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BRS 2 > CVR - Haemostasis > Flashcards

CVR - Haemostasis Flashcards

1
Q

What is haemostasis?

A

The cellular and biochemical process that enables both the specific and regulated cessation of bleeding in response to vascular insult

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2
Q

State the 3 functions of haemostasis

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

What occurs in primary haemostasis?

A
  • Platelet adhesion

- Platelet aggregation

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4
Q

What is the function of primary haemostasis?

A

Formation of a unstable platelet plug:

- Limit blood loss and provide a surface for coagulation

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5
Q

What occurs in secondary haemostasis?

A
  • Blood coagulation
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6
Q

What is the main function of secondary haemostasis?

A

Stabilisation of the platelet plug with fibrin

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7
Q

What is fibrinolysis?

A

Vessel repair and dissolution of clot

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8
Q

What is normal haemostasis maintaining a balance between?

A

Bleeding and thrombosis

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9
Q

What factor(s) cause platelet aggregations and adhesion?

A

VWF via the Gp1b or Glp1a (GLycoprotein 1a)

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10
Q

What is ITP?

A

Idiopathic thrombocytopenia purpura:

The presence of antiplatelet antibodies within the body which result in platelets being destroyed by macrophages

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11
Q

What are the potential causes for thrombocytopoenia?

A
  • Bone marrow failure
  • Accelerated clearance
  • Pooling and destruction in an enlarged spleen
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12
Q

What can cause imparied function of platelets?

A
  • Hereditary absence of glycoproteins or storage granules

- Acquired due to drugs

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13
Q

State the functions of VWF in haemostasis?

A

Binding to collagen and capturing platelets

Stabilising factor VIII:
- Factor VIII may be low if VWF is low

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14
Q

What inherited diseases can cause vessel wall damage ?

A
  • Hereditary haemorrhagic telangiectasia

- Ehlers-Danlos syndrome

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15
Q

What acquired factors/diseases can cause vessel wall damage ?

A
  • Steroid therapy
  • Ageing
  • Vasculitis
  • Scurvy (vitamin C deficiency)
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16
Q

What are some typical symptoms of primary haemostasic bleeding disorders?

A
  • Immediate
  • Prolonged bleeding
  • Nose bleeds: prolonged >20mins
  • Gum bleeding: prolonged
  • Heavy menstrual bleeding
  • Bruising: easy or spontaneous
  • Prolonged bleeding after trauma or surgery
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17
Q

What physical symptom is characteristic of thrombocytopoeania?

A

Petechiae - marks from bleeding under skin

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18
Q

State the tests for primary haemostatic disorders

A
  • Platelet count
  • Bleeding time
  • Assays of von Willebrand Factor
  • Clinical observation - petechiae or purpura?
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19
Q

What are the treatment options for abnormal haemostasis?

A
  • Failure of production /function:
    • Replace missing factor/platelets
      i) Prophylactic
      ii) Therapeutic
    • Stop drugs that impair platelet function; sucha as aspirin
  • Immune destruction
    • Immunosuppression
    • Splenectomy for ITP
  • Increased consumption of platelets:
    • Treat cause
    • Replace as necessary
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20
Q

What is the function of desmopressin?

A

Vasopressin analogue:
Leads to 2-5 fold increase in VWF (and VIII)
It also releases endogenous stores (so only useful in mild disorders)

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21
Q

What type of drug is tranexamic acid?

A

Antifibrinolytic

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22
Q

What is the role of coagulation?

A

To produce factor IIa which converts fibrinogen into fibrin

23
Q

What can cause disorders of coagulation?

A
  • Deficiency of coagulation factor production:
    • Hereditary
      • Factor VII/IX: haemophilia A/B
    • Acquired:
      • Liver disease
      • Anticoagulant drugs
  • Dilution:
    • Acquired
      • Blood transfusion
  • Increased consumption:
    • Disseminated intravascular coagulation
24
Q

Which factor is deficient in haemophilia A?

A

Factor VIII

25
Q

Which factor is deficient in haemophilia B?

A

Factor IX

26
Q

What is the hallmark of haemophilia?

A

Haemarthrosis - bleeding in joints

Can lead to muscle wasting

27
Q

What is the effect of prothrombin (Factor II) deficiency?

A

Death - very lethal

28
Q

What is the effect of Factor XI deficiency?

