看護師が、心房細動でワルファリンを服用している成人患者の朝の検査結果を確認している。最新のINRは5.8である。看護師が最初にとるべき行動はどれか。

INR 5.8は、治療域（心房細動では2.0～3.0）を大きく上回っており、出血リスクが高いことを示している。優先すべき行動は、次のワルファリン投与を保留し、ビタミンKの投与や用量調整の指示を安全に受けられるよう医師に報告することである。プロタミン硫酸はヘパリンの拮抗薬であり、ワルファリンではない（ワルファリンの拮抗薬はビタミンKである）。ビタミンKを多く含む食品を長期的に増やすことでINRは低下する可能性があるが、差し迫った出血リスクには対処できない。何の介入もせずに同量を継続すれば、出血リスクがさらに高まる。

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 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.