Venous Thromboembolism Flashcards

1
Q
  1. What are the consequences of thromboembolism?
A

Death (5% mortality)
Recurrence
Thrombophlebitic syndrome (recurrent pain, swelling and ulcers)
Pulmonary hypertension

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2
Q
  1. What are the components of Virchow’s triad?
A

Blood composition (viscosity – haematocrit, protein/paraprotein)
Vessel wall
Blood flow

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3
Q
  1. List some anticoagulant molecules produced by the endothelium.
A
Thrombomodulin
Endothelial protein C receptor 
Tissue factor pathway inhibitor
Heparans 
NOTE: it does not normally produce tissue factor
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4
Q
  1. Which antiplatelet factors are produced by the endothelium?
A

NO

Prostacyclin

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5
Q
  1. Which stimuli can make the endothelium prothrombotic?
A

Infection, malignancy, vasculitis, trauma

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6
Q
  1. List the effects of infection/inflammation on the vessel wall.
A

Downregulation of anticoagulant molecules
Upregulation of adhesion molecules
TF may be expressed
Downregulation of prostacyclin production

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7
Q
  1. Describe the mechanism by which stasis promotes blood flow.
A

Leads to an accumulation of activated factors which promotes platelet adhesion and promotes leucocyte adhesion and transmigration
Hypoxia has an inflammatory effect on the endothelium

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8
Q
  1. List some causes of blood stasis.
A

Immobility (e.g. surgery)
Compression (e.g. tumour, pregnancy)
Viscosity (e.g. polycythaemia, paraprotein)
Congenital (e.g. vascular abnormalities)

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9
Q
  1. Which coagulation factor abnormality confers the highest risk of thrombosis?
A

Antithrombin deficiency

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10
Q
  1. Which drugs can be used to achieve immediate anticoagulation?
A

Heparin

Direct acting anti-Xa and anti-IIa

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11
Q
  1. List some types of heparin.
A

Low molecular weight heparin (SC)
Pentasaccharide (SC)
Unfractionated (IV)

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12
Q
  1. What is the mechanism of action of heparin?
A

Increases anticoagulant activity by potentiating anti-thrombin III

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13
Q
  1. List some disadvantages of heparin.
A

Administered by injection
Risk of osteoporosis
Variable renal dependence

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14
Q
  1. Name an anticoagulant that has a delayed effect.
A

Warfarin (2-3 days)

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15
Q
  1. How is LMWH monitored?
A

It has reliable pharmacokinetics so does not usually need monitoring
Anti-Xa assays can be used if renal failure or extremes or weight/risk

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16
Q
  1. How is unfractionated heparin monitored?
A

It has variable pharmacokinetics and a variable dose-response
Must be monitored with APTT or anti-Xa levels

17
Q
  1. List some Anti-Xa DOACs.
A

Rivaroxaban
Apixaban
Edoxaban

18
Q
  1. Name an Anti-IIa DOAC.
A

Dabigatran

19
Q
  1. List some properties of DOACs.
A
Oral administration 
Immediate action (peak = 3-4 hours) 
Useful in long-term 
Short half-life 
No monitoring needed
20
Q
  1. Outline the mechanism of action of warfarin.
A

It is a vitamin K epoxide reductase inhibitor meaning that it inhibits the gamma-carboxylation of factors 2, 7, 9 and 10
It also causes a reduction in protein C and protein S

21
Q
  1. How can the action of warfarin be reversed?
A

Administering vitamin K – takes 12 hours

Giving factors 2, 7, 9 and 10 – immediate

22
Q
  1. How is warfarin monitored?
A

Measuring INR

23
Q
  1. Why is it difficult to control the effects of warfarin on INR?
A

Several variables that affect warfarin action including dietary vitamin K intake, variable absorption, interaction with other drugs and teratogenicity

24
Q
  1. What is the antidote for heparin?
A

Protamine

25
Q
  1. List some methods of thromboprophylaxis.
A

LMWH (e.g. tinzaparin 4500 u, clexane 40 mg OD)
TED stockings
Flotron (intermittent compression)
Sometimes DOAC with/without aspirin (orthopaedics)
NOTE: all hospital admissions should be assessed for thrombotic risk and receive heparin prophylaxis unless contraindicated

26
Q
  1. Outline the treatment of DVT/PE.
A
Start LMWH (e.g. tinzaparin 175 u/kg) + warfarin
Stop LMWH when INR > 2 for 2 days 
ALTERNATIVE: start a doac 
These should be continued for 3-6 months
27
Q
  1. When is thrombolysis used for DVT/PE?
A

Life-threatening PE

Limb-threatening DVT

28
Q
  1. Why is thrombolysis used sparingly?
A

Increases the risk of intracranial haemorrhage (4%)

NOTE: it reduces the risk of post-phlebitic syndrome

29
Q
  1. What factors must be considered when deciding whether to give a patient long-term anticoagulation?
A

Does the risk of thrombosis outweigh the risk of bleeding?
Assess risk of recurrence
Assess risk of therapy (bleeding)

30
Q
  1. Describe the gender difference regarding the risk of recurrent of VTE.
A

Men have a greater risk of recurrence

NOTE: proximal thrombosis has a higher rate of recurrence than distal thrombosis

31
Q
  1. What should all patients > 60 years old with idiopathic thromboembolic disease be offered?
A

CT scan to check for an underlying cause

32
Q
  1. What is the risk of recurrence of idiopathic thrombosis?
A

HIGH as there is no obvious precipitating factor