# A nurse is reviewing the morning lab results for an adult client receiving warfarin for atrial fibrillation. The most recent INR is 5.8. Which action should the nurse take first?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=360515&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

A nurse is reviewing the morning lab results for an adult client receiving warfarin for atrial fibrillation. The most recent INR is 5.8. Which action should the nurse take first?

## Option

1. Encourage the client to increase intake of leafy green vegetables
2. Administer protamine sulfate as the antidote
3. Hold the next dose of warfarin and notify the provider **✔ Correct answer**
4. Continue the prescribed warfarin dose and reassess in 24 hours

**Correct answer: 3**

## Explanation

An INR of 5.8 is significantly above the therapeutic range (2.0–3.0 for atrial fibrillation) and indicates a high bleeding risk. The priority action is to hold the next warfarin dose and notify the provider so that a vitamin K antidote or dose adjustment can be ordered safely. Protamine sulfate is the antidote for heparin, not warfarin (vitamin K is the warfarin antidote). Increasing vitamin K-rich foods over time may lower the INR but does not address the immediate bleeding risk. Continuing the same dose without intervention would compound the risk of hemorrhage.

## In-depth explanation

Clinical Judgment
The core of this question is the bleeding risk indicated by an INR of 5.8, which greatly exceeds the therapeutic range (INR 2.0–3.0). Using the NCJMM framework: Recognize Cues (abnormal INR 5.8) → Analyze Cues (excessive warfarin effect, impending bleeding) → Prioritize (safety-first: hold the medication) → Take Action (report to provider and consider vitamin K or FFP). Any option that implements another intervention without first discontinuing the drug itself violates safety.

Memory Tip
High INR → Hold + Call. If the INR deviates from the therapeutic range by more than 1 point (especially 4 or above), always "hold + report." Warfarin antidote = Vitamin K, Heparin antidote = Protamine — do not confuse them.

KR vs US
Although the same INR target range is applied in Korea, the NCLEX frequently uses the phrase "first action." In this case, you must select the single most urgent intervention directly related to patient safety. In Korean clinical practice, it is common to observe while waiting for a physician's order change, but the NCLEX differs by clearly asking about the nurse's autonomous authority (holding medication and reporting).

## Clinical scenario

Clinical Practice Guide
Warfarin monitoring is INR-based. Standard target for atrial fibrillation is INR 2.0–3.0. INR ≥4.5 sharply increases bleeding risk; for INR ≥5.0, standard practice is to immediately withhold the drug and notify the healthcare provider (ACCP Antithrombotic Therapy Guidelines). If bleeding signs are present, consider IV vitamin K + FFP/PCC.

Caution
On the NCLEX, the "first action" must be a single action that immediately ensures patient safety. "Education" or "observation" are usually lower priority. Drug-antidote pairs (warfarin↔vitamin K, heparin↔protamine, opioid↔naloxone) are tested every time, so memorize them.

## Key concepts

- **Warfarin (와파린)** — 비타민 K 길항제 경구 항응고제. 응고인자 II/VII/IX/X 합성을 억제하여 혈전 형성을 막음. 좁은 치료지수 약물로 정기적 INR 모니터링이 필수이며 식이·약물 상호작용에 민감.
- **INR (International Normalized Ratio)** — PT(prothrombin time)를 표준화한 응고 검사 지표. 정상 약 1.0, 항응고 치료 목표는 적응증에 따라 다름(심방세동·기계판막은 2.0–3.0, 급성 정맥혈전은 2.0–3.0). 5.0 이상은 출혈 고위험.
- **Vitamin K (피토나디온, 비타민 K1)** — Warfarin 길항제. 응고인자 II/VII/IX/X 합성을 회복시킴. 경증 INR 상승은 경구 1–5 mg, 출혈 동반 시 정맥 투여 + FFP/PCC 병용. 헤파린에는 효과 없음.

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