Haemostasis

Question 1

What is haemostasis?

Answer 1

The arrest of bleeding and maintenance of vascular patency

Question 2

What are the requirements of haemostasis?

Answer 2

Permanent state of readiness
Prompt response
Localised response
Protection against unwanted thrombosis

Question 3

What are the components of the normal haemostatic system?

Answer 3

Formation of plateplug- primary
Formation of fibrin clot- secondary
Fibrinolysis
Anticoagulant defences

Question 4

How are platelets formed in the bone marrow?

Answer 4

Budding from megakaryocytes

Question 5

Describe platelet adhesion

Answer 5

Endothelial damage exposes collagen and releases VWF, and other proteins to which platelets have receptors
There is then secretion of various chemicals from the platelets, which leads to aggregation of platelets at the site of injury

Question 6

What are the causes of failure of platelet plug formation?

Answer 6

Vascular
Platelets- reduced number, reduced function
VWF

Question 7

What are the consequences of failure of platelet plug formation?

Answer 7

Spontaneous Bruising and Purpura
Mucosal Bleeding-Epistaxis, Gastrointestinal, Conjunctival, Menorrhagia
Intracranial haemorrhage
Retinal haemorrhages

Question 8

What are screening tests for 1’ haemostasis?

Answer 8

Platelet count

No simple test for other components

Question 9

What converts fibrinogen to fibrin?

Answer 9

Thrombin

Question 10

What are the causes of failure of fibrin clot formation?

Answer 10

Single clotting factor deficiency- usually hereditary, eg Haemophilia
Multiple clotting factor deficiencies- usually acquired, eg DIC
Increased fibrinolysis- usually part of complex coagulopathy

Question 11

What converts plasminogen to plasmin?

Answer 11

Tissue Plasminogen Activator

Question 12

What converts Fibrin to Fibrin Degradation Products?

Answer 12

Plasmin

Question 13

What are the consequences of failure of Fibrin Clot Formation?

Answer 13

No characteristic clinical syndrome
May be combined primary/secondary haemostatic failure
Pattern of bleeding depends on- Single/multiple abnormalities, the clotting factors involved

Question 14

What are screening tests for fibrin clot formation?

Answer 14

Prothrombin time (TF/VIIa)
Activated Partial Thromboplastin Time (VIII/IXa)

Question 15

What clinical approach should you take to bleeding disorders?

Answer 15

History- Bleeding/bruising, duration (?life-long), previous surgery/dental extractions
Drug History
Family History
Examination

Question 16

What are naturally occurring anticoagulants?

Answer 16

Serine protease inhibitors (AT III)

Protein C and S

Question 17

What is thrombophilia?

Answer 17

Deficiency of naturally occurring anticoagulants that may be hereditary
Increased tendency to develop venous thrombosis (DVT/PE)