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Pathology And Medicine > Disorders of Haemostatsis > Flashcards

Disorders of Haemostatsis Flashcards

1
Q

Normal haemostasis
Clotting mechanisms

A

Clotting mechanisms = interchangeable = Clot lysis

thus:

  • Internal and external bleeding controlled
  • Pathological thrombosis prevented
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2
Q

What are the factors that maintain the clotting equilibrium

A
  • Blood vessel– vasoconstriction
  • Platelets– initial haemostatic plug
  • Blood coagulation – fibrin; permanent haemostatic plugs
  • Fibrinolysis– plasmin to remove fibrin thrombi
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3
Q

Role of platelets

A

Early phase of haemostasis via

  • Adhesion
    → Attracted to exposed collagen
    → Activation: release of cytoplasmic granules
  • Aggregation
    → Accumulation/aggregation of large numbers of platelets to form haemostatic plug
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4
Q

Blood coagulation

A
  • Plasma precursors → fibrin → permanent haemostatic plug
  • Activation of a series of clotting factors normally present in an inactive form → need to be activated
  • Thrombin - key enzyme → determines over clotting activity
  • Some factors are serine proteases
  • Many clotting factors are synthesised in the liver Some(II, VII, IX, X)require Vit K for their synthesis
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5
Q

Thrombin

A

key enzyme in blood coagulation
→ determines over clotting activity

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6
Q

Clinical laboratory testing for haemostasis

A
  • Clinical laboratory testing is a critical and main element in the diagnosis and treatment of haemostatic disorders
  • A vast array of laboratory tests can be used to assess haemostasis - normal and specific disorders
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7
Q

Laboratory testing of haemostatsis

A
  • internal control (control) is more reliable than published figures → not rely in normal value and add an internal control due to possible human, system, etc errors
  • Routine tests to determine normal haemostasis
  • Specialised tests to determine the type of abnormality if an abnormality found in routine testing.
  • All tests must have control plasma run with them
    →In many cases, the difference between patient and control that is more important than normal ranges
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8
Q

Sample collection of haemostatsis testing

A
  • A clean venous blood sample for coagulation
  • Blood should be immediately placed into plastic tubes containing appropriate anticoagulants:
    → potassium EDTA: full blood count
    → sodium citrate: clotting studies
  • blood should be gently mixed
  • blood should be tested ASAP (2-4 h) → if not may undergo abnormal changes
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9
Q

Preparation of PPP(platelet-poor plasma)

A
  • Accurate coagulation testing requires the plasma free of platelets (except platelet function tests)
  • Immediately spin the sample (3000rpm, 10 min)
  • Keep the sample at room temperature until PPP obtained to prevent platelet activation
  • Test immediately or remove the plasma and store (at 4oC for a few hours or - 40oC for several wks)
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10
Q

Pre-analytical & analytical variation

A
  • Common technical “errors” affect coagulation results
  • already affects results even before analysis
  • Pre-analytical variation−Poor sample collection−Wrong anticoagulant / no anticoagulant−Contamination−Storage / transportation
  • Analytical variation−Incorrect temperature for analysis - Out of date or poorly prepared reagents -Out of date or poorly prepared control material
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11
Q

Tests of haemostatic function

Routine tests

A
  • Bleeding time: an index ofplatelet integrity
  • Activated partial thromboplastin time (APTT): test for
    Intrinsic+ Common(XII, XI, IX, VIII, X, V, II & I)
  • Prothrombin time (PT): test forExtrinsic+ Common (VII, X, V, II & I)
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12
Q

Special Investigations - test of haemostatic function

A
  • 50:50 Correction Studies (APTT)−With normal plasma−With known deficient plasmas (which factor)
  • Factor Assays (level of deficiency of that factor)
  • Inhibitor Studies (abnormal inhibitor coagulation)
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13
Q

What are disorders of primary haemostasis?

A
  • Platelet abnormalities
  • Defects of small blood vessels

Skin and mucous membrane especially involved

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14
Q

What are disorders of blood coagulation?

A
  • Congenital clotting factor deficiency
  • Acquired disorders of coagulation

Typically: haemarthroses, muscle haematomas, bleeding after injury or surgery

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15
Q

Thrombocytopenia

A

reduction of platelet numbers

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16
Q

Causes of thrombocytopenia

A
  • Failure of production
  • Increased destruction
  • Sequestration
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17
Q

Where there is abnormalities of blood platelets, what is bleeding due to?

A

−Thrombocytopenia

−Abnormal platelet function

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18
Q

What is abnormalities of blood platelets characterised by?

A

Characterised bypurpuraandbleeding from mucous membranes

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19
Q

> 80 x109/L platelet count meaning

A

no clinical defect

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20
Q

< 50 x109/L platelet count meaning

A

bleeding after trauma

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21
Q

< 20x109/L platelet count meaning

A

spontaneous bleeding

22
Q

Causes of thrombocytopenia

A

Failure of production

Increased destruction/use of platelets

Sequestration

Idiopathic thrombocytopenic purpura (ITP)

23
Q

Causes of thrombocytopenia

-Failure of production

A
  • Megaloblastic anaemia
  • Haematological malignancy
  • Solid tumour infiltration
  • Aplastic anaemia/bone marrow failure
24
Q

Causes of thrombocytopenia

-Increased destruction/use of platelets

A
  • Autoimmune(ITP Idiopathic thrombocytopenic purpura )
  • Secondary immune(SLE, viruses, drugs)
  • Alloimmune(neonatal & post-transfusion purpura)
  • DIC(disseminated intravascular coagulation) → consume a lot of clotting factors
  • Thrombotic thrombocytopenic purpura
25
Q

