Brain death

Brain death occurs when a person no longer has any activity in their brain stem and no potential for consciousness, even though a ventilator is keeping their heart beating and oxygen circulating through their blood.

When brain stem function is permanently lost, the person will be confirmed dead.

Confirmation of death

In the past confirming death was straightforward – death occurs when the heart stops beating and a person is no longer breathing. In turn, the lack of oxygen as a result of no blood flow will quickly lead to the permanent loss of brain stem function.

Now confirmation of death can be more complex as it is possible to keep the heart beating after the brain stem has permanently stopped functioning. This is as a result of keeping someone on a ventilator thereby allowing the body (and the heart) to be artificially oxygenated.

But once the brain stem has permanently stopped functioning there is no way to reverse this and the heart will eventually stop beating even if a ventilator has been used.

To save family and friends from unnecessary suffering, once there is clear evidence that brain death has occurred the ventilator is turned off.

The brain stem

The brain stem is the lower part of the brain that is connected to the spinal cord (a column of nervous tissue located in the spinal column).

The brain stem is responsible for regulating most of the automatic functions of the body that are essential for life. These are:

• breathing
• heartbeat
• blood pressure
• swallowing

The brain stem also relays all information to and from the brain to the rest of the body, so it plays a fundamental role in the brain’s core functions, such as consciousness, awareness and movement. There is no possibility for consciousness once brain death has occurred and in combination with inability to breathe or maintain bodily functions this constitutes death of the individual.

Brain death can occur when the blood and oxygen supply to the brain is stopped. This can be caused by:

• cardiac arrest – this is when the heart stops beating and the brain is starved of oxygen
• heart attack – a serious medical emergency that occurs when the blood supply to the heart is suddenly blocked
• stroke – a serious medical emergency that occurs when the blood supply to the brain is interrupted
• blood clot – a blockage in one of your blood vessels that disturbs or blocks the flow of blood around your body

Brain death can also occur as a result of:

• a serve head injury
• infections, such as encephalitis (a viral infection of the brain) 
• a brain tumour (a growth of cells multiplying in an abnormal, uncontrollable way in the brain)

Persistent vegetative state

There is a difference between brain death and a persistent vegetative state (PVS), which can occur after extensive damage to the brain.

Someone in a PVS can show signs of wakefulness (they may open their eyes, for example) but have no response to their surroundings.

In rare cases, some patients may demonstrate some sense of response that can be detected using a brain scan, but not be able to interact with their surroundings.

However, the important difference between PVS and brain death is that a patient with PVS still has a functioning brain stem, therefore:

• Some form of consciousness may exist in someone in a PVS.
• A person in a PVS can still breathe unaided.
• A person in a PVS has a slim chance of recovering because the core functions of the brain stem are often unaffected, whereas a person with brain death has no chance of recovery as the body cannot survive without artificial support.

Confirming brain death

Although rare, there are some things that can make it appear as though someone is brain dead, such as:

• drug overdose
• severe hypothermia– where the body temperature drops below 28C
• diabetic coma – where the blood sugar becomes dangerously high and a person becomes dehydrated

So a number of tests are carried out to ensure that brain death has actually occurred, such as shining a torch into both eyes to see if they react to the light.

Organ donation

Once brain death occurs it is often possible to still remove organs from the body that can be used in, often life-saving, organ transplants.

Deciding whether to carry out a transplant can be a difficult decision for partners and relatives. Hospital staff are aware of these difficulties and will try to ensure the issue is handled sensitively and thoughtfully.

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Categories: brain diseases