Anti-coagulants Flashcards
What are indications for anti-coagulants?
Atrial fibrillation
VTE
MI
Stroke/TIA
Hypercoagulability disorders
What are some inherited hypercoagubility disorders?
Factor V Leiden deficiency
- blood vessels cannot heal normally
Protein C deficiency
- protein C prevents blood clotting
Protein S deficiency
- protein S regulates blood clotting
What are some examples of acquired hypercoagubility?
Cancer
Trauma
Immobility
What are the oral anticoagulants?
Warfarin
DOACs
- apixaban
- rivaroxaban
What are the parental anticoagulants?
Heparin
- UFH
- LMWH
Heparin alternatives
What is INR?
International normalised ratio
INR = patient prothrombin time / control
What is a normal INR?
1.1
What INR is required for elective surgery?
<1.5
What is the action of warfarin?
Vitamin K antagonist
- inhibits vitamin K epoxide reductase
- stops conversion of vitamin K to active form
- vitamin K required for synthesis of factors II, VII, IX, X
What is the absorption of warfarin?
Oral bio-availability 79-100%
What is the distribution of warfarin?
Protein binding 99%
What organ metabolises warfarin?
Liver
What organ excretes warfarin?
Kidney
What is the reversal of warfarin?
Vitamin K
How long before surgery do you need to stop warfarin?
5 days
Check INR
What are the actions of DOACs?
Factor Xa inhibitor
What is the absorption of DOACs?
Oral bio-availability 50-70%
What is the distribution of DOACs?
Protein binding 87%
What organ metabolises DOACs?
Liver
What organ excretes DOACs?
Kidney
Some excreted by bile
What is the reversal of DOACs?
Andexanet alfa
How long before surgery do you need to stop DOACs?
24 hours
48 hours if poor renal function
What is the action of unfractioned heparin?
Inhibits antithrombin III
- antithrombin III activates factors XIIa, XIa, IXa, Xa, IIa
What are the low molecular weight heparins?
Dalteparin
Enoxaparin
What is the action of LMWHs?
Inhibit factor Xa
What is the absorption of heparin?
IV (UFH)
SC (LMWH)
What is the distribution of heparin?
Plasma volume
What organ metabolises heparin?
Liver
How is heparin excreted?
Urine
What is heparin reversal?
Protamine
- forms an inactive ion pair with heparin
- dissociates heparin from ATIII
How long before surgery do you need to stop heparin?
Heparin stops working after 90 mins
Monitor APTT
What is APTT?
Activated partial thromboplastin time
Measure of the functionality of the intrinsic and common pathways of the coagulation cascade
How long before surgery do you need to stop LMWH?
Wait 12 hours - prophylactic dose
Wait 24 hours - treatment dose
What are the commonly used anti-platelet agents?
Aspirin
Clopidogrel
What is the action of aspirin?
Reduction of TXA2 synthesis by COX-1 inhibition - inhibits platelet aggregation
What is the action of clopidogrel?
ADP receptor antagonist
- inhibit activation of GPIIb/IIIa
How long before surgery do you need to stop aspirin?
Can continue it
How long before surgery do you need to stop clopidogrel?
Stop 7 days before