What is Carboxyhemoglobin Toxicity?
Carbon monoxide is a gas that you can’t see, smell, or taste, and it doesn’t irritate your skin. It forms when fossil fuels, like gas, coal or oil, burn. This gas has a dangerous tendency to stick to the red blood cells in your body (hemoglobin) more strongly than oxygen. Once attached, it becomes hard for these cells to carry and use the oxygen your body’s organs need to function. This can lead to a lack of oxygen in the body’s tissues, a state called ‘hypoxia’.
When this happens, serious health issues can arise like strokes (cerebrovascular ischemia), where parts of the brain lose blood supply, or heart attacks (myocardial infarctions). As carbon monoxide builds up in the blood, it acts like a poison at the cellular level, disrupting normal cell activities. It hampers the cells’ ability to generate energy from oxygen, triggering an unstoppable cycle of inflammation that can severely harm the brain and nervous system.
Acute exposure to this gas can be deadly. Carbon monoxide is responsible for many deaths each year caused by accidental exposure, like from faulty heaters, and intentional intake, such as with suicide attempts.
What Causes Carboxyhemoglobin Toxicity?
Carboxyhemoglobin is the compound that is formed when hemoglobin, the protein in red blood cells that carries oxygen, comes into contact with carbon monoxide. Carbon monoxide is a gas that doesn’t have any smell, taste, or color and attaches to hemoglobin about 200 times more easily than oxygen does.
Carbon monoxide is a by-product that comes from burning fossil fuels, things like gasoline or natural gas, but it makes up less than 0.001 percent of the air around us. You can find it in common sources like car exhaust, boats, heating appliances that aren’t working properly, gas generators, propane stoves, and charcoal grills. Poisoning from carbon monoxide is a risk when any of these items are used in areas that aren’t well-ventilated or that are semi-closed off. In fact, with cars, lethal levels of carbon monoxide can build up in confined spaces in just 10 minutes. This makes it a common method of suicide. You can also find carbon monoxide in other sources like fires, tobacco smoke, and methylene chloride, an industrial solvent and paint remover.
Interestingly, a small amount of carbon monoxide is produced naturally within our bodies when heme, an iron-containing compound in hemoglobin, breaks down. That’s why everyone has a small, detectable amount of carboxyhemoglobin in their blood at all times. For non-smokers, it’s typically between 1 and 3 percent. For smokers, it tends to be between 10 and 15 percent.
Risk Factors and Frequency for Carboxyhemoglobin Toxicity
Carbon monoxide (CO) poisoning is one of the main reasons for sickness from poisoning in the United States. Every year, it leads to 50,000 emergency room visits and causes around 1,200 deaths. People can face this unplanned or deliberately. Accidental CO exposure causes around 1,000 to 2,000 deaths annually, with a death rate of about 1% to 3%. However, intentional poisoning is much more deadly, with death rates 5 to 10 times higher.
- Intentional CO poisoning happens more often in the northern United States and colder climates.
- During winter months, the use of gasoline-powered generators and kerosene heaters increases, which can lead to more events of poisoning.
- The global concentration of CO can range between 0.06 and 0.14 mg/m3, but many factors such as weather, topography, and location can influence this.
- In cities, where there is a high concentration of gas burning, the concentration can be higher.
In the United States, less than 5% of people exposed to CO die from it, which is comparatively less than other countries. It’s difficult to calculate the exact number of CO poisonings and related deaths worldwide. This is because many cases go unreported or don’t get confirmed by testing. Some people don’t seek medical help for accidental exposure. Diagnosing CO poisoning can also be complicated, and sometimes doctors may think the symptoms are related to a different cause. Additionally, in less developed countries where CO exposure is common, it may be tougher to evaluate the situation.
Signs and Symptoms of Carboxyhemoglobin Toxicity
Carbon monoxide (CO) poisoning can cause a variety of symptoms, which are often difficult to diagnose because they can affect different parts of the body and mimic other illnesses. Common signs include headaches, dizziness, weakness, nausea, confusion, difficulty focusing, and shortness of breath. Less frequently, people may lose consciousness or experience chest pain which indicates a serious level of poisoning. In some cases, severe symptoms like coma, instability in heart function, difficulties in breathing, or even cardiac arrest can occur.
- Headaches
- Dizziness
- Weakeness
- Nausea
- Confusion
- Difficulty focusing
- Shortness of breath
- Loss of consciousness (in severe cases)
- Chest pain (in severe cases)
Keep in mind that exposure to CO can worsen existing heart or lung diseases symptoms in some people. Sometimes, exposure to carbon monoxide can cause widespread inflammation and stress in the body, leading to cell damage. As a rule of thumb, organs like the heart and brain that require a lot of oxygen are more vulnerable.
