Haemostasis

Question 1

What is haemostasis?

Answer 1

The arrest of bleeding and maintenance of vascular patency

Question 2

4 components of a normal haemostatic system?

Answer 2

Formation of platelet plug
Formation of fibrin clot
Fibrinolysis
Anticoagulant defences

Question 3

Process leading to aggregation of platelets at site of injury?

Answer 3

Endothelial damage exposes collagen and releases Von Willebrand factor and other proteins for which platelets have receptors -> platelet adhesion at site of injury .
Secretion of chemicals from platelets -> aggregation of platelets at site of injury

Question 4

Possible causes of failure of platelet plug formation?

Answer 4

Vascular
Platelets / thrombocytopenia / decreased function
Von willebrand factor

Question 5

What are consequences of failure of platelet plug formation?

Answer 5

Spontaneous bruising and purpura
Mucosal bleeding
Intracranial haemorrhage
Retinal haemorrhage

Question 6

Screening test for primary haemostasis?

Answer 6

Platelet count

Question 7

Causes of failure of fibrin clot formation?

Answer 7

Single clotting factor deficiency eg. Haemophilia
Multiple clotting factor deficiencies eg. DIC
Increased fibrinolysis

Question 8

What breaks down fibrin into fibrin degradation products (FDPs)?

Answer 8

Plasmin

Question 9

Naturally occurring anticoagulants?

Answer 9

serine protease inhibitors

Proteins C and S

Question 10

Extrinsic pathway?

Answer 10

Factor 7

Question 11

Intrinsic pathway?

Answer 11

Factors 8,9,11,12

Question 12

Common pathway?

Answer 12

Factors 10,5,2,1

Question 13

What is the extrinsic pathway also known as?

Answer 13

The tissue factor pathway

Question 14

An isolated increase in PT?

Answer 14

Factor VII deficiency

Question 15

Isolated increased APTT?

Answer 15

Haemophilia
Antiphospholipid syndrome
Von willebrand
Deficiency in factors 8,9,11,12

Question 16

Treatment of DIC?

Answer 16

Treat underlying Disease
Replacement therapy 
- cryoprecipitate 
- FFP
- platelet concentrate 
- packed red cells

Question 17

Decrease in fibrinogen?

Answer 17

DIC
liver disease
Inherited deficiencies
After thrombolytic therapy

Question 18

What factor is prothrombin?

Answer 18

II

Question 19

What factor is thrombin?

Answer 19

IIa

Question 20

What factor is fibrinogen?

Answer 20

I

Question 21

What factor is fibrin?

Answer 21

Ia