Point-of-Care INR 4.7 With Oozing Gums
A 71-year-old man on warfarin for atrial fibrillation comes in with two days of oozing gums after a dental cleaning and a 4 cm bruise on his forearm. He feels well: no melena, no hematuria, no headache, and his neurologic exam is normal. His pillbox shows he took 5 mg twice on Sunday instead of once, and he started trimethoprim-sulfamethoxazole four days ago for a urinary tract infection. Point-of-care INR is 4.7; a repeat on a second finger is 4.9. His last laboratory INR two weeks ago was 2.6. The clinic's device is CLIA-waived and validated for capillary samples, but it has not been compared with the hospital lab since it was replaced six months ago. He drove himself and wants to go home.
1. Is the point-of-care INR actionable at 4.7-4.9? How do you verify it, and what does verification change?
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Not by itself, and not for a decision that is hard to reverse. Capillary whole-blood INR is reliable in the 2-3.5 range but loses accuracy at higher values; devices drift, and this one has never been compared against the hospital lab since replacement.
Verify: send a stat venous plasma INR/PT, plus CBC and renal function. Document the POC value, the device, and the lot. Two readings of 4.7 and 4.9 are internally consistent but not independent - agreement between two readings on the same device is not confirmation.
What verification changes:
- Lab INR 4.5-10 with visible minor bleeding (oozing gums) -> hold warfarin, consider low-dose oral vitamin K, outpatient management with close follow-up.
- Lab INR above 10, or bleeding more than oozing -> ED evaluation.
- Lab INR around 3.5 -> the POC result was artifact and no reversal is needed at all.
Stop warfarin now regardless, because the clinical picture and the history of a double dose plus a strong interacting antibiotic make a supratherapeutic INR likely; the confirmatory lab then determines whether you add vitamin K.
2. Outline the anticoagulation plan and fix the precipitant.
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Hold warfarin now and for at least 1-2 doses, pending the venous INR.
Vitamin K: with visible minor mucosal bleeding and an INR in the 4.5-10 range, oral vitamin K 1-2.5 mg is reasonable. Use the oral route - IV vitamin K is for major bleeding and carries anaphylactoid risk - and avoid large doses, which cause prolonged warfarin resistance and make re-anticoagulation difficult in a patient with atrial fibrillation.
Fix both precipitants:
- Trimethoprim-sulfamethoxazole inhibits CYP2C9 and is one of the strongest warfarin potentiators. Stop it. Check creatinine and CrCl; if adequate, nitrofurantoin 100 mg BID for 5 days or fosfomycin 3 g as a single dose treats uncomplicated cystitis without this interaction.
- The Sunday double dose - reconcile the pillbox, ask about alcohol and NSAID use, and set up pharmacy blister packs or a family member's oversight.
Restart: recheck INR in 24 hours, then every 1-2 days until therapeutic. Restart at roughly 10-15% below his prior weekly total once the INR is under 3 and the bleeding has stopped. Loop in his anticoagulation clinic or PCP the same day - do not let him self-adjust.
3. What is the disposition, and what are your escalation triggers?
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He is hemodynamically stable with minor bleeding and no red flags: no melena, no hematuria, no headache, no focal deficit, and he is eating and drinking.
Discharge is reasonable if: the confirmatory venous INR returns within a manageable range, he has a responsible adult at home, reliable transportation, and a phone, and the 24-hour INR recheck is scheduled before he leaves. Give written return precautions and a same-day phone number.
Escalate to the ED for:
- INR above 10 or any bleeding that is more than oozing
- New headache, confusion, vomiting, or any focal neurologic change (intracranial hemorrhage)
- GI bleeding, hematuria, or inability to eat or drink
- Unreliable follow-up or no one at home
Written precautions to hand him: severe or sudden headache, vomiting blood or coffee-ground material, black or bloody stools, blood in the urine, bleeding that will not stop with pressure, weakness, confusion, or a fall - particularly any head strike, since a supratherapeutic INR makes even a minor head injury an ED visit.
Document the shared decision-making, the INR values and device, the drug interaction identified, and the follow-up plan.