Venous Thrombosis

Question 1

How do you test the extrinsic pathway?

Answer 1

PT

Question 2

How do you test the intrinsic pathway?

Answer 2

APTT

Question 3

What are two severe consequences of venous thrombosis?

Answer 3

Thrombophlebitic syndrome (recurrent pain, swelling, ulcers)
Pulmonary HTN

Question 4

What are the three components of Vichrows triad?

Answer 4

SHE
Stasis
Hypercoagulability
Endothelial injury

Question 5

What are anti platelet factors secreted by the endothelial wall?

Answer 5

NO

Prostacyclin

Question 6

What are anticoagulant molecules on the endothelial wall?

Answer 6

Thrombomodulin
Protein C receptor
TFPI

Question 7

What types of stimuli can make the vessel wall prothrombotic?

Answer 7

Infection (Covid 19)
Malignancy
Vasculitis
Trauma

Question 8

How does stasis promote thrombosis?

Answer 8

Accumulation of activated factors
Promotes platelet adhesion
Promotes leukocyte adhesion and transmigration
Hypoxia

Question 9

What are causes of stasis

Answer 9

immobility
compression (tumour, pregnancy)
viscosity (polycythaemia, paraprotein)
congenital (vascular abnormalities)

Question 10

What is the problem when there is interaction of multiple prothrombotic factors?

Answer 10

SYNERGISTIC effect

Question 11

What kinds of anticoagulant therapies can we give, in terms of time frames they act in?

Answer 11

IMMEDIATE

• heparin
• Anti-Xa (rivaroxaban)
• Anti-IIa (dabigatran)

DELAYED
- warfarin

Question 12

How does heparin work?

Answer 12

It directly activates antithrombin

Question 13

What are disadvantages of heparin?

Answer 13

Injection required for administration
Risk of osteoporosis
Renal dependence

Question 14

What are methods of administration for heparin?

Answer 14

Unfractionated - IV
LMWH - SC
Pentasaccharide - SC

Question 15

Which Moa for heparin requires monitoring?

Answer 15

Unfractionated ONLY

Question 16

How does warfarin work?

Answer 16

Vitamin K antagonist - prevents recycling of vitamin K

Thereby reduces levels of procoagulant factors 2,7,9,10

Question 17

What must you do if prescribing warfarin?

Answer 17

MONITOR - using INR

Question 18

Why is the effect of warfarin so variable?

Answer 18

because there are lots of variables at play

• dietary vit K intake
• variable absorption
• Drug interactions
• Teratogenic

Question 19

What is given to patients at increased thrombosis risk?

Answer 19

THROMBOPROPHYLAXIS
- LMWH (not monitored) e.g. tinzaparin, clean
- TED stocking
- Flotron (intermittent compression)b 
\+- DOAC, aspirin

Question 20

Summarise tx of DVT/PE

Answer 20

Thrombolysis - only for life-threatening DVT/PE (high risk of intracranial haemorrhage)

Start LMWH + warfarin

Stop LMWH when INR >2for 2 days

Question 21

What would you consider when prescribing long term anticoagulation?

Answer 21

Whether risk of recurrence outweighs risk of bleeding

Question 22

What is the risk of recurrence after a surgical precipitated VTE?

Answer 22

VERY LOW

No need for long term anticoag

Question 23

What is the risk of recurrence after idiopathic VTE?

Answer 23

VERY HIGH

consider long term anticoagulant

Question 24

What would you prescribe following VTE with minor precipitant e.g. COCP, trauma, flight?

Answer 24

3 months of anticoagulation

Longer if other RF