Year 2 - disorders of primary haemostasis

Question 1

What is Haemostasis?

Answer 1

The cellular and biochemical processes that enable the specific and regulated cessation of bleeding in response to vascular insult

Question 2

What is Haemostasis for? (3 things)

Answer 2

1- prevention of blood loss from intact vessels
2- arrest bleeding from injured vessels
3- enable tissue repair

Question 3

What does Von Willebrand factor do?

Answer 3

It has 2 functions in haemostasis
1- binds to collagen and captures platelets
(i.e. platelets bind indirectly to collagen via the surface glycoprotein GIpIB binding to VWF in platelet adhesion in primary haemostasis)
2-Stabilises factor VIII - so factor VIII may be low if VWF is very low

Question 4

What are 2 different causes of Von Willebrand Disease?

Answer 4

1- Hereditary (common) - Autosomal inheritance pattern (dominant/recessive depends on the type)
2-Acquired due to antibody (rare)

Question 5

What are the 3 things that can be affected in disorders of primary haemostasis?

Answer 5

1-Platelets
2-Von Willebrand Factor - Von Willebrand disease
3-The vessel wall

Question 6

What causes platelet dysfunction and are disorders of primary haemostasis that cause bleeding?

Answer 6

1- Thrombocytopenia (rare)

2- Drugs - steroids, NSAIDS, aspirin, clopidogrel (common)

Question 7

What affects vessel wall function and can cause disorders of primary haemostasis that cause bleeding?

Answer 7

1 - Inherited vascular disorders (rare) - Haemorrhagic telangiectasia, Ehlers-Danlos syndrome and other disorders of connective tissue
2- Acquired causes (common) - Vasculitis, Ageing (‘senile’ purpura), Scurvy (Vit C deficiency), Steroid therapy

Question 8

What are the clinical features of disorders of primary haemostasis?

Answer 8

Bleeding
-immediate
-prolonged bleeding from cuts
Mucocutaneous bleeding
-nose bleeds (epistaxis): prolonged>20 mins
-prolonged gum bleeding
-heavy menstrual bleeding (menorrhagia)
-Bruising (ecchymosis): spontaneous/easy
-Prolonged bleeding after trauma or surgery

Question 9

What is a particular clinical feature of thrombocytopenia?

Answer 9

Petechiae

Question 10

What causes petechiae and purpura?

Answer 10

bleeding under the skin

Question 11

How do you distinguish a rash from petechiae?

Answer 11

Petechiae do not blanch under pressure

Question 12

What are purpura?

Answer 12

Red or purple discoloured spots on the skin

Question 13

What is the difference between petechiae purpura and ecchymosis?

Answer 13

Petechiae - less than 3mm diameter
Purpura - between 3 and 10 mm diameter
Ecchymosis - more than 10 mm diameter

Question 14

In what disorders of primary haemostasis are purpura commonly seen?

Answer 14

Platelet disorders - Thrombocytopenic purpura

Vascular disorders

Question 15

What are ‘wet purpura’?

Answer 15

Purpura seen on mucosal surfaces e.g gums

Question 16

What can happen to the bleeding pattern in severe VWD?

Answer 16

Bleeding can be haemophilia-like due to low factor VIII

Question 17

What are the tests for disorders of primary haemostasis?

Answer 17

Platelet count, platelet morphology (light microscope usually not enough, may need an electron microscope)
Bleeding time in the past - not pleasant and also not sensitive or specific for these disorders so has been replaced by PFA100 in the lab
Assays of Von Willebrand factor - levels or function
Clinical observation

Question 18

Why is a coagulation screen not helpful in diagnosing disorders of primary haemostasis?

Answer 18

Because PT and APTT will be normal except in severe VWD where factor VII will be low

Question 19

What symptoms are seen at different levels of platelet counts?

Answer 19

normal range = 150-400 x10^9/l
no spontaneous bleeding, but bleeding with trauma= 40-100
spontaneous bleeding common = 10-40
severe spontaneous bleeding=<10

Question 20

What are the principles of treatment for abnormal haemostasis where there is a failure of production/function?

Answer 20

• replace missing factor/platelets
  can be either prophylactic i.e before operation or in severe forms of VWD or therapeutic
  -stop drugs - i.e. aspirin/NSAIDs

Question 21

What are the principles of treatment for abnormal haemostasis where there is immune destruction?

Answer 21

Immunosuppression (e.g.prednisolone) e.g in thrombocytopenia

Splenectomy for ITP

Question 22

What are the principles of treatment for abnormal haemostasis where there is increased consumption? e.g. DIC

Answer 22

• Treat cause

- replace as necessary

Question 23

What are the 4 additional (supportive) Haemostatic treatments and what do they do?

Answer 23

Desmopressin (DDAVP)

• vasopressin (anti diuretic hormone) analogue
• 2-5 times increase in VWF ( and factor VIII)
• releases endogneous stores of VWF from Weibel-Paladi bodies of endothelial cells so only useful in mild disorders
• useful in VWF, Haemophilia A, platelet function disorders

Tranexamic acid
Antifibrinolytic
used very widely even in trauma

Fibrin glue/spray
used in surgery

Other approaches e.g. hormonal (combined oral contraceptive pill for menorrhagia)