Management of INR 6.4 on Warfarin
For a patient with INR 6.4 without active bleeding, immediately withhold warfarin and administer oral vitamin K 2.5-5 mg, then recheck INR within 24 hours. 1
Immediate Assessment
First, determine if there is any active bleeding—this is the critical decision point that determines your entire management strategy. 1
- Check for signs of bleeding: melena, hematuria, hematemesis, excessive bruising, petechiae, or bleeding from any site 2
- Assess bleeding risk factors: advanced age (>65 years), history of bleeding, concomitant antiplatelet drugs, renal failure, or alcohol use 1, 3
- At INR 6.4, the bleeding risk is clinically significant but the absolute daily risk remains relatively low at <5.5 per 1000 per day 4
Management Without Active Bleeding
Withhold warfarin completely until INR falls back into therapeutic range. 1
Administer oral vitamin K 2.5-5 mg immediately for INR >6.0 without bleeding. 1, 5 This approach is superior to simply withholding warfarin alone because:
- Oral vitamin K reduces INR to <4.0 within 24 hours in 85% of patients 6
- It provides faster partial correction than subcutaneous routes 6
- The oral route avoids the risk of anaphylactoid reactions associated with IV administration (3 per 100,000 doses) 1
Do NOT use high-dose vitamin K (10 mg) as this creates warfarin resistance for up to a week and makes re-anticoagulation extremely difficult. 1, 6
Management With Active Bleeding
If the patient has major bleeding (hemoglobin drop ≥2 g/dL or bleeding at critical sites):
- Administer 4-factor prothrombin complex concentrate (PCC) 50 U/kg IV for INR >6.0 1
- Plus vitamin K 5-10 mg by slow IV infusion over 30 minutes 1
- Target INR <1.5 for hemostasis 1
- PCC achieves INR correction within 5-15 minutes versus hours with fresh frozen plasma 1
- Always co-administer vitamin K with PCC because factor VII has only a 6-hour half-life 1
Critical bleeding sites include: intracranial, intraspinal, intraocular, pericardial, retroperitoneal, intra-articular, or intramuscular with compartment syndrome. 1, 7
Monitoring and Follow-Up
Recheck INR within 24-48 hours after intervention to confirm appropriate reduction. 1, 6
Continue monitoring every 24-48 hours until INR stabilizes in therapeutic range. 6
Restarting Warfarin
Reduce the weekly warfarin dose by 20-30% when resuming therapy to prevent recurrence. 8, 6
Investigate the cause of INR elevation before restarting: 8
- New medications (especially antibiotics, NSAIDs)
- Dietary changes (vitamin K intake)
- Compliance issues
- Acute illness
- Changes in liver or renal function
Do not restart warfarin until: 1
- Bleeding is completely controlled (if present)
- The source of bleeding is identified and treated
- The patient is hemodynamically stable
- INR falls below 3.5 8
Critical Pitfalls to Avoid
- Never give IV vitamin K unless there is active bleeding due to anaphylactoid reaction risk 1, 6
- Never use doses >10 mg vitamin K as this creates a prothrombotic state 1
- Never restart at the original warfarin dose without reduction 8
- Never use fresh frozen plasma if PCC is available for major bleeding—PCC is vastly superior 1
- In hospitalized patients with INR >9, withholding warfarin or vitamin K alone may be ineffective within 24 hours due to comorbidities; plasma infusion may be needed 3