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Haematology Y2 > Abnormalities of Haemostasis > Flashcards

Abnormalities of Haemostasis Flashcards

1
Q

2 reasons people have abnormal haemostasis?

A

Lack of a specific factor

Defective function of a specific factor

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2
Q

Why might people have Lack of a specific factor (2)

A

 Failure of production- congenital or acquired

 Increased consumption/clearance

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3
Q

Why might people have Defective function of a specific factor

A

 Genetic defect

 Acquired- drugs, synthetic defect, inhibition

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4
Q

the 2 ways and receptors platelets use to bind to collagen

A

directly via Gp1a receptor, or via Gp1b using VWF as a bridge.

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5
Q

Platelet aggregation is mainly through X generation and release of platelet granular content containing Y

A

thromboxane A2

ADP amongst other things

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6
Q

TXA2 and ADP release activates what on platelets and this activation allows what?

A

Gp2b/3a receptors on platelets enabling them to bind to each other

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7
Q

What crosslinks platelets

A

fibrinogen

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8
Q

What ion is required for platelet coagulation and fibrinogen cross linking

A

Ca2+

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9
Q

Platelet linked problems with primary haemostasis?

A

Low numbers - thrombocytopenia

Impaired function

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10
Q

VWF linked problems with primary haemostasis?

A
  • Hereditary absence of glycoproteins or storage granules (Gp1b and Gb2b/3a)
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11
Q

Vessel wall linked problems with primary haemostasis?

A
  • Hereditary haemorrhagic telangiectasia, Ehlers-Danlos syndrome and other connective tissue disorders
  • Acquired- scurvy, steroid therapy, ageing (age-related purpura), vasculitis
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12
Q

Causes of thrombocytopenia? (4)

A
  • Bone marrow failure e.g. leukaemia (fills bone marrow with leukaemic cells not allowing normnal haematopoiesis to occur), B12 deficiency (megaloblastic anaemia, B12 is required for required for DNA synthesis, so the blood cells will grow but not be able to divide and so the marrow fills up with these cells and they are squeezed out)
  • Accelerated clearance e.g. immune (ITP – autoimmune thrombocytopaenia), (DIC – disseminated intravascular coagulation).
  • Pooling and destruction in an enlarged spleen
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13
Q

What is auto-immune thrombocytopenia purpura

A

Auto-ITP- antiplatelet autoantibodies bind to platelets and make them recognisable to macrophages in the reticuloendothelial system that kill them

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14
Q

3 causes of thrombocytopenia (brief)

A
  1. Failure of platelet production by megakaryocytes
  2. Shortened half-life of platelets
  3. Increased pooling of platelets in an enlarged spleen (hypersplenism) + shortened half-life
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15
Q

2 functions of VWF?

A

Binding to collagen and capturing platelets

Stabilising factor VIII

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16
Q

How do you acquire VWD

A

hereditary

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17
Q

Types of VWD?

A

Deficiency of vWF (type 1 (make some) or 3 (make none- autosomal recessive and rare))
vWF with abnormal function (type 2)

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18
Q

What is epistaxis

A

Nosebleeds

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19
Q

What is PETECHIAE

A

(fine dotted rash can be seen with purpura)

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20
Q

Examples of typical primary haemostasis bleeding?

A
  • Immediate
  • Prolonged bleeding from cuts
  • Epistaxes
  • Gum bleeding
  • Menorrhagia
  • Easy bruising
  • Prolonged bleeding after trauma or surgery
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21
Q

Tests for disorders of primary haemostasis? (4)

A
  1. Platelet count, platelet morphology
  2. Bleeding time (PFA100 in lab) Not done anymore
  3. Assays for vWF
  4. Clinical observation
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22
Q

What is secondary haemostasis

A

stabilisation of platelet plug with fibrin

23
Q

what is primary haemostasis

A

formation of the unstable platelet plug

24
Q

Deficiency of any coagulation factor results in a failure of X generation and hence Y formation

A

thrombin

Fibrin

25
Q
  • The primary platelet plug is sufficient for X injury

- In Y it will fall apart

A

small vessel

larger vessels

26
Q

What stabilises the platelet plug

A

Fibrin

27
Q

What is the issue in haemophilia

A

inability to generate fibrin

28
Q

Inability to generate VIIIa is known as

A

Haemophilia A

29
Q

Inability to generate FIXa is known as

A

Haemophilia B

30
Q

Inability to generate prothrombin is lethal/compatible with life?

A

Lethal

31
Q

How much bleeding is caused with an inability to generate factor XII

A

no excess bleeding

32
Q

How much bleeding is caused with an inability to generate factor XI

A

Bleed after trauma but not spontaneously

33
Q

3 ways of getting acquired coagulation factor production deficiency?

