Physicians could not reliably diagnose death in all cases until the early nineteenth century when a new technology, the stethoscope, was invented and medical scientists began to understand cardiorespiratory anatomy and physiology. Ironically, it was the introduction in the late twentieth century of more new technologies, such as the mechanical ventilator, that once again caused uncertainty about the definition and determination of death.
Before life-sustaining technology was introduced, critical vital functions such as heartbeat, breathing, and brain activity were so interdependent that when one function ceased, they all did. For example, when a person suffered a massive heart attack and cardiac arrest, breathing and consciousness were lost almost simultaneously because the heart pumps nutrient rich, oxygenated blood to the brain and the rest of the body. If a person stopped breathing, say from drowning, heartbeat and consciousness were almost immediately lost for the same reason—no oxygen reached the brain and heart. Similarly, when a massive brain injury occurred, consciousness and spontaneous breathing stopped because of destruction of the respiratory center in the brain stem. There was thus no need to choose between cardiac, respiratory, and brain function as the unique function whose loss signaled the transition from human being to corpse.
With the introduction of the mechanical ventilator and the modern intensive care unit (ICU), patients with severe head injuries, who previously would have died, were sustained with beating hearts and healthy functioning of all other organs such as kidney, liver, and pancreas. These patients, when they have lost all brain function, are termed "brain dead." In 1968 an ad hoc committee at Harvard Medical School proposed that such patients, who were legally and medically considered to be alive, be classified as dead.
Two Types of Death
Although brain death as death was quickly accepted in the United States by legal and medical communities and, seemingly, by the public at large, new debates began, at least in academic circles, about just what made these warm, pink, heart-beating patients dead. Interestingly, the Harvard Ad Hoc Committee did not address this issue. Rather, they gave two utilitarian reasons to reclassify brain-dead patients as dead. Brain death is relatively easy to diagnose and the prognosis is dismal: No person accurately diagnosed has ever recovered consciousness and, at least in the first decade, brain-dead patients were very unstable and would suffer cardiovascular collapse and "traditional" death within hours or days. Therefore, many people saw no point in keeping brain-dead patients "going" by mechanical ventilation. But in 1968, U.S. society had no experience with the removal of life-sustaining treatment (something that in the twenty-first century happens daily in leading hospitals), and physicians feared they would be charged with homicide if they turned off the ventilator. The Ad Hoc Committee suggested that by declaring such patients dead, this fear would be removed.
The second reason given by the Ad Hoc Committee had to do with organ transplantation, which was becoming an increasingly effective treatment for end-stage organ failure. Because of all the life remaining in brain-dead patients, they were potentially an excellent source of organs. But taking their vital organs would violate the so-called dead donor rule that forbids killing patients by removing their organs. Classifying them as dead would avoid this problem and quell any controversy.
It was not until 1981 that a coherent philosophical or conceptual argument was put forth to explain why brain-dead patients were actually dead. In that year, in a landmark article, James L. Bernat and his colleagues at Dartmouth College proposed that the integrating function of the brain stem was the critical one whose loss marked the transition from life to death. Bernat went on to explain that loss of integration meant the permanent cessation of functioning of the "organism as a whole"—that is, the loss of "spontaneous and innate activities carried out by all or most subsystems" and "the body's ability to organize and regulate itself" (Bernat, Culver, and Gert 1981, p. 390). He gave as examples neuroendocrine control, temperature regulation, and the ability to maintain blood pressure and fluid and electrolyte balance. Bernat gave no significance to another important brain function, consciousness and cognition.
In simple terms, the brain has two major functions. The integrative function, which Bernat found critical, resides primarily in the brain stem, the primitive part of the brain that lies buried under the much larger cerebral hemispheres, which are most developed in higher animals, especially primates. Consciousness and cognition reside primarily in the cerebral hemispheres.
Although brain death was quickly accepted legally and clinically throughout the United States, many philosophers (Veatch 1976, Bartlett and Youngner 1988, Gervais 1986) argued that consciousness and cognition were the critical functions that distinguished a living from a dead person. Their criticism was twofold. First, the integrative function was not actually lost; it was merely taken over from the brain stem by machines and ICU personnel who kept patients alive by breathing for them and maintaining blood pressure and other vital activities. Second, consciousness and cognition more accurately reflect what is unique about human beings—the function without which they are dead. In contrast to Bernat, who argued that loss of integrative function is what humans have always meant by death, his critics argued what people really care about is whether or not there is anybody home.
In fact, studies of health professionals have indicated that while some accept brain death as death because of loss of integrative function, an equal number do so because the patient has permanently lost consciousness and cognition (Youngner 1989). Interestingly, these studies also demonstrate that many health professionals do not really consider brain-dead patients to be dead, but rather good as dead because they will die soon despite intervention and have an unacceptable quality of life. A later study demonstrated a similar diversity of opinion and belief among the general public (Siminoff, Burant, and Youngner 2004).
