What is Carboxyhemoglobin (CO Hgb)?

From the Guidelines

Carboxyhemoglobin (COHgb) is a form of hemoglobin that has carbon monoxide (CO) bound to it instead of oxygen, with an affinity approximately 220 times that of oxygen, as noted in the study by 1. When carbon monoxide enters the bloodstream, it binds to hemoglobin, forming COHgb, which prevents hemoglobin from carrying oxygen effectively, leading to tissue hypoxia. Normal COHgb levels in non-smokers are typically less than 2%, while smokers may have levels between 5-10%. Elevated levels above these baselines indicate carbon monoxide exposure or poisoning. Some key points to consider about COHgb include:

• CO binds to hemoglobin with high affinity, leading to tissue hypoxia
• Normal COHgb levels are typically less than 2% in non-smokers and 5-10% in smokers
• Elevated COHgb levels can indicate carbon monoxide exposure or poisoning
• Symptoms of CO poisoning begin to appear at COHgb levels around 10-20% and include headache, dizziness, and nausea, as discussed in the study by 1. Treatment for elevated COHgb involves removing the person from the CO source and administering high-flow oxygen, which helps displace CO from hemoglobin, as recommended by 1 and 1. In severe cases, hyperbaric oxygen therapy may be necessary to accelerate CO elimination and reduce tissue damage. It's essential to note that CO poisoning can have severe and long-lasting effects, including neurologic sequelae and increased mortality, as highlighted in the study by 1. Therefore, prompt and effective treatment is crucial to minimize morbidity and mortality associated with CO poisoning. Some of the key mechanisms of CO toxicity include:
• Binding to intracellular proteins
• NO generation and peroxynitrite production
• Lipid peroxidation by neutrophils
• Mitochondrial oxidative stress
• Apoptosis and immune-mediated injury, as discussed in the study by 1. Overall, understanding COHgb and its effects on the body is critical for providing appropriate care and treatment for individuals exposed to carbon monoxide.

From the Research

Definition of CO Hgb

• CO Hgb, also known as carboxyhemoglobin, is a complex formed when carbon monoxide (CO) binds to hemoglobin in the blood 2, 3, 4, 5, 6.
• This binding process reduces the amount of oxygen that can be carried by the blood, leading to tissue hypoxia and oxidative stress 2, 5.

Formation and Effects of CO Hgb

• CO Hgb is formed when carbon monoxide is inhaled and binds to hemoglobin, displacing oxygen and reducing the oxygen-carrying capacity of the blood 2, 3, 5.
• The effects of CO Hgb can range from mild symptoms such as headache to severe illness and even death, depending on the level and duration of exposure to carbon monoxide 2, 5.

Measurement and Diagnosis of CO Hgb

• CO Hgb levels can be measured through blood co-oximetry, which is used to diagnose carbon monoxide poisoning 5.
• The diagnosis of CO Hgb is often made by measuring the level of carboxyhemoglobin in the blood, with elevated levels indicating exposure to carbon monoxide 2, 3, 4, 5, 6.

Treatment and Reduction of CO Hgb

• Treatment for CO Hgb typically involves removal from the source of exposure and administration of supplemental oxygen, which can help to reduce the level of carboxyhemoglobin in the blood 2, 3, 5.
• Hyperbaric oxygen therapy may also be used to treat CO Hgb, although its effectiveness is still a topic of debate 2, 4, 5.
• High flow nasal cannula oxygen therapy has been shown to be an effective method for reducing CO Hgb levels in patients with carbon monoxide poisoning 3.