It is odorless, has no taste, and you cannot see it. It is carbon monoxide (CO) and it is the leading cause of injury and death due to poison worldwide. The symptoms of carbon monoxide poisoning often go unrecognized until it is too late because the typical early symptom – headache, dizziness, nausea, and irritability – are so nonspecific. As we enter the winter months, this topic gains increasing importance as carbon monoxide poisonings most frequently occur in the winter months of January and December. In our discussion of carbon monoxide poisoning we will review its pathophysiology, common causes, signs and symptoms, treatment, and ways that it can be prevented.
Our bodies require oxygen to function. The oxygen that we inhale when we breath in binds to specific locations on red blood cells which are responsible for carrying the oxygen to tissues and organs thought our bodies. Carbon monoxide affects how the red blood cells transport oxygen in two important ways. First, the carbon monoxide takes the place of the oxygen so that the red blood cells are carrying less oxygen then they normally would. In fact, carbon monoxide binds to red blood cells about 230 times stronger than oxygen can. Secondly, the binding of carbon monoxide to a red blood cell also reduces the red blood cells ability to release the decreased amount of oxygen that it is hauling. This all results in the body not getting enough oxygen which can lead to hypoxia and death.
When the carbon monoxide binds to the red blood cells the combination becomes known as carboxyhemoglobin which has a much brighter red color than a normal red blood cell. This explains why, despite victims of carbon monoxide poisoning being hypoxic, their skin does not turn cyanotic, but rather pale or pink with cherry red lips. Carboxyhemoglobin can also limit the usefulness of a pulse oximeter because the device is unable to differentiate between red blood cells carrying oxygen and carboxyhemoglobin. A pulse oximeter may incorrectly determine that a person suffering from carbon monoxide poisoning has a normal oxygen saturation level.
Causes of Poisoning
Carbon monoxide is produced when organic matter undergoes combustion but lacks sufficient oxygen to become carbon dioxide (CO2). Inhaling smoke from a structural fire is the number one cause of unintentional carbon monoxide poisoning and it this poisoning, not the injuries due to burns, that is the leading cause of death for fire victims. Other potentially dangerous sources of carbon monoxide include automobiles, portable generators, faulty furnaces, propane heaters, and wood-burning stoves. Gasoline-powered equipment such as leaf blowers, lawnmowers, welders, and high-pressure washers are also potential sources.
Exposure to unsafe levels of carbon monoxide typically occur when such equipment is used in enclosed or semi-enclosed spaces, but poisoning can happen in any location. Cases of carbon monoxide poisoning have been reported when children have ridden in the back of pickup trucks or when an idling automobile has had its exhaust blocked with snow. There is a significant increase in carbon monoxide poisonings when electrical service has been disrupted which may occur after events like hurricanes, wind storms, blizzards and ice storms.
Anytime an EMS professional makes their scene assessment, it is important that they look for potential sources of carbon monoxide poisoning. Like their role in identifying and reporting on the mechanism of injury, they may be the only healthcare providers with an opportunity to recognize clues that would point to a case of carbon monoxide poisoning. There are a number of cases that have been reported of individuals transported to the Emergency Department with unrecognized symptoms of carbon monoxide poisoning who are then discharged back to the environment that initially poisoned them. This type of situation can often be prevented by a careful prehospital evaluation of the scene where the patient was found.
Signs and Symptoms
Identifying victims of carbon monoxide poisoning can often be difficult because many of the signs and symptoms are nonspecific and are often not recognized as the indicators of a potentially life-threatening condition. The following situations should increase your index of suspicion for carbon monoxide poisoning; emergencies during cold months, individuals in an enclosed space experiencing alterations in mental status, and if more than one patient is complaining of similar symptoms. Children, the elderly, and pregnant women and their unborn infants are the populations most susceptible to carbon monoxide poisoning.
In acute poisoning, the organs most affected are those with the highest oxygen consumption like the central nervous system and the heart. Initial complaints often include headache, dizziness, nausea, vomiting, malaise, and fatigue which makes it difficult to distinguish from a viral illness like influenza. The headache that is often described as being frontally located with a dull and continuous type of pain. Problems associated with the central nervous system include delirium, hallucinations, problems walking, abnormal reflexes, confusion, issues with memory, unconsciousness, respiratory arrest, and death. Cardiac abnormalities include tachycardia, hypotension, and arrhythmias.
Treatment and Rescuer Safety
The first rule of management for a suspected or confirmed incident of carbon monoxide poisoning is immediate evacuation of the victim and all rescue personnel from the area. The next step in management is to provide the patient with oxygen via a non-rebreather mask at 15 liters per minute. By providing 100% oxygen to the patient, the half-life of carbon monoxide, or the time it takes for the concentration of carbon monoxide in a person’s blood to drop by half, is reduced from 4 hours to 90 minutes. While oxygen is being provided, monitor the patient’s ABCs and offer support as needed. Before transporting the patient away from the scene, ensure that the building or house is being evacuated and that a fire crew is on site and has been briefed on the situation. Many ambulances now carry gas detectors and any reading higher than 12% will require treatment of those exposed.
As an EMS provider, promoting ways to prevent carbon monoxide poisoning in the community is an important part of avoiding future hospitalizations and deaths. For the general public, the Center for Disease Control (CDC) recommends the following:
- Have your gas-, oil-, or coal burning appliances inspected yearly by a qualified technician
- Every home should have a battery-operated carbon monoxide detector
- If you suspect carbon monoxide poisoning is the cause of your dizziness or nausea, seek medical attention immediately
- Never use gas- or oil-burning device inside the home or outside the home near a window
- Never run a motor vehicle inside the garage
- Never burn anything in a fireplace or stove that is not vented to the outside
- Never use your gas oven to heat your house
Sources and More Information
EMS World, “Carbon Monoxide Poisoning: Incidence, Diagnosis & Treatment” https://www.emsworld.com/article/10323668/carbon-monoxide-poisoning-incidence-diagnosis-treatment
EMS World, “A Silent Death” https://www.emsworld.com/article/10319139/silent-death
JEMS, “Sneak Attack: What makes carbon monoxide so insidious?” https://www.jems.com/articles/2010/10/sneak-attack.html
WebMD ,“Carbon Monoxide: A Winter Killer” https://www.webmd.com/children/news/20071220/carbon-monoxide-winter-killer
Jeremiah Johnson, MA, BS