Medically Reviewed By William C. Lloyd III, MD, FACS

What is anoxia?

Anoxia is an extreme form of hypoxia (low levels of oxygen in the blood) in which there is a complete lack of oxygen supply to the body as a whole or to a specific organ or tissue region. Anoxia can result from inadequate amounts of oxygen in the air, such as at high altitudes, from an inability of your blood to load and carry oxygen to tissues and organs, from the inability of the heart to pump and distribute the oxygenated blood adequately, or from respiratory failure that prevents the blood from picking up oxygen in the lungs.

Anoxia can affect any tissue or organ in your body and is always serious. However, cerebral anoxia, or a lack of oxygen supply to the brain, is particularly threatening because brain cells begin to die within several minutes of oxygen deprivation.

Anoxia may occur in anyone, but it is more likely to occur in babies during birth and older people who are at higher risk of heart attacks or strokes.

Symptoms of localized anoxia depend on the part of the body that is affected. Symptoms of generalized anoxia reflect the lack of oxygen to the brain and rapidly progress to unconsciousness and coma.

Anoxia is a serious condition that should always be treated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, are experiencing any of the symptoms of anoxia, such as altered thought processes, dizziness, breathing difficulties, or confusion.

What are the symptoms of anoxia?

Symptoms of anoxia are serious and will begin to appear within minutes. Milder symptoms could indicate a hypoxic event that could lead to anoxia and should be immediately treated in an emergency setting.

Common milder symptoms of anoxia

Most symptoms of anoxia are severe. However, anoxia typically begins with milder symptoms including:

  • Bluish coloration of the lips or fingernails

  • Confusion or loss of consciousness for even a brief moment

  • Dizziness

  • Poor decision-making

  • Rapid breathing (tachypnea) or shortness of breath

Serious symptoms that might indicate a life-threatening condition

In all cases, anoxia is a serious and potentially life-threatening condition. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms:

What causes anoxia?

Anoxia may be caused by a number of environmental factors or by underlying diseases or conditions.

Environmental factors that cause anoxia

Anoxia may be caused by a lack of oxygen or the presence of other chemicals in the air that affect the ability of your blood to load oxygen. These environmental effects may be caused by factors including:

  • Carbon monoxide

  • Cyanide poisoning

  • High altitude

  • Smoke

    Underlying diseases or conditions that cause anoxia

    Certain underlying diseases or conditions can lead to an insufficient uptake or delivery of oxygen to tissues and organs, leading to anoxia. These conditions include:

    Other events that cause anoxia

    Anoxia may also be caused by other conditions or events including:

    What are the risk factors for anoxia?

    Anoxia may be caused by a number of underlying conditions. Therefore, if you have one of these underlying conditions or you have a family history of these conditions, you may be at increased risk of experiencing anoxia. Additionally, certain activities may increase your risk of experiencing anoxia. Risk factors for anoxia include:

    • Asthma and allergies

    • Climbing or hiking at high altitude

    • Flying in nonpressurized planes

    • Heart or lung disease

        How is anoxia treated?

        The treatment of anoxia depends on its severity and the amount of damage to the tissue or organ that experienced the anoxia.

        Common treatments for anoxia

        In general, treatment for anoxia includes restoring the oxygen supply, through either increasing the amount of oxygen taken in, such as with an oxygen mask, or assistance with breathing. Other treatment options include:

        • Administration of fluids and medication to increase blood pressure
        • Administration of medications to reduce seizure activity
        • Administration of medications to regulate heart function
        • Application of life support systems

          What are the potential complications of anoxia?

          Anoxia is a severe condition that can lead to serious complications. Treatment for anoxia should be sought immediately in order to reduce these complications. Additionally, anoxia may sometimes be caused by serious underlying conditions that may themselves lead to complications. Once you have sought medical attention for anoxia or the underlying conditions that caused your anoxia, it is important for you to follow the treatment plan you and your health care professional design specifically for you. By doing so, you can help minimize your risk of serious complications, which include:

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          1. NINDS Cerebral Hypoxia Information Page. National Institute of Neurological Disorders and Stroke.
          2. Cerebral hypoxia. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
          3. Luauté J, Maucort-Boulch D, Tell L, et al. Long-term outcomes of chronic minimally conscious and vegetative states. Neurology 2010; 75:246.
          Medical Reviewer: William C. Lloyd III, MD, FACS
          Last Review Date: 2021 Jan 16
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          THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.