When diagnosing CO poisoning, doctors will typically ask about potential exposure to gas appliances, propane stoves, fireplaces, and certain workplaces that might involve using gas-powered equipment. They’ll also check if other family members or coworkers are experiencing similar symptoms. If many people from the same environment present with the same issues, CO poisoning might be suspected.
Neurological examinations and mental health assessments are often done to spot subtle issues like memory loss, concentration difficulties, mood changes, or motor problems. Despite not always being immediately noticeable, such symptoms could signal long-term damage, particularly if there have been earlier obvious neurological issues or instances of unconsciousness.
Testing for Carboxyhemoglobin Toxicity
As part of the first check-up, your doctor will likely want to measure the level of carboxyhemoglobin, a chemical produced when carbon monoxide enters your bloodstream, in your body. This is usually tested through a blood sample, but you don’t need to worry about them needing to take it directly from an artery; a sample from a vein is enough. While there’s an approved device that pulses to measure the level of carboxyhemoglobin in your blood, it hasn’t been very reliable in studies when compared to measurements from blood tests.
Being a nonsmoker with a level over 3% or a smoker with a level over 10% shows that you have indeed been exposed to more carbon monoxide than usual. However, don’t get too worried if your levels appear to be high at the beginning as these initial measurements don’t provide a perfect representation of how severe your condition is or how well you may recover in the future. Those numbers are somewhat deceiving because, in the time that passes between the moment of exposure and when your blood sample is collected, your blood could have already begun to get rid of the chemical. It’s also key to note that the impacts of carbon monoxide poisoning are not exclusively related to how much oxygen is getting to your body tissues.
Your doctor may also want to check your heart through an ECG and keeping an eye on your heart rates and rhythms, particularly in case you’re having chest pains or already have a heart condition. If you’re female, be aware that a pregnancy test could influence the doctor’s plan for treatment. Some protein levels in your blood may also be monitored by your doctor, as well as the potential presence of toxic drugs if there is a suspicion that there may have been an intentional carbon monoxide poisoning.
If you’re experiencing any changes in how your brain is functioning, such as memory loss or confusion, your doctor may want to get scans of your brain to look for anything abnormal. A CT scan is generally normal in these cases, but an MRI could pick up changes related to oxygen deprivation in the brain, although these changes could be due to other factors.
Lastly, there are two other tests that may give the doctors useful information regarding the health of your brain, by measuring levels of certain chemicals in your blood that tend to increase when the cells in your brain aren’t getting enough oxygen. One study suggested that those with carbon monoxide poisoning who had higher levels of one protein, S100B, were more likely to show delayed mental impairment.
Treatment Options for Carboxyhemoglobin Toxicity
If a person is suspected of being exposed to carbon monoxide (a harmful, odorless gas), the critical first step is to remove them from the source of the exposure. They should then be given oxygen to breathe, usually via a non-rebreather mask, which is a mask that delivers high concentrations of oxygen. Giving oxygen helps to eliminate carbon monoxide from the body more quickly by competing with the gas at the binding site in the blood.
Providing 100% oxygen effectively reduces the duration of carbon monoxide in the body from around 4 hours to between 40 to 80 minutes. In extreme cases, using hyperbaric oxygen treatment, or HBO (where you breathe in pure oxygen in a pressurized room or tube), can reduce this time even further to just 23 minutes.
However, there’s ongoing debate about the effectiveness of HBO therapy. While it speeds up the removal of carbon monoxide, it hasn’t been shown to prevent long-term mental health effects of severe carbon monoxide poisoning or improve survival rates. Also, this treatment can inadvertently cause potential hazards, including damage from pressure changes (barotrauma), lung damage (pulmonary edema), or seizures. Therefore, HBO therapy is generally only suggested for severe carbon monoxide poisoning cases, under guidance from poison control or a specialized doctor.
Doctors are also exploring the use of a substance called erythropoietin, or EPO, which is known to protect nerve cells, as a new potential way to treat carbon monoxide poisoning. However, more research is needed to confirm its effectiveness and safety.
What else can Carboxyhemoglobin Toxicity be?
Diagnosing carbon monoxide (CO) toxicity can be quite tricky due to its unspecific symptoms and varied presentations. Sometimes, it can be misdiagnosed or its diagnosis may be delayed. This difficulty is because the symptoms could be tied to a variety of other health issues. Depending on present symptoms which can include headache, vomiting, confusion, chest pain, difficulty breathing, and fainting, physicians should consider:
- Viral illnesses like the flu
- Viral or bacterial meningitis
- Brain hemorrhage
- Conditions causing high pressure in the brain
- Temporal arteritis (inflammation of blood vessels)
- Altitude sickness
- Tick-borne diseases
- Cyanide poisoning
- Alcohol intoxication
- Poisoning from ethylene glycol or methanol
- Stomach flu or colitis
- Heart-related issues like acute coronary syndrome, heart failure, or heart inflammation
- Lung-related conditions like pneumonia or pulmonary embolism
- Tearing of the aorta (aortic dissection)
- High blood sugar (Hyperglycemia)
Thus, doctors need to carefully examine patients and their symptoms to ensure they make the correct diagnosis.
