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MedEd + PathSoc + Laz's Qs + Romesh Path > Haem 6: Haemostasis and Bleeding disorders > Flashcards

Haem 6: Haemostasis and Bleeding disorders Flashcards

1
Q

Describe the process of Haemostasis?

A
  1. Damage to endothelium leaves sub-endothelial structures exposed
  2. Platelet adhesion:
    DIRECTLY - via Glp1a
    INDIRECTLY - via binding to vWF via Glp1b (More important)
  3. This leads to release of mediators ADP and Thromboxane A2 by platelets
  4. This promotes platelet aggregation and they attach to each other using the GlpIIb / IIIa receptor (aka fibrinogen recepton - fibrinogen can also bind to this receptor)
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2
Q

What are the 3 stages of the coagulations cascade?

A
  1. Initiation
  2. Amplication
  3. Propagation
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3
Q

Outline the initiation phase of the clotting cascade.

A

Damage to the endothelium results in exposure of tissue factor which binds to factor 7 and activates it to factor 7a

The tissue factor-factor 7a complex then activates factors 9 and 10

Factor 10a binds to factor 5a resulting in the first step of the coagulation cascade

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4
Q

Outline the amplification phase of the clotting cascade.

A

Activated factors 5 and 10 will result in the production of a small amount of thrombin

This thrombin will activate platelets
Thrombin will also activate factor 11 which activates factor 9
Thrombin also activates factor 8 and recruits more factor 5a

Factors 5a, 8a and 9a will bind to the activated platelet

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5
Q

Outline the propagation phase of the clotting cascade

A

Activated factors 5, 8 and 9 will recruit factor 10a

This results in the generation of a large amount of thrombin (thrombin burst)

This enables the formation of a stable fibrin clot

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6
Q

List some pro-coagulant factors in the body

A

Platelets

Endothelium

vWF

Coagulation cascade

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7
Q

List some anti-coagulant factors in the body

A

Fibrinolysis

Anti-thrombins

Protein C/S

Tissue factor pathway inhibitor

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8
Q

How can disorders of haemostasis be categorised and what do these mean?

A

Disorders of primary or secondary haemostasis

  • Primary – platelet adhesion and aggregation (quantitative and qualitative defects)
  • Secondary – coagulation cascade (inherited and acquired)
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9
Q

What are disorders of thrombosis caused by?

A

Due virchow’s triad

Inherited causes = Factor V leiden, Anti-thrombin deficiency and protein C/S deficiency

Accquired = HIT, malignancy and immobilisation

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10
Q

What is Virchow’s triad?

A

Stasis of blood flow

Endothelial injury

Hypercoagulability

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11
Q

What does a dysfunction in primary haemostasis cause? How can this be categorised?

A

Bleeding disorders (superficial bleeding)

Qualitative defect in platelets – von Willebrand disease

Quantitative defect in platelets – ITP, HIT (heparin induced thrombocytopaenia)

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12
Q

What does a dysfunction in secondary haemostasis cause? How can this be categorised?

A

Coagulation disorders (deep bleeding):

Inherited disorders – haemophilia A, haemophilia B

Acquired disorders – liver disease, vitamin K deficiency

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13
Q

What are some causes of platelet disorders ?

A

Decreased Number (Thrombocytopaenia) ​

  • Decreased production  ​
  • Decreased survival (ITP) ​
  • Increased consumption (DIC)  ​
  • Dilution ​

Defective Platelet Function ​

  • Acquired (e.g. aspirin, end-stage renal failure)  ​
  • Congenital (e.g. thrombasthenia) ​
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14
Q

What are the different causes of platelet disorders?

A

Immune-Mediated ​

  • Idiopathic ​
  • Drug-induced (e.g. quinine, rifampicin, vancomycin) ​
  • Connective tissue disease (e.g. rheumatoid arthritis, SLE) ​
  • Lymphoproliferative disease ​
  • Sarcoidosis ​

Non-Immune Mediated ​

  • DIC ​
  • MAHA ​

NB: this isnt really tested that much

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15
Q

What is the most common coagulation disorder and how is this inherited?

A

Von Willebrand disease - AD (mainly) (1/10,000)

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16
Q

What are the subtypes of vWD? main symptom?

A

Type I – AD, quantitative defect

Type II – AD, qualitative defect

Type III – AR, quantitative and qualitative defects

Superficial bleeds eg mucocutaneous bleeding

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17
Q

What can ix show in vWD?

A

↓platelet adhesion, ↓factor VIII (generally vWF prevents VIII breakdown in circulation), abnormal ristocetin

Clotting screen: ↓platelet count, ↑bleeding time, ↑APTT, normal PT

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18
Q

What are the differences and similarites between vWD and Haemophilia A?

A

Very similar to haemophilia A because there is a strong relationship between vWF and factor 8 ​(both go down together)

These cases will both present similarly however in vWD there will be REDUCED PLATELET ADHESION which you would not see in Haemophilia A

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19
Q

What are ddx to consider in vWD?

A

These present similarly however have different findings on ix:
Bernard-Soulier disease (large platelets) and

Glanzmann’s thrombasthaenia (normal ristocetin)

20
Q

Mx of vWD?

