Brain hypoxia is a form of hypoxia or oxygen deficiency affecting the brain. It occurs when the brain does not receive enough oxygen even though blood is still flowing. When oxygen supply is totally cut off, it is called brain anoxia.
Brain hypoxia is a medical emergency because the brain needs a constant supply of oxygen and nutrients to function properly.
There are several causes of brain hypoxia. They include drowning, suffocating, cardiac arrest, and stroke. Mild symptoms include memory loss and problems with motor function, such as movement. Severe cases can result in seizures and brain death.
Read on to learn more about brain hypoxia, also known as cerebral hypoxia.
The symptoms of a lack of oxygen to the brain, or brain hypoxia, may be mild or severe and depend on the level and duration of oxygen deprivation.
Mild symptoms of brain hypoxia include:
- temporary loss of memory
- problems moving parts of the body
- poor judgment
Brain cells can begin to die after just 5 minutes of oxygen loss. Symptoms become more dangerous the longer oxygen flow to the brain is cut off.
Severe symptoms of brain hypoxia include:
- brain death
In cases of brain death, there is no brain activity. The pupils of the eyes do not respond to light and people cannot breathe without assistance from a life-support machine. However, the heart continues to pump blood around the body.
There are many reasons why someone may experience brain hypoxia.
Some medical conditions and situations that reduce oxygen supply to the brain include:
- amyotrophic lateral sclerosis (ALS) and other diseases that paralyze the breathing muscles
- brain injury
- carbon monoxide poisoning
- cardiac arrest
- complications arising from anesthesia
- drug overdose
- high altitudes
- irregular heartbeat
- lung diseases, such as chronic obstructive pulmonary disease or COPD
- lung infections, including pneumonia
- respiratory arrest
- severe asthma attack
- smoke inhalation, for example, in a house fire
- trauma to the windpipe or lungs
- trauma that causes blood loss
- very low blood pressure, also called hypotension
Brain hypoxia can affect anyone who experiences a shortage or lack of oxygen to the brain, but some people are at higher risk than others.
Risk factors for brain hypoxia include:
Playing specific sports
Sports enthusiasts may be at higher risk if they engage in activities that have a higher risk than others of resulting in a head injury or trauma to the windpipe.
Those who must hold their breath for long periods or travel to high altitudes are also at increased risk.
Examples of risky activities include:
- mountain climbing
Having certain medical conditions
Many medical conditions have the potential to affect the oxygen flow to the brain. Examples of such conditions include:
- heart problems
- lung diseases
- muscle diseases
Working in some professions
People experiencing exposure to intense smoke or carbon monoxide through their job, such as firefighters, may be at increased risk of brain hypoxia.
A doctor will usually diagnose brain hypoxia based on a person's medical history, a physical examination, and other tests.
During the medical history and physical examination, the doctor will ask about someone's current symptoms and recent activities.
The doctor may request tests to confirm hypoxia and find out its cause. These tests include:
- angiogram of the brain
- blood tests to check for blood oxygen levels
- CT scan of the head
- chest X-ray to see the lungs
- echocardiogram, to see the heart
- electrocardiogram (ECG) to measure the electrical activity of the heart
- electroencephalogram (EEG) to measure the brain's electrical activity and understand the cause of seizures
- MRI imaging scan of the head
Brain hypoxia is a medical emergency that requires immediate treatment. It is vital that normal oxygen supply to the brain resumes quickly to prevent complications or brain death.
Treatment will vary, depending on the cause and severity of the hypoxia. Basic life support systems are often necessary. People with severe hypoxia may need a machine known as a ventilator to breathe for them.
Other treatments include:
- blood, fluids, and medications to restore blood pressure and heart rate
- medications for seizure control
In some cases, a doctor may cool the person down to slow their brain activity and reduce its need for oxygen. However, it is unclear how beneficial this treatment is.
How long a person has experienced oxygen deprivation will determine their outlook and recovery from brain hypoxia.
It is difficult to predict how quickly a person will recover, but some factors can help foresee the outcome.
Having low brain oxygen levels for several hours can suggest a poorer recovery. Also, research suggests that a person's functional status on admission to hospital strongly indicates their recovery prospects.
According to the Family Caregiver Alliance, in cases of hypoxic or anoxic brain injury, other factors that predict outcome include:
- Length of coma. The longer a person remains in a coma, the poorer the outcome. They may have a reduced risk of damage if the coma lasts less than 12 hours. However, every case is different.
- Eye movement. If both eyes have fixed or dilated pupils, it suggests damage to the brain stem, which indicates a worse outlook.
- Age. People under 25 years of age may recover better than older adults.
- Results of diagnostic tests. These often give a good indication of recovery. For example, EEG tests that show brain activity may suggest a better outlook.
During recovery from brain hypoxia, people may experience several challenges. These typically resolve over time. They include:
- memory loss
- mood changes
- muscle spasms and twitches
- personality changes
- vision problems
Complications include a prolonged vegetative state, where a person has basic functions but is not awake or alert. These people may develop conditions such as:
Eventually, brain hypoxia can be fatal.
It can be challenging to avoid all cases of brain hypoxia. For example, it is difficult to prevent a brain injury received during an unexpected car collision.
To have the best chance of preventing hypoxia, people should monitor health conditions and avoid high altitudes. People should wear proper protective equipment, such as helmets when playing sports with high risks of head injury.
If a person receives cardiopulmonary resuscitation (CPR) after a fire or head injury, they may be less likely to experience brain hypoxia, or for it to be less severe. CPR can save lives, especially if carried out immediately.
Brain hypoxia is a medical emergency. If someone displays the symptoms of brain hypoxia or if they are losing consciousness, call the emergency services without delay.
People have their best chance of recovery if they receive medical treatment right away. Prompt medical attention reduces the amount of time that oxygen flow to the brain is limited.