TRADITIONAL DEFINITION OF DEATH
The processes of human life are sustained by many factors, but oxygen is a key to life. Respiration and blood circulation provide the body's cells with the oxygen needed to perform their life functions. When an injury or a disease compromises respiration or circulation, a breakdown in the oxygen supply can occur. As a result, the cells, deprived of essential life-sustaining oxygen, deteriorate. Using the criteria of a working heart and lungs, defining death was once quite simple: a person was considered dead once he or she stopped breathing or was without a detectable heartbeat.
A NEW CRITERION FOR DEATH
Advances in medical science have complicated the definition of death. Life-saving measures such as cardiopulmonary resuscitation or defibrillation (electrical shock) can restart cardiac activity. The development of the mechanical respirator in the 1950s also prompted a change in the concept of death. An unconscious patient, unable to breathe without assistance, could be kept alive with a respirator and, based on the heart and lung criteria, the patient could not be declared dead.
Further complicating the issue was the transplantation of the first human heart. Experimental organ transplantation has been performed since the early 1900s. In the 1960s transplantation of organs such as kidneys became routine practice. Kidneys could be harvested from a patient whose heart had stopped and who therefore could be declared legally dead. By contrast, a successful heart transplant required a beating heart from a “dead” donor. On December 3, 1967, the South African surgeon Christiaan Barnard (1922–2001) transplanted a heart from a fatally injured accident victim into Louis Washkansky (1913–1967). Washkansky's health declined within a week after the surgery, and he died eighteen days later from pneumonia.
Physicians who had been debating how best to handle patients whose life functions were supported mechanically now faced a new dilemma. With the first successful heart transplant, such patients now became potential heart donors, and it became necessary to ensure that a patient was truly dead before the heart was actually removed. Thus, physicians proposed a new criterion for death: irreversible cessation of brain activity, or what many called brain death.
The Harvard Criteria
In 1968 the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death was organized. The goal of the Harvard Brain Death Committee, as it was also known, was to redefine death. On August 5, 1968, the committee published the report “A Definition of Irreversible Coma” (Journal of the American Medical Association, vol. 205, no. 6). This landmark report, known as the Harvard Criteria, listed the following guidelines for identifying irreversible coma:
- Unreceptivity and unresponsivity—the patient is completely unaware of externally applied stimuli and inner need. He or she does not respond even to intensely painful stimuli.
- No movements or breathing—the patient shows no sign of spontaneous movements and spontaneous respiration and does not respond to pain, touch, sound, or light.
- No reflexes—the pupils of the eyes are fixed and dilated. The patient shows no eye movement even when the ear is flushed with ice water or the head is turned. He or she does not react to harmful stimuli and exhibits no tendon reflexes.
- Flat electroencephalogram (EEG)—this shows lack of electrical activity in the cerebral cortex.
The Harvard Criteria could not be used unless reversible causes of brain dysfunction, such as drug intoxication and hypothermia (abnormally low body temperature—below 90·F core temperature), had been ruled out. The committee further recommended that the four tests be repeated twenty-four hours after the initial test.
The Harvard committee stated, “Our primary purpose is to define irreversible coma as a new criterion for death.” Despite this, the committee in effect reinforced brain death—a lack of all neurological activity in the brain and brain stem—as the legal criterion for the death of a patient. A patient who met all four guidelines could be declared dead, and his or her respirator could be withdrawn. The committee added, however, “We are concerned here only with those comatose individuals who have no discernible central nervous system activity.” Brain death differs somewhat from irreversible coma; patients in deep coma may show brain activity on an EEG, even though they may not be able to breathe on their own. People in a persistent vegetative state are also in an irreversible coma; however, they show more brain activity on an EEG than patients in deep coma and are able to breathe without the help of a respirator. Such patients were not considered dead by the committee's definition because they still had brain activity.
