Resuming Warfarin After Surgery
Resume warfarin within 24 hours after surgery (on the evening of the procedure or the next morning) at your usual maintenance dose when adequate hemostasis is achieved. 1, 2
Timing of Resumption
Start warfarin 12-24 hours postoperatively rather than delaying beyond 24 hours, as early resumption significantly reduces arterial thromboembolism risk (0.1% vs 2.4% with delayed resumption). 1, 2
For most patients, this means resuming on the evening of surgery (Day 0) or the following morning (Day 1). 1, 2
Use the patient's usual maintenance dose—do not double the dose, as this increases bleeding risk without significantly accelerating time to therapeutic INR. 1, 2, 3
Expected Time to Therapeutic Effect
Warfarin requires 2-3 days for partial anticoagulant effect and 4-8 days for full therapeutic effect (INR ≥2.0) after resumption. 1, 2
The mean time to achieve therapeutic INR is approximately 5.1 days when warfarin is resumed within 24 hours at the usual dose. 1
When to Delay Resumption
Delay warfarin beyond 24 hours only in these specific circumstances: 1, 2
- Inadequate surgical site hemostasis or active bleeding
- Anticipated need for additional surgical intervention
- Patient unable to take oral medications
- High bleeding risk procedures (major neurosurgical or cardiovascular surgeries)—consider waiting 48-72 hours 1, 2
Bridging Anticoagulation Considerations
For moderate thromboembolic risk patients: Bridging with LMWH is generally not required after most surgeries. 2
For high-risk patients (mechanical heart valves, recent stroke/TIA, antiphospholipid syndrome with recurrent VTE): 1, 2
- Wait 24 hours minimum after low-to-moderate bleeding risk procedures before starting LMWH bridging
- Wait 48-72 hours after high bleeding risk procedures before resuming therapeutic-dose LMWH
- Consider prophylactic-dose LMWH (enoxaparin 40 mg daily) for the first 24-72 hours, then transition to therapeutic dosing
Monitoring Strategy
Check INR on the day before surgery to ensure it is ≤1.5 before proceeding. 1
After resuming warfarin, monitor INR every 1-2 days initially until stable in therapeutic range, then extend intervals based on stability. 4, 3
Daily INR monitoring postoperatively reduces bleeding complications compared to intermittent testing. 3
Common Pitfalls to Avoid
Do not unnecessarily delay warfarin resumption—this substantially increases thrombotic risk without improving bleeding outcomes. 2
Do not double the warfarin dose when restarting (despite some older literature suggesting this)—it increases bleeding risk without meaningful benefit in time to therapeutic INR. 1, 2
Do not restart therapeutic-dose LMWH bridging too early after high bleeding risk procedures—this can cause major bleeding in up to 20% of patients. 1
Ensure clear communication with the patient about when and how to resume warfarin, as medication errors are common during transitions of care. 2
Special Populations
Elderly patients (>75 years) and those with high baseline INR requirements (INR 3.0-4.0) may need longer preoperative interruption and may have slower INR normalization postoperatively. 1, 5, 6
Patients starting amiodarone postoperatively have significantly increased warfarin sensitivity and require closer monitoring and potential dose reduction. 5
Patients with renal insufficiency on LMWH bridging require dose adjustments due to prolonged drug half-life. 7