NB: For anticoagulation and neuraxial anesthesia, please see the chapter 119 on safety in regional anesthesia.
- VKAs block the carboxylation of factors II, VII, IX, and X as well as proteins C and S (coagulation inhibitors)
- Equilibrium is reached only after about 5 days as factors have different half-lives
- Initial hypercoagulable state as protein C has the shortest half-life
Table 12-1 Indications and Therapeutic Targets of VKAs |Favorite Table|Download (.pdf)
Table 12-1 Indications and Therapeutic Targets of VKAs
|Indications for target INR of 2.5; range 2–3||Indications for target INR of 3; range 2.5–3.5|
- Atrial fibrillation (AF)
- Rheumatic mitral valve disease and AF or a history of previous systemic embolism
- St. Jude Medical aortic bileaflet valve
- Bioprosthetic valves: VKA for first 3 months after aortic or mitral valve insertion
- AF and a recent CVA or TIA
- Tilting disk valves and bileaflet mechanical valves in the mitral position
- Caged ball or caged disk valves; give VKA in combination with aspirin, 75–100 mg/day
The following procedures do not warrant VKA discontinuation if INR 2–3:
- Cataract surgery without retrobulbar block
- EGD without biopsy, colonoscopy without biopsy/polypectomy, ERCP without sphincterotomy
- Minor dental procedures
- Joint and soft tissue injections and arthrocentesis
For AF, assess thromboembolic risk based on the CHADS2 score (0–6 points).
Table 12-2 CHADS2 Score for Assessment of Thromboembolic Risk |Favorite Table|Download (.pdf)
Table 12-2 CHADS2 Score for Assessment of Thromboembolic Risk
|Age >75 years||1 point|
|History of stroke||2 points|
- 0 points: no indication for chronic anticoagulation; discontinue warfarin 5 days before surgery; do not resume unless other indication
- 1–2 points: discontinue warfarin 5 days before surgery; resume 5 days after surgery
- 3 points or more: discontinue warfarin 5 days before surgery; LMWH, or IV UFH relay
- Discontinue warfarin at least 5 days before elective procedure, or longer if INR >3.0
- Assess INR 1–2 days before surgery; if INR >1.5, consider 1–2 mg of oral vitamin K
- Reversal for urgent surgery: consider 2.5–5 mg of oral or intravenous vitamin K
- Immediate reversal for emergent surgery: consider fresh frozen plasma, prothrombin complex concentrate, or recombinant factor VIIa
Patients at high risk for thromboembolism:
- For patients who have a mechanical valve, high risk includes those who have mitral valve prostheses, older aortic valve prostheses, or had a CVA or TIA in the past 6 months
- For patients who have atrial fibrillation, high risk includes a CHADS2 score of 5–6, a CVA or TIA within the past 3 months, or rheumatic valvular heart disease
- For patients who had a venous thromboembolism (VTE), high risk includes a VTE within the past 3 months, ...
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