What is hypoxic brain injury / anoxic brain injury?
Oxygen is needed for the brain to make use of glucose, its major energy source. If the oxygen supply is interrupted, consciousness will be lost within 15 seconds and damage to the brain begins to occur after about four minutes without oxygen.

A complete interruption of the supply of oxygen to the brain is referred to as cerebral anoxia. If there is still a partial supply of oxygen, but at a level which is inadequate to maintain normal brain function, this is known as cerebral hypoxia. In practice, these two terms tend to be used interchangeably.


What causes hypoxic/anoxic brain injury?
There are many potential causes of cerebral anoxia, including:

Cardiac or respiratory arrest
Irregular heart rhythm or poor function of the heart muscle after a heart attack, resulting in inefficient supply of blood to the brain
Very low blood pressure (shock), resulting from blood loss (haemorrhage) or disturbed heart function
Suffocation
Choking
Strangulation
Very severe asthma attack
Complication of general anaesthesia (where there has been inadequate oxygen supply or cardiac arrest)
Near drowning
Exposure to high altitudes
Smoke inhalation
Carbon monoxide inhalation
Poisoning
Drug overdose
Electric shock