Anoxic and Hypoxic Brain Injury

The brain uses up 20 per cent of the oxygen supply for the entire body and injuries to the brain can become very serious in the event of a shortage of oxygen. Once the supply of oxygen to the brain is reduced, damage can occur very quickly.

Anoxic brain injuries occur when there is a complete blockage in oxygen supply to the brain, while hypoxic injuries occur when oxygen supply is disrupted or reduced. Both types of injury can be extremely serious and contribute to long-lasting effects.

Oxygen is essential because it enables the body to metabolise glucose, which provides energy and fuel for the cells. Without oxygen, this process cannot take place and nerve cells can start to die very quickly. A lack of oxygen can result in life-threatening consequences.

Causes of hypoxic and anoxic brain injuries

Possible causes of hypoxic and anoxic brain injuries include:

  • stroke
  • drowning
  • asphyxiation
  • strangulation
  • drug overdose
  • carbon monoxide poisoning
  • trauma that results in excessive blood loss
  • injuries that cause swelling in the brain

What are the different types or anoxic and hypoxic injury?

There are various different types of anoxic and hypoxic injuries, including:

  • Toxic anoxia: this occurs when toxins disrupt the flow of oxygen and examples include cyanide and carbon monoxide poisoning, alcohol poisoning and drug abuse.
  • Anoxic anoxia: this occurs when there is a shortage of oxygen available; examples include suffocation and altitude sickness.
  • Stagnant hypoxia: this occurs when there is a reduced supply of oxygen to the brain as a result of decreased blood pressure or blood flow; examples include heart attacks, brain haemorrhages and strokes. Increased pressure on the brain can also lead to reduced oxygen supply.
  • Anaemic anoxia: this occurs when a reduction in haemoglobin decreases blood supply to the brain. This can also result from impaired function of the haemoglobin, which prevents it from carrying oxygen effectively.

What are the effects of an anoxic or hypoxic brain injury?

As soon as there is a reduction in blood flow to the brain, there is a risk of damage and it’s essential to act quickly to prevent the nerve cells from dying and restore normal oxygen flow. Within the first three minutes, injuries can occur and generally speaking, the longer the reduction in oxygen flow, the more serious the consequences.

The severity of a brain injury will vary according to the nature of the injury and the extent of damage to the brain cells. Some areas of the brain are more susceptible to long-term damage than others and some patients recover better than others. Severe injuries may result in loss of consciousness and patients may be in a coma for several days, weeks or even months. After injury, there may be significant effects on cognitive function and memory, awareness, motor skills, balance and problems with vision. There may also be changes in personality and an increased risk of depression, stress, anxiety and anger.

What is the prognosis for brain injuries?

The prognosis varies for each individual depending on the severity of the injury; some people will make a full recovery, while others will suffer significant long-term health problems related to brain damage.

Recovery time is usually dependent on the length of time oxygen supply was reduced or cut, the extent of brain damage, the cells affected and the age and general health of the individual patient. If oxygen supply is interrupted only very briefly, there is every chance of an excellent recovery.

Recovery and rehabilitation are extremely important and individuals who have suffered a brain injury will usually be cared for by a team of specialists and therapists, from neurologists to physiotherapists and occupational therapists.

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