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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

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

  • 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

For valve replacements:

  • 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, severe thrombophilia
  • Bridge with ...

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