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Flashcards in Haemostasis Deck (23):
1

what is haemostasis?

Make a clot
Control the clotting
Breaking the clot down

2

What is the role of platelets in clotting?

Platelets are produced by megakaryocytes in the bone marrow.

They adhere to the vessel wall when it is damaged and there is exposure of underlying tissues.

Platelets adhere to collagen via von willebrand factor

Platelets then activate each other by secreting ADP and thromboxane. This also activates the clotting cascade

The result of this is to form a platelet plug.

3

What is the role of thrombin and fibrin in blood clotting?

Amplification system of precursor proteins generates thrombin

Thrombin converts soluble fibrinogen into insoluble fibrin

This enmeshes the platelet plug to make a stable clot

4

What is the role of thrombin inhibitors in blood clotting?

Stop excessive clotting.

Anticoagulation factors are: protein C, protein S, antithrombin, tissue factor pathway inhibitor

5

What is APTT?

Measures extrinsic pathway- injury to blood vessel from external force

6

What is PT?

Measures intrinsic pathway- damage to blood vessel from internal force eg atheroma.

7

Which clotting factors influence PT?

12,11,10,9,8,5

8

Which clotting factors influence APTT?

10,7,5

9

What are the 3 major reasons why you might develop thrombocytopenia?

Decreased production
Trapping of platelets
Increased destruction

10

What might cause decreased production of platelets?

Aplastic anaemia
Leukemia
Viral infections
Chemotherapy
Heavy alcohol consumption

11

Why might platelets become trapped in the spleen?

In cases of splenomegaly eg portal hypertension/ viral infections/ EBV

12

What might cause increased destruction of platelets?

Immune thrombocytopenia (lupus and RA), bacteremia, thrombotic thrombocytopenic purpura
Pregnancy
Medications- such as heparin

13

Which clotting factor are haemophilia A patients deficient in?

Factor VIII

14

What clotting factor are haemophilia B patients deficient in?

IX

15

How is haemophilia inherited?

X linked recessive

16

How will patients with haemophilia present?

Bleeding into muscles and joints

17

How is haemophilia treated?

With recombinant clotting factor that is missing.

18

What is the mode of inheritance of von willebrand disease?

Autosomal dominant

19

What is von willebrand disease?

Abnormal platelet adhesion to vessel wall which causes skin and mucous membrane bleeding.

20

What is hereditary haemorrhagic telangiectasia?

Autosomal dominant condition which is characterised by microvascular swellings. GI haemorrhage can lead to iron deficiency anaemia.

21

What is DIC?

Disseminated intravascular coagulation
Its a type of microangiopathic haemolytic anaemia
Pathological activation of coagulation, numerous mimcrothrombi are formed in circulation, this uses up clotting factors and platelets

22

What will you expect in the blood results of A. DIC patient?

Prolonged INR, APTT, low fibrinogen, raised D dimers.

23

What can cause DIC?

Malignancy
Massive tissue injury
Infections eg gram negative sepsis
Massive haemorrhage and transfusion
ABO transfusion reaction
Pre eclampsia
Amniotic fluid embolus