Venous Thrombosis Flashcards
How do you test the extrinsic pathway?
PT
How do you test the intrinsic pathway?
APTT
What are two severe consequences of venous thrombosis?
Thrombophlebitic syndrome (recurrent pain, swelling, ulcers) Pulmonary HTN
What are the three components of Vichrows triad?
SHE
Stasis
Hypercoagulability
Endothelial injury
What are anti platelet factors secreted by the endothelial wall?
NO
Prostacyclin
What are anticoagulant molecules on the endothelial wall?
Thrombomodulin
Protein C receptor
TFPI
What types of stimuli can make the vessel wall prothrombotic?
Infection (Covid 19)
Malignancy
Vasculitis
Trauma
How does stasis promote thrombosis?
Accumulation of activated factors
Promotes platelet adhesion
Promotes leukocyte adhesion and transmigration
Hypoxia
What are causes of stasis
immobility
compression (tumour, pregnancy)
viscosity (polycythaemia, paraprotein)
congenital (vascular abnormalities)
What is the problem when there is interaction of multiple prothrombotic factors?
SYNERGISTIC effect
What kinds of anticoagulant therapies can we give, in terms of time frames they act in?
IMMEDIATE
- heparin
- Anti-Xa (rivaroxaban)
- Anti-IIa (dabigatran)
DELAYED
- warfarin
How does heparin work?
It directly activates antithrombin
What are disadvantages of heparin?
Injection required for administration
Risk of osteoporosis
Renal dependence
What are methods of administration for heparin?
Unfractionated - IV
LMWH - SC
Pentasaccharide - SC
Which Moa for heparin requires monitoring?
Unfractionated ONLY
How does warfarin work?
Vitamin K antagonist - prevents recycling of vitamin K
Thereby reduces levels of procoagulant factors 2,7,9,10
What must you do if prescribing warfarin?
MONITOR - using INR
Why is the effect of warfarin so variable?
because there are lots of variables at play
- dietary vit K intake
- variable absorption
- Drug interactions
- Teratogenic
What is given to patients at increased thrombosis risk?
THROMBOPROPHYLAXIS - LMWH (not monitored) e.g. tinzaparin, clean - TED stocking - Flotron (intermittent compression)b \+- DOAC, aspirin
Summarise tx of DVT/PE
Thrombolysis - only for life-threatening DVT/PE (high risk of intracranial haemorrhage)
Start LMWH + warfarin
Stop LMWH when INR >2for 2 days
What would you consider when prescribing long term anticoagulation?
Whether risk of recurrence outweighs risk of bleeding
What is the risk of recurrence after a surgical precipitated VTE?
VERY LOW
No need for long term anticoag
What is the risk of recurrence after idiopathic VTE?
VERY HIGH
consider long term anticoagulant
What would you prescribe following VTE with minor precipitant e.g. COCP, trauma, flight?
3 months of anticoagulation
Longer if other RF
