Skip to main content
Select Source:

brain death

brain death applies to the situation when the heart continues to beat with the breathing maintained mechanically after the brain has permanently ceased to function — and it is an unnatural artefact of medical technology.

Under natural conditions when the brain ceases to function breathing immediately stops, and soon after that the heart stops from lack of oxygen. If breathing is taken over by a mechanical ventilator, oxygenation is maintained and the heart can continue to beat, for days at least, because the heart muscle acts on its own independently of the brain. That death is a process rather than a sudden event is now well recognized. Most often the process is initiated by the heart stopping, and this is then followed by brain failure due to lack of oxygen. Sometimes it is the breathing that stops first, the lack of oxygen leads to brain failure and later the heart also stops.

The relevant part of the brain for the maintenance of breathing, as well as for the activation of higher cerebral function, is the brain stem — the lowest part of the brain above its junction with the spinal cord. Because function in this region is crucial for the whole of the brain, cessation of that function, strictly ‘brain stem death’, is commonly referred to as brain death.

Brain death is the result of unsuccessful resuscitation — the price paid for the many patients whose lives are saved, and who make a good recovery, when a ventilator is used during brain failure which proves to be temporary. When mechanical ventilation was begun it was not known whether or not the brain could recover — only a trial period of ventilation could settle that question.

The problem with waiting for the heart to stop following brain death is that it can go on beating for several days, occasionally for weeks, during which time other organs fail and the extremities may begin to decompose. To continue artificial ventilation is therefore regarded as both futile and undignified. In many countries it has been accepted that when the brain is dead the person is dead; in some jurisdictions laws have been enacted to acknowledge this, but in others it has been considered unnecessary.

This matter has, however, been complicated by the development of organ transplantation. Kidney transplantation was well established before the concept of brain death was widely accepted, because it was possible to use organs from donors whose hearts had stopped beating, but the transplantation of hearts, lungs, and livers is possible only from donors whose hearts are still beating, and therefore only from those who are brain dead.

There is clearly need for strict criteria for the diagnosis of brain death, whether or not there is any question of organ donation, because the consequence of this diagnosis will be the withdrawal of artificial ventilation. This is regarded as discontinuing an inappropriate intervention for a person who is already dead, rather than letting that person die. In the UK the medical Royal Colleges agreed criteria for the diagnosis of brain death in 1976. These require satisfying certain pre-conditions and then undertaking tests to confirm that there is no function in the brain stem. The pre-conditions must establish that the patient is in coma and on a ventilator because breathing has ceased due to irreversible structural brain damage — usually due to severe head injury, brain haemorrhage, or an episode of oxygen starvation of the brain. It is also necessary to exclude reversible causes of failure of brain function, including depressant drugs and hypothermia. The tests for absence of brain stem function require there to be no reflex responses in the pupils or the muscles of the face, throat, or eyes. The final test is to confirm that there has been no recovery of spontaneous breathing by disconnecting the ventilator temporarily, whilst maintaining a passive flow of oxygen to the lungs. These tests are carried out twice and by two experienced doctors. The time of death, for legal purposes, is when the first set of tests were completed, although death is not declared until after the second test. Additional tests are not required in the UK but are used in some countries. These include demonstrating lack of electrical activity in the brain by electro-encephalography (EEG), or lack of blood circulation in the brain using either radioactive isotopes or radio-opaque dyes injected into the bloodstream.

Bryan Jennett


See also coma; life support; organ donation; vegetative state.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"brain death." The Oxford Companion to the Body. . Encyclopedia.com. 13 Dec. 2017 <http://www.encyclopedia.com>.

"brain death." The Oxford Companion to the Body. . Encyclopedia.com. (December 13, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/brain-death

"brain death." The Oxford Companion to the Body. . Retrieved December 13, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/brain-death

Brain Death

Brain Death

The term brain death is defined as "irreversible unconsciousness with complete loss of brain function," including the brain stem, although the heartbeat may continue. Demonstration of brain death is the accepted criterion for establishing the fact and time of death. Factors in diagnosing brain death include irreversible cessation of brain function as demonstrated by fixed and dilated pupils, lack of eye movement, absence of respiratory reflexes (apnea), and unresponsiveness to painful stimuli. In addition, there should be evidence that the patient has experienced a disease or injury that could cause brain death. A final determination of brain death must involve demonstration of the total lack of electrical activity in the brain by two electroencephalographs (EEGs) taken twelve to twenty-four hours apart. Finally, the physician must rule out the possibilities of hypothermia or drug toxicities, the symptoms of which may mimic brain death. Some central nervous system functions such as spinal reflexes that can result in movement of the limbs or trunk may persist in brain death.