A

Liver disease
Dilution coagulopathy
Anticoagulant drugs

34
Q

Causes of secondary haemostasis problems?

A

Deficiency of coagulation factor production

INCREASED CONSUMPTION

35
Q

Acquired and immune causes of increased consumption

A

DIC (disseminated intravascular coagulation)

Immune- autoantibodies

36
Q

What is DIC

A

Generalised activation of coagulation- tissue factor

  • Associated with sepsis, major tissue damage, inflammation
  • Consumes and depletes coagulation factors
  • Platelets consumed
  • Activation of fibrinolysis depletes fibrinogen
  • Deposition of fibrin in vessels causes organ failure
37
Q
  • Superficial cuts do not bleed with secondary haemostasis problems because XXXX
A

the platelet plug can still form and that is enough as it is a small vessel injury.

38
Q
  • Bruising is common, nosebleeds are rare in problems of …
A

secondary haemostasis

39
Q

Differences in bleeding between platelet problems and coagulation factor problems?

A

Platelet: superficial bleeding into skin and mucosal membranes
bleeding is immediate after injury

CoagulationL bleeding into deep tissues, muscles and joints
delayed but severe bleeding after injury, bleeding often prolonged

40
Q

Tests for coagulation disorders? (3, 1 has another 3)

A
  1. Screening tests (‘clotting screen’):
     Prothrombin time (PT) Prolonged in haemophilia
     Activated partial thromboplastin time (APTT) Prolonged in haemophilia
     Full blood count (platelets)
  2. Factor assays (e.g. for factor VIII)
  3. Tests for inhibitors
41
Q

Do routine clotting tests pick up all bleeding disorders? E.g.?

A

NO, e.g. VWF, platelet disorders, vessel wall disorders

42
Q

Disorders of fibrinolysis? (hereditary and acquired)

A 
-	Hereditary:
 Antiplasmin deficiency
-	Acquired:
 Drugs such as tPA
 DIC
43
Q

VON WILLEBRAND DISEASE is what type of genetic disease

A

AUTOSOMAL dominant (apart type 3 which is recessive)

44
Q

How to treat failure of production/function of coagulation components?

A
  • Replace missing factor/platelets:
    Prophylactic
    Therapeutic
  • Stop drugs
45
Q

How to treat immune destruction?

A
  • Immunosuppression (e.g. prednisolone)

- Splenectomy for ITP

46
Q

How to treat INCREASED CONSUMPTION (OF CLOTTING FACTORS)

A
  • Treat cause

- Replace as necessary

47
Q

Plasma contains which coagulation components?

A

All

48
Q

Cryoprecipitate contains which coagulation components?

A
  • Rich in fibrinogen, FVIII, vWF, FXIII
49
Q

Factor concentrates contains which coagulation components?

A
  • Concentrates available for all factors except FV

- Prothrombin complex concentrates (PCCs) Factors II, VII, IX, X – use these to replace the effects of warfarin

50
Q

4 ways of treating haemostatic disorders

A

FACTOR REPLACEMENT THERAPY:
GENE THERAPY:
NOVEL APPROACHES:
ADDITIONAL HAEMOSTATIC TREATMENTS:

51
Q

What novel treatments for haemostatic disorders are in development (3)

A
  • Bispecific antibody – mimics binding effects of FVIII by binding to FIX but it doesn’t have the other effects of FVIII which is good because then the body doesn’t form inhibitors
  • Anti-TFPI antibody (TFPI switches off tissue factor but carries the risk of thrombosis)
  • Antithrombin RNAi – dampens down thrombin
52
Q

What drugs can be used to treat haemostatic disorders

A
  1. DDAVP – desmopressin, analogue of vasopressin, it increases endothelial cell release of VWF for some reason. Cheap and safe and doesn’t involve exogenous sources of VWF.
  2. Tranexamic acid – used in major trauma, analogue of lysine. To get fibrinolysis you need TPA and plasminogen to bind to the lysine on fibrin. Tranexamic acid binds to TPA instead of the lysin on fibrin so no fibrinolysis occurs.
  3. Fibrin glue/spray
53
Q

How does desmopressin work for haemostatic disorders

A
  • 2-5 fold increase in vWF and in FVIII
  • Releases endogenous stores Only useful in mild disorders
  • Can be given as nasal spray or orally
54
Q

How does tranexamic acid work for haemostatic disorders

A

Inhibits fibrinolysis (competitively inhibits tPA binding to fibrin)

  • Widely distributed Crosses placenta
  • Low concentration in breast milk

Haematology Y2 (11 decks)

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