Brain death
Encyclopedia
Brain death is the irreversible end of all brain activity (including involuntary activity necessary to sustain life) due to total necrosis
of the cerebral neurons following loss of brain oxygenation
. It should not be confused with a persistent vegetative state
. Patients who are classified as Brain dead can have their organs surgically removed to help others in need.
Brain death, either of the whole brain or the brain stem
, is used as a legal indicator of death in many jurisdictions.
through the end of certain bodily
functions, 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 a better definition of death became obvious. This need gained greater urgency with the widespread use of life support
equipment, which can maintain body functions indefinitely, 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 (or indicator) of death was Finland
in 1971. In the United States
, Kansas
enacted a similar law earlier.
An ad hoc
committee at Harvard Medical School
published a pivotal 1968 report to define irreversible coma
. The Harvard criteria gradually gained consensus towards what is now known as brain death. In the wake of the 1976 Karen Ann Quinlan
controversy, state legislatures moved to accept brain death as an acceptable indication of death. Finally, a presidential commission issued a landmark 1981 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 is now the law in almost all fifty states. 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 1976 and 1977, rejecting the whole brain death criterion as scientifically worthless, and adopting the notion of irreversible brain stem dysfunction
as an indicator of death.
. This includes no response to pain
and no cranial nerve reflex
es. Reflexes include pupillary response (fixed pupils), oculocephalic reflex, corneal reflex
, no response to the caloric reflex test
and no spontaneous respiration
s.
It is important to distinguish between brain death and states that may mimic brain death (e.g., barbiturate overdose
, alcohol intoxication, sedative
overdose, hypothermia
, hypoglycemia
, coma
or chronic vegetative states). Some comatose patients can recover, 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. Thus, anencephaly
, in which there is no higher brain present, is generally not considered brain death, though it is certainly an irreversible condition in which it may be appropriate to withdraw life support.
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.
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 in the USA they require neurological examinations by two independent physicians. The exams must show complete absence of brain function (brain stem function in UK), and may include two isoelectric (flat-line) EEGs 24 hours apart (less in other countries where it is accepted that if the cause of the dysfunction is a clear physical trauma there is no need to wait that long to establish irreversibility). The widely-adopted Uniform Determination of Death Act in the United States attempts to standardize criteria. 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.
Alternatively, a radionuclide
cerebral blood flow scan that shows complete absence of intracranial blood flow can be used to confirm the diagnosis without performing EEGs.
. Those who view the neo-cortex of the brain as solely responsible for consciousness, however, argue that electrical activity there should be the only consideration when defining death. In many cases, especially when elevated intracranial pressure
prevents blood flow into the brain
, the entire brain is nonfunctional; however, some injuries may affect only the neo-cortex.
During the death process, brain function can be lost gradually. When going through such a change, a small proportion of subjects have reported a variety of "near-death experiences".
, but still with the heart
beating, and with mechanical ventilation
all other vital organs may be kept completely alive and functional, providing optimal opportunities for organ transplantation.
Most organ donation for organ transplantation is done in the setting of brain death.
In some nations (for instance, Belgium
, Poland
, Portugal
and France
) everyone is automatically an organ donor, although some jurisdictions (such as Singapore
, France
and Portugal
) allow opting out of the system. Elsewhere, consent from family members or next-of-kin may be required for organ donation. In New Zealand
, preference for organ donation is indicated at the time a Driver's license is applied for. The non-living donor is kept on ventilator support until the organs have been surgically removed. If a brain-dead individual is not an organ donor, ventilator and drug support is discontinued and cardiac death is allowed to occur.
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
of the cerebral neurons following loss of brain oxygenation
Oxygenation (medical)
Oxygenation occurs when oxygen molecules enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood...
. It should not be confused with a persistent vegetative state
Persistent vegetative state
A persistent vegetative state is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. It is a diagnosis of some uncertainty in that it deals with a syndrome. After four weeks in a vegetative state , the patient is...
. Patients who are classified as Brain dead can have their organs surgically removed to help others in need.
Brain death, either of the whole brain or the brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
, is used as a legal indicator of death in many jurisdictions.
Legal history
Traditionally, both the legal and medical communities determined deathDeath
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
through the end of certain bodily
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
functions, especially respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
and heartbeat
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
. With the increasing ability of the medical community to resuscitate people with no respiration, heartbeat, or other external signs of life, the need for a better definition of death became obvious. This need gained greater urgency with the widespread use of life support
Life support
Life support, in medicine is a broad term that applies to any therapy used to sustain a patient's life while they are critically ill or injured. There are many therapies and techniques that may be used by clinicians to achieve the goal of sustaining life...
equipment, which can maintain body functions indefinitely, 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 (or indicator) of death was Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
in 1971. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
enacted a similar law earlier.
An ad hoc
Ad hoc
Ad hoc is a Latin phrase meaning "for this". It generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes. Compare A priori....
committee at Harvard Medical School
Harvard Medical School
Harvard Medical School is the graduate medical school of Harvard University. It is located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts....
published a pivotal 1968 report to define irreversible coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
. The Harvard criteria gradually gained consensus towards what is now known as brain death. In the wake of the 1976 Karen Ann Quinlan
Karen Ann Quinlan
Karen Ann Quinlan was an important figure in the history of the right to die controversy in the United States....
controversy, state legislatures moved to accept brain death as an acceptable indication of death. Finally, a presidential commission issued a landmark 1981 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
Uniform Determination of Death Act
The Uniform Determination of Death Act is a draft state law that was approved for the United States in 1981 by the National Conference of Commissioners on Uniform State Laws, in cooperation with the American Medical Association, the American Bar Association, and the President's Commission on...
