# A 72-year-old on chronic warfarin for atrial fibrillation comes for routine follow-up. After reviewing the EHR, which finding requires the MOST urgent intervention? > source: MyMerci (mymerci.kr) > url: https://mymerci.kr/pages/nclex_q.php?qn_id=374949&lang=en > language: en > subject: Pharmacological and Parenteral Therapies > category: PPT ## Question A 72-year-old on chronic warfarin for atrial fibrillation comes for routine follow-up. After reviewing the EHR, which finding requires the MOST urgent intervention? History Vitals Labs Orders Notes 72-year-old female with persistent atrial fibrillation. Chronic warfarin for 10 years; last INR (3 weeks ago) was 2.6 — therapeutic. Recent UTI diagnosed 5 days ago at urgent care; started on sulfamethoxazole-trimethoprim. No known liver or kidney disease. BP 132/80, HR 78 (controlled rate AF), RR 16, T 36.7 C, no acute distress. (데이터 없음) INR drawn today: 6.8. Last week INR (before antibiotic): 2.4. Continue warfarin 5 mg daily (current order). Bactrim DS 1 tab BID for 7 days (started 5 days ago). Lisinopril 10 mg daily. No known new bleeding. Patient reports new bruising on both forearms over past 2 days. Denies bleeding gums or hematuria. Diet unchanged including evening cooked spinach. No fall or trauma. Family member also notes more bruising than usual. 1 Patient continues to eat one cup of cooked spinach (consistent vitamin K source) most evenings as has been the case for 10 years. ✕ 2 Patient started a NEW antibiotic (sulfamethoxazole-trimethoprim — Bactrim) 5 days ago for UTI and the INR today is 6.8 with new bruising. ✕ 3 Patient drinks one cup of green tea most mornings as has been the case for years. ✕ 4 Patient takes lisinopril 10 mg daily as has been ordered for years. ✕ ## Explanation Choice 2 is the most urgent — sulfamethoxazole-trimethoprim (Bactrim) is a high-risk warfarin interaction (potentiates anticoagulation by displacing warfarin from albumin and inhibiting CYP2C9 metabolism), and the INR of 6.8 with new bruising indicates clinically significant overshoot with bleeding risk. Action: hold warfarin, notify provider, anticipate vitamin K (oral 2.5-5 mg if no major bleeding) or PCC if major bleeding, monitor for bleeding signs. Choice 1 (consistent spinach) is fine because warfarin patients should keep vitamin K intake CONSISTENT, not avoid it. Choice 3 (green tea) is consistent and no INR change implied. Choice 4 (lisinopril) has no significant warfarin interaction. ## In-depth explanation The "consistent vitamin K diet" is the most-tested warfarin teaching point — patients should NOT avoid green vegetables; they should keep intake CONSISTENT week-to-week. The high-risk antibiotic interactions (Bactrim, metronidazole, fluconazole, ciprofloxacin) potentiate warfarin and elevate INR within days. Memorize antibiotic interaction list for any warfarin patient. ## Clinical scenario **72-year-old on chronic warfarin** for atrial fibrillation comes for routine follow-up. The nurse reviews the chart for medication reconciliation and dietary review. ## Key concepts - **Warfarin and antibiotics** — Sulfamethoxazole-trimethoprim, metronidazole, fluconazole, ciprofloxacin elevate INR; check INR within 3-5 days of new antibiotic. - **Consistent vitamin K diet** — Maintain steady intake of green leafy vegetables (NOT avoid); large fluctuations cause INR instability. - **INR > 5 management** — Hold warfarin, vitamin K oral 2.5-5 mg if no major bleeding; PCC + IV vitamin K + reversal for major bleeding; close monitoring. ## Related questions - [A nurse is programming a high-alert IV medication on a smart infusion pump. 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