Bleeding and Thrombosis Flashcards Preview

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Flashcards in Bleeding and Thrombosis Deck (54)
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1
Q

List causes of failure of platelet plug formation (failure of primary haemostasis)

A

Vascular disease
Low platelet count (thrombocytopenia)
Impaired platelet function
Von Willbrand Factor disease

2
Q

What is the main vascular cause of failed primary haemostasis?

A

Vasculitis e.g. Henoch-Schonlein purpura

3
Q

Thrombocytopenia can be due to what 2 factors?

A

Reduced platelet production (marrow disorder)

Increased platelet destruction

4
Q

List the main causes of platelet destruction

A

Coagulopathy (DIC)
Autoimmunity
Hypersplenism

5
Q

Von Willebrand Factor deficiency is mainly hereditary and follows what inheritance pattern?

A

Autosomal dominant

6
Q

List causes of failure of fibrin clot formation (failure of secondary haemostasis)

A

Multiple clotting factor deficiency

Single clotting factor deficiency

7
Q

List causes of multiple clotting factor deficiency

A

DIC
Liver failure
Vitamin K deficiency
Warfarin therapy

8
Q

What is the main cause of single clotting factor deficiency?

A

Haemophilia

9
Q

Which clotting factors are carboxylated (activated) by vitamin K?

A

II
VII
IX
X

10
Q

List causes of vitamin K deficiency

A
Poor dietary intake
Malabsorption
Obstructive jaundice
Antagonists (warfarin)
Haemorrhagic disease of newborn
11
Q

What is disseminated intravascular coagulation (DIC)?

A

Excessive activation of the haemostatic system, causing depletion of all clotting factors

12
Q

What are the main signs of DIC?

A

Abdominal bruising/purpura

Generalised bleeding

13
Q

What are the main screening tests/investigations for haemostasis?

A

Platelet count
Prothrombin time
APT time

14
Q

List the main causes of DIC

A

Sepsis
Obstetric emergencies
Malignancy
Hypovolaemic shock

15
Q

How is DIC treated?

A

Treat underlying cause

Replace clotting factors

16
Q

What pattern of inheritance does haemophilia follow?

A

X-linked

17
Q

What are the two types of haemophilia? Which is more common?

A
Haemophilia A (VIII deficiency)
Haemophilia B (IX deficiency)
A is more common than B
18
Q

Where does bleeding usually occur in haemophilia?

A

Ankles
Knees
(haemarthroses)

19
Q

Is haemophilia a disorder of primary or secondary haemostasis?

A

Secondary haemostasis

20
Q

Prothrombin time is usually normal in a haemophiliac. True/False?

A

True

Isolated prolonged APT time

21
Q

What is the main cause of arterial thrombosis?

A

Atherosclerosis

22
Q

How is atherosclerosis treated?

A

Antiplatelet (aspirin)

23
Q

Venous thrombosis is caused by Virchow’s triad. List the components of this triad

A

Hypercoagulability
Vessel wall damage
Stasis of blood flow

24
Q

What is the risk of a deep vein thrombosis in the leg?

A

Clot can form and end up in pulmonary circulation, causing pulmonary embolism

25
Q

List risk factors for venous thromboembolism

A
Age
Obesity
Pregnancy
Oestrogen therapy (OCP)
Trauma/surgery
Infection
Paralysis
Thrombophilia
Previous DVT/PE
26
Q

What are the main mechanisms of thrombophilia?

A

Increased coagulation activity
Decreased fibrinolytic activity
Decreased anticoagulant activity

27
Q

What are the main naturally occuring anticoagulants?

A

Serine protease inhibitors (antithrombin)

Protein C and S

28
Q

What is Factor V Leiden?

A

Variant of factor V that cannot be inhibited as effectively - increases risk of venous thrombosis due to less anticoagulation

29
Q

List the main hereditary thrombophilias

A

Factor V Leiden
Antithrombin deficiency
Protein C and S deficiency
Prothrombin mutation

30
Q

What is the main acquired thrombophilia?

A

Antiphospholipid syndrome

31
Q

How does atherosclerosis form?

A

Foamy macrophages rich in cholesterol are attracted to damaged arterial endothelium, forming atherosclerotic plaques

32
Q

What are the consequences of unstable atherosclerotic plaques?

A

Can rupture and cause arterial thrombosis/embolism (resulting in unstable angina/MI/stroke)

33
Q

Which chemicals released by platelets encourage platelet aggregation?

A
Thromboxane A2 (TXA2)
ADP
34
Q

List risk factors for arterial thrombosis

A

Hypertension
Smoking
High cholesterol
Diabetes

35
Q

How does aspirin work?

A

Inhibit COX enzyme causing decreased TXA2 production and thus reduced platelet aggregation

36
Q

List some side effects of aspirin

A

Bleeding
GI ulceration
Bronchospasm

37
Q

How does clopidogrel work?

A

ADP receptor antagonist (blocks P2Y1) to reduce platelet aggregation

38
Q

Through which receptors do platelets bind together?

A

GP IIb/IIIa

39
Q

How does atrial fibrillation increase the risk of stroke?

A

Stasis of blood flow (due to irregular heartbeat) causes congealing and clot formation in atrium, which may travel and lodge in the brain

40
Q

Which factors do protein C and S inhibit in the clotting cascade?

A

V
VIII
IX
Xa

41
Q

How does heparin work?

A

Potentiates action of antithrombin (inhibitor of thrombin) to reduce clotting

42
Q

Which factors are inhibited by unfractionated heparin?

A

Thrombin

Xa

43
Q

Which factors are inhibited by LMW heparin?

A

Xa only (indirectly inhibits thrombin since X is higher in the cascade)

44
Q

Which coagulation test is used to monitor heparin?

A

APT time for unfractionated heparin

Anti-Xa assay for LMW heparin

45
Q

List some side effects of heparin

A

Bleeding
Thrombocytopenia, causing thrombosis
Osteoporosis long-term

46
Q

How can the effects of heparin be reversed?

A
Stop heparin
Protamine sulphate (reverses AT so complete reversal for unfractionated heparin)
47
Q

How does warfarin work?

A

Inhibits vitamin K to cause reduced clotting factor activation

48
Q

What is required for vitamin K absorption?

A

Bile salts

49
Q

Which factors are vitamin K -dependent?

A
II
VII
IX
X
Protein C and S
50
Q

How is acute thrombosis in hospital treated - heparin or warfarin?

A

Heparin (works immediately)

51
Q

What is the equation for calculating a patient’s INR?

A

(PT time / mean normal PT time)^ISI

52
Q

How can the effects of warfarin be reversed?

A

Omit warfarin dose
Oral vitamin K
Administer clotting factors

53
Q

Give an example of a direct thrombin inhibitor

A

Dabigatran

54
Q

Give an example of an oral Xa inhibitor

A

Rivaroxaban