Haemostasis

Question 1

What is haemostasis?

Answer 1

The arrest of bleeding while maintaining vascular patency

Question 2

What is required for haemostasis?

Answer 2

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

Question 3

What are the components of normal haemostasis system?

Answer 3

Formation of platelet plug -Primary
Formation of fibrin clot - Secondary
Fibrinolysis
Anticoagulant defences

Question 4

How are platelets formed?

Answer 4

In the bone marrow by budding from megakaryocytes

Question 5

Why is it important to know how long a platelet lives for?

Answer 5

E.g. If a person on aspirin is needing surgery, know how ling they should be off aspirin for prior to surgery to prevent over bleeding

Question 6

How long does a platelet live for?

Answer 6

7-10 days

Question 7

Describe platelets?

Answer 7

Small anucleated discs

Question 8

What causes platelet adhesion at injury site?

Answer 8

Endothelial (vessel wall) damage exposes collagen and releases Von Willebrand Factor (VWF) and other proteins to which platelets have receptors

Question 9

After adhesion, what do various chemicals from the platelets cause?

Answer 9

Platelet aggregation

Question 10

What problems can cause failure of the platelet plug?

Answer 10

Vascular
Platelet - reduced number (thrombocytopenia) and reduced function
Von Willebrand Factor

Question 11

What are the consequences of failure of platelet plug formation?

Answer 11

Spontaneous bruising and purpura
Mucosal bleeding - epistaxes, GI, conjuctival, menorrhagia
Intracranial haemorrhage
Retinal haemorrhages

Question 12

What test is there for primary haemostasis?

Answer 12

Platelet count

Question 13

What releases calcium onto the vessel surface?

Answer 13

Platelets

Question 14

What initiates secondary heamostasis?

Answer 14

TF and VIIa

Question 15

What generates thrombin?

Answer 15

V/Xa

Question 16

What does thrombin do?

Answer 16

Helps convert fibrinogen to fibrin

Question 17

What are failures of fibrin clot?

Answer 17

Single clotting factor deficiency -usually hereditary e.g. haemophilia
Multiple clotting factor - usually acquired, e.g. disseminated intravascular coagulation
Increased fibrinolysis - usually part of complex coagulopathy

Question 18

What causes haemophilia A?

Answer 18

Problems with factor 8

Question 19

What causes haemophilia B?

Answer 19

Problems with factor 9

Question 20

What gives plasmin and what does plasmin do?

Answer 20

Plasminogen

Causes Fibrin to become FDPs (Fibrin Degredation Products)

Question 21

What causes plasminogen to become plasmin?

Answer 21

Tissue Plasminogen Activator (tPA)

Question 22

What does prothrombin check?

Answer 22

TF/VIIa

Question 23

What does ATTP check?

Answer 23

Factor VIII/IXa

Question 24

What is clinical approach to bleeding disorders?

Answer 24

History - bleeding/bruising,duration, previous surgey/dental extractions
Drug history
Family history
Examination

Question 25

What are some naturally occurring anticoagulants?

Answer 25

Serine protease inhibitors

Protein C and Protein S

Question 26

What is thrombophilia?

Answer 26

Deficiency of naturally occuring anticoagulants may be hereditary
Increased tendancy to develop venous thrombosis (deep vein thrombosis/pulmonary embolism