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Flashcards in BLEEDING DISORDERS Deck (50):
1

What are the five main components of normal haemostasis?

Coagulation factors

Coagulation inhibitors

Fibrinolysis

Platelets

Blood vessels

2

Where are the coagulation factors mainly produced?

In the liver

3

How are coagulation factors normally found in the blood stream?

In their inactivated form

4

What is the ultimate goal of the both sides of the coagulation cascade?

To generate thrombin, which allows fibrinogen to become fibrin and form a clot are the aggregated platelets

5

What are the two pathways of the coagulation cascade?

Extrinsic pathway - tissue factor pathway caused by cellular injury releasing tissue factor

Intrinsic pathway - contact system

6

What are the coagulation factors involved exclusively in the extrinsic or tissue factor pathway?

Tissue factor (FIII) - activates FVII

FVII - used to activate factor X

7

What are the coagulation factors involved exclusively in the intrinsic or contact pathway?

FXII - activates FXI

FXI - activates FIX

FIX - used with FVIII to activate factor X

FVIII - used with FIX to activate factor X

8

What are the factors that make up the common pathway of the coagulation cascade?

FX

FV

FII (Prothrombin) -- FIIa (Thrombin)

Fibrinogen -- Fibrin

FXIII

9

What investigations may be useful as screening tools in patients with a history of bleeding?

FBC and blood film - thrombocytopenia

Prothrombin time

Activated partial thromboplastin time

Thrombin time

Quantitative fibrinogen assay

D-Dimer

U+Es and LFTs

10

What does the prothrombin time (PT) represent?

Measure of the extrinsic pathway of coagulation.

Therefore activity of factors VII, X, V and II

11

What does the activated partial thromboplastin time (APTT) represent?

Measure of the intrinsic pathway of coagulation

Therefore activity of factors XII, XI, IX, VIII, X, V and II

12

When monitoring heparin therapy do we use PT or APTT?

APTT

13

What is the inheritance pattern of haemophilia?

X-linked recessive

14

What is the coagulation factor affected in haemophilia A?

Factor VIII

15

What is the coagulation factor affected in haemophilia B?

Factor IX

16

What is the alternative name for haemophilia B?

Christmas disease

17

How do we grade haemophilia?

By Factor VIII:C (or FIX:C)

More than 5% is mild

Between 1 - 5% is moderate

Less than 1% is severe

18

What are the bleeding tendencies of someone with mild haemophilia?

Bleed after surgery

19

What are the bleeding tendencies of someone with moderate haemophilia?

Bleed after minor trauma

20

What are the bleeding tendencies of someone with severe haemophilia?

Spontaneous joint/muscle bleeds - this can lead to crippling arthritis if not treated

21

When do most children with haemophilia present?

Towards the end of the first year of life, when they start to crawl or walk (and hence fall over)

22

When neonates present with haemophilia, what are the common sites of bleeding?

Intracranial haemorrhage

Bleeding post-circumcision

Prolonged oozing from heel prick test

23

How do we treat someone with haemophilia?

Recombinant FVIII or FIX whenever there is a bleed

Prophylactic recombinant factor for all those with severe disease

In mild disease, desmopressin can stimulate release of FVIII:C and von Willebrand factor.

24

What are the complications of recombinant factor VIII or IX?

5 - 20% develop antibodies to the recombinant factor, which reduces or completely inhibits effect treatment

Transfusion-transmitted infections such as hepatitis A, B and C, HIV and prions

Vascular access can be difficult. Central venous access may be required which may become infected or thrombosed.

25

What are the two main functions of von Willebrand factor?

Facilitates platelet adhesion to damaged endothelium

Acts as carrier protein for FVIII:C, protecting it from inactivation and clearance.

26

What is the inheritance pattern of von Willebrand disease?

Usually autosomal dominant

27

When is the most common type of von Willebrand disease (type 1) usually diagnosed?

Not until puberty or even adulthood

28

What are the clinical features of von Willebrand disease?

Bruising

Excessive, prolonged bleeding after surgery

Mucosal bleeding such as epistaxis and menorrhagia

Unlike haemophilia, soft tissue haematomas and haemarthrosis are uncommon

29

How do we manage a patient with von Willebrand disease?

Depends on severity.

