What are the recommendations for stopping warfarin before elective surgery, including how many days to hold it, target International Normalized Ratio (INR) level, and whether bridging anticoagulation is needed for patients with high versus moderate thromboembolic risk?

Warfarin Management Before Elective Surgery

Preoperative Warfarin Discontinuation

Stop warfarin 5 days (approximately 115 hours) before elective surgery to allow the INR to fall to ≤1.5, which is the target for safe surgical hemostasis. 1, 2

• This 5-day interruption period is based on warfarin's half-life of 36-42 hours and allows sufficient time for most patients with baseline INR 2.0-3.0 to reach safe levels. 1
• In prospective studies, 93% of patients achieved INR ≤1.5 after 5 days of warfarin interruption. 1
• Longer interruption periods (>5 days) demonstrated reduced major bleeding risk (RR 0.29) without increasing arterial thromboembolism. 1

Special Populations Requiring Extended Interruption

• Elderly patients may require >5 days due to delayed decay of anticoagulant effect. 1, 2
• Patients with high-intensity INR targets (3.0-4.0) need longer washout periods. 1, 2
• Patients on very low warfarin doses may have prolonged sensitivity and require extended interruption. 1

Day-Before-Surgery INR Assessment

Check INR the day before surgery to confirm it is ≤1.5 before proceeding. 1, 2

• If INR ≤1.5: Proceed with surgery as planned. 1, 2
• If INR 1.6-1.8: Administer low-dose oral vitamin K (1-2.5 mg) and recheck INR on the morning of surgery. 1, 2
• If INR >1.8: Consider postponing the procedure rather than using higher vitamin K doses, which can cause prolonged warfarin resistance postoperatively. 3, 2

Critical Pitfall to Avoid

Never use high-dose vitamin K (≥10 mg) preoperatively, as this creates difficulty achieving therapeutic INR postoperatively and may induce a hypercoagulable state. 3, 2

Bridging Anticoagulation Decision Algorithm

The decision to bridge depends on balancing thromboembolic risk against surgical bleeding risk. 1, 2

HIGH Thromboembolic Risk (Bridging Recommended)

Initiate therapeutic-dose LMWH bridging for patients with: 1, 2

• Mechanical mitral valve (any type)
• Any mechanical valve with additional risk factors (atrial fibrillation, prior thromboembolism, LV dysfunction)
• Recent VTE within 3 months
• Antiphospholipid syndrome with recurrent thrombosis
• Mechanical tricuspid valve

Bridging Protocol for High-Risk Patients: 1, 2

• Day -5 or -6: Stop warfarin
• Day -3: Start therapeutic-dose LMWH (36 hours after last warfarin dose)
• Day -1: Give last LMWH dose at half the usual daily amount, 24 hours before surgery (to minimize residual anticoagulant effect)
• Day 0: Surgery
• Day +1: Resume full-dose LMWH 24 hours after surgery for low-bleeding-risk procedures

MODERATE Thromboembolic Risk (Consider Bridging)

Individualize based on specific patient and procedural factors. 1

LOW Thromboembolic Risk (No Bridging Required)

Do not bridge patients with: 1, 2

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

Simply stop warfarin 5 days preoperatively and resume postoperatively. 1, 2

High-Bleeding-Risk Procedures

For surgeries with catastrophic bleeding potential (neurosurgical, major cardiovascular, spinal procedures with neuraxial anesthesia): 1, 2

• Delay postoperative LMWH bridging for 48-72 hours after surgery
• Consider stepwise escalation from prophylactic to therapeutic LMWH over the first 24-48 hours
• Alternatively, omit postoperative bridging entirely and use mechanical prophylaxis instead
• Major bleeding rates as high as 20% occur when treatment-dose LMWH is given too close to high-risk surgery. 1

Postoperative Warfarin Resumption

Resume warfarin at the usual maintenance dose within 12-24 hours after surgery (evening of surgery or next morning) once adequate hemostasis is achieved. 1, 2

• Early resumption (within 24 hours) is associated with lower rates of major bleeding (2.7%) and arterial thromboembolism (0.1%) compared to delayed resumption. 1
• It takes 2-3 days for partial anticoagulant effect and 4-8 days for full therapeutic effect after restarting warfarin. 1
• Continue LMWH bridging (if used) until INR is therapeutic (≥2.0) for two consecutive days. 2

Optional Loading Dose Strategy

Consider doubling the warfarin dose for the first 1-2 postoperative days to accelerate return to therapeutic INR. 1

• One randomized trial showed 50% of patients achieved INR ≥2.0 by day 5 with doubled dosing versus only 13% with usual dosing. 1
• However, standard maintenance dosing is acceptable, and the evidence for loading is weak. 3

Low-Risk Procedures

For minor dermatologic, dental, or cataract procedures, consider continuing warfarin without interruption if INR is in therapeutic range (2.0-3.0). 1, 3

• Meta-analyses show increased minor bleeding (self-limiting) but rare major bleeding with continued anticoagulation during low-risk procedures. 1
• This avoids thromboembolic risk during the interruption period. 1

Common Pitfalls Summary

• Avoid stopping LMWH too close to surgery time (must be ≥24 hours before, at half-dose). 1, 2
• Never use high-dose vitamin K preoperatively in mechanical valve patients due to valve thrombosis risk. 3, 2
• Do not resume therapeutic-dose LMWH within 24 hours after high-bleeding-risk procedures. 1, 2
• Provide written perioperative anticoagulation calendars to patients and surgical teams to minimize dosing errors. 1