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1B Cardiorespiratory > primary disorders of Haemostasis > Flashcards

primary disorders of Haemostasis Flashcards

1
Q

what is haemostasis?

A

cellular and biochemical processes that enable both the specific and regulated cessation of bleeding in response to vascular insult

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2
Q

what are the uses of haemostasis?

A
  • Prevention of blood loss from intact vessels
  • Arrest bleeding from injured vessels
  • Enable tissue repair
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3
Q

what is the mechanism of hemostasis?

A
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4
Q

how does platelet adhesion and platelet aggregation work?

A
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5
Q

what can cause a decrease in coagulant factor platelets?

A
  • Lack of specific factor
    • Failure of production: congenital/ acquired
    • Increased consumption/ clearance
  • Defective function of a specific factor
    • Genetic
    • Acquired: drugs, synthetic defect, inhibition
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6
Q

where can disorders occur from primary haemostasis?

A

platelets

von willebrand factor

the vessel wall

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7
Q

what disorders can occur from platelet dysfunction in primary haemostasis?

A

low numbers: thrombocytopenia

impaired function

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8
Q

what can cause low numbers of platelets? (thrombocytopenia)

A
  1. Bone marrow failure e.g leukaemia, B12 deficiency
  2. Accelerated clearance e.g immune (ITP), disseminated intravascular coagulation (DIC)
  3. Pooling and destruction in an enlarged spleen
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9
Q

what occurs in immune thrombocytopenia purpura (ITP)?

A

antiplatelet autoantibodies bind to sensitised platelet and cause macrophage recreuitment

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10
Q

what impaired defects with platelets can cause low platelet numbers?

A
  1. Hereditary absence of glycoproteins or storage granules (Rare)
  2. Acquired due to drugs: aspirin, NSAIDs, clipidogrel (common)
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11
Q

what is Glanzmann’s thrombasthenia?

A

hereditary platelet defect

Glp IIb/IIIa disorder

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12
Q

what is Bernard Soulier syndrome?

A

hereditary platelet defect

Glp1b disorder

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13
Q

where do drugs aspirin and clopidogrel act on aggregation pathway?

A

inhibit production thromboxane A2 (thromboxane causes platelet aggregation)

aspirin irreversibly blocks COX
clopidogrel irreversibly blocks ADP receptor on platelets

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14
Q

what is a primary haemostasis disorder of vWF?

A
  1. Von Willebrand disease
    1. Hereditary disease of quantity +/- function (common)
    2. Acquired due to antibody (rare)
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15
Q

what is a primary haemostasis disorder of the vessel wall?

A
  1. Inherited (rare) (hereditary vascular disorders)
    1. hereditary haemorrhagic telangiectasia
    2. Ehlers-Danlos syndrome
    3. Other connective tissue disorders
  2. Acquired (common)
    1. Steroid therapy
    2. Ageing (‘senile’ purpura)
    3. Vasculitis
    4. Scurvy (vit C deficiency)
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16
Q

what is the function of vWF in haemostasis?

A
  • Binding to collagen and capturing platelets
  • Stabilising factor VIII
    • Factor VIII may be low if VWF is very low
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17
Q

what can occur to VWF in von willebrand disease?

A
  • deficiency of VWF (platelet cannot bing to VWF which have become uncoiled under sheer stress)
    • Type 1= lower levels VWF
    • Type 3= no VWF
  • VWF with abnormal function
    • Type 2= abnormal VWF
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18
Q

what are the clinical features of disorders of primary haemostasis?`

A

bleeding

thrombocytopenia

purpura ( platelet or vascular disorders)

severe VWD= haemophilia like bleeding (due to low FVIII)

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19
Q

what are the bleeding clinical features of disorders of primary haemostasis?

A
  • Immediate
  • Prolonged bleeding from cutes
  • Nose bleeds (epistaxis): prolonged >20mins
  • Gum bleeding: prolonged
  • Heavy menstrual bleeding (menorrhagia)
  • Bruising (ecchymosis), may be spontaneous/easy
  • Prolonged bleeding after trauma or surgery
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20
Q

what are the clinical features of thrombocytopenia?

A

petechiae

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21
Q

what are the tests for disorders of primary haemostasis?

A
  1. Platelet count, platelet morphology
  2. Bleeding time (PFA100 in lab)- platelet function analysis
  3. Assays of VWF
  4. Clinical observation
  5. Non-coagulation screen (PT,APTT) is normal (except in more severe VWD cases FVIII is low)
22
Q

what is the treatment for failure of production/function (abnormal haemostasis)?

A
  • Reproducing missing factor/ platelets e.g VWF containing concentrates
    1. Prophylactic (preventative before operation)
    2. Therapeutic
  • Stop drugs e.g aspirin/ NSAIDS
23
Q

what is the treatment for primary haemostasis immune destruction?

A
  • Immunosuppression e.g prednisolone
  • Splenectomy for ITP
24
Q

what is the treatment for primary haemostasis increased consumption?

A
  • Treat cause
  • Replace as necessary
25
Q

what additional haemostatic treatments can be given for primary haemostasis disorders?