Causes of thrombocytopenia
- Sequestration

A

Hypersplenism

26
Q

Idiopathic thrombocytopenic purpura (ITP)

A

Bleeding disorder due to immune destruction of platelets

27
Q

Idiopathic thrombocytopenic purpura (ITP) - Causes & pathogenesis

A

Immune system produces platelet Ab→ Ab attach to platelets→spleen destruction

28
Q

ITP in children

A

usually acute but self-limiting; bone marrow examination not usual

29
Q

ITP in adult

A

less acute than in children; characteristically in women; associated with other autoimmune disorders (e.g. SLE); platelets Ab in 60-70% patients

30
Q

Clinical features of ITP

A
  • Major haemorrhage rare, seen only with severe thrombocytopenia
  • Easy bruising, purpura, epistaxis, menorrhagia−Physical examination: normal except evidence of bleeding
31
Q

Laboratory investigation of ITP

A
  • Thrombocytopenia: the only blood count abnormality
  • Anti-platelet auto-antibodies
32
Q

ITP Treatment

A

In children, not usually require treatment; if necessary:

  • High dose anti-inflammatory steroid → inhibit the immune responses
  • i.v. immunoglobin (very serious bleeding, urgent surgery)
33
Q

What level does platelets need to be for an adult patient to require no treatment?

A

Platelets ≥30x109/L - no treatment

34
Q

What is the first line of treatment in adults for ITP?

A

corticosteroids(iv IgG if rapid platelets rise desired)

35
Q

What is the second line of treatment in adults for ITP?

A

splenectomy(majority respond),
- if fails other treatments (high dose corticosteroids, immunosuppresion; recombinant thrombopoietin).

Platelet transfusion (intracranial or other extreme haemorrhage)

36
Q

ITP treatment for adults

A

First line:
corticosteroids (iv IgG if rapid platelets rise desired)

Second line:
splenectomy(majority respond),

if fails other treatments (high dose corticosteroids,immunosuppresion; recombinant thrombopoietin)

Platelet transfusion (intracranial or other extreme haemorrhage)

37
Q

Disorders of blood coagulation

A
  • Coagulation/fibrinolytic disorders may cause thrombosis or haemorrhage
  • Congenital or acquired
  • Majority of these are acquired
38
Q

Congenital coagulation disorder

A
  • Uncommon and usually involve deficiency of one factor only
  • not all factors express bleeding → they are not important
  • factor 8 and 9 are important
39
Q

Congenital coagulation disorder types

A

−Haemophilia A

−Haemophilia B

−Von Willebrand’s disease

40
Q

Haemophilia A genetic relation

A
  • inherited as X-linked
  • recessive trait
  • Occurring mainly in males → show phenotype in men- rare to show in women
41
Q

What is haemophilia A deficiency of?

A

factorVIII (FVIII)

42
Q

Clinical features of Haemophilia A

A

−Clinical severity depends on residual FVIII activity

  • 1-5%, bleeding after minor trauma
  • < 1%, bleeding spontaneously
  • > 5%, asymptomatic

Coagulation deficiency type bleeding; purpura is not a feature
- spontaneous bleeding into muscle, joints; bleeding after dental surgery typical

Aids is a major complication in some patients (due to treatment with FVIII concentrate)

43
Q

Laboratory feature go haemophilia A

A
  • Partial thromboplastin time prolonged; FVIII↓ (<20%)
  • Prothrombin time & bleeding time: normal
44
Q

Treatment of haemophilia A

A

Maintaining plasmaFVIIIactivity activity without bleedingat a level that per

45
Q

Haemophilia B

A
  • Haemophilia B (Christmas disease) is uncommon (1 in 50,000)
  • Deficiency of factorIX
  • X-linked recessive inheritance, greater prevalence in males
  • Clinical picture identical to haemophilia A
46
Q

Von Willebrand’s disease

A
  • A moderate to mild bleeding disorder
  • Deficiency or abnormality of Von Willebrand Factor
    (vWF, a glycoprotein; essential cofactor for platelet adhesion & also stabilising factor VIII)
47
Q

What does Von Williebrand’s disease cause?

A
  • abnormal platelet adhesion- low factorVIIIclotting activity
  • Autosomal gene, numerous mutations identified
48
Q

Acquired coagulation disorder

A

Coagulation factor deficiency developed in some diseases or by drug therapies

  • Vitamin K deficiency
  • Liver disease
  • Anticoagulant & fibrinolytic drugs DIC
49
Q

Vitamin K deficiency

A
  • Some factors(II, VII, IX & X)are Vit K dependent
  • Source of Vit K - green vegetables, gut microflora
  • Lipid soluble, hence requires bile for absorption
  • Therefore Vit K deficiency in obstructive jaundice & liver disease
  • Haemorrhagic disease of the newborn– lack of gut flora
50
Q

Warfarin

A
  • A coumarin, potent Vit K antagonist
  • Inhibiting complete synthesis of coagulation factors
51
Q

How is liver disease related to haemostatic diseases?

A

Liver disease→ a number of defects in haemostasis

52
Q

Liver disease as a haemostatic disease

A
  • Vit K deficiency (over disease affects the absorption) due tointra/extra hepatic cholestasis
  • Reduced synthesis as a result of severe hepatocellular damage
  • Thromocytopenia due to hypersplenism
  • Functional abnormalities fibrinogen
  • DIC – in acute liver failure in platelets and e

Pathology And Medicine (15 decks)

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