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.
It binds to fibrin rich clots and converts plasminogen to plasmin- lyses the clot.
Atleplase.
What is dabigatran?
Direct thrombin inhibitor with a rapid onset of action.
Irreversibly inhibits COX-1, blocking the formation of thromboxane.
Aspirin
What is thrombin?
Thrombin cleaves fibrinogen, activates factor XIII, causes platelet aggregation, stimulates cell proliferation and modulates smooth muscle contraction.
Warfarin initially decreases ________ and _______ levels faster than coagulation factors.
_______is an innate anticoagulant that relies on vitamin K-dependent carboxylation for activity.
_______ is a vitamin K dependent anticoagulation protein.
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.
How does the thrombus in an arterial thromboembolism differ from that in a venous 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.
The type of thrombus where plateletes are uniformly distributed through a mesh of fibrin and other cellular components. The platelet component is smaller than the fibrin content.
Thrombus found in venous thromboembolism.
The type of thrombus that involves athersclerosis and a large platelet component with leukocytes in a fibrin mesh.
Arterial thrombus.
What is protein C?
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.
What is protein S?
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.
What is alteplase? (TPA)
Tissue plasminogen activator (activates the conversion of plasminogen -> plasmin which dissolves the fibrin component of clots)
How does apixaban work?
Apixaban is a direct factor Xa inhibitor.
How does aspirin work?
COX inhibition.
How does bivalirudin work?
Factor 2a (thrombin) inhibitor.
How does clopidogrel work?
ADP inhibitor. PY12?
How does dabigatran work?
Thrombin (2a) inhibitor. Normally 2a catalyses the conversion of fibrinogen -> fibrin.
How does edoxaban work?
Direct factor 10a inhibitor.
How does fondaparinux sodium work?
Indirect thrombin inhibitor via factor 10a.
How do LMWHs work?
Impact factor Xa and factor 2a which catalyses the conversion of fibrinogen to fibrin.
How does prasugrel work?
Platelet inhibitor.
How does rivaroxaban work?
Factor Xa inhibitor.
What is streptokinase?
A plasminogen activator (for arterial and venous thrombosis)
How does ticagrelor work?
ASA platelet aggregation inhibitor.
How is apixaban monitored?
LFTs, renal function, bleeding and bruising.
Protamine is a reversal agent for
LMWH
Vitamin K can be used to reverse
Warfarin
