Can You Proceed to Surgery with INR 1.37?
Yes, you can safely proceed to surgery with an INR of 1.37, as this falls well below the standard safety threshold of INR <1.5 recommended for most surgical procedures. 1, 2
INR Safety Thresholds for Surgery
The current guidelines establish clear INR cutoffs based on bleeding risk:
- For high bleeding risk procedures (including most major surgeries and neuraxial anesthesia): Target INR <1.5 1
- For low/moderate bleeding risk procedures: INR <1.5 is standard, though some procedures may tolerate slightly higher values 1
- For minimal bleeding risk procedures (cataract surgery, minor dental/dermatological): Can proceed with therapeutic INR (2.0-3.0) without warfarin interruption 1, 2
Your INR of 1.37 meets the safety criteria for essentially all surgical procedures, including those with the highest bleeding risk. 1
Context: Standard Preoperative Management
For patients on warfarin requiring surgery, the ACC/AHA guidelines recommend:
- Low thrombotic risk patients (bileaflet mechanical aortic valve without risk factors): Stop warfarin 48-72 hours before surgery to achieve INR <1.5, with no heparin bridging needed 1
- High thrombotic risk patients (mechanical mitral valve or mechanical aortic valve with risk factors): Stop warfarin 48 hours before surgery, start therapeutic heparin when INR falls below 2.0, and discontinue heparin 4-6 hours before the procedure 1
The typical timeline shows that after stopping warfarin, it takes approximately 4-5 days for INR to reach 1.5 in most patients with baseline therapeutic INR of 2.0-3.0. 3
Special Considerations for Specific Procedures
Transseptal or left ventricular puncture procedures require more stringent control, with INR <1.2 recommended due to the risk of pericardial bleeding. 1 Your INR of 1.37 would require additional time off anticoagulation for these specific high-risk cardiac procedures.
Percutaneous lung biopsy guidelines suggest that PT ratio or INR >1.4 should be considered a relative contraindication, requiring discussion with a hematologist before proceeding. 1 However, this represents a more conservative threshold than most surgical guidelines.
Important Caveats
- Verify INR timing: The 2024 AHA/ACC guidelines recommend checking INR on the day before or day of surgery, particularly for neuraxial anesthesia, to ensure the value remains stable. 1
- Age considerations: Elderly patients may have slower INR normalization after warfarin discontinuation, with age being a significant predictor of smaller INR decreases (approximately 6.8% slower per decade). 3
- Thrombotic risk assessment: If this patient has high thrombotic risk factors (mechanical mitral valve, recent thromboembolism, atrial fibrillation with prior stroke), ensure appropriate postoperative anticoagulation resumption timing has been planned. 1
Postoperative Management
Plan to resume warfarin 12-24 hours after surgery when adequate hemostasis is achieved, using the patient's usual maintenance dose rather than loading doses. 2 For high thrombotic risk patients, consider bridging with therapeutic heparin until INR returns to therapeutic range. 1