Coagulation/anticoagulation Workshop Flashcards
What monitoring is needed for warfarin?
On starting:
Check baseline INR, FBC and LFTs.
The loading dose is usually 10mg daily for 2 days.
Why are interactions so common with warfarin?
Metabolised by CP450 and other drugs can interfere with this.
Also is heavily protein bound (albumin) and other drugs can have a competitive effect.
Why can the blood’s tendency to coagulate be paradoxically increased when warfarin treatment is first begun?
Warfarin initially decreases protein C and protein S levels faster than coagulation factors.
Protein C is an innate anticoagulant that relies on vitamin K-dependent carboxylation for activity.
Protein S is a vitamin K dependent anticoagulation protein.
Venous thromboembolism is generally due to
poor blood flow, as a result of immobility, concurrent medication, dehydration; hypercoagulability or vascular injury.
Venous thromboembolism normally causes
DVT or PE
Arterial thromboembolism results mostly in
MI, Ischaemic stroke or transient ischaemic attack (TIA)
How does the thrombus in a venous thromboembolism differ from that in an arterial thromboembolism?
Venous = red = platelets are uniformly distributed through a mesh of fibrin and other cellular components. Platelet component is smaller than fibrin content.
Arterial = white = atherosclerosis and large platelet component with leukocytes in a fibrin mesh.
Medication to treat thrombosis or prevent thromboembolism can be used in three different ways.
- Modifying blood coagulation (i.e. fibrin formation)
- Modifying platelet function
- Affecting fibrin removal (i.e. fibrinolysis)
Antiplatelets (aspirin) and fibrinolytics are used for the treatment or prevention of
Arterial thrombi
Anticoagulants (oral and injectable) are used for the treatment or prevention of
Venous thrombi
What is Alteplase? (TPA)
Alteplase is a tissue plasminogen activator (tPA). It works by helping to break down unwanted blood clots.
Where does Alteplase work?
It binds to fibrin rich clots and converts plasminogen to plasmin- lyses the clot.
What is Apixaban?
A direct factor Xa inhibitor.
How does Apixaban work?
It is a direct factor Xa inhibitor (blocks conversion of prothrombin -> thrombin).
How does aspirin work?
Irreversibly inhibits COX-1, blocking the formation of thromboxane.
What is Bivalrudin?
Thrombin inhibitor
What is clopidogrel?
Non-competitively and irreversibly prevents the binding of adenosine diphosphate to P2Y12 receptors on the platelet membrane, thus inhibiting platelet aggregation.
