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About anoxic and hypoxic brain injury

Oxygen is crucial to the brain as it is used to metabolise glucose, which provides energy for all body cells. Brain cells are sensitive to the effects of restricted oxygen supply and can die within minutes of oxygen restriction. The immediate outcome of severe oxygen restriction is often coma and in very severe cases brain death.  

Causes include: 

  • near drowning 
  • drug overdose 
  • strangulation 
  • severe asthma 
  • accidents involving anaesthesia 
  • carbon monoxide inhalation and poisoning
  • stroke 
  • heart attack  

Hypoxia can also occur as a secondary injury following a traumatic brain injury, e.g. when there is serious blood loss resulting in low blood pressure, or as a result of brain swelling that restricts oxygen supply to areas of the brain. 

Types of anoxic/hypoxic brain injury

Anoxic anoxia occurs when inadequate oxygen is breathed in and absorbed by the body, e.g. altitude sickness or suffocation 

Anaemic anoxia is an inadequate oxygen supply due to a decrease in total haemoglobin or change in the haemoglobin’s ability to carry oxygen 

Stagnant hypoxia is inadequate oxygen supply to the brain due to the reduction of cerebral blood flow or pressure, e.g. stroke, heart attack 

Toxic anoxia occurs when toxins or substances interfere with oxygen supply, e.g. carbon monoxide, cyanide, narcotics, alcohol.

Effects of anoxic and hypoxic brain injury

The overall effects of a hypoxic/anoxic brain injury vary depending upon the severity of damage. Areas of the brain particularly vulnerable to lack of oxygen include those responsible for coordination, movement and memory. A significant hypoxic brain injury can result in coma and possibly post-coma unresponsiveness. 

Symptoms following a return to consciousness can include memory difficulties, abnormal movements, weakness in arms and legs, lack of coordination and visual problems. Movement disorders are quite common, including lack of coordination, spasticity (involuntary muscle tightness), tremors and an impaired ability to adjust the body’s position. 

 As with other types of brain injury, people can develop challenging behaviours and emotional problems, such as depression, agitation or a reduced ability to tolerate stress and frustration. 

Outcomes and recovery

Recovery is similar to that of other types of brain injury, but because a hypoxic injury usually results in widespread injury to the brain, outcomes are likely to be lower than other brain injuries. 

A holistic level of support is important, e.g. a physiotherapist and occupational therapist for movement disorders, speech pathologist for communication difficulties, and a neuropsychologist to assess for cognitive deficits. Support from a good team of specialists and family and friends will ensure the best recovery possible. 

References and further information

Hypoxic-Anoxic Brain Injury

National Institute of Neurological Disorders and Stroke- NINDS Cerebral Hypoxia Information Page

Powell, T. (1994). Head Injury: A Practical Guide. United Kingdom: Winslow Press (IN BIAQ LIBRARY) 

Family Caregiver Alliance. (2004). Hypoxic-Anoxic Brain Injury. Retrieved April 1, 2008.

The Free Dictionary. (2007). Hypoxia. Retrieved April 1, 2008.  

Wikipedia. (2008). Cerebral Hypoxia. Retrieved April 1, 2008.  

Middelkamp, w., Moulaert, V. R., Verbunt, J. A., van Heugten, C. M., Bakx, W. G., & Wade, D. T. (2007). Life after survival: long-term daily life functioning and quality of life of patients with hypoxic brain injury as a result of cardiac arrest. Clinical Rehabilitation, 21, 425-43