What Are the Effects of Lack of Oxygen to the Brain?

Cerebral hypoxia is the condition in which the brain experiences a lack of oxygen. Any number of conditions can cause hypoxia, including stroke, carbon monoxide poisoning, heart dysfunction, drowning and injuries sustained at birth. Compared with other types of cells, brain cells are especially sensitive to hypoxia, and they quickly begin to die when they are deprived of oxygen. Cerebral hypoxia can impair brain function, damage brain cells and lead to death. Oxygen deprivation can be mild, causing slow onset of symptoms, or severe, leading to rapid changes.

Brain function depends on oxygen.


When oxygen is severely limited or lacking for long periods of time, the body shuts down and becomes comatose. If you are comatose, you are unconscious and do not respond to stimuli such as noise or pain. Others will not be able to wake you, and you will not perform any voluntary actions. If oxygen supply is regained, you may recover enough to wake from a coma, but permanent brain damage is likely to have occurred.

Cognitive, Behavioral and Personality Changes

The components of personality reside in the frontal lobe of the brain and when cerebral hypoxia causes frontal lobe damage, changes in personality can occur. After a stroke, sometimes loved ones report that the stroke victim is "like a different person." The severity of the changes is related to the severity of the hypoxia.

According to The National Institute of Neurological Disorders and Stroke, cognitive and behavioral changes can also occur after cerebral damage associated with hypoxia. Such changes can include decreased attention, poor judgment and memory loss.

Motor Skills

One symptom that is often recognized with cerebral hypoxia is the loss of motor skills or proper coordination. The cerebellum is responsible for much of our coordinated movement and balance. Cell death can lead to jerkiness and other motor problems.

Heart Rate

When the brain is not receiving enough oxygen, the heart rate will increase in an attempt to deliver more oxygen. If hypoxia is severe enough, the heart will be unable to keep up with the demand and may eventually fail, causing a heart attack.


Brain oxygen levels can sometimes suddenly drop, such that your nonessential body processes shut down, allowing the vital functions of the brain to continue. Fainting is the result. Symptoms such as light-headedness, nausea and a feeling of warmth may precede fainting, according to the Mayo Clinic. If you faint regularly, see your doctor to determine if there is a serious underlying cause.

Brain Death

The eventual outcome of severe hypoxia, if not reversed, is brain death. According to the American Association of Critical Care Nurses, brain death is determined by a patient demonstrating coma, an absence of response to pain, a lack of all the cranial nerve reflexes and apnea, or a failure to breathe independent of machinery.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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