What is Carbon Monoxide Toxicity?
Carbon monoxide (CO) is a substance produced when materials containing carbon don’t burn completely. Common sources can contribute to a lot of carbon monoxide in the environment. Other than carbon dioxide (CO2), carbon monoxide is one of the most common pollutants at ground level. It’s important to be aware that carbon monoxide is invisible, has no taste or smell, and can knock you unconscious before you even know you’re being exposed to it. People can react differently to carbon monoxide poisoning and doctors and other health care experts are still learning more about these effects.
What Causes Carbon Monoxide Toxicity?
Carbon monoxide (CO) poisoning is caused by the way this gas interferes with the process in our body that carries oxygen in our blood. Normally, oxygen combines with a part of our blood called hemoglobin, which then carries the oxygen to our body’s cells. However, carbon monoxide has a much stronger attraction to hemoglobin (about 220 times stronger!) than oxygen does. So, when carbon monoxide is present, it takes up the space on the hemoglobin that should be occupied by oxygen.
This interaction forms a substance called carboxyhemoglobin (COHb). Having too much COHb in our body means there’s less room for oxygen to attach to our hemoglobin, leading our body’s cells to not get the amount of oxygen they need (a condition we call ‘cellular hypoxia’).
Another problem is that having high levels of COHb makes the remaining unbound hemoglobin in our body hold on to its oxygen tighter than usual. This makes it harder for oxygen to be released to the cells where it’s needed.
Also, carbon monoxide can bind to another important part of our cells, called cytochrome c oxidase, that helps generate energy. This binding process can cause interruption in energy production in our cells.
All these actions combined make our body struggle to get and distribute needed oxygen, even if the hemoglobin concentration and the amount of oxygen in the blood seem normal. However, the actual level of oxygen carried in our blood is much lower than it should be.
Risk Factors and Frequency for Carbon Monoxide Toxicity
Every year, there are more than 40,000 instances of carbon monoxide (CO) poisoning occurring in the United States. It’s a serious matter as it contributes to around half of all fatal poisonings. Moreover, CO poisoning turns out to be the primary cause of death in fire victims. Nearly 30-40% of people affected by CO poisoning unfortunately pass away before getting to the hospital. For those who do make it to the hospital, the outlook varies; around 2% die, 10% have partial recovery, and between 23% to 47% experience delayed neurological problems.
- Every year, the US sees over 40,000 cases of CO poisoning.
- CO poisoning contributes to 50% of all fatal poisonings.
- It is the main cause of death in fire victims.
- About 30-40% of CO poisoning victims die before reaching the hospital.
- Of those who get hospitalized, around 2% die.
- Approximately 10% of the hospitalized victims recover partially.
- Between 23% to 47% experience delayed neurological problems.
Signs and Symptoms of Carbon Monoxide Toxicity
Carbon monoxide (CO) poisoning can cause a variety of symptoms, which is why only a small percentage of patients (about 5% to 6%) who come to the emergency room with symptoms of CO poisoning receive hyperbaric oxygen therapy (HBOT).
The most common symptoms that patients experience include headaches, dizziness, weakness, and nausea. Their heart rate may speed up, and they might breathe faster than normal. Some other possible changes include a drop in blood pressure and confusion or disorientation. Memory loss may also occur. Eye-specific symptoms could involve bleeding in the back of the eyes and optic nerve swelling.
The kidneys can also be damaged due to lack of oxygen from CO poisoning. Despite the common belief, cherry-red nail beds and mucous membranes are not usually seen in living patients and are typically found in those who have passed away from CO poisoning.
Additionally, individuals may develop balance issues, difficulties in performing certain movements, loss of bladder or bowel control, and even blindness that originates in the brain, rather than in the eyes.
- Headaches
- Dizziness
- Weakness
- Nausea
- Increased heart rate
- Fast breathing
- Lower blood pressure
- Confusion or disorientation
- Memory loss
- Eye symptoms such as retinal bleeding and optic nerve swelling
- Possible kidney injury
- In severe cases, balance issues, loss of muscle control, incontinence, and brain-originated blindness
Testing for Carbon Monoxide Toxicity
When treating patients suspected of carbon monoxide (CO) poisoning, the basics of ensuring a clear airway, good breathing, and strong blood circulation still apply. Oxygen treatment is typically the first step because it helps replace the carbon monoxide in the blood with the oxygen your body needs.
However, it’s important to understand that the standard devices used to measure oxygen in your blood can’t tell the difference between oxygen and carbon monoxide. So, even if the device readings seem normal, carbon monoxide poisoning can still exist.