A
  • Desmopressin (DDAVP)
    • Vasopressin analogue
    • 2-5 fold increased in VWF (and FVIII)
    • Releases endogenous stores (so only useful in mild disorders)
  • Tranexamic acid
    • Antifibrinolytic
  • Fibrin glue/ spray (in theatre during surgery)
  • Other approaches (e.g hormonal (coral contraceptive pill for menorrhagia)
26
Q

what is secondary haemostasis?

A

disorders of coagulation

27
Q

what is the role of coagulation?

A

generate thrombin (IIa) which will convert fibrinogen to fibrin

28
Q

what does a deficiency in any coagulation factor result in?

A

failure of thrombin generation and hence failure fibrin formation

29
Q

what are the causes of deficiency of coagulation factor production?

A

hereditary

  • factor VIII/IX: haemophilia A/B

acquired

  • liver disease
  • anticoagulant drugs (Warfarin, DOACs)

dilution

  • acquired-blood transfusion

increased consumption

  • acquired - disseminated intravacular coagulation (DIC) and immune autoantibodies
30
Q

what are the symptoms of factor VIII and IX deficiency?

A

haemophilia= failure to generate fibrin to stabilise platelet plug

  • Hallmark haemophilia= hemarthrosis
  • Chronic hemarthrosis= muscle wasting
  • Avoid intramuscular injections in patients with haemophilia
  • haemophilia A (factor VII deficiency)
  • haemophilia B (factor IX deficiency)
    • sex linked
  • spontaneous joint and muscle bleeding
  • severe but compatible with life
31
Q

what is the consequence of prothrombin (FII) deficiency?

A

lethal

32
Q

what is the consequence of FXI deficiency?

A

bleeding after trauma but not spontaenously

33
Q

what is the consequence of factor XII deficiency?

A

no bleeding at all

34
Q

why does liver failure cause secondary haemostasis disorder?

A
  • most coagulation factors are synthesised in liver (except VWF-synthesised in endothelial cells lining RCB and factor VI- synthesised In platelets)
  • decreased production of coagulation factors
35
Q

how does dilation coagulation disorders occur?

A

red cell transfusions no longer contain plasma

major haemorrhage requires transfusion of plasma as well as red cells and plasma

36
Q

what is disseminated intravascular coagulation?

A
  • generalised activation of coagulation- tissue factor
  • associated with sepsis, major tissue damage (pre-eclampsia), inflammation, cancer
  • consumes and depletes coagulation factors
  • platelets consumed- results in thrombocytopenia
  • activation of fibrinolysis depletes fibrinogen- raised D-dimer (a breakdown product of fibrin)
  • deposition of fibrin in vessels causes organ failure and sheering of red blood cells that flow through these vessels causing red cell fragmentation
  • treatment of underlying cause required
  • give replacement factors through FFP and platelets for supportive treatment
37
Q

clinical features of coagulation disorders?

A
  • superficial cuts do not bleed (platelets working fine and platelet plug sufficient in smaller blood vessels)
    • in larger blood vessels the plug breaks down causing bleeding
  • bruising is common, nosebleeds are rare
  • spontaneous bleeding is deep, into muscles and joints
  • bleeding after trauma may be delayed and is prolonged
  • bleeding frequently restarts after stopping
38
Q

what is the difference in bleeding due to platelet and coagulation disorders?

A

platelet/vascular:

superficial bleeding into skin, muscular membranes

bleeding immediate after injury

coagulation:

bleeding into deep tissue, muscles, joints

delayed, but severe bleeding after injury

bleeding often prolonged

39
Q

what are the screening tests for coagulation disorders?

A

prothrombin time

activated partial thromboplastin time (APTT)

full blood count (platelets)

40
Q

when are PT and APTT increased?

A

liver disease

anticoagulant drugs e.g warfarin

DIC (platelets and D dimer)

dilution following red cell transfusion

deficiency of factor of the common pathway (FX, V or II)

41
Q

what are the causes of increased APTT?

A

haemophilia A

haemophilia B

FXI deficiency

FXII deficiency

42
Q

causes of increased PT?

A

factor VII deficiency

43
Q

what does prothrombin time measure?

A

extrinsic pathway

the shorter pathway of secondary hemostasis.

Once the damage to the vessel is done, the endothelial cells release tissue factor which goes on to activate factor VII to factor VIIa. Factor VIIa goes on to activate factor X into factor Xa.

44
Q

what does APTT measure?

A

intrinsic pathway

45
Q

draw the coagulation pathway

A
46
Q

what does FFP contain?

A

all coagulation factor

47
Q

what does cryoprecipitate contain?

A

rich in fibrinogen, FVIII, VWF and FXIII

48
Q

what factor concentrates are available?

A

all except FV

prothrombin complex concentrates (PCCs) factor II, VII, IX, X

49
Q

what factor recombinant forms are available?

A

FVIII and FIX

on demand to treat bleeds

prophylaxis: e.g haemophilia

50
Q

what novel treatments are available for coagulation disorders?

A
  • Gene therapy (haem A and B)
  • Bispecific antibodies (Haem A)
    • Emixizumab
    • binds to FIXa and FX
    • mimic procoagulant function of FVIII
  • RNA silencing (Haem A and B)
    • Targets natural anticoagulant- antithrombin

1B Cardiorespiratory (15 decks)

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