being taken up by the spleen

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