A

Bleed after trauma but not spontaneously

29
Q

What is the effect of Factor XII deficiency?

A

No bleeding at all

30
Q

Why does liver failure result in coagulation disorders?

A

Most coagulation factors are synthesised in the liver

31
Q

How does dilution of coagulation factors occur?

A

Red cell transfusions no longer contain plasma, which contains the coagulation factors - blood volume increase but coagulation factor number remains same, so concentration decreases

32
Q

What occurs in disseminated intravascular coagulation?

A
  • A generalised activation of coagulation occurs which uses up platelets and clotting factors around the body
  • This means there are little to no platelets or clotting factors left for coagulation elsewhere to occur
  • Deposition of fibrin in vessels an cause organ failure
33
Q

What can cause disseminated intravascular coagulation?

A

Associated with :

  • Sepsis
  • Major tissue damage
  • Inflammation
  • Cancer
34
Q

What are the clinical features of coagulation disorders?

A
  • Superficial cuts do not bleed
  • 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
35
Q

What is the clinical distinction between bleeding due to platelet and coagulation defects?

A 
Platelet:
- Superficial bleeding into skin
- Bleeding immediately after injury
Coagulation:
- Bleeding deep
- Bleeding delayed but severe bleeding after injury
36
Q

What are the tests for coagulation disorders?

A 
Screening tests:
- Prothrombin time
- Activated partial thromboplastin time
- Full blood count (platelets)
Coagulation factor assays (for Factor VIII etc)
Test for inhibitors
37
Q

What pathway does the prothrombin time test measure?

A

The ‘extrinsic’ pathway

38
Q

What pathway does the partial thromboplastin time measure?

A

The ‘intrinsic’ pathway

39
Q

By what methods can missing coagulation factors be replaced?

A

Plasma (fresh frozen plasma)
- contains all coagulation factors
Cryoprecipitate
- rich in fibrinogen, factor VIII, VWF, factor XIII
Factor concentrates
- Concentrates available for all factors except factor V
- Prothrombin complex concentrates; factors II, VII, IX, X
Recombinant forms of Factor VIII AND Factor IX are available
- ‘On demand’ to treat bleeds
- Prophylaxis to prevent bleeds

40
Q

What novel treatments are there for haemophilia?

A
  • Gene therapy (Haem A and B)
  • Bispecific antibodies:
    • Emicizumab
    • Binds to factor IXa and X
    • This mimics the procoagulant function of Factor VIII
41
Q

What are the associated symptoms of a pulmonary embolism?

A
  • Tachycardia
  • Hypoxia
  • Shortness of breath
  • Chest pain
  • Haemoptysis - coughing up blood
  • Can lead to sudden death
42
Q

What are the associated symptoms of a deep vein thrombosis?

A
  • Painful leg
  • Swelling
  • Red
  • Warm
  • May embolise to lungs
  • Post thrombotic syndrome
43
Q

What is Virchow’s triad?

A

The three contributory factors to thrombosis:

  • Blood
  • Vessel wall
  • Blood flow
44
Q

What is meant by thrombophilia?

A

Increased chance of venous thrombosis

45
Q

What factors do protein C and S activate?

A

Factor VIIIa and Va

46
Q

What type of cells produce heparin?

A

Mast cells

47
Q

What affect does the difference in heparin chain length cause?

A 
Long chain:
- Intravenous
- Short half life
Low molecular weight:
- Subcutaneous
48
Q

What are the target proteases of antithrombin?

A
  • Factor Xa

- Thrombin

49
Q

Why does low molecular weight (Short chain) heparin not affect thrombin?

A

The heparin chain has to wrap around the thrombin to have its desired affect however the LMW heparin is too short to do so
Still affects Xa

50
Q

How does warfarin work?

A

It prevents vitamin K from being recycled into it’s hyroquinone state, required for the activation of factors II, VII, IX, X, Protein C and S

51
Q

What are the side-effects of the warfarin?

A
  • Bleeding:
    • Ranges from minor to fatal
  • Skin necrosis
  • Purple toe syndrome
  • Embryopathy - Chrondodysplasia punctata
52
Q

What is chrondodysplasia punctata?

A

Early fusion of the epiphyses

53
Q

What can cause resistance to warfarin?

A
  • Diet: if they intake too much vitamin K
  • Increased metabolism
  • Reduced binding

BRS 2 (45 decks)

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