Type 1 (mild) - usually treated with desmopressin

More severe - plasma-derived FVIII (contain vWF unlike recombinant FVIII)

30

What are the main acquired disorders of coagulation affecting children?

Vitamin K deficiency leading to haemorrhagic disease of the newborn.

Liver disease

Immune thrombocytopenia

Disseminated intravascular coagulation

31

What is vitamin K used for in terms of coagulation?

Essential for production of active forms of factors II, VII, IX, X

32

Why might children become deficient in vitamin K?

Inadequate intake - neonates, long term chronic illness

Malabsorption - coeliac disease, cystic fibrosis, obstructive jaundice

Vitamin K antagonists - warfarin

33

What is the definition of thrombocytopenia?

Platelet count less than 150 x 10^9/L

34

What are the different grades of thrombocytopenia by platelet count?

Mild is 50 - 150 x 10^9/L - low risk of bleeding unless there is major operation or severe trauma

Moderate is 20 - 50 x 10^9/L - risk of excess bleeding during operations or trauma but low risk of spontaneous bleeding

Severe is less than 20 x 10^9/L - risk of spontaneous bleeding

35

What are the clinical features of thrombocytopenia?

Bruising

Petechiae

Purpura

Mucosal bleeding - epistaxis, bleeding from gums

36

What is the most common cause of thrombocytopenia in children?

Immune thrombocytopenia (ITP)

37

What is the incidence of ITP?

4 per 100, 000 children per year

38

What is the pathophysiology of ITP?

Usually caused by destruction of circulating platelets by anti-platelet IgG autoantibodies. Usually follows 1-2 weeks after a viral infection.

39

What is the peak age of incidence for ITP in children?

Between 2 and 10 years old

40

What are the clinical features of ITP?

Widespread petechiae and purpura

Superficial bruising

Epistaxis and other mucosal bleeding

41

How do we diagnose ITP in children?

It is a diagnosis of exclusion. FBC will show low platelet count. The differentials to exclude include:

Leukaemia - any atypical features should prompt bone marrow examination

DIC

Wiskott-Aldrich syndrome

Bernard-Soulier syndrome

SLE

42

How do we manage a child with ITP?

ITP is usually self-limiting, remitting spontaneously after 6-8 weeks.

Normally do not require admission

Treatment should be given if there is evidence of major bleeding or persistent bleeding that affects daily life (eg epistaxis)

Treatment options:

Oral prednisolone

IV anti-D

IVIG

Platelet transfusion (only in life-threatening scenarios)

43

If steroids are to be started in someone with suspected ITP, what investigation must be done first and why?

Bone marrow examination as steroid therapy can mask undiagnosed ALL. Steroid therapy will compromise the long-term outcome of such patients.

44

What do we define as chronic ITP?

When platelet count remains low 6 months after diagnosis

45

What percentage of children with ITP will develop chronic ITP?

20%

46

How do we manage children with chronic ITP?

Usually supportive therapy is all that is needed

Drug treatment includes Rituximab and thrombopoietic growth factor

Must also perform regular screening for SLE

47

What is disseminated intravascular coagulation?

A process characterised by the widespread activation of the clotting cascade that results in the formation of blood clots in the small blood vessels throughout the body. This leads to compromise of tissue blood flow and can ultimately lead to multiple organ damage. In addition, as the coagulation process consumes clotting factors and platelets, normal clotting is disrupted and severe bleeding can occur from various sites.

48

Disseminated intravascular coagulation occurs as a complicating factors for other underlying conditions. What conditions can lead to DIC in children?

Cancer - both solid and blood (particularly acute promyelocytic leukemia)

Massive tissue injury - eg burns

Sepsis

Transfusion reaction

Severe allergic or toxic reaction - eg snake venom

49

What investigations might be ordered to further assess someone with suspected disseminated intravascular coagulation? For each state what might be found in a positive result.

Prothrombin time increase

Activated partial thromboplastin time increase

Low fibrinogen

Rapidly declining platelet count

Positive D-dimer

Blood film shows schistocytes

Reduction in naturally occuring anticoagulants protein C and S and antithrombin.

50

How is disseminated intravascular coagulation treated?

Treat underlying cause

Supportive care includes FFP, cryoprecipitate and platelets.