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Encyclopedia > Brain death

Brain death is defined as a complete and irreversible cessation of brain activity. Absence of apparent brain function is not enough. Evidence of irreversibility is also required. Brain-death is often confused with the state of vegetation. Comparative brain sizes In the anatomy of animals, the brain, or encephalon (Greek for in the head), is the higher, supervisory center of the nervous system. ... The point of no return or the Rubicon is the point at which someone, or some group of people, must continue on their current course of action. ... A persistent vegetative state (PVS) is a condition of patients with severe brain damage in whom coma has progressed to a state of wakefulness without detectable awareness. ...


Traditionally, death has been defined as the cessation of all body functions, including respiration and heartbeat. Since it became possible to revive some people after a period without respiration, heartbeat, or other visible signs of life, as well as to maintain respiration and blood flow artificially using life support treatments, an alternative definition for death was needed. In recent decades, the concept of "brain death" has emerged. By brain-death criteria, a person can be pronounced legally dead even if the heart continues to beat due to life support measures. Death is the cessation of physical life in a living organism or the state of the organism after that event. ... With regard to living things, a body is the integral physical material of an individual, and contrasts with soul, personality and behavior. ... Respiration is the process of exchanging oxygen and carbon dioxide between an organism and its external environment (breathing). ... The heart rate is the number of contractions of the heart in one minute. ... Life is a multi-faceted concept. ... Blood flow is the flow of blood in the cardiovascular system. ... Life support, in the medical field, refers to a set of therapies for preserving a patients life when essential body systems are not functioning sufficiently to sustain life unaided. ...


A brain-dead individual has no electrical activity and no clinical evidence of brain function on neurologic examination (no response to pain, no cranial nerve reflexes (pupillary response (fixed pupils), oculocephalic reflex, corneal reflexes), and no spontaneous respirations). It is important to distinguish between brain death and states that mimic brain death (eg. barbiturate intoxication, alcohol intoxication, sedative overdose, hypothermia, hypoglycemia, coma or chronic vegetative states). Some comatose patients can recover, and some patients with severe irreversible neurologic dysfunction will nonetheless retain some lower brain functions such as spontaneous respiration, loss of both cortex and brainstem function. Thus anencephaly, in which there is no higher brain present, is generally not considered brain death, although it is certainly an irreversible condition in which it may be appropriate to withdraw life support. EEG can mean: Electroencephalography - the method and science of recording and interpreting traces of brain electrical activity as recorded from the skull surface or the device used to record such traces Emperor Entertainment Group - A Hong Kong entertainment company. ... Neurology is a branch of medicine dealing with the nervous system and its disorders. ... Pain is an unpleasant sensation which may be associated with actual or potential tissue damage and which may have physical and emotional components. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... A reflex action or reflex is a biological control system linking stimulus to response and mediated by a reflex arc. ... In medicine, pupil constriction (also known as the pupillary reflex) is reduction of pupil size. ... In medicine, the oculocephalic reflex, also dolls eye reflex, is an eye movement to maintain forward gaze in response to neck rotation. ... Corneal reflex This is an automated involuntary blinking of the eyelids (See : Reflex) elicited by stimulation (such as touching or a foreign body) of the eyeballs cornea. ... Barbiturates are drugs that act as central nervous system (CNS) depressants, and by virtue of this they produce a wide spectrum of effects, from mild sedation to anesthesia. ... ... In general usage, alcohol (from Arabic al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ... A sedative is a drug that depresses the central nervous system (CNS), which causes calmness, relaxation, reduction of anxiety, sleepiness, slowed breathing, slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes. ... Hypothermia is a medical condition in which the victims core body temperature has dropped to significantly below normal and normal metabolism begins to be impaired. ... Hypoglycemia is a medical term referring to a pathologic state produced by a lower than normal amount of sugar (glucose) in the blood. ... This article is in need of attention from an expert on the subject. ... A persistent vegetative state (PVS) is a condition of patients with severe brain damage in whom coma has progressed to a state of wakefulness without detectable awareness. ... Cephalic disorders are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system. ...


Note that brain electrical activity can stop completely, or apparently completely (a "flat EEG") for some time in deep anaesthesia or during cardiac arrest before being restored. Brain death refers only to the permanent cessation of electrical activity. Numerous people who have experienced such "flat line" experiences have reported near-death experiences, the nature of which is controversial. Electroencephalography is the neurophysiologic exploration of the electrical activity of the brain by the application of electrodes to the scalp. ... Anesthesia (AE), also anaesthesia (BE), is the process of blocking the perception of pain and other sensations. ... Ascent in the Empyrean (Hieronymous Bosch) A near-death experience (NDE) is the perception reported by a person who nearly died or who was clinically dead and revived. ...


It is presumed that a permanent cessation of electrical activity indicates the end of consciousness. Those who view the neo-cortex of the brain as solely responsible for consciousness, however, argue that only electrical activity there should be considered when defining death. In many cases, especially when elevated intracranial pressure prevents blood flow into the skull, the entire brain is nonfunctional; however, some injuries may affect only the neo-cortex. Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ... In the anatomy of animals, the neopallium or neocortex is a part of the telencephalon in the brain. ... Intracranial pressure, or ICP, is the pressure of the brain, Cerebrospinal fluid (CSF), and the brains blood supply within the intracranial space. ... A hippopotamuss skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ...


The diagnosis of brain death needs to be made quite rigorously to be certain the condition is truly irreversible. Legal criteria vary from place to place, but generally require neurologic exams by two independent physicians showing complete absence of brain function, and may include two isoelectric (flat-line) EEGs 24 hours apart. The proposed Uniform Determination Of Death Act in the United States is an attempt 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. The Uniform Definition of Death Act was a law proposed by the National Conference of Commissioners on Uniform State Laws to define the legal meaning of death. ... Atoms of chemical elements may have many isotopes (different forms) with different atomic numbers and different atomic weights. ...


Most organ donation for organ transplantation is done in the setting of brain death. In some nations (for instance, Belgium, Poland and Portugal) everyone is automatically an organ donor, unless you get a special attest stating that you are not an organ donor. In others, consent from family members or next-of-kin is required. 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. An organ transplant is the transplantation of an organ (or part of one) from one body to another, for the purpose of replacing the recipients damaged or failing organ with a working one from the donor. ...


The term brain death was used briefly in the 1985 Horror/Comedy Re-Animator (based on H.P. Lovecraft's short story Herbert West, Re-Animator) in which Herbert West has conquered brain death by creating a re-agent which re-animates bodies & parts back to life. Although after re-animated, the bodies/parts become incredibly animate, so much that they tend to use uncontrollable force to anything without any regard of right or wrong. Re-Animator is the first in a series of films based on an H.P. Lovecraft story made in 1985 starring Jeffrey Combs as Dr. Herbert West. ... H. P. Lovecraft Howard Phillips Lovecraft (August 20, 1890 – March 15, 1937) was an American author of fantasy and horror fiction, noted for giving horror stories a science fiction framework. ...


References

  • 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

See also


  Results from FactBites:
 
Howstuffworks "How Brain Death Works" (520 words)
The diagnosis of "brain death" is only possible because of modern medicine's ability to maintain the functions of supporting organs of the body after the brain is no longer viable.
Once the examination of the brain has determined that it is no longer viable and there is no chance of any recovery of function, the "brain death" diagnosis is made.
Families of a brain dead patient must, by federal regulations, be provided the option of organ donation.
  More results at FactBites »

 
 

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