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:
- blood pressure
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 severe 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.
Read more about confirming brain death.
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.
Read more about considerations around brain death.
A diagnosis of brain death is considered when:
- A person fails to respond to any outside stimulation.
- The person is unconscious.
- The person's heartbeat and breathing can only be maintained using a ventilator.
- There is clear evidence that serious damage to the brain has occurred, and it cannot be cured.
Ruling out other conditions
Before testing for brain death can begin, doctors must carry out a series of checks to make sure that the symptoms are not being caused by other factors. Possible factors include:
- an overdose of illegal drugs, tranquillisers, poisons or other chemical agents
- having an abnormally low body temperature (hypothermia)
- having a condition that can affect the metabolism (the process that turns food into energy), such as diabetes (a long-term condition caused by too much glucose in the blood) or liver disease, which can be connected to alcohol abuse (alcoholic liver disease) and obesity (non-alcoholic fatty liver disease)
Once these have been ruled out, tests are carried out to confirm brain death. The diagnosis of brain death has to be made by two senior doctors. Neither of them can be involved with the hospital's transplant team.
The doctors will explain the tests to you and will keep you informed about your loved one's condition at all times.
The doctors will run a series of tests. Both of them have to agree on the results for a diagnosis of brain death to be confirmed. The tests are carried out twice to minimise any chance of error.
The tests used to determine whether brain stem death has occurred are outlined below:
- A torch is shone into both eyes to see if they react to the light.
- The cornea (transparent outer layer of the eye), which is normally very sensitive, is stroked with a tissue or piece of cotton wool to see if the eye reacts.
- Pressure is applied to the forehead and the nose is pinched to see if there is any movement in response.
- Ice-cold water is inserted into each ear, which would normally cause the eyes to move.
- A thin, plastic tube is place down the trachea (windpipe) to see if this provokes gagging or coughing.
- The person is withdrawn from the ventilator for a short period of time to see if they make any attempt to breathe on their own.
If a person fails to respond to all of these tests, a diagnosis of brain death is made.
Occasionally, a person’s limbs or their torso (the upper part of their body) may move, even after brain stem death has been diagnosed. These are spinal reflex movements, which means they are generated by the spinal cord and do not involve the brain at all. They will not affect the diagnosis of brain death.
Brain stem The brain stem is the lower part of the brain that is connected to the spinal cord and is responsible for regulating most of the automatic functions of the body that are essential for life, such as breathing. Liver The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and turn food into energy. Spinal cord The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.
Before the use of devices such as ventilators, people with brain death would always die within minutes. Today it is possible to keep oxygen-rich blood circulating inside the body for some time using these devices.
Usually the ventilator and the medications supporting the blood pressure will be turned off once brain death is diagnosed. However, these patients may also donate organs for transplantation, which is often life-saving for others.
If the deceased person carried an organ donor card, signed the NHS organ donor register or has otherwise consented to a transplant before brain death occurred, there is no legal requirement for the transplant team to obtain consent from a partner or relative.
However, most primary care trusts (PCTs) will not do a transplant if relatives or a partner have strong objections to a transplant going ahead.
If the deceased person had not made their feelings about organ transplants known, hospital staff have to make reasonable enquires to check that:
- The deceased person had not expressed an objection to their body being used in this way after their death.
- There are no objections from a spouse, partner or relatives.
- There are no religious reasons why a transplant cannot go ahead (all the major religions in the UK support the principle of organ donation).
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.
Read more about organ donation.
Brain stem The brain stem is the lower part of the brain that is connected to the spinal cord and is responsible for regulating most of the automatic functions of the body that are essential for life, such as breathing.