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Flashcards in Haemostasis Deck (26)
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1
Q

What is haemostasis?

A

The arrest of bleeding while maintaining vascular patency

2
Q

What is required for haemostasis?

A

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

3
Q

What are the components of normal haemostasis system?

A

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

4
Q

How are platelets formed?

A

In the bone marrow by budding from megakaryocytes

5
Q

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

A

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

6
Q

How long does a platelet live for?

A

7-10 days

7
Q

Describe platelets?

A

Small anucleated discs

8
Q

What causes platelet adhesion at injury site?

A

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

9
Q

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

A

Platelet aggregation

10
Q

What problems can cause failure of the platelet plug?

A

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

11
Q

What are the consequences of failure of platelet plug formation?

A

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

12
Q

What test is there for primary haemostasis?

A

Platelet count

13
Q

What releases calcium onto the vessel surface?

A

Platelets

14
Q

What initiates secondary heamostasis?

A

TF and VIIa

15
Q

What generates thrombin?

A

V/Xa

16
Q

What does thrombin do?

A

Helps convert fibrinogen to fibrin

17
Q

What are failures of fibrin clot?

A

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

18
Q

What causes haemophilia A?

A

Problems with factor 8

19
Q

What causes haemophilia B?

A

Problems with factor 9

20
Q

What gives plasmin and what does plasmin do?

A

Plasminogen

Causes Fibrin to become FDPs (Fibrin Degredation Products)

21
Q

What causes plasminogen to become plasmin?

A

Tissue Plasminogen Activator (tPA)

22
Q

What does prothrombin check?

A

TF/VIIa

23
Q

What does ATTP check?

A

Factor VIII/IXa

24
Q

What is clinical approach to bleeding disorders?

A

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

25
Q

What are some naturally occurring anticoagulants?

A

Serine protease inhibitors

Protein C and Protein S

26
Q

What is thrombophilia?

A

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