Other problems with brain death have emerged. First, although the clinical and legal criteria inevitably call for loss of all brain functions, it turns out that clinical tests commonly used to assure the criterion has been fulfilled simply do not test for some functions that often remain (Halevy and Brody 1993). For example, the production of vasopressin, a hormone essential for maintaining fluid and electrolyte balance, continues in many patients declared brain dead. Bernat responded to the dilemma by saying that it is only critical functions that count, but gave little guidance about how to distinguish critical from noncritical ones (Bernat 1998).
A second problem with brain death is that the clinical course of patients who have been declared brain dead is not as certain as when the syndrome was first encountered in the 1960s. Then, patients who were brain dead were notoriously unstable and suffered cardiovascular collapse and cardiac arrest within hours or days. Now, with more clinical experience and more sophisticated interventions, brain-dead patients can survive the period of instability to enter a chronic state in which they can be maintained at home with little more than ventilatory support. Some have continued in this state for months and years (Shewmon 1998). An editorial in a prominent neurology journal proclaimed "even the dead are not terminally ill anymore" (Cranford 1998, p. 1530), an ironic statement that captures much of the ambiguity surrounding clinical states in which some, but not all, vital functions remain.
Despite the ambiguities about brain death and how poorly it is understood by the public, acceptance of brain death at the public policy level seems fairly solid. The prognosis for brain-dead patients is uniformly bleak, even for those retaining residual brain functions such as the production of vasopressin. None ever recover consciousness, and most die traditional deaths within days. Moreover, unlike abortion, brain death remains off the radar screen of the religious right, which is very concerned about a culture of death in the United States that reduces human dignity and value. Perhaps brain death was "grandfathered in" before the religious right was politically galvanized by Roe v. Wade in 1973.
Interestingly, while brain death was quickly accepted and remains relatively uncontroversial in the United States, the situation is quite different in some other countries, most notably Japan, where brain death was not recognized by law until 1997. Patients who have lost brain function may be declared dead only for the purpose of organ transplantation, and then only if both the patient, when living, and the family, after death, have signed written documents. Unlike in the United States, brain death has been the subject of much public discussion and controversy for more than four decades, including the publication of more than 100 books on the subject for the general public and its inclusion as subject matter in popular comic books for children (Lock 2002). While not as contentious as it is in Japan, the debate over brain death in Denmark and Germany has been much stormier than that in the United States.
Because of the growing gap between the demand and supply for transplantable organs, it is unlikely that brain death will become a subject of controversy in the United States. Controversy is more likely to come if desperate patients and transplanters try to expand the current definition of death to include patients with brain injuries less severe than brain death.
STUART J. YOUNGNER
Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death. (1968). "A Definition of Irreversible Coma." Journal of the American Medical Association 205(6): 337–340. This landmark article introduced the concept of brain death to the medical community and lay public nearly 40 years ago.
Bartlett, Edward T., and Stuart J. Youngner. (1988). "Human Death and the Destruction of the Human Cortex." In Death: Beyond Whole-Brain Criteria, ed. Richard M. Zaner. Dordrecht, Netherlands: Kluwer Academic.
Bernat, James L. (1998). "A Defense of the Whole-Brain Concept of Death." Hastings Center Report 28(2): 14–23.
Bernat, James L.; Charles M. Culver; and Bernard Gert. (1981). "On the Definition and Criterion of Death." Annals of Internal Medicine 94: 389–394.
Cranford, Ronald. (1998). "Even the Dead Are Not Terminally Ill Anymore." Neurology 51(6): 1530–1531.
Halevy, Amir, and Baruch Brody. (1993). "Brain Death: Reconciling Definitions, Criteria, and Tests." Annals of Internal Medicine 119: 519–525.
Shewmon, D. Alan. (1998). "Chronic 'Brain Death': Meta-Analysis and Conceptual Consequences." Neurology 51(6): 1538–1545.
Siminoff, Laura; Burant, Christopher; and Youngner, Stuart J. (2004). "Death and Organ Procurement: Public Beliefs and Attitudes." Social Science & Medicine 59(11): 2325–2234.
Youngner, Stuart J.; C. Seth Landefeld; Claudia J. Coulton; et al. (1989). "Brain Death and Organ Retrieval: A Cross-Sectional Survey of Knowledge and Concepts among Health Professionals." Journal of the American Medical Association 261(15): 2205–2210.
Youngner, Stuart J.; Robert M. Arnold; and Renie Schapiro, eds. (1999). The Definition of Death: Contemporary Controversies. Baltimore: Johns Hopkins University Press. A collection of essays about problems in the diagnosis and determination of death from philosophical and clinical perspectives.
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.
See also coma; life support; organ donation; vegetative state.
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.
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):37–46.
ALFRED R. MARTIN
brain death • n. irreversible brain damage causing the end of independent respiration, regarded as indicative of death.