Carbon monoxide

CAS RN: 630-08-0

Treatment Overview

0.4.3 INHALATION EXPOSURE
  • A) MANAGEMENT OF MILD TO MODERATE TOXICITY
    • 1) The primary treatments for carbon monoxide (CO) poisoning are oxygen supplementation and supportive care. An initial carboxyhemoglobin level should be obtained as soon as possible. Treat with 100% oxygen until asymptomatic and carboxyhemoglobin levels are below 5%. Perform a Mini-Mental State Exam and careful neurologic exam. An abnormal Mini-Mental State Exam or ataxia or other neurological abnormalities may be a subtle sign of more severe poisoning. Signs or symptoms of metabolic acidosis would indicate a more severe poisoning. Identifying the source of the exposure is critical to prevent recurrent poisoning.
  • B) MANAGEMENT OF SEVERE TOXICITY
    • 1) In addition to oxygen supplementation, patients who are comatose or patients with smoke inhalation injuries may need mechanical respiratory support. Standard treatment protocols for hypotension and cardiac dysrhythmias should be followed. The role of hyperbaric oxygen therapy is controversial. While data are conflicting regarding improved outcome with hyperbaric oxygen therapy, patients with severe poisoning should generally receive hyperbaric oxygen. Some of the suggested indications include syncope, altered mental status or neurologic deficits, evidence of cardiac injury, and persistent or severe metabolic acidosis. Pregnancy, especially with fetal distress, is generally considered an indication for hyperbaric therapy because fetal carboxyhemoglobin concentration is generally higher, and its elimination slower, than corresponding maternal carboxyhemoglobin. Other experts have suggested patients with milder poisoning may also benefit.
  • C) DECONTAMINATION
    • 1) PREHOSPITAL: Remove from the source and administer high-flow oxygen.
  • D) AIRWAY MANAGEMENT
    • 1) Patients who are comatose or who have lung injury from smoke inhalation injuries may need mechanical respiratory support and orotracheal intubation.
  • E) ANTIDOTE
    • 1) 100% oxygen should be administered to the patient via nonrebreather and continued until the patient is asymptomatic and carboxyhemoglobin levels are below 5%. Pregnant women need to be treated for a longer time since CO elimination may be slower in the fetus. Some evidence supports the use of hyperbaric oxygen to prevent delayed cognitive and neurologic sequelae; however, there is controversy around the use of hyperbaric therapy. In general, the risks of hyperbaric oxygen treatment (which include seizures and barotrauma) are low. In complex cases, a poison center or hyperbaric center should be contacted.
  • F) ENHANCED ELIMINATION
    • 1) Oxygen increases the elimination of CO.
  • G) PATIENT DISPOSITION
    • 1) HOME CRITERIA: Asymptomatic, nonpregnant patients can be observed at home, provided it is certain that the source of exposure has been eliminated and the patient has been moved to a CO-free environment. Most area fire departments and utility companies can perform ambient CO monitoring to determine the source of exposure.
    • 2) OBSERVATION CRITERIA: Mildly to moderately symptomatic patients should be sent to a healthcare facility for evaluation and treated until symptoms resolve.
    • 3) ADMISSION CRITERIA: Patients who remain symptomatic despite adequate treatment with oxygen, patients with abnormal neurological exams or myocardial injury, and pregnant women with fetal distress should be admitted.
    • 4) CONSULT CRITERIA: Consult a poison center or medical toxicologist for assistance in managing severe poisonings and for recommendations on determining the need for hyperbaric oxygen treatment. Contact your nearest hyperbaric chamber for recommendations and arrangements for hyperbaric oxygen therapy.
  • H) PITFALLS
    • 1) Pulse oximetry will measure normal oxygen saturations even in the presence of significant carboxyhemoglobin levels. Carboxyhemoglobin levels and initial severity of the patient's symptoms are not good predictors for delayed neurocognitive sequelae. The clinical manifestations of mild toxicity are nonspecific and often mistaken for viral illnesses. A high index of suspicion is necessary; the diagnosis of CO poisoning should be considered in patients presenting with nausea, vomiting, or headache, especially if these occur in family clusters or at the beginning of cold weather. Failure to determine the source of exposure may result in recurrent poisoning.
  • I) TOXICOKINETICS
    • 1) The half-life of carboxyhemoglobin in a patient breathing ambient air is approximately 4 to 6 hours. In a patient breathing 100% oxygen at sea level, the half-life is approximately 60 to 75 minutes, and during hyperbaric oxygen treatment, it is approximately 20 minutes.
  • J) DIFFERENTIAL DIAGNOSIS
    • 1) The differential diagnosis for the nonspecific symptoms of CO poisoning is extremely broad and includes influenza, viral syndrome, headache (eg, migraine or tension), and food poisoning. Cyanide gas poisoning should also be considered when a patient is comatose due to a house fire.
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