What Evaluation Should be Done for Carbon Monoxide Poisoning?

Patient Presentation
A 14-year-old male was brought to the emergency room by ambulance after he was found sitting in his room groaning in pain in the early morning after his mother returned from her overnight work shift.
The adolescent was lethargic but could answer questions. His mother quickly checked on other people in the home who were also either unarousable or in pain.
The mother suspected carbon monoxide poisoning, tried to move all the family out of the home, and called for emergency services.
With later questioning, the history revealed that a fireplace fire was lit in the late evening the previous night and was lit throughout the night.
No carbon monoxide detector was in the home.
Upon the ambulance’s arrival, he was placed on 100% oxygen. In the emergency room he complained of headache, nausea and vomitted once.
The pertinent physical exam showed a lethargic but appropriate adolescent with a Glascow Coma Scale of 13. His heart rate was 145, respiratory rate was 22 and he had normal blood pressure.
He was described as having reddish skin with bluish fingernail beds. He complained of muscle pain but had normal strength and tone. The rest of his examination was normal.
The work-up included an electrocardiogram which showed sinus tachycardia.
The radiologic evaluation showed a normal chest x-ray.
The laboratory evaluation revealed an arterial blood gas of 7.4/40/300/-1 (pH/Carbon Dioxide/Oxygen/Base excess).
The hemoglobin was 16.2 mg/dl, hematocrit of 47% with a white blood cell count of 25.6 WBC x 1000/mm2 with predominant polymorphonuclear cells.
A creatinine phosphokinase level was 580 U/L (normal 40-200 U/L).
The carboxyhemoglobin level was 26% (normal 1-3%) confirming the diagnosis of carbon monoxide poisoning.
During the patient’s clinical course he was transferred to a regional children’s hospital which had hyperbaric oxygen treatment available and he received two treatments because of continued confusion and lethargy. His carboxyhemoglobin decreased to 0.5% with treatment.
A consultation for neuropsychiatric testing was completed and showed some discrepancy between verbal and non-verbal testing but no memory problems.
There was no previous testing available for comparison.
He was discharged to home after the fireplace was fixed and the furnace also inspected. Other family members were discharged to home after appropriate treatment also. He was to follow-up with neurology and have repeated neuropsychiatric testing in 1-2 months.

Carbon monoxide (CO) is a by-product of incomplete burning of carbon fuels.
It is colorless and odorless and therefore difficult to detect.
Common causes of CO poisoning are faulty or inadequately ventilated home heating sources (e.g. furnaces, fireplaces, kerosene heaters, etc.), automobiles with obstructed exhaust systems, gas-powered generators, home fires or tobacco smoke.
Other sources may be recreational or employment related including propane-fueled forklifts, gas-powered concrete saws, swimming behind motorboats, being in enclosed spaces with ice-cleaning machines (i.e. Zamboni&reg) or automobiles (e.g. indoor tractor pulls, demolition derbys). Inhalation of methylene chloride vapors also can cause CO poisoning.

CO binds to hemoglobin significantly more readily than oxygen (230-270 times more) and therefore, it causes toxicity by cellular hypoxia. CO can cause problems whether it is a chronic or acute exposure.
CO binds to myocardial tissue even more readily than hemoglobin and therefore the heart is at high risk. Obviously the brain is also at high risk because of its need for a consistent oxygen supply.
CO is eliminated through the lungs with a half-life at room air of 3-4 hours.
Supplemental oxygen reduces the half-life to 30-90 minutes and hyperbaric oxygen (2.5 atmospheres at 100% oxygen) reduces it to 15-23 minutes.

Chronic CO poisoning may present with the same symptoms but often presents with new changes in cognitive ability or gradual onset of neuropsychiatric symptoms.

