5. Haemostasis, Thrombosis and Embolism

Question 1

What does successful haemostasis rely on?

Answer 1

Vessel wall, platelets, coagulative system and fibrinolytic system.

Question 2

What is the role of blood vessles in haemostasis?

Answer 2

Constrict ot limit blood loss.

Question 3

What are the roles of platelets in haemostasis?

Answer 3

Adhere to damaged vessel wall and each other to form a platelet plug. Also platelet release reaction.

Question 4

What is the platelet release reaction?

Answer 4

ATP -> ADP. ADP causes platelet aggregation. 5HT and platelet factor 3 are also released, PF3 is important in coagulation.

Question 5

What type of reaction is coagulation?

Answer 5

A cascade of reactions where a series of inactive components are converted to active components.

Question 6

What are the key conversions in the coagulation cascade?

Answer 6

Prothrombin to thrombin. Thrombin causes fibrinogen to convert to fibrin.

Question 7

What are some thrombin inhibitors?

Answer 7

Anti-thrombin III, alpha 1 anti-trypsin, alpha 2 macroglobulin, protein C and S.

Question 8

What could an inherited deficiency of protein C and S lead to?

Answer 8

Thrombosis.

Question 9

What is fibrinolysis?

Answer 9

Breakdown of fibrin.

Question 10

How is the endothelium anti-thrombotic?

Answer 10

Plasminogen activators, prostacyclin, nitric oxide and thrombomodulin.

Question 11

What is thrombosis?

Answer 11

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

Question 12

Why does thrombosis occur?

Answer 12

Abnormalities of the vessel wall: atheroma, direct injury or inflammation.
Abnormalities of blood flow: stagnation or turbulence.
Abnormalities of blood components: smokers, post-partum, post-op.

Question 13

What is the appearance of arterial thrombi?

Answer 13

Pale, granular, lines of Zahn, and lower cell content.

Question 14

How does the amount of blood cells and fibrin in a thrombi change the colour?

Answer 14

More blood cells makes it more red/brown, more fibrin makes it more yellow.

Question 15

What is the appearance of venous thrombi?

Answer 15

Soft, gelatinous, deep red and higher cell content.

Question 16

What are the outcomes of thrombosis?

Answer 16

Lysis, propagation, organisation, recanalisation, or embolism.

Question 17

What happens in lysis of thrombi?

Answer 17

There is complete dissolution of the thrombus. The fibrinolytic system is active and bloodflow is restored. This is most likely when thrombi are small.

Question 18

What happens in propagation of thrombi?

Answer 18

There is progressive spread of thrombosis. Distally in arteries and proximally in veins, the thrombus gets bigger in the direction of flow of blood.

Question 19

What happens in organisation of thrombi?

Answer 19

It is a reparative process with ingrowth of fibroblasts and capillaries. The lumen remains obstructed.

Question 20

What happens in recanalisation of thrombi?

Answer 20

Bloodflow is re-established but usually incompletely. One of more channels formed through organising thrombus.

Question 21

What happens in embolism of thrombi?

Answer 21

Parts of the thrombus breaks off and travels through the bloodstream until it lodges at a distant site.

Question 22

What are the effects of arterial thrombosis?

Answer 22

Ischaemia or infarction - depends on site and collateral circulation.

Question 23

What are the effects of venous thrombosis?

Answer 23

Congestion, oedema, ischaemia and infarction (more unlikely if venous).

Question 24

What is an embolism?

Answer 24

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

Question 25

What is the most common type of embolism?

Answer 25

Thrombo-embolism, 90% of emboli.

Question 26

What causes air embolism commonly?

Answer 26

Slitting the throat as the air and residual blood mixes to form a froth that is difficult to circulate and causes an embolism.

Question 27

When can amniotic fluid by a cause of embolism?

Answer 27

Mostly with illegal abortions but can still happen in childbirth today or miscarriages.

Question 28

Where will the following thrombo-emboli end up?

a. from systemic veins
b. from the heart
c. from atheromatous carotid arteries
d. from atheromatous abdominal aorta

Answer 28

a. to the lungs, pulmonary embolism.
b. via the aorta to renal, mesenteric, and other arteries.
c. pass to the brain, causes a stroke.
d. to arteries of the legs.

Question 29

What are the predisposing factors of deep vein thrombosis?

Answer 29

Immobility or bed rest, post-operative, pregnancy and post-partum, oral contraceptive especially in the past, sever burns, cardiac failure, and disseminated cancer.

Question 30

How can DVT be prevented?

Answer 30

High risk patients identified and offered prophylaxis: heparin sub-cutaneously, or leg compression during surgery.

Question 31

How can DVT be treated?

Answer 31

Using intravenous heparin or oral warfarin.

Question 32

Wat are the effects of the different classes of pulmonary embolism?

Answer 32

Massive PE: >60% reduction in bloodflow and is rapidly fatal.
Major PE: medium sized vessels blocked, short of breath and coughing up blood stained sputum.
Minor PE: small peripheral pulmonary arteries blocked, asymptomatic or minor shortness of breath.

Question 33

What does recurrent minor pulmonary embolism lead to?

Answer 33

Pulmonary hypertension.