Haemostasis, Thrombosis and Embolism

Question 0

Explain the extrinsic pathway.

Answer 0

Triggered by trauma. 3A, 7A, 10A+5A, 2A (thrombin), 1A (fibrin clot).

Question 1

Explain the intrinsic clotting cascade.

Answer 1

Triggered by damage to tthe endothelial lining. 12A, 11A, 9A+8A, 10A+5A, 2A (thrombin), 1A (fibrin clot).

Question 2

What is the role of platelets?

Answer 2

Adhere to damaged vessel walls, and each other to form a platelet plug. ADP and thromboxane A2 (prostaglandin) cause platelet aggregation.

Question 3

What activates the platelet coagulation cascade?

Answer 3

Platelet factor 3.

Question 4

What is fibrinolysis and how does it occur?

Answer 4

The breakdown of fibrin by converting plasminogen to plasmin. This is achieved by plasminogen activators.

Question 5

Name 2 therapeutic plasminogen activators and state how they work.

Answer 5

Streptokinase and tissue plasminogen activators. Start to dissolve a thrombus.

Question 6

Why is it important for there to be a balance between coagulant and anti-coagulant factors?

Answer 6

Coagulation is a cascade which is amplified to the extent that 1ml of blood can convert all he fibrinogen to fibrin.

Question 7

What are the 3 factors in Virchow’s triad for thrombosis?

Answer 7

1) Changes in blood components.
2) Changes in blood flow.
3) Changes in vessel wall.

Question 8

What are the effects of arterial thrombi? Where is the effect worst?

Answer 8

Loss of pulse distally to thrombus.
Ischaemia and infarction.
Worst effect if in end artery, e.g. retinal artery.

Question 9

Wha are the effects of venous thrombi?

Answer 9

Congestion
Ischaemia
Infarction
Tenderness and redness.

Question 10

What are the 5 possible outcomes following a thrombus?

Answer 10

Lysis
Propagation
Organisation
Recanalisation
Embolism

Question 11

What does lysis mean, in relation to following a thrombus?

Answer 11

Complete dissolution of thrombus via fibrinolytic system.

Question 12

What does propagation mean, in relation to following a thrombus?

Answer 12

Progressive spread of thrombus, distally in arteries and proximally in veins.

Question 13

What does organisation mean, in relation to following a thrombus?

Answer 13

Ingrowth of fibroblasts and capillaries. The lumen remains obstructed.

Question 14

What does recanalisation mean, in relation to following a thrombus?

Answer 14

Lysis + organisation. Blood flow is re-established but is incomplete. One or more channels form.

Question 15

What is the most common type of embolism?

Answer 15

Thromboembolism.

Question 16

Apart from thromboembolism, name some other types of embolism.

Answer 16

Air, amniotic fluid, medical equipment and nitrogen.

Question 17

When is DVT likely to occur?

Answer 17

Pregnancy, cardiac failure, severe burns and you’ve been stationary for a long time, e.g. flight or hospital.

Question 18

If a PE reduces blood flow by 60%, what is the result?

Answer 18

Death.

Question 19

What symptoms occur if a medium sized vessel is blocked by a PE?

Answer 19

Shortness of breath, cough and blood stained sputum.

Question 20

What are the symptoms when a small peripheral vessel is blocked by an PE?

Answer 20

Can be asymptomatic or have a slight shortness of breath.

Question 21

What can recurrent PE cause?

Answer 21

Pulmonary hypertension.

Question 22

Name some types of embolism other hen PE or thromboembolism.

Answer 22

Fat embolism
Cerebral embolism
Nitrogen embolism
Iatrogenic embolism

Question 23

Explain how fat embolism occurs.

Answer 23

Fracture of a long bone and/or laceration of adipose tissue.

Question 24

Explain how a cerebral embolism occurs and what problems it causes.

Answer 24

Occurs due to atrial fibrillation. Can cause TIA.

Question 25

How does an iatrogenic embolism form?

Answer 25

Due to medical treatment, e.g. air from an injection.

Question 26

What is a nitrogen embolism?

Answer 26

Nitrogen bubbles form in the blood due to rapid decompression, i.e. the bends.

Question 27

How does heparin work as an anti-coagulant therapy?

Answer 27

Binds to anti-thrombin 3, and in doing so inactivates thrombin and factor 10a.

Question 28

How does warfarin work as an anti-coagulant therapy?

Answer 28

Slows clotting as it interferes with the synthesis of vitamin K dependent clotting factors.

Question 29

What is haemophilia? How is it treated?

Answer 29

X-linked recessive disease. Type A lack factor 8 and type B lack factor 9, so get excessive bleeding and haemorrhage. Treat with self-administered factor replacement therapy.

Question 30

What is disseminated intravascular coagulation?

Answer 30

Pathological activation of coagulation mechanism. Small clots form so disrupts normal clotting, as it uses up all tthe clotting factors, so get abnormal bleeding.

Question 31

What is thrombocytopaenia?

Answer 31

Low platelet count due to failure of platelet reduction, increased platelet destruction and/or sequestering platelets. Often associated with bone marrow dysfunction, e.g. leukaemia?

Question 32

What is thrombophilia and why is it problematic?

Answer 32

Blood has an increased tendency to clot, so have an increased risk of DVT.

Question 33

How does the endothelium prevent excessive blood loss in bleeding?

Answer 33

The endothelium produces anti-thrombotic factors such as plasminogen. This detects leaks and prevents excessive blood less by constricting. Completely severed blood vessels contract more, so have less bleeding then partially severed ones.