Common acute signs and symptoms:

  • Dermatologic
    • Cherry-red skin – is the classic description, often remembered by the saying, “cherry-red, you’re dead!”
    • Pallor
    • Cyanosis
  • Cardiac
    • Chest pain
    • Hypotension
    • Palpitations
    • Tachycardia
  • Gastrointestinal
    • Abdominal pain
    • Diarrhea
    • Emesis
    • Nausea
  • Musculoskeletal
    • Muscle pain secondary to rhabdomyolysis
  • Neurologic
    • Ataxia
    • Aggitation
    • Amnesia
    • Coma
    • Confabulation
    • Confusion
    • Depression
    • Distractability
    • Dizziness
    • Emotional lability
    • Gait disturbances
    • Hallucination
    • Headache – one of the earliest signs
    • Hearing and vestibular problems
    • Impaired cognition
    • Impaired judgement
    • Impulsivenss
    • Increased reflexes
    • Memory impairment – the most common neuropsychiatric finding
    • Papilledema
    • Psychosis
    • Seizures
    • Retinal hemorrhages
    • Visual acuity changes including hemianopsia
  • Respiratory
    • Dyspnea on exertion
    • Tachypnea (mild generally)
    • Pulmonary edema
  • Other
    • Fatigue

Treatment includes:

  • Oxygen – 100% at room air begun immediately and possibly hyperbaric oxygen. The Undersea and Hyperbaric Medical Society offers a directory of locations where hyperbaric oxygen is available at: http://www.uhms.org/Chambers/Chambersearch.asp or Divers Alert Network (DAN) at Duke University can be contacted at (919) 684-2948.
  • Intensive care unit admission for management of neurological, cardiac, respiratory, renal or muscular disease
  • Outpatients who are asymptomatic with a carboxyhemoglobin levels less than 10% generally can be discharged home but with early follow-up and reduced activity for 2-4 weeks.
  • Prevention should be discussed at health maintenance visits including the importance of CO detectors with audible alarms in the home and proper maintenance of home heating equipment. In areas with snow fall, reminding parents to keep the exhaust system clear if stranded and running the motor for heat is important.

Patients usually (~67%) have a full recovery. Variability of clinical severity, lab values, and outcome all limit prognostic accuracy.
Poor outcomes are associated with cardiac arrest, coma, metabolic acidosis, extremely high carboxyhemoglobin levels, and head imaging abnormalities.
Neuropsychiatric testing may have some prognostic ability in determining delayed cognitive problems.

Learning Point

Workup for CO poisoning often includes:


    • Carboxyhemoglobin – confirmation of disease process and treatment indications
    • Arterial blood gas – screening for acid/base deficit, metabolic and respiratory status
    • Creatine kinase with MB fraction – screening for rhabdomyolysis and myocardial injury
    • Myoglobin – screening for rhabdomyolysis
    • Complete blood count – usually mild leukocytosis
    • Electrolytes and glucose screening for lactic acidosis, hypokalemia, and hyperglycemia seen in severe poisoning
    • BUN and creatinine – screening for acute renal failure secondary to myoglobinuria.
    • Liver function tests – screening for hepatic failure
    • Urine analysis – screening for chronic poisoning which may show albumin and glucose
    • Cyanide levels – screening if industrial fire or other possible exposure
    • Blood alcohol levels – screening for intentional and unintentional injury
    • Toxicology screens – screening for possible suicide attempt or co-toxicity

    Imaging Studies are sometimes done

    • Chest x-ray – usually normal
    • Computed tomography scan or magnetic resonance imaging of the head – looking for cerebral edema and focal lesions, most typically of the basil ganglia.
      Other tests

      • Electrocardiogram – screening for arrhythmias
      • Neuropsychologic testing – screening for cognitive deficits

Questions for Further Discussion
1. What are the components of the Glascow Coma Scale?
2. What are the indications for hyperbaric oxygen treatment?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MEDLINEplus for this topic: Carbon Monoxide Poisoning
and at Pediatric Common Questions, Quick Answers for this topic: Fire Safety.

To view current news articles on this topic check Google News.

Rudolph CD, et.al. Rudolph’s Pediatrics. 21st edit. McGraw-Hill, New York, NY. 2003:363-364.

Lucchesi M, Schochat G. Toxicity, Carbon Monoxide. eMedicine.
Available from the Internet at http://www.emedicine.com/ped/topic315.htm (rev. 11/1/2004, cited 12/12/05).

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effecively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competency performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    February 13, 2006