# A nurse is caring for a 45-year-old patient brought to the emergency department after being found unconscious in a garage with a running car. The patient is now conscious but confused, complaining of headache and nausea. Vital signs: BP 120/80 mmHg, HR 100 bpm, RR 22/min, SpO2 99% on room air, temperature 98.6°F (37°C). The patient's skin appears cherry-red in color. Which nursing action should be the highest priority?

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## 문제

A nurse is caring for a 45-year-old patient brought to the emergency department after being found unconscious in a garage with a running car. The patient is now conscious but confused, complaining of headache and nausea. Vital signs: BP 120/80 mmHg, HR 100 bpm, RR 22/min, SpO2 99% on room air, temperature 98.6°F (37°C). The patient's skin appears cherry-red in color. Which nursing action should be the highest priority?

## 보기

1. Obtain arterial blood gas analysis to assess acid-base balance
2. Administer 100% oxygen via non-rebreather mask immediately **✔ 정답**
3. Insert an IV line and prepare for fluid resuscitation
4. Perform a complete neurological assessment to evaluate mental status

**정답: 2**

## 해설

In carbon monoxide poisoning, immediate administration of 100% oxygen via non-rebreather mask is the priority to displace CO from hemoglobin and restore oxygen-carrying capacity. Other interventions like ABG or neurological assessment are secondary.

## 심화 해설

Understanding the Priority: Immediate Airway and Breathing Management in CO Poisoning

The highest priority in this clinical scenario is to administer 100% oxygen via a non-rebreather mask immediately. This decision is rooted in the fundamental pathophysiological mechanism of carbon monoxide (CO) poisoning and the standard of care for emergency management. The patient's history of being found unconscious in a garage with a running car, combined with the classic sign of cherry-red skin and neurological symptoms (confusion, headache, nausea), points directly to acute carbon monoxide poisoning.

The core problem is that CO has an affinity for hemoglobin that is over 200 times greater than that of oxygen, forming carboxyhemoglobin (COHb). This not only reduces the blood's oxygen-carrying capacity but also shifts the oxyhemoglobin dissociation curve to the left, severely impairing the release of oxygen to the tissues. A crucial clinical pitfall highlighted in the literature is that standard pulse oximetry cannot differentiate COHb from oxyhemoglobin, leading to a deceptively normal SpO2 reading [1]. In this case, an SpO2 of 99% reflects the saturation of available hemoglobin binding sites, but it masks a profound state of tissue hypoxia. The immediate, evidence-based intervention is to displace CO from hemoglobin by creating a high partial pressure gradient of oxygen in the alveoli. Administering 100% oxygen via a non-rebreather mask is the first-line treatment to accelerate the dissociation of CO from hemoglobin, reducing the half-life of COHb from 4-6 hours on room air to approximately 60-90 minutes. This directly addresses the life-threatening tissue hypoxia and must be initiated without delay.

Analysis of Incorrect Options

- Option 1: Obtain arterial blood gas analysis to assess acid-base balance. While an ABG is a critical diagnostic and prognostic tool in CO poisoning, it is not the first action. The study by Ke et al. demonstrates that ABG parameters like pH and lactate are valuable for stratifying risk and predicting ICU admission, with an acidosis group (pH < 7.35) showing a significantly higher ICU admission rate of 44.8% [3]. However, obtaining an ABG is a diagnostic procedure that takes time. The patient's immediate threat is ongoing cellular asphyxiation, which must be treated empirically and instantly. The ABG can and should be drawn shortly after oxygen therapy is initiated, but it does not take precedence over the therapeutic intervention.

- Option 3: Insert an IV line and prepare for fluid resuscitation. Establishing intravenous access is an important component of emergency care, but it is a secondary priority in this specific context. The patient's vital signs show a blood pressure of 120/80 mmHg and a heart rate of 100 bpm, which is a compensatory sinus tachycardia but does not indicate hemodynamic instability requiring immediate fluid resuscitation. The primary pathology is not hypovolemia but hypoxemia at the cellular level. While cardiac complications like myocardial fibrosis and dysfunction are known severe outcomes of acute CO poisoning , the immediate life-saving measure is to reverse the hypoxemia with high-flow oxygen.

- Option 4: Perform a complete neurological assessment to evaluate mental status. A neurological assessment is vital for determining the severity of poisoning and identifying potential stroke mimics, as CO poisoning can present with focal neurological deficits [1]. The patient is already noted to be conscious but confused, which is a significant neurological finding. However, performing a detailed, time-consuming neurological exam before initiating oxygen therapy would delay the critical treatment that can prevent further neurological damage. The priority is to halt the ongoing neurological injury by maximizing oxygen delivery to the brain, after which a thorough assessment can be conducted. The research by Yüceer also supports that the presence of neurological symptoms is a key determinant for considering advanced therapies like hyperbaric oxygen, but only after initial stabilization with normobaric oxygen .References (research sources)

- [1]Gas Geyser-Related Carbon Monoxide Poisoning Presenting as Stroke Mimic and Syncope in Closed-Space Exposure: A Report of Two Cases.Research articleHareeth Reddy RG, Mrganayani V, Somasundar C, Teja B SS, N F. (2026) · DOI: 10.7759/cureus.108695

- [3]Arterial blood gas analysis in risk stratification of acute carbon monoxide poisoning.Research articleKe J, Yin L, Gao Y, Hu J, Zhu D. (2026) · DOI: 10.25259/ijmr_3619_2025

## 임상 시나리오

Emergency Management of Carbon Monoxide PoisoningPrioritizing Oxygen Therapy for Cellular Asphyxiation
The highest priority for suspected carbon monoxide poisoning is immediate administration of 100% oxygen via a non-rebreather mask. This creates a high oxygen partial pressure gradient to displace CO from hemoglobin, reducing the half-life of carboxyhemoglobin from hours to minutes.

A key clinical pitfall is that pulse oximetry cannot distinguish carboxyhemoglobin from oxyhemoglobin. A normal SpO2 reading, such as 99%, is falsely reassuring and masks severe tissue hypoxia.

CautionDo not delay oxygen therapy for diagnostic procedures like ABG analysis or a complete neurological exam. Treat the patient's hypoxia first, as altered mental status is a direct consequence of cellular asphyxiation.

## 핵심 개념

- **Carboxyhemoglobin** — A form where carbon monoxide binds to hemoglobin. It causes tissue hypoxia by impairing oxygen transport capacity.
- **Hyperbaric Oxygen Therapy** — A treatment that involves breathing 100% oxygen at high pressure. In cases of CO poisoning, it dramatically shortens the half-life of COHb, supplies dissolved oxygen to tissues, and can reduce the risk of delayed neurological sequelae.
- **Non-rebreather Mask** — A mask with a one-way valve and an oxygen reservoir bag, which prevents the patient from rebreathing exhaled air and can deliver the highest possible concentration of oxygen (over 90-95%).
- **Pulse Oximetry (SpO2) Limitation** — Limitations of pulse oximetry. It cannot distinguish carboxyhemoglobin (COHb) from oxyhemoglobin (O2Hb), so it may incorrectly display normal readings in cases of CO poisoning.
- **Cherry-Red Skin** — Late signs of carbon monoxide poisoning. Occurs when high levels of COHb dilate skin vessels and alter blood hue. Not always present, but suggests severe poisoning.

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