# A 60-year-old patient is brought to the emergency department after being found unconscious in a garage with a running car. The patient is conscious but confused, with cherry-red skin coloration. Vital signs are: BP 130/85 mmHg, HR 95 bpm, RR 20/min, SpO2 97% on room air. Which nursing action should be the highest priority?

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## 문제

A 60-year-old patient is brought to the emergency department after being found unconscious in a garage with a running car. The patient is conscious but confused, with cherry-red skin coloration. Vital signs are: BP 130/85 mmHg, HR 95 bpm, RR 20/min, SpO2 97% on room air. Which nursing action should be the highest priority?

## 보기

1. Obtain arterial blood gas analysis immediately
2. Administer activated charcoal via nasogastric tube
3. Administer 100% oxygen via non-rebreather mask **✔ 정답**
4. Prepare the patient for hyperbaric oxygen therapy

**정답: 3**

## 해설

Administering 100% oxygen via non-rebreather mask is the highest priority to treat carbon monoxide poisoning by displacing CO from hemoglobin, despite normal SpO2 readings. Other interventions like ABG or hyperbaric therapy should not delay oxygen administration.

## 심화 해설

Clinical Context and Pathophysiology

The scenario describes a classic presentation of carbon monoxide (CO) poisoning. The patient was found unconscious in a garage with a running car, a common source of CO exposure. The "cherry-red" skin coloration, while a late and unreliable sign, is a textbook finding associated with severe CO toxicity. Critically, the pulse oximetry reading (SpO2 97%) is deceptive. Standard pulse oximeters cannot differentiate between oxyhemoglobin and carboxyhemoglobin (COHb). CO binds to hemoglobin with an affinity over 200 times greater than oxygen, forming COHb, which reduces the blood's oxygen-carrying capacity and impairs oxygen release at the tissue level, leading to cellular hypoxia. This explains why the SpO2 can appear normal despite severe tissue hypoxia [3,4].

Priority Nursing Action and Rationale

The highest priority nursing action is to administer 100% oxygen via a non-rebreather mask. The cornerstone of CO poisoning management is the immediate initiation of normobaric oxygen therapy to accelerate the dissociation of CO from hemoglobin. Administering 100% oxygen at the highest possible flow rate reduces the half-life of COHb from approximately 4-6 hours on room air to about 60-90 minutes [1]. This intervention directly combats the underlying pathophysiology of tissue hypoxia and should not be delayed for diagnostic procedures. The position statement from the Section of Clinical Toxicology emphasizes that oxygen therapy must be started immediately upon suspicion of CO poisoning [1].

Analysis of Incorrect Options

Option 1: Obtain arterial blood gas analysis immediately. While an arterial blood gas (ABG) with co-oximetry is the definitive method to measure COHb levels and confirm the diagnosis, obtaining it is not the highest priority action. The patient is displaying neurological symptoms (confusion, loss of consciousness), indicating significant tissue hypoxia. The immediate clinical priority is to reverse this hypoxia with oxygen. Delaying oxygen administration to perform a diagnostic test would prolong the period of cellular injury and worsen outcomes [1,4].

Option 2: Administer activated charcoal via nasogastric tube. Activated charcoal is indicated for gastrointestinal decontamination following the ingestion of certain toxins. CO poisoning occurs exclusively through inhalation. Therefore, activated charcoal has no role in its management and would be an inappropriate and potentially harmful intervention in this context.

Option 4: Prepare the patient for hyperbaric oxygen therapy. Hyperbaric oxygen (HBO2) therapy is an important treatment modality for severe CO poisoning, but it is not the first-line, immediate priority in the emergency department. Normobaric 100% oxygen therapy via a non-rebreather mask must be initiated first without delay. The decision to pursue HBO2 is made subsequently, based on specific criteria such as loss of consciousness, neurological deficits, cardiac ischemia, or very high COHb levels. The immediate nursing action is to start the high-flow oxygen and then prepare for potential transfer to a hyperbaric facility if indicated [1].References (research sources)

- [1]Management of acute intoxication with carbon monoxide - Polish Medical Society, Section of Clinical Toxicology position statement.Research articleAnand J, Pawlas N, Schetz D, Kot J. (2025) · DOI: 10.13075/ijomeh.1896.02653

## 임상 시나리오

Clinical Practice Guide: Carbon Monoxide Poisoning

Immediate Priorities

- **Scene Safety:** Ensure the patient is removed from the source of CO exposure. Do not enter an unsafe environment without proper personal protective equipment.

- **Airway and Breathing:** Assess and secure the airway. Administer 100% oxygen via a tight-fitting non-rebreather mask at the highest possible flow rate (15 L/min) immediately. Do not delay oxygen therapy for diagnostic tests.

- **Cardiac Monitoring:** Initiate continuous cardiac monitoring. CO poisoning can cause myocardial ischemia, arrhythmias, and conduction delays.

Key Assessment Findings

- **Neurologic:** Confusion, headache, dizziness, syncope, seizures, or coma. The patient's altered mental status is a critical indicator of severity.

- **Skin:** Cherry-red coloration is a classic but late and unreliable sign. Cyanosis may be absent even with severe hypoxia.

- **Vital Sign Deception:** Pulse oximetry (SpO2) is falsely normal or elevated. It cannot distinguish carboxyhemoglobin from oxyhemoglobin. Treat the patient, not the monitor.

Diagnostic and Treatment Pathway

- **Laboratory Confirmation:** Obtain a carboxyhemoglobin (COHb) level via co-oximetry on an arterial or venous blood gas, but only after initiating oxygen therapy.

- **Normobaric Oxygen:** Continue 100% oxygen until the patient is asymptomatic and COHb levels fall below 5-10%. The half-life of COHb on room air is 4-6 hours; on 100% oxygen, it is reduced to 60-90 minutes.

- **Hyperbaric Oxygen (HBO) Consultation:** Prepare for transfer to a hyperbaric facility if the patient has loss of consciousness, neurologic deficits, cardiac ischemia, COHb >25%, or is pregnant with COHb >15%. HBO is an adjunct, not a replacement for immediate normobaric oxygen.

- **Supportive Care:** Treat seizures with benzodiazepines. Manage hypotension with IV fluids and vasopressors if needed. Avoid administering activated charcoal, as it is ineffective for inhaled toxins.

## 핵심 개념

- **Carboxyhemoglobin (COHb)** — A stable complex of carbon monoxide and hemoglobin that forms in red blood cells upon exposure to CO, reducing oxygen-carrying capacity.
- **Non-rebreather Mask** — A medical device used to deliver high concentrations of oxygen, typically 60-90%, with a reservoir bag and one-way valves to prevent rebreathing of exhaled air.
- **Pulse Oximetry SpO2** — An indirect, non-invasive measure of arterial oxygen saturation that cannot differentiate oxyhemoglobin from carboxyhemoglobin, often yielding falsely normal readings in CO poisoning.
- **Cellular Hypoxia** — A condition in which cells are deprived of adequate oxygen supply, which in CO poisoning occurs despite normal arterial oxygen levels because CO blocks oxygen utilization.

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