How to Bridge Warfarin
For most patients requiring temporary warfarin interruption for elective procedures, bridging with heparin is NOT recommended due to a consistent 2-3 fold increase in major bleeding risk without reduction in thromboembolism. 1
When Bridging is Indicated
Bridge only high-risk thromboembolism patients: 2
- Mechanical heart valves (especially mitral position or older generation valves) 2
- Recent stroke or TIA (within 3 months) 2
- CHADS₂-VASc score ≥5-6 in atrial fibrillation 2
- Recent VTE (within 3 months) 2
Do NOT bridge: 1
- Atrial fibrillation with CHADS₂-VASc ≤4
- Remote stroke (>12 months)
- Bioprosthetic heart valves
- Remote VTE (>12 months)
Bridging Protocol: Pre-Procedure
Stop warfarin 5 days before procedure to allow INR to normalize (4-5 half-lives). 2
Start therapeutic-dose LMWH 3 days before procedure: 2, 3
- Enoxaparin 1 mg/kg subcutaneously every 12 hours 2
- Dalteparin 100 IU/kg subcutaneously every 12 hours 2, 3
Give last LMWH dose 24 hours before surgery (not 12 hours) to minimize residual anticoagulation at procedure time. 2 Studies show 34% of patients have therapeutic anticoagulation levels at surgery when LMWH is given 12 hours pre-operatively. 2
Special Consideration: Renal Impairment
For severe renal impairment (CrCl <30 mL/min), use IV unfractionated heparin instead of LMWH: 2, 4
- UFH infusion at 18 IU/kg/hour (after 80 IU/kg bolus), adjusted to aPTT 1.5-2.0 times control 2
- Stop UFH infusion 4-6 hours before procedure 2
- UFH undergoes hepatic metabolism, eliminating accumulation risk 4
If LMWH must be used in renal impairment: 4, 5
- Dalteparin 5000 IU daily (no bioaccumulation in CrCl <30 mL/min) 4
- Enoxaparin 1 mg/kg once daily (not twice daily) for CrCl <30 mL/min 5
- Enoxaparin demonstrates 2-3 fold increased bleeding risk at standard doses in severe renal impairment 4, 5, 6
Bridging Protocol: Post-Procedure
Timing depends on bleeding risk of procedure: 2
Low-to-Moderate Bleeding Risk Procedures
- Resume warfarin evening of procedure 2, 3
- Resume therapeutic LMWH 12-24 hours post-procedure when adequate hemostasis confirmed 2, 3
- Continue LMWH until INR ≥2.0 (typically 2-3 days) 2, 3
High Bleeding Risk Procedures
- Resume warfarin evening of procedure 2
- Do NOT resume therapeutic LMWH post-operatively 2
- Consider prophylactic-dose LMWH (enoxaparin 40 mg daily) instead 2
Assess hemostasis before resuming LMWH by evaluating wound drainage amount, type (serous vs bloody), and progression. 2 Peak anticoagulant effect occurs 2-4 hours after LMWH administration. 2
Critical Pitfalls to Avoid
Never bridge patients with low thromboembolism risk - Recent randomized trials show bridging increases bleeding 2-3 fold without reducing stroke risk. 1
Never use standard LMWH dosing in CrCl <30 mL/min - This consistently leads to drug bioaccumulation and substantially increased bleeding. 4, 5, 6
Never give last pre-operative LMWH dose <24 hours before surgery - Residual anticoagulation at surgery increases bleeding risk. 2
Never resume therapeutic LMWH immediately post-procedure - Wait for adequate hemostasis (12-24 hours minimum). 2
Avoid tinzaparin in elderly patients (≥70 years) with renal insufficiency - Associated with substantially higher mortality rates (11.2% vs 6.3%). 4
Alternative: Subcutaneous UFH for Outpatient Bridging
Fixed-dose subcutaneous UFH 250 IU/kg every 12 hours can be used for outpatient bridging without aPTT monitoring. 2 This is particularly useful for patients with renal impairment who cannot use LMWH. 2, 4