, which is now the law in almost all fifty states. 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 1976 and 1977, rejecting the whole brain death criterion as scientifically worthless, and adopting the notion of irreversible brain stem dysfunction
Brain stem death
Brain Stem Death is a clinical concept, implying an irreversibly unconscious patient, with irreversible apnea and irreversible loss of brain stem reflexes. The concept defines the core physiological basis for neurological diagnosis of death in the United Kingdom and elsewhere...
as an indicator of death.
Religious views
Religious views on organ donation are generally very favourable, although there is a debate in certain religious groups on the validity of current brain death criteria. Accordingly, the more theologians are accepting of current brain death criteria, the more they are likely to support organ donation. It is clearly not compatible with some Shinto beliefs due to handling corpses and bodily fluids being unacceptable, and is controversial in certain Buddhist, Christian, Jewish and Muslim circles. Japan has been a very late adopter of brain centric indicators of death as a result.Medical criteria
A brain-dead individual has no clinical evidence of brain function upon physical examinationPhysical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...
. This includes no response to pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
and no cranial nerve reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
es. Reflexes include pupillary response (fixed pupils), oculocephalic reflex, corneal reflex
Corneal reflex
The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea , or bright light, though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response...
, no response to the caloric reflex test
Caloric reflex test
In medicine, the caloric reflex test is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal.-Utility:...
and no spontaneous respiration
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
s.
It is important to distinguish between brain death and states that may mimic brain death (e.g., barbiturate overdose
Barbiturate overdose
A barbiturate overdose results when a person takes a larger-than-prescribed dose of barbiturates. Symptoms of an overdose typically include sluggishness, incoordination, difficulty in thinking, slowness of speech, faulty judgment, drowsiness, shallow breathing, and staggering. In severe cases, coma...
, alcohol intoxication, sedative
Sedative
A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....
overdose, hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
, hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
, coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
or chronic vegetative states). Some comatose patients can recover, 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. Thus, anencephaly
Anencephaly
Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp...
, in which there is no higher brain present, is generally not considered brain death, though it is certainly an irreversible condition in which it may be appropriate to withdraw life support.
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
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
or cardiac arrest
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
. 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.
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 in the USA they require neurological examinations by two independent physicians. The exams must show complete absence of brain function (brain stem function in UK), and may include two isoelectric (flat-line) EEGs 24 hours apart (less in other countries where it is accepted that if the cause of the dysfunction is a clear physical trauma there is no need to wait that long to establish irreversibility). The widely-adopted Uniform Determination of Death Act in the United States attempts to standardize criteria. 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.
Alternatively, a radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
cerebral blood flow scan that shows complete absence of intracranial blood flow can be used to confirm the diagnosis without performing EEGs.
Consciousness
Medical science argues that a permanent cessation of electrical activity indicates the end of consciousnessConsciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
. Those who view the neo-cortex of the brain as solely responsible for consciousness, however, argue that electrical activity there should be the only consideration when defining death. In many cases, especially when elevated intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
prevents blood flow into the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, the entire brain is nonfunctional; however, some injuries may affect only the neo-cortex.
During the death process, brain function can be lost gradually. When going through such a change, a small proportion of subjects have reported a variety of "near-death experiences".
Organ donation
Brain death may result in legal deathLegal death
Legal death is a legal pronouncement by a qualified person that further medical care is not appropriate and that a patient should be considered dead under the law. The specific criteria used to pronounce legal death are variable and often depend on certain circumstances in order to pronounce a...
, but still with the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
beating, and with mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
all other vital organs may be kept completely alive and functional, providing optimal opportunities for organ transplantation.
Most organ donation for organ transplantation is done in the setting of brain death.
In some nations (for instance, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
) everyone is automatically an organ donor, although some jurisdictions (such as Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
) allow opting out of the system. Elsewhere, consent from family members or next-of-kin may be required for organ donation. In New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, preference for organ donation is indicated at the time a Driver's license is applied for. The non-living donor is kept on ventilator support until the organs have been surgically removed. If a brain-dead individual is not an organ donor, ventilator and drug support is discontinued and cardiac death is allowed to occur.
See also
- Brain stem deathBrain stem deathBrain Stem Death is a clinical concept, implying an irreversibly unconscious patient, with irreversible apnea and irreversible loss of brain stem reflexes. The concept defines the core physiological basis for neurological diagnosis of death in the United Kingdom and elsewhere...
- Clinical deathClinical deathClinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain life. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research.Stopped blood...
- DeathDeathDeath is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
- Persistent vegetative statePersistent vegetative stateA persistent vegetative state is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. It is a diagnosis of some uncertainty in that it deals with a syndrome. After four weeks in a vegetative state , the patient is...
External links
- Informational Portal about Brain Death
- Brain Death from the Encyclopedia of Death and Dying
- How Stuff Works - Brain Death
- Textbook section
- Parents' Hospital Lawsuit Says Teen Was 'Killed' For Organs
- Why the Concept of Brain Death is Valid as a Definition of Death: Statement by Neurologists and Others and Response to Objections. Pontifical Academy of Science
- extensible bibliography: „Brain Death“: Alive body – dead person?