Carbon Monoxide

Synonym/Acronym

Rationale

To identify the amount of carbon monoxide in the blood related to poisoning, toxicity from smoke inhalation, or exhaust from cars.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

Method: Spectrophotometry, co-oximetry.

		% Saturation of Hemoglobin
Newborns		10%–12%
Nonsmokers		Up to 2%
Smokers		Up to 10%

CO levels in smokers may reach levels greater than 20%. Variation is due in part to factors such as cigarette brand, number of cigarettes smoked per day, and the time interval during which multiple cigarettes are smoked. Research as to whether electronic cigarettes (vaping) produce clinically significant levels of CO are conflicting; further study is needed.

Critical Findings and Potential Interventions ⬆ ⬇

CO % of Total Hemoglobin		Symptoms
10%–20%		Asymptomatic
10%–30%		Disturbance of judgment, headache, dizziness
30%–40%		Dizziness, muscle weakness, vision problems, confusion, increased heart rate, increased breathing rate
50%–60%		Loss of consciousness, coma
Greater than 60%		Death

Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.

Women and children may suffer more severe symptoms of carbon monoxide poisoning at lower levels of carbon monoxide than do men because women and children usually have lower RBC counts.

A possible intervention in moderate CO poisoning is the administration of supplemental oxygen given at atmospheric pressure. In severe CO poisoning, hyperbaric oxygen treatments may be used.

Overview ⬆ ⬇

Study type: Blood collected in a green-top [heparin] or lavender-top [EDTA] tube; related body system: Respiratory system. Carboxyhemoglobin is stable at room temperature; however, the specimen should be transported tightly capped (anaerobic) and in an ice slurry if blood gases are to be performed simultaneously.

Exogenous carbon monoxide (CO) is a colorless, odorless, tasteless by-product of incomplete combustion derived from the exhaust of automobiles, coal and gas burning, and tobacco smoke. Endogenous CO is produced as a result of RBC catabolism. CO levels are elevated in newborns as a result of the combined effects of high hemoglobin turnover and the inefficiency of the infant’s respiratory system. CO binds tightly to hemoglobin with an affinity 250 times greater than oxygen, competitively and dramatically reducing the oxygen-carrying capacity of hemoglobin. The increased percentage of bound CO reflects the extent to which normal transport of oxygen has been negatively affected.

Overexposure causes hypoxia, which results in headache, nausea, vomiting, vertigo, collapse, or convulsions. Toxic exposure causes anoxia, increased levels of lactic acid, and irreversible tissue damage, which can result in coma or death. Acute exposure may be evidenced by a cherry red color to the lips, skin, and nailbeds; this observation may not be apparent in cases of chronic exposure. A direct correlation has been implicated between carboxyhemoglobin levels and symptoms of atherosclerotic disease, angina, and myocardial infarction.

Indications ⬆ ⬇

Assist in the diagnosis of suspected CO poisoning.
Evaluate the effect of smoking on the patient.
Evaluate exposure to fires and smoke inhalation.

Interfering Factors ⬆ ⬇

Factors That May Alter the Results of the Study

Specimen should be collected before administration of oxygen therapy.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Increased In

CO poisoning
Hemolytic disease(CO released during RBC catabolism)
Tobacco smoking

Decreased In

N/A

Nursing Implications, Nursing Process, Clinical Judgement ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Discuss how this test can assist in evaluating the extent of carbon monoxide poisoning or toxicity.
Explain that a blood sample is needed for the test.
Discuss the cause of symptoms; headache, vomiting, weakness, dizziness, confusion, blurred vision, convulsions, shortness of breath, or coma could be related to CO exposure.
Discuss the potential causes of carbon monoxide poisoning; poor ventilation with fireplaces, portable generators, wood burning stoves, charcoal burning grills, water and space heaters, and gas cooking ranges.
Explain the importance of having carbon monoxide detectors strategically placed within the home or other area.
Explain that treatment for carbon monoxide poisoning ranges from administration of oxygen to hyperbaric therapy.

After the Study: Implementation & Evaluation Potential Nursing Actions

Treatment Considerations

A mechanical ventilator may be needed to support adequate ventilation.

Clinical Judgement

Consider how to mitigate the emotional impact of an accidental exposure that could have devastating results and focus on how to solve the problem of environmental safety.

Follow-Up and Desired Outcomes

Agrees to evaluate at risk areas of home or work environment (e.g., indoor gas heaters or gas cooktops) for carbon monoxide leakage and place detectors where needed.