Haemostasis

Question 1

What are the main steps of Haemostasis?

Answer 1

1- Artery contacts
2- Primary Haemostatic plug forms (from platelets, fragile)
3-Secondary Haemostatic plug forms (fibrin filaments stabalise primary)

Question 2

What is the role of platelets?

Answer 2

Stick to exposed subendothelium 
Aggregate with other platelets (plugs form)
Swell and change shape 
Secreate factors (to aid plug growth)

Question 3

What is the role of vessel walls?

Answer 3

Atrial media contracts
Subendothelium traps platelets
Endothelium (balances between opposing and favouring clotting)

Question 4

What mediates platelet clotting?

Answer 4

Platelet receptors 
Von Willebrand factor (platelets adhear to it)
Fribinogen (links platelets)
Collagen (binds platelets)
ADP & Thromboxine (make plug)
Thrombin (fribinogen to fibrin)

Question 5

What is the purpose of the clotting cascade?

Answer 5

Produce Thrombin (11a) to convert soluble fribinogen to insoluble fibrin

Question 6

What are the two cascade pathways?

Answer 6

Intrinsic- from blood itself (factor 12, 11, 9)
Extrinsic- from tissue fator release (factor 7)

Common - factor 10

Question 7

What are common Coagulation tests?

Answer 7

Prothrombin time (PT)- measure extrinsic pathway (prolonged = 7 defficiency)

Activated partial thromboplastin time (APTT)- measure intrinsic pathway (prolonged =8,9,11,12 one defficient)

5,10 thrombin and fibriogen common to both pathways

Thrombin clotting time

Question 8

What is DIC?

Answer 8

Disseminated Intravascular coaguloathy

Microangiopathic haemolytic anaemia
Multiple micrthrombi formed in circulation
Consumption clotting factors and platelets
Leads to haemorrages

Question 9

What causes DIC?

Answer 9

There is always a trigger

Eg. Malignancy, massive tissue injury, infections

Question 10

What is the treatment for DIC?

Answer 10

Treat underlying cause

Transfusion platelets and FFP

Question 11

Key features of Haemiphilia

Answer 11

A- lack of factor 8

• X linked recessive
• prolonged APTT, normal PT
• recombinant factor 8

B-X linked recessive
-lack factor 9
-prolonged APTT, normal PT
Recombinant factor 9

Question 12

Presentation of Haemophilia

Answer 12

Muscle haematomas
Joint pain
Prolonged dental bleeding
Intracerebral haemorrhage

Question 13

Features of Von Willebrand disease

Answer 13

Abnormal platelet to vessel walls
Reduced factor 8

Prolonged bleeding time, excessive bleeding from wounds, mild tendency

Question 14

Thrombophilia features

Answer 14

Congenital or acquired haemostais defects that increase risk of thrombosis

Congenital (defficiency in natural anticoagulants, abnormal factor 5)

Aquired (antiphosphoolipod syndrome)

Question 15

What are the natural anticoagulants?

Answer 15

Protein C - inactivates factor 5&8
Activated by thrombin binding to receptor
Protein S is cofactor

Antithrombin 3- activated by heparin, prevents clot spread by rapidly inactivating factors that are carried away from clotting site

Question 16

Common anticoagulants

Answer 16

Vitamin K inhibitors (warfrin)- affect vit K dependant factors

direct oral anticoagulants- Inhibit thrombin or factor 10

Low molecular weight hearins

Heparin

Question 17

What are complications of anti coagulants?

Answer 17

Bleeding

Stop takking drug, may need vit k