What to expect with Carboxyhemoglobin Toxicity
In the United States, less than 5% of people exposed to carbon monoxide die as a result. But it’s not uncommon for people to have problems with their nerves or brain afterwards; about 34% of patch patients reported having headaches or memory problems four weeks later, and 45% noticed changes in their feelings, thinking, or behavior after six weeks. Important to note is that the rate of carbon monoxide in your body when you first get help doesn’t predict these later problems.
One study tracked adult patients over the age of 36 who had been significantly exposed to carbon monoxide (defined as being exposed for 24 hours or more, or those who had brain abnormalities detected when they first sought treatment), and were treated with a type of oxygen therapy called normobaric oxygen. It found that these patients were more likely to have problems six weeks later compared to those who didn’t have these risk factors.
Information about problems one year after exposure is limited. One study followed up with an adult group six years after exposure, and it found that 19% of the group still had problems with thinking and 37% showed abnormal results in a nervous system exam. For treatment, there is some evidence to show that treatment using a high-pressure oxygen chamber, known as hyperbaric treatment, can reduce the risk of cognitive deficits. However, its use is somewhat controversial. For children, they tend to recover faster, as children breathe more quickly.
In case of unborn children, severe poisoning can result in death in over half of the cases. Also, while the levels of carbon monoxide-bound hemoglobin (carboxyhemoglobin) in the blood usually do not correlate with the severity of symptoms, studies have shown that people with levels below 18% did not experience changes in vision or behavior. But, very high levels – above 50% can be fatal, and for patients with heart condition, even levels between 10% to 30% can be lethal.
Possible Complications When Diagnosed with Carboxyhemoglobin Toxicity
One of the major concerns after exposure to carboxyhemoglobin, which is a toxic compound, is brain damage. This may appear as persistent neurologic sequelae (PNS) or delayed neurologic sequelae (DNS). Symptoms can include loss of vision, loss of coordination, cognitive difficulties (like problems with thinking or understanding), personality or mood changes, short-term memory loss, dementia, psychosis, incontinence, and symptoms similar to Parkinson’s disease.
For some people, these symptoms might not stay around for too long. However, in the persistent group, the neurological damage begins right after exposure and doesn’t go away. The delayed group includes those who start to develop these symptoms days to weeks after being exposed. Experts reckon that anywhere between 10% to 30% of people might experience these delayed-onset complications. But it’s really hard to come up with an exact number because mental and cognitive tests can vary widely, depend on the person’s age and intelligence quotient (IQ), and measuring any changes is made difficult by the fact that we don’t really know what their state of mind was like before exposure.
Another factor that adds complexity is that the levels of carboxyhemoglobin in your system might not exactly represent the extent of the damage caused and aren’t a surefire way to predict it. However, some more recent studies have been looking into whether neuron-specific enolase and S100B could be used as biological markers.
Another potentially serious complication is cardiac ischemia, where the heart muscle doesn’t get enough oxygen. This can occur due to a lack of oxygen and inflammatory changes after exposure to carbon monoxide, which can make angina worse and cause heart damage. This is especially the case in people with pre-existing heart disease, but it can also happen in people without any heart disease. If the troponin level in the blood increases after carbon monoxide poisoning, this suggests a higher risk of death.
On a positive note, it has been seen that issues related to cardiac ischemia can improve following treatment. In fact, a study showed that 80% of individuals who had impaired left ventricular systolic function (where the left side of the heart doesn’t pump blood properly) returned to normal just 3 days after exposure.
- Brain damage
- Vision loss
- Loss of coordination
- Cognitive impairment
- Personality/mood changes
- Short-term memory loss
- Dementia
- Psychosis
- Incontinence
- Parkinsonism
- Cardiac ischemia
Preventing Carboxyhemoglobin Toxicity
Preventing carbon monoxide poisoning primarily involves educating the public, especially before major events like hurricanes, floods, power outages, and snowstorms, when people might use different sources of fuel or electricity for heating, cooling, or cooking. This education often happens through public health resources, TV, radio broadcasts, and social media.
Furthermore, devices like generators, camp stoves, space heaters, and others should come with clear instructions warning not to use them in closed areas. These areas can trap carbon monoxide, leading to dangerous levels of exposure.
On a larger scale, the US government sets standards for air quality. This includes making sure the amount of carbon monoxide in the air, along with other harmful substances, stays low. Plus, the government issues an air quality index to keep the public informed. This is a number that tells you how clean or polluted the air is.
Even private companies, like insurance providers, might reward clients who install carbon monoxide alarms in their homes. These alarms can alert you if there’s too much carbon monoxide in your home, keeping you safe.
