When should warfarin (anticoagulant) be stopped before surgery and bridged with low molecular weight heparin (LMWH) or unfractionated heparin (UFH)?

Perioperative Management of Warfarin Therapy

Warfarin should be stopped 5 days before surgery, with bridging therapy using heparin or LMWH reserved only for patients at high risk of thromboembolism. 1

Preoperative Warfarin Management

When to Stop Warfarin

• Stop warfarin 5 days before elective surgery to allow INR to normalize to <1.5 at the time of surgery 1
• For most patients, this 5-day interruption is sufficient to normalize the INR, with only 7% of patients having an INR >1.5 on the day of surgery 1
• Older patients may require longer periods off warfarin as age is associated with a slower rate of INR decrease 2

Preoperative INR Monitoring

• Check INR the day before surgery to ensure it has normalized (<1.5) 1
• If INR remains elevated (>1.5) the day before surgery, consider administering 1-2.5 mg of vitamin K orally to expedite INR normalization 1, 3

Risk Stratification for Bridging Therapy

High Thrombotic Risk (Requires Bridging)

• Mechanical mitral valve
• Prosthetic valve with prior thromboembolism
• Recent (<3 months) venous thromboembolism
• Atrial fibrillation with prior stroke or multiple risk factors (CHADS₂ score >4) 1, 4

Low Thrombotic Risk (No Bridging Required)

• Non-valvular atrial fibrillation with CHADS₂ score ≤4
• Bileaflet aortic valve without risk factors
• VTE >3 months prior 4

Bridging Protocol for High-Risk Patients

When to Start Bridging

• Begin therapeutic-dose heparin or LMWH 2-3 days after stopping warfarin (when INR falls below therapeutic range) 1

Dosing for Bridging

• LMWH: 100 U/kg subcutaneously every 12 hours
• UFH: 15,000 U subcutaneously every 12 hours or continuous IV infusion (1300 U/hour) for highest-risk patients 1

When to Stop Bridging Before Surgery

• LMWH: Last dose 24 hours before surgery
• IV UFH: Stop 5 hours before surgery 1

Postoperative Management

Resuming Warfarin

• Resume warfarin 12-24 hours after surgery (evening of or next morning) when hemostasis is adequate 1
• Use the patient's usual maintenance dose 1
• Time to reach therapeutic INR after resuming warfarin is typically 5-10 days 1

Postoperative Bridging

• For high-risk patients: Resume prophylactic-dose heparin or LMWH 12-24 hours after surgery, then increase to therapeutic dose when hemostasis is secure 1
• Continue bridging until INR returns to therapeutic range 1, 4

Special Considerations

Minor Procedures

• For low-bleeding-risk procedures (diagnostic colonoscopy, dental procedures, cataract surgery), warfarin can be continued without interruption 4
• For dental procedures, consider using tranexamic acid or aminocaproic acid mouthwash without interrupting anticoagulation 1

High Bleeding Risk Procedures

• Even with proper warfarin discontinuation and normalized INR, patients may still experience increased intraoperative blood loss compared to patients not on chronic anticoagulation 5
• Surgeons should be prepared for potentially increased bleeding despite protocol adherence 5

Common Pitfalls and Caveats

1. Insufficient time off warfarin: Stopping warfarin less than 5 days before surgery often results in elevated INR at the time of surgery 1, 2

2. Unnecessary bridging: Most patients do not require bridging therapy, which increases bleeding risk without significant thrombotic protection in low-risk patients 1

3. Delayed warfarin resumption: Delaying warfarin resumption beyond 24 hours after surgery may prolong the time to therapeutic anticoagulation 1

4. Failure to check preoperative INR: Always verify INR normalization before proceeding with surgery 1, 3

5. Overestimating thrombotic risk: Carefully assess each patient's actual risk of thromboembolism to avoid unnecessary bridging therapy 1, 4