What is a brain death?
Death of the brain is the complete death of the brain, in which resuscitation can artificially support respiratory activity, blood circulation and heart function, which creates the appearance of life. The concepts of brain death and the death of the whole organism are identical. To date, the term “brain death” is used when it comes to the pathological condition associated with complete necrosis of the brain tissue and the first cervical segments of the spinal cord, while maintaining gas exchange and cardiac activity, which are provided by continuous artificial ventilation of the lungs.
The brain is organized so that the unconscious functions (breathing, balance, posture and walking for example), are nearest to the base of the brain and the brain stem. The more sophisticated functions associated with consciousness (speech, language, complex thought, and imagination for example), are nearer the upper and outer surfaces.
The outer layer of the brain in which most of the higher functions take place is called the cerebral cortex. The cerebral cortex is the most vulnerable part of the brain, as it needs a lot of oxygen and energy to function. If oxygen is cut off, the cerebral cortex can die in just a few minutes. It is therefore possible for the brain stem to still be alive after the cerebral cortex has died.
Brain death is the complete and irreversible loss of brain stem function.
If there is still activity in the brain stem, a person is considered to have sustained brain damage, rather than brain death. For example, a person in a persistent vegetative state has a working brain stem, but the higher levels of the brain may have been destroyed. Although unconscious, they are able to breathe unaided. There may even be some spontaneous movement in response to stimuli such as loud noises or pain.
Causes of brain death
In adults, the main causes of brain death are severe head injury from physical trauma, often from car crashes, and from the type of stroke known as subarachnoid hemorrhage.
In children, an important cause of brain damage is injury from physical, violent abuse.
Brain death diagnosis
The brain is so fundamental that when the brain is dead, the person cannot function without a life support machine and usually dies within a few days. In brain death, all the brain stem functions, including those that maintain breathing, stop working.
The diagnosis of brain death involves making a distinction between severe brain damage and the complete absence of brain function. The decision that there is brain death is made only after certain very critical points have been checked. These are:
- There is no question of deep intoxication from drugs, poisons or other chemical agents.
- The condition is not due to the effects of paralyzing drugs.
- It is not the result of lowered body temperature (hypothermia).
- There is no question of any neurological condition that could simulate brain death.
- There are no spontaneous breathing movements.
- The pupils are round or oval and dilated 4-6mm.
- The pupils do not change size when a bright light is projected into them.
- There are no reflex responses above the neck: no response to corneal contact (touching the surface of the eye), no gag reflex when the back of the soft palate is touched, no coughing in response to tube suction of the windpipe.
- There are no eye movements when the outer ear canal is irrigated with warm or cold water (caloric test).
- The electroencephalogram shows no sign of electrical activity in the brain, as recorded from a minimum of eight points. All channels must be flat. An electroencephalogram (EEG) is a multiple tracing, made by voltmeter-operated pens, of the electrical activity of the brain.
Brain death treatment: is it possible?
Before the use of life support machines, people with severe brain injuries would almost always die within minutes. Today, body cells can be kept alive indefinitely using life support systems, even when the brain is no longer functioning.
The difficulty is to make the distinction between severe brain damage and brain death. If the brain is dead there is no chance that the person will recover, and therefore no reason to continue with life support.
Prevention of brain death
Many head injuries are the result of unforeseen accidents that would be very difficult to predict or prevent. However, there are some measures that can be taken to reduce the risk of brain damage in the event of a head injury.
Cyclists and motorcyclists can protect themselves by wearing properly fitting safety helmets. British standard safety helmets are a legal requirement for motorcyclists. Safety helmets can reduce the risk of serious head injury in the event of an accident by up to 85%. A cyclist’s safety helmet should absorb the impact of a blow or fall evenly, preventing one spot on the head from taking the full force of the impact.
Accidents and work and in the home can be prevented by following sensible health and safety guidelines.