Haemostasis

Question 1

What is haemostasis?

Answer 1

Arrest of bleeding and maintenance of vascular patency

Question 2

What is the lifespan of platelets?

Answer 2

7-10 days

Question 3

When is Von Willebrand Factor released?

Answer 3

When there is vessel endothelial damage which exposes collagen.

Question 4

What is the screening test for primary haemostats?

Answer 4

Platelet count

can measure von Willebrand factor if history indicates it

Question 5

What converts plasminogen to plasmin? When can it be used as a treatment?

Answer 5

tissue plasminogen activator (tPA)

To break down clots e.g. acute stroke

Question 6

What are D-dimers?

Answer 6

Cross-linked Fibrin Degradation Products (FDPs)

Question 7

What 2 factors convert prothrombin to thrombin?

Answer 7

Factor V and Xa

Question 8

What factors are affected in prolonged PT?

Answer 8

Tissue factor

Factor VIIa

Question 9

What factors are affected in prolonged APTT?

Answer 9

Factor VIII

Factor IXa

Question 10

What condition can cause isolated prolonged APTT?

Answer 10

Haemophilia

Question 11

What is thrombophilia?

Answer 11

Deficiency of naturally occurring anticoagulants (may be hereditary). Therefore, increased tendency to develop venous thrombosis.

Question 12

What proteins are involved in natural anticoagulation by switching off factor V and VII?

Answer 12

Protein S and Protein C

Question 13

What is primary haemostats?

Answer 13

Formation of platelet plug

Question 14

What is secondary haemostats?

Answer 14

Formation of fibrin clot

Question 15

What are the causes pf platelet functional defects?

Answer 15

Hereditary (rare)
Acquired:
- drugs (aspirin, NSAIDs etc)
- renal failure

Question 16

Where are all the clotting factors produced?

Answer 16

Liver

Question 17

What is the significance of low albumin in the context of abnormal bleeding?

Answer 17

Liver produces both albumin and clotting factors, so if there is low albumin due to liver disease, suggests the liver won’t be producing enough clotting factors either.

Question 18

What are the multiple clotting factor deficiencies?

Answer 18

Liver failure
Vitmain K deficiency/Warfarin therapy
Complex coagulopathy: DIC

Question 19

What is the effect of multiple clotting factor deficiencies on PT and APTT?

Answer 19

Both prolonged

Question 20

What causes Haemorrhagic disease of the newborn and how is it prevented?

Answer 20

Babies don’t have dietary intake of vitamin K or any gut flora to make vit K so they have clotting deficiency. Newborns get IM vitamin K to prevent this

Question 21

Why do you get end organ failure in DIC

Answer 21

Microvascular thrombus formation

Question 22

If both PT and APTT are prolonged, what does this suggest?

Answer 22

Multiple clotting factors problem

Question 23

What happens to D-dimer levels in DIC and why?

Answer 23

Increase, due to excess fibrinolysis

Question 24

What are the PT and APTT in haemophilia?

Answer 24

PT: normal
APTT: very prolonged (because the problem is with Factor VIII or IX)

Question 25

What is the main component of arterial thrombus vs venous thrombus and what are the targeted treatments in each case?

Answer 25

arterial: platelet-rich clot - treat with anti-platelets Venous: fibrin-rich clot - treat with fibrinolytics and drugs that interfere with fibrin clots (heparin, warfarin etc)

Question 26

What are the complications of PE?

Answer 26

``` pulmonary infarction pleuritic chest pain cardiovascular collapse/sudden death hypoxia right heart strain ```

Question 27

What are the risk factors of VTE?

Answer 27

``` age marked obesity pregnancy puerperium oestrogen therapy previous DVT/PE trauma/surgery malignancy paralysis infection thrombophilia ```

Question 28

Which naturally occurring anticoagulant binds to thrombin?

Answer 28

Anti-Thrombin III

Question 29

What is the commonest hereditary thrombophilia?

Answer 29

Factor V Leiden (Impairs protein C/S)

Question 30

When would you consider hereditary thrombophilia screening?

Answer 30

Venous thrombosis

Question 31

How is hereditary thrombophilia managed?

Answer 31

Advice on avoiding risk Short term prophylaxis - to prevent thrombotic events during periods on known risk (e.g. pregnancy) Short term anticoagulation - to treat thrombotic events Long term anticoagulation - if recurrent thrombotic events

Question 32

What is acquired thrombophilia?

Answer 32

Antiphospholipid antibody syndrome

Question 33

What happens to ATPP in Antiphospholipid syndrome?

Answer 33

It is prolonged - paradoxical as you would expect this make pt prone to bleeding but the clotting factors are unaffected and pts are actually prone to thrombosis

Question 34

How is anti-phospholipid syndrome treated and why?

Answer 34

aspirin and warfarin | anti-platelet and anti-coagulant because there is activation of primary and secondary haemostasis

Question 35

What are the immune causes of thrombocytopenia?

Answer 35

ITP Drugs (penicillin, thiazides, oral hypoglycaemics, heparin, blood transfusion) SLE HIV

Question 36

What drugs are used to prevent strokes?

Answer 36

Atherosclerosis - anti-platelets | AF (fibrin-rich clot in LA) - anti-coagulants

Question 37

What do you monitor in patients on Warfarin?

Answer 37

PT (INR)

Question 38

What do you monitor in patients on unfractionated Heparin?

Answer 38

APTT

Question 39

Give an example of a coumarin anticoagulant

Answer 39

Warfarin

Question 40

What is a complication of long term heparin therapy?

Answer 40

Osteoporosis

Question 41

What is the target INR for most patients in warfarin? | What might make you aim for higher?

Answer 41

2 - 3 | Further event despite warfarin treatment - aim for a max of about 3.5 - 4

Question 42

What are the bleeding complications of warfarin therapy?

Answer 42

``` Mild: - skin bruising - epistaxis - haematuria Severe: - GI bleeds - intracranial bleeds (risk is about 1 in 200) - significant drop in Hb ```

Question 43

How long does it take for vitamin K to reverse the effects of warfarin therapy?

Answer 43

6 hours

Question 44

What can you given for immediate reversal of warfarin therapy in a life-threatening situation?

Answer 44

Administer clotting factors (FFP or factor concentrates)

Question 45

What are the 2 groups of new anticoagulants? Give an example of each

Answer 45

Oral direct thrombin inhibitors e.g. Dabigatran | Oral Factor Xa inhibitors e.g. Rivaroxaban, Apixaban

Question 46

What is the risk of giving Dabigabtran to elderly patients?

Answer 46

Dabigatran is renally excreted so patients with renal impairment are at risk of build-up of the drug - risk of bleeding.

Question 47

What do platelets do in arterial thrombosis?

Answer 47

Plaque rupture due to high pressure environment of arteries Platelets adhere to exposed endothelium and there is release of vWF Platelets become activated - release granules that activate coagulation and recruit other platelets to developing platelet plug platelet aggregation via membrane glycoproteins

Question 48

A 21 year old girl has a history of heavy periods and investigations indicate a defect in primary haemostasis. Her blood count is normal. What is the most likely diagnosis?

Answer 48

Von Willebrand's Disease (primary haemostats failure but normal platelet count)

Question 49

What does an isolated prolonged APTT suggest?

Answer 49

Deficiency of factors involved in the ‘intrinsic’ pathway of coagulation (Factor VIII, IX, vWF [as it binds Factor VIII]) or the presence of an anti-phospholipid antibody (lupus anticoagulant) that is not associated with a bleeding phenotype