Criticisms of the Harvard Criteria
In 1978 Public Law 95-622 established the ethical advisory body called the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. President Ronald Reagan (1911–2004) assigned the commission the task of defining death. In Defining Death: Medical, Legal, and Ethical Issues in the Determination of Death (July 1981, http://www.bioethics.gov/reports/past_commissions/defining_death.pdf), the commission reported that “the ‘Harvard Criteria’ have been found to be quite reliable. Indeed, no case has yet been found that met these criteria and regained any brain functions despite continuation of respirator support.”
However, the commission noted the following deficiencies in the Harvard Criteria:
- The phrase “irreversible coma” is misleading. Coma is a condition of a living person. A person lacking in brain functions is dead and, therefore, beyond the condition called coma.
- The Harvard Brain Death Committee failed to note that spinal cord reflexes can continue or resume activity even after the brain stops functioning.
- “Unreceptivity” cannot be tested in an unresponsive person who has lost consciousness.
- The committee had not been “sufficiently explicit and precise” in expressing the need for adequate testing of brain stem reflexes, especially apnea (absence of the impulse to breathe, leading to an inability to breathe spontaneously). Adequate testing to eliminate drug and metabolic intoxication as possible causes of the coma had also not been spelled out explicitly. Metabolic intoxication refers to the accumulation of toxins (poisons) in the blood resulting from kidney or liver failure. These toxins can severely impair brain functioning and cause coma, but the condition is potentially reversible.
- Even though all people who satisfy the Harvard Criteria are dead (with irreversible cessation of whole-brain functions), many dead individuals cannot maintain circulation long enough for retesting after a 24-hour interval.
THE GOVERNMENT REDEFINES DEATH
The President's Commission proposed in Defining Death a model statute, the Uniform Determination of Death Act, the guidelines of which would be used to define death:
- [Determination of Death.] An individual who has sustained either (1) irreversible cessation of circulatory and respiratory functions, or (2) irreversible cessation of all functions of the entire brain, including the brain stem, is dead. A determination of death must be made in accordance with accepted medical standards.
- [Uniformity of Construction and Application.] This act shall be applied and construed to effectuate its general purpose to make uniform the law with respect to the subject of this Act among states enacting it.
In Defining Death, the President's Commission incorporated two formulations or concepts of the “whole-brain definition” of death. It stated that these two concepts were “actually mirror images of each other. The Commission has found them to be complementary; together they enrich one's understanding of the ‘definition’ [of death].”
The first whole-brain formulation states that death occurs when the three major organs (heart, lungs, and brain) suffer an irreversible functional breakdown. These organs are closely interrelated, so that if one stops functioning permanently, the other two will also stop working. Even though traditionally the absence of the “vital signs” of respiration and circulation have signified death, this is simply a sign that the brain, the core organ, has permanently ceased to function. Even if individual cells or organs continue to live, the body as a whole cannot survive for long. Therefore, death can be declared even before the whole system shuts down.
The second whole-brain formulation “identifies the functioning of the whole brain as the hallmark of life because the brain is the regulator of the body's integration.” Because the brain is the seat of consciousness and the director of all bodily functions, when the brain dies, the person is considered dead.
Reason for Two Definitions of Death
The President's Commission claimed in Defining Death that its aim was to “supplement rather than supplant [take the place of] the existing legal concept.” The brain-death criteria were not being introduced to define death in a new way. In most cases the cardiopulmonary definition of death would be sufficient. Only comatose patients on respirators would be diagnosed using the brain-death criteria.
Criteria for Determination of Death
The President's Commission did not include in the proposed Uniform Determination of Death Act any specific medical criteria for diagnosing brain death. Instead, it had a group of medical consultants develop a summary of currently accepted medical practices. The commission stated that “such criteria—particularly as they relate to diagnosing death on neurological grounds—will be continually revised by the biomedical community in light of clinical experience and new scientific knowledge.” These Criteria for Determination of Death read as follows (with medical details omitted here):
- An individual with irreversible cessation of circulatory and respiratory functions is dead. A) Cessation is recognized by an appropriate clinical examination. B) Irreversibility is recognized by persistent cessation of functions during an appropriate period of observation and/or trial of therapy.