A

Desmopressin, vWF and factor VIII concentrates

21
Q

What is ITP? pathophysiology?

A

This is when autoantibodies are generated against platelets ​

Platelets tagged by antibodies are then destroyed in the reticuloendothelial system

Causing an immune mediated thrombocytopaenia

22
Q

What are the different types of ITP + who is more likely to get it?

A

Acute = children 1:1 (m:f)

Chronic (relapsing-remitting disease) = adults 1:3 (m:f)

23
Q

What are the features of acute ITP? mx?

A

Generally occurs in children with preceding infection

Mx:

  • Can be severe but SELF-LIMITING
  • Treatment with steroids and IVIG if platelet count ↓↓↓, major bleeding
24
Q

What are the features of chronic ITP? mx?

A

More likely in adults, 3:1 female ratio

No trigger
Long-term relapsing-remitting

Mx:
Treatment with steroids, IVIG or splenectomy

25
Q

What is Haemophilia A and what is the inheritance?

A

X-linked recessive, Factor VIII deficiency (intrinsic pathway)

26
Q

What are the clinical features + ix findings in Haemophillia A

A

Spontaneous, deep bleeding, haemarthrosis (IMPORTANT), lots of bleeding after dental extractions (IMPORANT)

Normal platelet count, normal bleeding time, ↑APTT, normal PT

27
Q

Which Haemophillia is more common A or B? How can you differentiate between these two?

A

Haemophillia A > B

Clinically there is no way to differentiate - only possible by factor VIII or IX assay

28
Q

What is Haemophilia A mx?

A

Factor VIII concentrate

29
Q

What is Haemophilia B and what is the inheritance?

A

X-linked recessive, Factor IX deficiency (intrinsic pathway)

30
Q

What are the key features of Haemophilia B?

A

Spontaneous, deep bleeding, haemarthrosis (IMPORTANT), lots of bleeding after dental extractions (IMPORANT)

Normal platelet count, normal bleeding time, ↑APTT, normal PT

31
Q

What is Haemophilia B mx?

A

Factor IX concentrate

32
Q

What is Vitamin K important for?

A

For synthesis of factors II, VII, IX and X, protein C/S (natural anticoagulants)

33
Q

What are some common causes of vitamin K deficiency?

A

Secondary to malabsorption, warfarin (MOST COMMON), antibiotic therapy

34
Q

What factor is the first to be depleted in vitamin K deficiency and why?

A

Factor VII - has the shortest halflife

35
Q

What are the ix findings in vitamin K deficiency? mx?

A

Ix - Normal platelet count, normal bleeding time, ↑APTT, ↑PT (affects both extrinsic and intrinsic pathways)

Management – vitamin K replacement, PCC (Prothrombin complex concentrate), FFP (Fresh frozen plasma)

36
Q

What are some differentials to consider in vitamin K deficiency?

A

Differentials include liver disease (↓platelet count), scurvy (corkscrew hair)

37
Q

What is the most common inherited prothombotic disorder? what is its mode of inheritance?

A

Factor V Leiden - AD

38
Q

What are the key features of Factor V leiden? mx?

A

Resistance to protein C -> failure to degrade factor V -> hypercoagulable state

Predisposition to venous thromboembolism (arterial thromboembolism rare)

Mx = long-term anticoagulation

39
Q

What is thrombin used for? what opposes this action?

A

Covert fibrinogen into fibrin hence increases coagulation

Anti-thrombin acts against this and decreases coagulation

40
Q

What is the inheritance of anti-thrombin deficiency?

A

AD

41
Q

What are the key features of anti-thrombin deficiency?

A

Carries highest risk of thrombosis - IMPORTANT

Develop thromboembolism in unusual locations (e.g. splenic or mesenteric veins)

Anti-thrombin assay used to make diagnosis

Key differentials include protein C/S deficiency

42
Q

Mx of anti-thrombin / protein C/S deficiency?

A

Management – long-term anti-coagulation with warfarin(AVOID WARFARIN IN PROTEIN C/S) and argatroban

43
Q

Which patients are most likely to suffer from warfarin-induced skin necrosis?

A

Protein C/S deficiency - Paradoxical blood clotting.
Blood clots block the blood vessels and cause necrosis, where an area of skin is destroyed.

44
Q

Inheritance of Protein C/S deficiency?

A

Autosomal dominant

45
Q

A 19-year-old boy comes in with an acutely swollen knee. He does not recollect any trauma.

He has been known to have history of bleeding after dental extraction. What is the most likely factor deficiency?

Factor X
Factor VII
Factor IX
Factor VIII
Factor XI

A

Factor VIII - Haemophilia is the dx A or B

A is way more common, no way to clinically distinguish

46
Q

What is the most common inherited Thrombophilia?

VWD
Hereditary Activated Protein C Resistance
Anti-Thrombin Deficiency
Hemophilia B
Protein S Deficiency

A

Hereditary Activated Protein C Resistance - This is simply there to throw you off -> it’s referring to Factor V Leiden

47
Q

Describe the extrinc,intrinsic and common pathways of coagulation

A

MedEd + PathSoc + Laz's Qs + Romesh Path (99 decks)

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