# A nurse is caring for a patient receiving warfarin therapy. Which set of laboratory values requires immediate intervention?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=543507  
> language: ko  
> subject: Pharmacology

## 문제

A nurse is caring for a patient receiving warfarin therapy. Which set of laboratory values requires immediate intervention?

The nurse is monitoring a patient on long-term warfarin therapy for atrial fibrillation prevention.

## 보기

1. PT: 18 seconds, INR: 2.1
2. PT: 22 seconds, INR: 2.8
3. PT: 25 seconds, INR: 3.2
4. PT: 45 seconds, INR: 6.8 **✔ 정답**

**정답: 4**

## 해설

An INR of 6.8 indicates severe overanticoagulation, requiring immediate intervention to prevent bleeding. Other options show INR values within or slightly above therapeutic range, not critical.

## 심화 해설

Understanding the Therapeutic Range for Warfarin

When caring for a patient on warfarin, a vitamin K antagonist, the primary laboratory monitoring tool is the prothrombin time (PT), standardized and reported as the international normalized ratio (INR). The goal of therapy is to achieve a delicate balance: reducing the risk of thromboembolic events without causing hemorrhage. For most indications, including atrial fibrillation, the standard therapeutic INR target range is 2.0 to 3.0, with a mechanical heart valve often requiring a slightly higher range of 2.5 to 3.5 [1,3].

The clinical challenge with warfarin is its narrow therapeutic window and significant inter-individual variability, which necessitates frequent monitoring to maintain the time in therapeutic range (TTR) [3,4]. A high TTR indicates stable anticoagulation control and is associated with better clinical outcomes [4]. The risk of major bleeding, particularly intracranial hemorrhage, escalates sharply as the INR rises above the therapeutic threshold.

Analyzing the Laboratory Values

Let's evaluate each option against the standard therapeutic INR range for atrial fibrillation (2.0-3.0):

1.  PT: 18 seconds, INR: 2.1

This INR falls within the desired therapeutic range. The patient is adequately anticoagulated, and no immediate intervention is needed. This represents stable control.

2.  PT: 22 seconds, INR: 2.8

This INR is also within the standard therapeutic range, though near the upper limit. It requires continued monitoring but does not constitute a critical value requiring immediate intervention.

3.  PT: 25 seconds, INR: 3.2

This INR is slightly above the standard therapeutic range for atrial fibrillation. While it warrants attention, such as a potential minor dose adjustment and closer follow-up, it is not typically considered a critical value that demands an emergent response unless the patient is actively bleeding.

4.  PT: 45 seconds, INR: 6.8

This value is critically supratherapeutic. An INR of 6.8 indicates severe anticoagulation, placing the patient at an imminent and high risk for life-threatening spontaneous bleeding [3]. This finding requires immediate intervention, which may include withholding the next warfarin dose, administering oral or intravenous vitamin K, or even transfusing prothrombin complex concentrates or fresh frozen plasma if active bleeding is present.

Why Immediate Intervention is Required for Option 4

The primary safety concern with warfarin therapy is the prevention of hemorrhagic complications. The relationship between the intensity of anticoagulation and bleeding risk is not linear; the risk increases exponentially with higher INR values. An INR of 6.8 far exceeds the therapeutic threshold and represents a state of profound coagulopathy. The nurse's immediate priority is patient safety, which involves recognizing this critical value, holding the medication, notifying the prescriber, and preparing to administer reversal agents as ordered. The narrow therapeutic window of warfarin, as highlighted in studies focusing on management challenges, makes this recognition a cornerstone of safe nursing practice [3].References (research sources)

- [3]AI-WAR: a novel warfarin management software with a bidirectional LSTM dosing model improves time in therapeutic range.Research articleLi Y, Xu N, Song L, Liu Y, Pei Q, Kuang Y, Yang G. (2026) · DOI: 10.3389/fphar.2026.1750503

- [4]Time in Therapeutic Range in Patients with Venous Thromboembolism on Vitamin K Antagonist in a Moroccan Thrombosis Unit : An Observational Study.Research articleTazi Mezalek Z, Mounfaloti W, Iraqi FZ, Ammouri W, Harmouche H, Maamar M, Razine R. (2026) · DOI: 10.1055/a-2890-0814

## 임상 시나리오

Managing Supratherapeutic INR from WarfarinImmediate Steps for Critical Bleeding Risk
A patient on warfarin for atrial fibrillation has an INR of 6.8. This is a critically supratherapeutic level, far exceeding the standard target of 2.0 to 3.0, and poses an imminent risk of major hemorrhage.

Immediate intervention requires holding the next warfarin dose and assessing for any signs of active bleeding. The provider must be notified urgently to consider administering oral vitamin K for reversal, especially if bleeding is present or the risk is high.

CautionDo not confuse an INR of 3.2 with a critical value. While it requires a dose adjustment, it does not typically necessitate emergency reversal with vitamin K unless bleeding occurs. Over-correction can lead to thrombosis.

## 핵심 개념

- **International Normalized Ratio (INR)** — A standardized calculation of prothrombin time used to monitor warfarin therapy, with a therapeutic range typically between 2.0 and 3.0 for most indications.
- **Warfarin** — An oral vitamin K antagonist anticoagulant used to prevent thromboembolic events, requiring frequent INR monitoring due to its narrow therapeutic window.
- **Prothrombin Time (PT)** — A blood test measuring the time it takes for plasma to clot, which is prolonged by warfarin; results are standardized using the INR.
- **Supratherapeutic INR** — An INR level above the target range that significantly increases the risk of major hemorrhage, including intracranial bleeding.
- **Atrial Fibrillation** — A common cardiac arrhythmia that increases stroke risk, often managed with long-term warfarin anticoagulation to maintain an INR of 2.0 to 3.0.

## 같은 주제 문제

- [A nurse is caring for a patient receiving warfarin therapy. Which laboratory value require…](https://mymerci.kr/pages/nclex_q.php?qn_id=543508)

---

More free questions: [기출문제](https://mymerci.kr/)

_학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._