Haemostasis, Thrombus And Embolism

Question 1

What is Haemostasis a balance between?

Answer 1

It is a balance between anticoagulant and procoagulant factors.

Question 2

Name four factors which affect Haemostasis.

Answer 2

Vessel wall, platelets, coagulation system and fibrinolytic system.

Question 3

What is thrombosis?

Answer 3

This is formation of a solid mass of components of the blood which occurs during life.

Question 4

What two features of blood flow can increase the risk of thrombus formation?

Answer 4

Stagnation and turbulence

Question 5

What is Virchow’s triad?

Answer 5

Predisposing factors to thrombus include abnormalities to: vessel wall, blood flow and constituents of blood.

Question 6

What is the clinical relevance of thrombus formation?

Answer 6

It can lead to a possible MI or PE.

Question 7

What is an embolism?

Answer 7

This is a blockage of a vessel by a solid liquid or gas which is at a site distant from its origin.

Question 8

Give some examples of embolisms.

Answer 8

Air, fat, thrombus, medical equipment, tumour cells, nitrogen (the bends after scuba diving)

Question 9

Following injury, what stops blood flow?

Answer 9

The blood vessels constrict to limit blood loss and then platelets adhere to the wall and each other to form a plug.

Question 10

Name two chemicals released when platelets aggregate.

Answer 10

5HT and PF3 (platelet factor 3)

Question 11

What are two causes of platelet aggregation?

Answer 11

Thromboxane A2 and ATP –> ADP

Question 12

Why is control of coagulation particularly important?

Answer 12

Control of coagulation is important because 1ml of blood has sufficient thrombin to change all fibrinogen in the body to fibrin in clotting cascade.

Question 13

Give an example in which coagulation can be controlled.

Answer 13

Anti thrombin III and other thrombin inhibitors

Question 14

What is a consequence of inherited deficiency of anti thrombin III?

Answer 14

This can lead to excessive clot formation

Question 15

Name two substances which lead to fibrinolysis:

Answer 15

Streptokinase and tPA (tissue plasminogen activator)

Question 16

What is the structure of an arterial thrombus like?

Answer 16

These are pale and granular and tend to have a lower cell content. When lots of red blood cells are present they are red or brown in colour.

Question 17

What is a side effect of a venous thrombus?

Answer 17

This can cause infarction, ischaemia, oedema and congestion.

Question 18

What is thrombus lysis?

Answer 18

This is when the fibrinolysis system is active and leads to complete dissolution of the thrombus - common when they are small.

Question 19

What is propagation of a thrombus and in which direction does it occur?

Answer 19

This is when a thrombus increases in size. In the arteries this occurs distally, however in the veins this occurs proximally (it occurs in the direction of blood flow).

Question 20

What is organisation of a thrombus?

Answer 20

This is where there is in growth of fibroblasts and capillaries and the lumen remains obstructed.

Question 21

What is recanalisaiton?

Answer 21

This is where channels form through a blood clot in a lumen and this leads to partial reestablishment of blood flow.

Question 22

What is the most common predisposing factor to DVT?

Answer 22

When there is immobility particularly of the calf.

Question 23

Name two drugs that are given post-clot formation to prevent it getting any bigger

Answer 23

IV heparin and oral warfarin

Question 24

What is a massive PE?

Answer 24

This is where there is 60% reduction to blood flow and this is fatal

Question 25

What can a minor PE cause?

Answer 25

This is when the small arteries are blocked and can be asymptomatic. If there are recurrent PEs then this can lead to hypertension.

Question 26

When do fat embolisms typically occur?

Answer 26

These typically occur when there are long bone fractures as these give potential for fat and bone marrow to move into the blood stream.

Question 27

What type of embolism can cause a stroke?

Answer 27

Cerebral embolism

Question 28

What is INR?

Answer 28

This is an anticoagulant test which is used to check that a patients anti-coagulant medicines are at the correct levels.

Question 29

What is haemophilia?

Answer 29

This is where there is a sex linked recessive disorder which leads to deficiency of some clotting factors and so clotting does not occur as efficiently and it can take days for bleeding to stop.

Question 30

What is thrombocytopenia?

Answer 30

This is where there is platelet deficiency. As the number of platelets drops the amount of time to stop bleeding after injury increases. Once it becomes very low then spontaneous haemorrhage of the mucosa or skin can occur.

Question 31

What is thrombophilia?

Answer 31

This is where there is a deficiency in the control mechanisms to prevent inappropriate fibrin deposition and so this occurs.

Question 32

What is Disseminated intravascular coagulation?

Answer 32

This occurs when coagulation and haemorrhage complicate another disorder. Inappropriate coagulation leads to formation of many microthrombi in organs and this leads to reduction in the number of clotting factors which means that haemorrhage can occur.

Question 33

What is haemophilia?

Answer 33

This is where there is a sex linked recessive disorder which leads to deficiency of some clotting factors and so clotting does not occur as efficiently and it can take days for bleeding to stop.

Question 34

What is thrombocytopenia?

Answer 34

This is where there is platelet deficiency. As the number of platelets drops the amount of time to stop bleeding after injury increases. Once it becomes very low then spontaneous haemorrhage of the mucosa or skin can occur.

Question 35

What is thrombophilia?

Answer 35

This is where there is a deficiency in the control mechanisms to prevent inappropriate fibrin deposition and so this occurs.

Question 36

What is Disseminated intravascular coagulation?

Answer 36

This occurs when coagulation and haemorrhage complicate another disorder. Inappropriate coagulation leads to formation of many microthrombi in organs and this leads to reduction in the number of clotting factors which means that haemorrhage can occur.