Anti-coagulants and Anti-Platelets Flashcards
What is the mechanism of action of aspirin?
Aspirin irreversibly inhibits COX-1 and COX-2, preventing thromboxane A2 synthesis and reducing platelet aggregation.
How does clopidogrel inhibit platelet aggregation?
Clopidogrel irreversibly blocks the P2Y12 ADP receptor on platelets, preventing activation of the GPIIb/IIIa complex.
What are the two major mechanisms of direct oral anticoagulants (DOACs)?
DOACs inhibit specific clotting factors. They can either inhibit factor Xa, which is the MOA for apixaban and rivaroxaban, they can work via the inhibition of thrombin (factor IIa), which is the MOA of DOACs like dabigatran.
What are the factor Xa inhibitors?
apixaban, rivaroxaban, edoxaban, betrixaban
What is the MOA of warfarin?
Warfarin inhibits vitamin K epoxide reductase, reducing synthesis of factors II, VII, IX, and X, as well as proteins C and S.
How does unfractionated heparin work?
Unfractionated heparin enhances antithrombin III activity, inhibiting thrombin (IIa) and factor Xa.
What is the difference in MOA between unfractionated heparin and LMWH?
LMWH primarily inhibits factor Xa, while unfractionated heparin inhibits both thrombin and factor Xa.
What are the common indications for aspirin use?
Aspirin is used for prevention of arterial thromboembolism, ACS, stroke, and as an antipyretic/analgesic.
In what conditions is warfarin contraindicated?
Warfarin is contraindicated in pregnancy (teratogenic), active bleeding, and recent surgery with a high risk of bleeding.
When are DOACs preferred over warfarin?
DOACs are preferred in non-valvular atrial fibrillation and DVT/PE management due to fewer dietary and drug interactions.
What is the typical half-life of warfarin?
Warfarin has a half-life of 36-42 hours.
Patients with heart valves will always get … ?
Warfarin.
How are DOACs metabolized and excreted?
DOACs are metabolized in the liver (CYP enzymes) and excreted renally; dose adjustment is required in renal impairment.
Why does heparin require continuous monitoring?
Heparin requires monitoring due to variable bioavailability and short half-life.
What lab test is used to monitor warfarin therapy?
INR (International Normalized Ratio) is used to monitor warfarin therapy.
Which laboratory test is monitored for unfractionated heparin?
aPTT (activated partial thromboplastin time) is used to monitor unfractionated heparin.
Do DOACs require routine lab monitoring? Why or why not?
DOACs do not require routine monitoring because of their predictable pharmacokinetics.
What is a major side effect of aspirin?
Gastrointestinal bleeding is a major side effect of aspirin.
What are the risks associated with long-term warfarin use?
Risks of long-term warfarin use include bleeding, skin necrosis, and teratogenicity.
What is heparin-induced thrombocytopenia (HIT)?
HIT is an immune-mediated complication of heparin characterized by thrombocytopenia and thrombosis.
When is bridging with LMWH indicated in patients on warfarin?
Bridging with LMWH is indicated in patients with high thromboembolic risk undergoing surgery.
Do patients on DOACs require bridging therapy? Why or why not?
DOACs do not require bridging due to their rapid onset of action upon reinitiation.
What is the reversal agent for warfarin?
Vitamin K (oral or IV) is the reversal agent for warfarin.
How should anticoagulation be managed perioperatively for a patient on warfarin?
Warfarin should be stopped 3-5 days before surgery; bridging may be needed for high-risk patients.
When should warfarin be stopped before a procedure with low bleeding risk?
Warfarin should typically be stopped 3-5 days before a low bleeding risk procedure.
How is major bleeding managed in patients on DOACs?
DOACs can be reversed with idarucizumab (for dabigatran) or andexanet alfa (for factor Xa inhibitors).
Is warfarin safe during pregnancy?
Warfarin is not safe in pregnancy; LMWH is preferred.
How should anticoagulation with heparin be adjusted for patients with renal impairment?
For patients with renal impairment, unfractionated heparin (UFH) is preferred over low-molecular-weight heparins (LMWH) like enoxaparin, as UFH is not significantly renally excreted and can be easily titrated and reversed. If LMWH must be used, dose adjustments are required based on creatinine clearance.
What is the first step in managing bleeding in a patient on DOACs?
For bleeding on DOACs, stop the drug and administer reversal agents (e.g., andexanet alfa or idarucizumab) if indicated.
When should warfarin be stopped before a procedure with moderate or high bleeding risk?
Warfarin should be stopped 3-5 days before a moderate or high bleeding risk procedure, with INR monitored before surgery.
How many days before surgery should DOACs be stopped for low/moderate/high bleeding risk procedures?
DOACs should generally be stopped 1-3 days before surgery, depending on renal function and bleeding risk.
What factors determine when to stop DOACs before surgery?
Factors include the type of DOAC, the patient’s renal function, and the surgical bleeding risk.
When is bridging therapy indicated for patients on warfarin undergoing surgery?
Bridging is indicated for patients with high thromboembolic risk, such as those with mechanical heart valves or recent stroke.
What thromboembolic risk factors warrant bridging with LMWH for patients on warfarin?
High thromboembolic risk factors include CHA2DS2-VASc ≥ 7, recent stroke (< 3 months), or a mechanical mitral valve.
Why is bridging not required for DOACs during perioperative management?
DOACs do not require bridging due to their rapid onset of action upon reinitiation after surgery.
What is the perioperative management for a patient with a mechanical mitral valve on warfarin?
Stop warfarin 5 days before surgery, bridge with LMWH, and resume warfarin postoperatively with bridging until therapeutic INR is achieved.
How should anticoagulation be managed for a patient with atrial fibrillation and CHA2DS2-VASc ≥ 7 undergoing surgery?
Stop warfarin 5 days before surgery, bridge with LMWH preoperatively, and restart both warfarin and bridging postoperatively.
How should anticoagulation be managed for a patient with atrial fibrillation and CHA2DS2-VASc ≤ 4 undergoing surgery?
Stop warfarin 3-5 days before surgery; bridging is not necessary for low thromboembolic risk patients.
What is the protocol for stopping warfarin in a patient with low thromboembolic risk?
Stop warfarin 3-5 days before surgery and ensure INR is below the target range; no bridging is required for low-risk patients.
For minimal bleeding risk procedures, what is the anticoagulation strategy for patients on DOACs?
For minimal bleeding risk procedures, DOACs may not need to be stopped and can often be continued through the procedure.