- An individual with irreversible cessation of all functions of the entire brain, including the brainstem, is dead. A) Cessation is recognized when evaluation discloses findings that cerebral functions are absent and brainstem functions are absent. B) Irreversibility is recognized when evaluation discloses findings that the cause of coma is established and is sufficient to account for the loss of brain functions; the possibility of recovery of any brain functions is excluded; and the cessation of all brain functions persists for an appropriate period of observation and/or trial of therapy.
The Criteria for Determination of Death further warn that conditions such as drug intoxication, metabolic intoxication, and hypothermia may be confused with brain death. Physicians should practice caution when dealing with young children and people in shock. Infants and young children, who have more resistance to neurological damage, have been known to recover brain function. Shock victims might not test well due to a reduction in blood circulation to the brain.
The Brain-Death Concept and Brain-Death Criteria around the World
Since the development of brain-death criteria in the United States, most countries have adopted the brain-death concept. Nevertheless, determining brain death varies worldwide. One reason has to do with cultural or religious beliefs. For example, in Japan it is believed that the soul lingers in the body for some time after death. Such a belief may influence the length of time the patient is observed before making the determination of death.
Eelco F. M. Wijdicks of the Mayo Medical Center in Rochester, Minnesota, surveyed brain-death criteria throughout the world and reported his results in “Brain Death Worldwide: Accepted Fact but No Global Consensus in Diagnostic Criteria” (Neurology, vol. 58, no. 1, 2002). Wijdicks obtained brain-death guidelines for adults in eighty countries and determined that seventy of the eighty countries had guidelines for clinical practice in determining brain death. In examining these guidelines, Wijdicks finds major differences in the procedures used for diagnosing brain death in adults. For example, in some countries brain-death criteria are left up to the physician to determine, whereas in other countries written guidelines are extremely complicated. In some countries confirmatory laboratory tests are mandatory, whereas in others they are not. Because of these and many other differences in brain-death diagnostic criteria across countries, Wijdicks suggests that countries worldwide consider standardizing procedures to determine brain death.
What are the diagnostic criteria for determining brain death in the United States? In “Variability among Hospital Policies for Determining Brain Death in Adults” (Critical Care Medicine, vol. 32, no. 6, June 2004), David J. Powner, Michael Hernandez, and Terry E. Rives explain that there is no federally mandated definition for brain death or method for certifying brain death. Thus, states have adopted the Uniform Determination of Death Act as described in the previous section. However, within each hospital clinical practice is determined by the medical staff and administrative committees. The researchers studied six hundred randomly selected hospitals to determine whether differences exist among hospital policies for the certification of brain death. They determine that differences exist and suggest that policies be standardized. Wijdicks and Ronald E. Cranford list in “Clinical Diagnosis of Prolonged States of Impaired Consciousness in Adults” (Mayo Clinic Proceedings, vol. 80, no. 8, August 2005) clinical criteria for brain death. (See Table 2.1.)
In the editorial “The Clinical Criteria of Brain Death throughout the World: Why Has It Come to This?” (Canadian Journal of Anesthesia, vol. 53, no. 6, June 2006), Wijdicks emphasizes the variability of international brain-death guidelines, as well as the variability of hospital policies and practices in the United States. Wijdicks concludes that “what is required is standardization of policy, appropriate education of staff, introduction of checklists in intensive care units, and brain death examination by designated, experienced physicians who have documented proficiency in brain death examination.” David M. Greer et al. confirm in “Variability of Brain Death Determination Guidelines in Leading US Neurologic Institutions” (Neurology, vol. 70, no. 4, January 22, 2008) the continuing variation in determining brain death in the United States via a survey of leading neurologic hospitals.
