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Brain death is the irreversible end of brain activity (including involuntary activity necessary to sustain life) due to total necrosisverification needed of the cerebral neurons following loss of brain oxygenationverification needed. It should not be confused with a persistent vegetative state.
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" (death of the cerebrum), the US National Library of Medicine Medical Subject Headings (MeSH) 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 (which includes brain stem death), only life support equipment would keep those functions going.
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 (or indicator) of death was Finland, in 1971. In the United States, Kansas had enacted a similar law earlier.1 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.2
An ad hoc committee at Harvard Medical School published a pivotal 1968 report to define irreversible coma.3 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 4 – 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 brainstem dysfunction as an indicator of death.citation needed
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 (fixed pupils), 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 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; 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.citation needed
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 (brain stem function in UK),5 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-adopted6 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.
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.7 Zack Dunlap in 2008 had a false positive of this type, likely due to temporary cerebral edema.
- Brainstem death
- Clinical death
- Persistent vegetative state
- Information-theoretic death
- Consciousness after death
- (Randell T. (2004). "Medical and legal considerations of brain death". Acta Anaesthesiologica Scandinavica 48 (2): 139–144. doi:10.1111/j.0001-5172.2004.00304.x. PMID 14995934.
- Epstein, Sue (April 28, 2010). "N.J. court to rule whether hospitals may refuse life support despite wishes of families, patients". NJ.com. Retrieved March 5, 2014.
- Life-sustaining Technologies and the Elderly
- "Defining death: a report on the medical, legal and ethical issues in the determination of death".
- Waters, C. E.; French, G.; Burt, M. "Difficulty in brainstem death testing in the presence of high spinal cord injury". British Journal of Anaesthesia 92 (5): 762. doi:10.1093/bja/aeh117.
- "Legislative Fact Sheet – Determination of Death Act". Uniform Law Commission. Retrieved 8 May 2012.
- Murray, Stephen. “Brain Death: Some of the Questions and Answers,” The Philosopher (Journal of the English Philosophical Society), Spring 1990, 1–12. http://www.the-philosopher.co.uk/contents.htm
- Lock M. Twice Dead: Organ Transplants and the Reinvention of Death. 2002, University of California Press, Berkeley, CA.
- Howsepian AA. In defense of whole-brain definitions of death. Linacre Quarterly. 1998 Nov;65(4):39–61. PMID 12199254
- Karasawa H, et al. Intracranial electroencephalographic changes in deep anesthesia. Clin Neurophysiol. 2001 Jan;112(1):25–30. PMID 11137657
- Brain Death from the Encyclopedia of Death and Dying
- How Stuff Works – Brain Death
- Textbook section
- 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
- An extensible bibliography: „Brain Death“: Alive body – dead person?
- Describing Life to Define Death. MEDICC Rev. 2010;12(4):40.