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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 if a hypoxic injury results in widespread injury to the brain, the outcomes will be worse.

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.