Brain death is the complete and irreversible loss of brain function. Brain death is one
of the two ways of determination of death, according to the Uniform Determination of
Death Act of the United States. It is not the same as persistent vegetative state, in
which the person is "alive". Brain death is used as an indicator of legal
death in many jurisdictions, but it is defined inconsistently. Various parts of the brain
may keep living when others die, and the term "brain death" has been used to refer to various
combinations. For example, although a major medical dictionary says that "brain death"
is synonymous with "cerebral death", the US National Library of Medicine Medical Subject
Headings system defines brain death as including the brainstem. The distinctions can be important
because, for example, in someone with a dead cerebrum but a living brainstem, the heartbeat
and ventilation can continue unaided, whereas in whole-brain death, only life support equipment
would keep those functions going. Patients classified as brain-dead can have their organs
surgically removed for organ donation.
Legal history Traditionally, both the legal and medical
communities determined death through the permanent end of certain bodily functions in clinical
death, especially respiration and heartbeat. With the increasing ability of the medical
community to resuscitate people with no respiration, heartbeat, or other external signs of life,
the need for another definition of death occurred, raising questions of legal death. This gained
greater urgency with the widespread use of life support equipment, as well as rising
capabilities and demand for organ transplantation. Since the 1960s, laws on determining death
have, therefore, been implemented in all countries with active organ transplantation programs.
The first European country to adopt brain death as a legal definition of death was Finland,
in 1971. In the United States, Kansas had enacted a similar law earlier. In the 1970s,
the Supreme Court of the state of New Jersey ruled that patients and their families have
the right to decide when and whether to remove life support.
An ad hoc committee at Harvard Medical School published a pivotal 1968 report to define
irreversible coma. The Harvard criteria gradually gained consensus toward what is now known
as brain death. In the wake of the 1976 Karen Ann Quinlan controversy, state legislatures
in the United States moved to accept brain death as an acceptable indication of death.
In 1981 a Presidential commission issued a landmark report – Defining Death: Medical,
Legal, and Ethical Issues in the Determination of Death – that rejected the "higher brain"
approach to death in favor of a "whole brain" definition. This report was the basis for
the Uniform Determination of Death Act, which has been enacted in 39 states of the United
States the Uniform Determination of Death Act in the United States attempts to standardize
criteria. Today, both the legal and medical communities in the US use "brain death" as
a legal definition of death, allowing a person to be declared legally dead even if life support
equipment keeps the body's metabolic processes working.
In the UK, the Royal College of Physicians reported in 1995, abandoning the 1979 claim
that the tests published in 1976 sufficed for the diagnosis of brain death and suggesting
a new definition of death based on the irreversible loss of brain stem function alone. This new
definition, the irreversible loss of the capacity for consciousness and for spontaneous breathing,
and the essentially unchanged 1976 tests held to establish that state, have been adopted
as a basis of death certification for organ transplant purposes in subsequent Codes of
Practice. Medical criteria
A brain-dead individual has no clinical evidence of brain function upon physical examination.
This includes no response to pain and no cranial nerve reflexes. Reflexes include pupillary
response, oculocephalic reflex, corneal reflex, no response to the caloric reflex test, and
no spontaneous respirations. It is important to distinguish between brain
death and states that may be difficult to differentiate from brain death. Some comatose
patients can recover to pre-coma or near pre-coma level of functioning, and some patients with
severe irreversible neurological dysfunction will nonetheless retain some lower brain functions
such as spontaneous respiration, despite the losses of both cortex and brain stem functionality;
such is the case with anencephaly. Note that brain electrical activity can stop
completely, or drop to such a low level as to be undetectable with most equipment. An
EEG will therefore be flat, though this is sometimes also observed during deep anesthesia
or cardiac arrest. Although in the United States a flat EEG test is not required to
certify death, it is considered to have confirmatory value. In the UK it is not considered to be
of value because any continuing activity it might reveal in parts of the brain above the
brain stem is held to be irrelevant to the diagnosis of death on the Code of Practice
criteria. The diagnosis of brain death needs to be rigorous,
in order to be certain that the condition is irreversible. Legal criteria vary, but
in general they require neurological examinations by two independent physicians. The exams must
show complete and irreversible absence of brain function, and may include two isoelectric
EEGs 24 hours apart. The patient should have a normal temperature and be free of drugs
that can suppress brain activity if the diagnosis is to be made on EEG criteria.
Also, a radionuclide cerebral blood flow scan that shows complete absence of intracranial
blood flow must be considered with other exams – temporary swelling of the brain, particularly
within the first 72 hours, can lead to a false positive test on a patient that may recover
with more time. Zack Dunlap in 2008 had a false positive of this type, likely due to
temporary cerebral edema. CT angiography is neither required nor sufficient
test to make the diagnosis. Organ donation
While the diagnosis of brain death has become accepted as a basis for the certification
of death for legal purposes, it should be clearly understood that it is a very different
state from biological death - the state universally recognized and understood as death. The continuing
function of vital organs in the bodies of those diagnosed brain dead, if mechanical
ventilation and other life-support measures are continued, provides optimal opportunities
for their transplantation. When mechanical ventilation is used to support
the body of a brain dead organ donor pending a transplant into an organ recipient, the
donor's date of death is listed as the date that brain death was diagnosed.
In some countries, everyone is automatically an organ donor after diagnosis of death on
legally accepted criteria, although some jurisdictions allow opting out of the system. Elsewhere,
consent from family members or next-of-kin may be required for organ donation. In New
Zealand, Australia, United Kingdom and most states in the United States, drivers are asked
upon application if they wish to be registered as an organ donor.
In the United States, if the patient is at or near death, the hospital must notify a
transplant organization of the person's details and maintain the patient while the patient
is being evaluated for suitability as a donor. The patient is kept on ventilator support
until the organs have been surgically removed. If the patient has indicated in an advance
health care directive that they do not wish to receive mechanical ventilation or has specified
a do not resuscitate order and the patient has also indicated that they wish to donate
their organs, some vital organs such as the heart and lungs may not be able to be recovered.
See also
Brainstem death Clinical death
Death Persistent vegetative state
Information-theoretic death Consciousness after death
References