Until the late twentieth century, death was defined in terms of loss of heart and lung functions, both of which are easily observable criteria. However, with modern technology these functions can be maintained even when the brain is dead, although the patient's recovery is hopeless, sometimes resulting in undue financial and emotional stress to family members. French neurologists were the first to describe brain death in 1958. Patients with coma depasse were unresponsive to external stimuli and unable to maintain homeostasis. A Harvard Medical School committee proposed the definition used in this entry, which requires demonstration of total cessation of brain function. This definition is almost universally accepted.

Brain death is not medically or legally equivalent to severe vegetative state. In a severe vegetative state, the cerebral cortex, the center of cognitive functions including consciousness and intelligence, may be dead while the brain stem, which controls basic life support functions such as respiration, is still functioning. Death is equivalent to brain stem death. The brain stem, which is less sensitive to anoxia (loss of adequate oxygen) than the cerebrum, dies from cessation of circulation for periods exceeding three to four minutes or from intracranial catastrophe, such as a violent accident.

Difficulties with ethics and decision making may arise if it is not made clear to the family that brain stem death is equivalent to death. According to research conducted by Jacqueline Sullivan and colleagues in 1999 at Thomas Jefferson University Hospital, roughly one-third to one-half of physicians and nurses surveyed do not adequately explain to relatives that brain dead patients are, in fact, dead. Unless medical personnel provide family members with information that all cognitive and life support functions have irreversibly stopped, the family may harbor false hopes for the loved one's recovery. The heartbeat may continue or the patient may be on a respirator (often inaccurately called "life support") to maintain vital organs because brain dead individuals who were otherwise healthy are good candidates for organ donation. In these cases, it may be difficult to convince improperly informed family members to agree to organ donation.

See also: Cell Death; Definitions of Death; Life Support System; Organ Donation and Transplantation; Persistent Vegetative State

Bibliography

Ad Hoc Committee of the Harvard Medical School. "The Harvard Committee Criteria for Determination of Death." In Opposing Viewpoint Sources, Death/Dying, Vol. 1. St. Paul, MN: Greenhaven Press, 1984.

"Brain (Stem) Death." In John Walton, Jeremiah Barondess, and Stephen Lock eds., The Oxford Medical Companion. New York: Oxford University Press, 1994.

Plum, Fred. "Brain Death." In James B. Wyngaarden, Lloyd H. Smith Jr., and J. Claude Bennett eds., Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 1992.

Sullivan, Jacqueline, Debbie L. Seem, and Frank Chabalewski. "Determining Brain Death." Critical Care Nurse 19, no. 2 (1999):3746.

ALFRED R. MARTIN

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Brain Death." Macmillan Encyclopedia of Death and Dying. . Encyclopedia.com. 13 Dec. 2017 <http://www.encyclopedia.com>.

"Brain Death." Macmillan Encyclopedia of Death and Dying. . Encyclopedia.com. (December 13, 2017). http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/brain-death

"Brain Death." Macmillan Encyclopedia of Death and Dying. . Retrieved December 13, 2017 from Encyclopedia.com: http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/brain-death

brain death

brain death The permanent absence of vital functions of the brain, which is marked by cessation of breathing and other reflexes (including the pupillary reflex) controlled by the brainstem and by a zero reading on an electroencephalogram. Organs may be removed for transplantation when brain death is established, which may not necessarily be associated with permanent absence of heart beat.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"brain death." A Dictionary of Biology. . Encyclopedia.com. 13 Dec. 2017 <http://www.encyclopedia.com>.

"brain death." A Dictionary of Biology. . Encyclopedia.com. (December 13, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/brain-death

"brain death." A Dictionary of Biology. . Retrieved December 13, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/brain-death

brain death

brain death • n. irreversible brain damage causing the end of independent respiration, regarded as indicative of death.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"brain death." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 13 Dec. 2017 <http://www.encyclopedia.com>.

"brain death." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (December 13, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/brain-death

"brain death." The Oxford Pocket Dictionary of Current English. . Retrieved December 13, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/brain-death

brain death

brain death n. see death.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"brain death." A Dictionary of Nursing. . Encyclopedia.com. 13 Dec. 2017 <http://www.encyclopedia.com>.

"brain death." A Dictionary of Nursing. . Encyclopedia.com. (December 13, 2017). http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/brain-death

"brain death." A Dictionary of Nursing. . Retrieved December 13, 2017 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/brain-death