Brain Death
How is ‘brain death’ different from ‘circulatory
death’?
Most people understand that death occurs when a
person’s heart and breathing stop. This can also be called
circulatory death and it is how most people die. When
someone has died a circulatory death, they do not
breathe or move, they do not have a heart beat and their
skin is cold and dusky.
Death also occurs when the brain and brainstem have
stopped working completely – this is called brain death.
The kinds of serious injuries which may lead to brain
death include accidents where there is trauma to the
head, bleeding into the brain, infections or a period of
time without oxygen or blood flow to the brain. As part of
the treatment for these conditions, the person will be
connected to a ventilator, which pushes oxygen into the
lungs, causing the chest to rise/fall and sustaining the
heartbeat. Despite having a beating heart and a chest
that rises and falls, if basic brain functions are absent,
determined using specific tests, then death has occurred
as a result of brain death. Brain death is not the same as
“brain damage, “brain injury,” or “coma”, it is permanent,
irrecoverable and as such is equivalent to circulatory
death in terms of outcome. Nevertheless this is a difficult
concept to understand. Observing the tests and
investigations performed can be helpful for relatives in
demonstrating the absence of basic brain function in
brain death and the reality of death.
What causes the brain to die?
The brain requires a constant supply of oxygen rich
blood. Interruption of this supply causes injury and like
other parts of the body – the brain swells as a result.
For example, an injured finger or ankle swells, but can
keep expanding because there is no restriction. The brain
however, is contained within the rigid skull that limits
how much it can expand. As the brain continues to swell,
pressure builds up within the skull.
This document was last reviewed on 28 August 2014
© The Children’s Hospital at Westmead, Sydney Children’s Hospital, Randwick and Kaleidoscope Children, Young People and Families.
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This increased pressure within the skull causes
permanent irrecoverable damage to the brain:
Blood vessels supplying the brain get compressed; this
stops blood and oxygen flowing to the brain.
Without the oxygen, brain cells die and cannot recover.
This causes even more swelling.
The swollen brain expands in a downwards direction
further injuring the brainstem (where the spinal cord and
the brain connect) and this swelling results in injury to
the brain stem and brain death.
The brain stem is fundamental to life - it controls
breathing, coughing, heart rate, blood pressure, response
to pain and body temperature.
A person who is brain dead cannot and will not breathe.
They cannot feel pain and will never feel pain – e.g a
cotton wool ball gently touched on their eyeball will not
cause blinking. They have not and will not have any
awareness of self. They cannot and will not cough, gag,
get dizzy, move their eyes or do anything that they have
learnt during their lifetime. They have lost all their
basic/primitive reflexes and everything more advanced as
well.
There are times when some patients may not be able to
have all of these tests performed. This is maybe due to
the nature of the injuries which have been sustained. For
example, a spinal injury, an eye injury, or a facial injury
will mean those nerves cannot be adequately tested. In
these cases, perfusion scans are done to determine if
there is any blood flow to the brain. This may be either a
cerebral angiogram or a cerebral perfusion scan.
What happens after a person is confirmed to
be brain dead?
Once death has been confirmed, appropriate members of
the medical team will speak with the family. In the setting
of brain death it may be possible for the relatives or
family to consider discussing organ donation with the
doctors involved.
If organ donation is wanted then a donation specialist will
provide information to families about what needs to
happen, if donation is not an option the family wish to
pursue or there are medical reasons why the person
cannot be an organ donor, the medical staff will speak
with the family about the timing of removing the
ventilator.
How can the doctors tell when a person’s brain
has died?
There are a number of physical changes in pupil reaction,
heart rate, blood pressure and body temperature that
are seen with brain death. These changes, together with
the loss of other natural responses such as breathing,
coughing and blinking, cause doctors to suspect that
brain death has occurred. A number of specific tests are
then done to find out whether or not the brain is
working. Two senior doctors independently perform
testing of cranial nerves originating in the brainstem
(which control all vital basic brain reflexes). For a person
to be declared brain dead there must be no responses to
these tests. These tests are done after a number of
preconditions are met; following a period of observation
and on 2 separate occasions. The doctors will ensure that
they are completely certain of the results of these tests
prior to making the diagnosis of brain death.
© The Children’s Hospital at Westmead, Sydney Children’s Hospital, Randwick and Kaleidoscope Children, Young People and Families.
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