In a patient on warfarin with a therapeutic International Normalized Ratio (2.0‑3.0) who is scheduled for a surgical or invasive procedure, should the warfarin be continued, held, or bridged, and what INR target is required before proceeding?

Perioperative Warfarin Management for Elective Surgery with Therapeutic INR

For elective surgery in a patient on warfarin with therapeutic INR (2.0–3.0), stop warfarin 5 days before the procedure to achieve INR ≤1.5, verify INR the day before surgery, and bridge with therapeutic-dose LMWH only if the patient has high thromboembolic risk (mechanical mitral valve, recent VTE <3 months, or antiphospholipid syndrome with recurrent thrombosis). 1

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Pre-Operative Warfarin Discontinuation

Stop warfarin 5 days (≈115 hours) before elective surgery to allow the INR to fall to ≤1.5, which is the safe threshold for surgical hemostasis. 1 This 5-day interval reflects warfarin's half-life (36–42 hours) and allows 93% of patients with baseline INR 2.0–3.0 to reach the safe range. 1

Special Populations Requiring Longer Washout

• Elderly patients (>75 years) require approximately 1 mg/day less warfarin than younger individuals to maintain comparable INR levels and may need a longer washout period due to delayed decay of anticoagulant effect. 2, 1, 3
• Patients whose therapeutic INR target is 3.0–4.0 (e.g., certain mechanical valves) need extended interruption. 1
• Patients on very low warfarin doses (<2–3 mg/day) demonstrate heightened sensitivity and may require individualized timing. 1

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Day-Before-Surgery INR Verification

Obtain INR the day before surgery and proceed only if INR ≤1.5. 1 This verification step is critical because it identifies the minority of patients who have not achieved adequate reversal.

Management of Elevated Pre-Operative INR

• If INR is 1.6–1.8: Give low-dose oral vitamin K (1–2.5 mg) and repeat INR on the morning of surgery. 1
• If INR remains ≥1.8 on the morning of surgery: Consider delaying the procedure or administering additional vitamin K, but avoid high-dose vitamin K (≥10 mg) as it causes prolonged warfarin resistance and complicates post-operative re-anticoagulation. 1, 4

Critical pitfall: In patients with mechanical heart valves, high-dose vitamin K should be avoided to prevent increased risk of valve thrombosis. 1

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Bridging Anticoagulation Decision

The need for heparin/LMWH bridging is determined by balancing the patient's thromboembolic risk against the surgical bleeding risk. 1

High Thromboembolic Risk (Bridging Recommended)

Indications for therapeutic-dose LMWH bridging: 1

• Mechanical mitral valve (any type) or mechanical tricuspid valve
• Any mechanical valve plus additional risk factors (atrial fibrillation, prior thromboembolism, left-ventricular dysfunction)
• Recent venous thromboembolism (≤3 months)
• Antiphospholipid syndrome with recurrent thrombosis

Bridging protocol for high-risk patients: 1

• Day –5 or –6: Discontinue warfarin
• Day –3: Start therapeutic-dose LMWH (≈36 hours after last warfarin dose)
• Day –1: Give a half-dose of LMWH 24 hours before surgery to limit residual anticoagulation
• Day +1: Resume full-dose LMWH 24 hours after low-bleeding-risk surgery

Low Thromboembolic Risk (No Bridging Required)

Patients who do NOT require bridging: 1

• Atrial fibrillation without prior stroke/TIA
• Mechanical aortic valve (bileaflet or tilting-disc) without additional risk factors
• Remote VTE (>12 months ago)

Management: Simply stop warfarin 5 days pre-operatively and restart post-operatively without LMWH bridging. 1

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High-Bleeding-Risk Procedures

For surgeries with catastrophic bleeding potential (neurosurgery, major cardiovascular, spinal procedures with neuraxial anesthesia): 1

• Delay postoperative LMWH bridging 48–72 hours after the operation
• Consider a stepwise escalation from prophylactic to therapeutic LMWH over the first 24–48 hours
• Major bleeding rates can reach ≈20% when treatment-dose LMWH is administered too close to the procedure 1

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Post-Operative Warfarin Resumption

Resume warfarin at the usual maintenance dose within 12–24 hours after surgery once adequate hemostasis is confirmed. 1 Early resumption (≤24 hours) is associated with lower major bleeding (2.7%) and lower arterial thromboembolism (0.1%) compared with delayed restart. 1

Timeline for Therapeutic Effect

• Warfarin provides partial anticoagulant effect in 2–3 days 1
• Full therapeutic effect is achieved in 4–8 days 1
• Continue LMWH bridging (if used) until INR is therapeutic for two consecutive days 1

Optional Loading-Dose Strategy

Doubling the warfarin dose for the first 1–2 post-operative days may accelerate INR normalization: 50% achieved INR ≥2.0 by day 5 versus 13% with standard dosing, though overall evidence is weak. 1

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Low-Risk Procedures

For minor dermatologic, dental, or cataract procedures, continue warfarin without interruption if the INR is therapeutic (2.0–3.0). 1 Meta-analyses report increased minor, self-limiting bleeding but rare major bleeding when warfarin is continued, and maintaining anticoagulation avoids thromboembolic risk during the interruption window. 1

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Critical Pitfalls to Avoid

• Do not use high-dose vitamin K (≥10 mg) pre-operatively, as it causes prolonged warfarin resistance and complicates post-operative re-anticoagulation. 1, 4
• Do not discontinue LMWH too close to surgery, because residual anticoagulant effect raises bleeding risk. 1
• Do not give routine pre-operative vitamin K for mildly elevated INR (>1.5) 1–2 days before surgery due to uncertainty about dosing and potential for resistance to post-operative re-anticoagulation. 1
• Provide written peri-operative anticoagulation calendars to patients and surgical teams to minimize dosing errors. 1