Carbon monoxide (CO) is an odorless, colorless gas, and poisoning can cause hypoxia, cell damage, and death. Approximately 1% to 3% of all poisonings are fatal.
Poisoning can occur following exposure from incomplete combustion that includes smoke inhalation from fire, motor vehicle exhaust and other engine exhausts in poorly ventilated spaces, and various industrial sources.
Early symptoms are nonspecific and include headache, dizziness, and nausea.
If symptoms of CO poisoning are suspected, individuals should leave the building or space immediately and call the emergency medical services.
More severe exposure results in cardiovascular manifestations that can include myocardial ischemia, myocardial infarction, cardiac dysfunction, dysrhythmias, and cardiac arrest.
Patients with moderate to severe CO poisoning should be assessed for cardiac involvement with an ECG and measurement of cardiac biomarkers to identify acute myocardial injury, as this can predict poor long-term outcomes.
Neurologic symptoms include acute stroke-like symptoms, altered mental status, confusion, coma, and syncope.
Up to 40% of survivors of CO poisoning suffer from delayed neurocognitive deficits that can become permanent.
Diagnosis is based on a clinical triad: history of CO exposure, elevated carboxyhemoglobin levels, and symptoms consistent with CO poisoning.
High-flow oxygen therapy, hyperbaric oxygen, and supportive therapy are the key treatments.
Issues with hyperbaric treatment include difficulty caring for critically ill patients at some centers, and logistical barriers for timely transfer to facilities offering hyperbaric therapy.
Complications of hyperbaric therapy include seizures related to oxygen toxicity, pulmonary edema, and ear barotrauma.
Carbon monoxide (CO) poisoning is the most common human poisoning. CO is formed by incomplete combustion, with fire smoke inhalation, motor vehicles, and other engine exhausts being the most prevalent sources of exposure. The increased affinity of CO with hemoglobin results in decreased systemic oxygen delivery and the effects of CO on cytochrome c oxidase results in impairment of cellular respiration.
The symptoms of CO poisoning vary widely and are mostly nonspecific. Symptoms can range from headache, nausea, and dizziness, to severe cardiovascular and neurologic symptoms, depending on the dose and duration of the exposure. Mortality of acute CO poisoning is approximately 1% to 3%. Those at highest risk for mortality are those who: are of an older age; are exposed to fire as a source of CO; experience loss of consciousness; and those with very high carboxyhemoglobin levels and respiratory failure. Survivors of CO poisoning have a higher long-term mortality rate than their nonpoisoned counterparts, and 15% to 40% suffer from near-permanent neurocognitive sequelae.
History and exam
Jason J Rose, MD, MBA
Assistant Professor of Medicine and Biomedical Engineering
University of Pittsburgh
JJR is a co-inventor on patent applications for the use of heme-based molecules as antidotes for CO poisoning. JJR is a shareholder, officer, and director of Globin Solutions, Inc. Globin Solutions, Inc. has an exclusive license to this technology. Globin Solutions, Inc. had an option agreement to technology directed at using hydroxycobalamin for CO poisoning from Virginia Commonwealth University in the last 12 months. JJR is an author of publications cited within this topic.
Dr Jason Rose would like to gratefully acknowledge Dr Prasanthi Govindarajan, a previous contributor to this topic. PG declares that she has no competing interests.
Richard S. Weisman, PharmD
Florida Poison Center
RSW declares that he has no competing interests.
Sean Patrick Nordt, MD, PharmD
Department of Emergency Medicine
University of California
SPN declares that he has no competing interests.
Paul Hamilton, MD
Department of Emergency Medicine
Mount Sinai School of Medicine
PH declares that he has no competing interests.
Ruben Thanacoody, MD, FRCP(Edin)
Consultant Physician and Clinical Toxicologist
Regional Drugs and Therapeutics Centre
RT declares that he has no competing interests.
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