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What is an Anoxic Brain Injury?

An anoxic brain injury occurs due to a total lack of oxygen to the brain. Though many different types of brain injuries can occur, anoxic brain injuries are characterized as one of the most dangerous and difficult from which to recover. Anoxic brain damage is also referred to as anoxia. This type of brain injury is commonly associated with hypoxic damage or hypoxia. The two classifications are quite different, though. An anoxic brain injury results from a total lack of oxygen to the brain while a hypoxic brain injury results from a partial lack, or inadequate supply, of oxygen to the brain. In these particular cases of brain injury, medical professionals often use the abbreviation HAI or Hypoxic-Anoxic Injury.

Anoxic brain injuries, specifically, are the more severe of the two classifications. The brain begins to lose cells after only 4 minutes without oxygen. Brain cells cannot be recovered; when they are lost, they are gone and considered dead. A complete absence of oxygen in the brain can quickly cause widespread, irreversible damage and can also lead to death quite quickly.

Categories of Anoxic Brain Injury

Anoxic Brain Injuries typically fall under one of the four following general classifications:

1. Anemic anoxia: This condition occurs when blood is no longer able to carry oxygen to the brain. Certain types of lung disease may contribute to very low blood oxygen levels. Therefore, the brain will not receive sufficient oxygen. In addition, chronic anemia, hemorrhages, and carbon monoxide poisoning may cause acute anemic anoxia.

2. Toxic anoxia: Toxic anoxia is caused by toxins built up in the body which prevent the blood’s oxygen from being processed adequately in the brain. For example, carbon monoxide poisoning can also cause toxic anoxia.

3. Stagnant anoxia: This occurrence is also referred to as hypoxicischemic injury (HII). In HII, an internal injury, disease, or related condition prevents oxygen-rich blood from circulating to the brain. Common causes are strokes, cardiac arrhythmia, and cardiac arrest.

4. Anoxic anoxia: Though redundant in its name, this injury is caused by a lack of oxygen concentration in the environment outside of the body. This is commonly experienced at high altitudes where very early stages are evident when a novice mountain climber becomes tired and weak. This is the reason why pressurized cabins or oxygen masks are necessary in high-flying aircraft.

Causes of Anoxic Brain Injury

Anoxic Brain Injuries can result from a number of different environmental or physical conditions, diseases, or accidents. Many things can happen to stop the supply of oxygen to the brain:

• Electrocution
• Drowning
• Poisoning
• Asphyxiation (Choking or Suffocation)
• Illicit Drug Abuse
• Cardiac / Respiratory Arrest
• Brain Tumors
• Extreme Low Blood Pressure
• Respiratory conditions which restrict or prevent breathing

Evidence of Anoxic Brain Injuries

In most cases, anoxic brain injuries may follow a long period of unconsciousness. Often times, a person may be comatose or can enter a vegetative state as a result of one of the causes listed above. Once the person regains consciousness and becomes responsive, he/she may experience conditions commonly observed after head trauma. Lack of coordination, a numbness or tingling in the extremities, memory loss (short or long term), reduced cognition, or impaired speech can all be signs of anoxic brain damage.


Unknown Author. (n.d.) Anoxic Brain Injury – What Is It? Retrieved on July 21 2013, from brain-injury-online.com