Usually, a sample of arterial blood is taken for a special test called co-oximetry, which measures the specific levels of carbon monoxide in your blood. However, these numbers alone should not determine the treatment plan. This is because the levels of carbon monoxide found in the blood do not always match up exactly with the severity of the symptoms or the likelihood of serious health risks. Generally speaking though, results showing more than 3% to 4% in non-smokers and more than 10% in smokers is usually considered higher than normal. In adults, anything over 20% is considered serious, and in children, anything over 15% is seen as significant.
But remember – the goal is to treat the patient’s actual symptoms and condition, not just the number.
Other lab tests might also be ordered such as a complete blood count, electrolyte levels, kidney function, and a protein called troponin that’s linked to heart damage. An electrocardiogram (ECG) might be done to check for possible heart problems, since heart trouble can be a sign of severe CO poisoning. Chest X-rays can also be helpful. Although a brain scan (CT scan) isn’t usually required, it might give helpful information in some cases because CO poisoning can cause a specific type of bleeding in the brain.
Treatment Options for Carbon Monoxide Toxicity
The main treatment for carbon monoxide poisoning is using extra oxygen, and this should be started as soon as possible and kept up throughout the treatment process. If the poisoning is severe, seen through symptoms such as temporary loss of consciousness, heart issues, changes in mental status, elevated heart rate, low blood pressure, and high levels of carboxyhemoglobin (a type of compound formed when carbon monoxide binds with the blood), emergency treatment using hyperbaric oxygen is required.
Hyperbaric oxygen centers, while present in every state, number only a few hundred in the whole of the United States. These centers provide a highly concentrated oxygen environment for quick recovery. The best results are seen when individuals receive this kind of treatment within six hours of the carbon monoxide exposure. Typically, doctors at these facilities would provide three treatments in the first 24 hours, then see how the patient is doing before deciding whether to continue with daily treatments.
Even though hyperbaric treatment can be very effective, as many as 40% of patients might still experience long-term impacts on brain function. Therefore, doctors recommend these patients have a neuropsychological evaluation, which is an assessment of how your brain functions, around one to two months after they have recovered.
There is a need for alternative treatments that are more readily available and useful. Currently, several new therapy options are being studied, including ones based on light therapy for the lungs, but these are yet to come into regular use.
What else can Carbon Monoxide Toxicity be?
Some conditions that might present similar symptoms include:
- Alcohol toxicity
- Depression and suicide
- Diabetic Ketoacidosis (DKA)
- Encephalitis
- Hypothyroidism
- Labyrinthitis
- Meningitis
- Methemoglobinemia
- Migraine headache
- Opioid toxicity
These conditions need to be considered and ruled out by healthcare professionals to ensure they are providing the correct treatment.
What to expect with Carbon Monoxide Toxicity
The outlook for patients with carbon monoxide (CO) poisoning can differ greatly based on how severe the poisoning is, other existing health conditions the individual may have, and certain lab results. It’s worth noting that individuals who show abnormal results on MRI and CT scans typically have a less favourable outlook. Individuals who continue to display neurological issues are also likely to have an uncertain recovery prognosis.
Carbon monoxide poisoning can sometimes lead to problems with cognitive function, which involves mental activities like learning, understanding, and remembering. Hyperbaric oxygen treatment (HBO) can help reduce the occurrence of these cognitive problems in some patients.
Possible Complications When Diagnosed with Carbon Monoxide Toxicity
There are various health conditions and symptoms that could signify a serious medical issue, such as:
- Amnesia (memory loss)
- Dementia (a decline in thinking, reasoning, and memory)
- Irritability (being easily upset)
- Psychosis (a severe mental condition causing a disconnection from reality)
- Loss of executive function (difficulty with planning, organizing, and completing tasks)
- Speech deficit (difficulty with talking or understanding speech)
- Parkinson’s disease (a neurodegenerative disorder causing tremors, stiffness, and balance problems)
- Depression (a persistent feeling of sadness, loss of interest, and other physical symptoms)
- Cortical blindness (loss of vision caused by damage to the brain’s visual processing areas)
Recovery from Carbon Monoxide Toxicity
Patients should only be discharged from hospital if their hemoglobin and carbon monoxide (HbCO) levels are stable. After they leave the hospital, it’s important for them to have a follow-up appointment within 4 to 8 weeks. This is to check for any issues with their nervous system that might have developed. If a patient has been exposed to carbon monoxide on purpose, they should see a psychiatrist before they are discharged from the hospital.
Preventing Carbon Monoxide Toxicity
It’s crucial for patients to understand the necessity of having carbon monoxide (CO) detector alarms in the home. These devices are designed to protect you and your family from potentially dangerous levels of carbon monoxide, a colorless, odorless gas that can be harmful when inhaled. By installing and properly maintaining a CO detector, you can ensure the safety of your household.
