INR 5.4 in an elderly woman after co-trimoxazole and self-started aspirin

Assess bleeding first, then act on the number. An INR of 5.4 without bleeding is not an emergency, but it is not 'skip two doses and drive home' either.

• Look for bleeding: bruising, gum or nose bleeding, haematuria, melaena, abdominal or flank pain, headache and any neurological change - intracranial bleeding is the one that kills. Ask directly about falls and knocks.
• Hold today's warfarin dose and do not give vitamin K. Reversal is a prescriber's decision; in a well patient with no bleeding the usual course is to withhold warfarin and recheck, not to reverse.
• Inform the doctor who manages her anticoagulation the same day, giving the INR value, the co-trimoxazole course and the self-started aspirin.
• Tell her to take no further aspirin until the doctor has spoken to her, and check her other medicines and any herbal products.
• Arrange a repeat INR in 2–3 days: the coagulation system will not be normal tomorrow, and co-trimoxazole's enzyme inhibition persists for several days after the course ends.
• Give written advice on bleeding warning signs and when to call an ambulance.

Document: INR values, examination findings, whom you informed and at what time, and the advice given. If something goes wrong, this note is the difference between a clinical event and a negligence finding.

Use three plain sentences and then ask her to repeat them back.

1. 'Co-trimoxazole makes warfarin stay in your body longer and work more strongly. That is why your blood became too thin.' Mechanistically, co-trimoxazole inhibits CYP2C9, which metabolises S-warfarin, and displaces warfarin from albumin - both effects raise the INR, and they combine.
2. 'Aspirin adds a second risk: it stops platelets working and irritates the stomach, so if bleeding starts it is harder to stop.' Starting it on a neighbour's advice, on top of warfarin, is genuinely dangerous, even at 100 mg.
3. 'For now: no warfarin today, no aspirin, no diclofenac or ibuprofen for pain - paracetamol is the safer choice. Keep eating green vegetables as usual, but do not suddenly change the amount.' Vitamin K in food shifts the INR; consistency matters more than restriction.

Practical checks that decide whether the plan works: can she read the labels and open the boxes, who collects her prescriptions, does she have an emergency number on the fridge, does she drink alcohol, and does she understand that any new medicine - including one bought without a prescription - must be checked first?

Acknowledge her right to decide, then make the safer option the easiest one. She has capacity and can refuse advice; the nurse cannot physically restrain her or take her keys, and escalating to force would damage the relationship she needs for the next four years of anticoagulation.

• Restate the risk once, concretely: with an INR of 5.4 and aspirin on board, a faint at the wheel or a minor collision could bleed heavily and, if the head is involved, fatally.
• Offer alternatives in the same breath: wait until the doctor calls back, call a relative or a taxi, use the clinic's phone, arrange a home visit.
• If she still leaves: document the advice, her refusal and that she appeared to have capacity; give written warning signs and emergency numbers; arrange a same-day telephone call and a repeat INR date; tell the prescribing doctor that she left.
• Do not give any drug on your own initiative 'to be safe'. That is outside the nurse's scope and could do harm.
• The plan changes if she develops bleeding, chest pain, severe headache or confusion: emergency call, not a discussion.

The judgement the exam tests here is the balance between autonomy, beneficence and a defensible record - not winning the argument.