Management of INR 5.91
For an INR of 5.91 without bleeding, omit the next 1-2 doses of warfarin and administer 1-2.5 mg of oral vitamin K (phytonadione), especially if bleeding risk factors are present. 1, 2
Assessment First
- Immediately assess for active bleeding (check for hemoglobin drop, signs of intracranial/GI/urinary bleeding) and evaluate bleeding risk factors (age >65, history of bleeding, concurrent antiplatelet therapy, recent procedures, falls risk). 2
Management Algorithm for INR 5.91 Without Bleeding
Primary Approach
- Omit the next 1-2 doses of warfarin to allow INR to drift downward naturally. 1
- Administer oral vitamin K 1-2.5 mg - this dose is appropriate for INR 5-10 range and will reduce INR to <4.0 within 24 hours in approximately 85% of patients. 2, 3, 4
- Oral route is preferred over IV due to the risk of anaphylactoid reactions with IV administration (3 per 100,000 doses), which can result in cardiac arrest. 5, 3
Route-Specific Efficacy
- Oral vitamin K is as effective as IV for non-emergent situations, with both achieving target INR in approximately 77-82% of patients at 24 hours. 4, 6
- Avoid subcutaneous administration - this route achieves target INR in only 31% of patients at 24 hours and is similar to placebo, with unpredictable and delayed response. 2, 7, 4
Monitoring and Follow-up
- Recheck INR within 24 hours to ensure appropriate decrease. 2
- Resume warfarin at adjusted dose once INR falls to safe therapeutic range (typically 2-4), usually within 24-48 hours. 1
- Investigate the underlying cause of INR elevation - common culprits include drug interactions (antibiotics, NSAIDs), dietary changes (decreased vitamin K intake), acute illness, or medication non-adherence. 2
Critical Pitfalls to Avoid
- Do not give high-dose vitamin K (>2.5 mg) routinely - doses of 5-10 mg create warfarin resistance lasting up to one week and may create a hypercoagulable state, particularly dangerous in patients with mechanical heart valves or high thrombotic risk. 1, 3
- Do not use IV route unless bleeding is present - reserve IV administration (5-10 mg by slow infusion over 30 minutes) for active bleeding scenarios only. 5, 3
- Avoid excessive correction - rapid INR reduction below therapeutic range increases thromboembolism risk, especially in patients with mechanical valves, atrial fibrillation, or prior thrombotic events. 1
Special Considerations for Mechanical Valve Patients
- Exercise particular caution in patients with mechanical heart valves - the benefit of vitamin K is uncertain in this population, and overly aggressive correction can precipitate valve thrombosis. 1, 2
- Consider simply holding warfarin without vitamin K in low-risk mechanical valve patients (bileaflet aortic valve, no other risk factors) if INR is only mildly elevated. 1