|SOURCE: Eelco F.M. Wijdicks and Ronald E. Cranford, “Table 3. Clinical Criteria for Brain Death,” in “Clinical Diagnosis of Prolonged States of Impaired Consciousness in Adults,” Mayo Clinic Proceedings, vol. 80, no. August 2005, http://www.mayoclinicproceedings.com/pdf%2F8008%2F8008-r1%2Epdf (accessed March 25, 2008). Data from E.F.M. Wijdicks, “The Diagnosis of the Brain,” New England Journal of Medicine, no. 344 (2001): 1215–21.|
Absence of motor responses
Absence of pupillary responses to light and pupils at midposition with respect to dilatation (4–6 mm)
Absence of corneal reflexes
Absence of caloric responses
Absence of gag reflex
Absence of coughing in response to tracheal suctioning
Absence of respiratory drive at PaCO2 that is 60 mm Hg or 20 mm Hg above normal baseline values
Brain Death and Persistent Vegetative State
In the past people who suffered severe head injuries usually died from apnea. In the twenty-first century rapid emergency medical intervention allows them to be placed on respirators before breathing stops. In some cases the primary brain damage may be reversible, and unassisted breathing eventually resumes. In many cases, however, brain damage is irreversible, and, if the respirator is not disconnected, it will continue to pump blood to the dead brain.
The brain stem, traditionally called the lower brain, is usually more resistant to damage from anoxia (oxygen deprivation). Thus, oxygen deprivation may cause irreversible damage to the cerebrum, or higher brain, but may spare the brain stem. (See Figure 2.1.) When the cerebrum is irreversibly damaged yet the brain stem still functions, the patient goes into a persistent vegetative state, also called persistent noncognitive state. Persistent vegetative state patients, lacking in the higher-brain functions, are awake but unaware. They swallow, grimace when in pain, yawn, open their eyes, and may even breathe without a respirator. Table 2.2 lists the criteria for the diagnosis of the persistent vegetative state.
The case of Karen Ann Quinlan called attention to the ramifications of the persistent vegetative state. In 1975 Quinlan suffered a cardiopulmonary arrest after ingesting a combination of alcohol and drugs. In 1976 Joseph Quinlan was granted court permission to discontinue artificial respiration for his comatose daughter. Even after life support was removed, Karen remained in a persistent vegetative state until she died of multiple infections in 1985.
|SOURCE: Eelco F.M. Wijdicks and Ronald E. Cranford, “Table 1. Criteria for the Diagnosis of a Persistent Vegetative State,” in “Clinical Diagnosis of Prolonged States of Impaired Consciousness in Adults,” Mayo Clinic Proceedings, vol. 80, no. 8, pp. 1037–1046, August 2005. Reproduced with permission from Dowden Health Media.|
A more recent case that has refocused national attention on the persistent vegetative state is that of Terri Schiavo, who entered a persistent vegetative state in 1990, when her brain was deprived of oxygen during a heart attack brought on by an eating disorder. Her husband argued that she would never recover and that his wife would not want to be kept alive by artificial means. He petitioned a Florida court to remove her feeding tube. In October 2003 a Florida judge ruled that the tube should be removed. However, Schiavo's parents believed their daughter would recover and requested that the Florida governor Jeb Bush (1953–) intervene. The Florida legislature subsequently gave Governor Bush the authority to override the courts, and the feeding tube was reinserted six days after its removal.
In May 2004 the law that allowed Governor Bush to intervene in the case was ruled unconstitutional by a Florida appeals court. The case was then appealed to the U.S. Supreme Court, which in January 2005 refused to hear the appeal and reinstate the Florida law. In March 2005 doctors removed Terri Schiavo's feeding tube. She died thirteen days later. An autopsy showed extensive damage throughout the cerebrum.
Patients in a persistent vegetative state are not dead, and so the brain-death criteria do not apply to them. They can survive for years with artificial feeding and antibiotics for possible infections. The President's Commission reported on a patient who remained in a persistent vegetative state for thirty-seven years: Elaine Esposito lapsed into a coma after surgery in 1941 and died in 1978.
THE NEAR-DEATH EXPERIENCE
The term near-death experience was first used by Raymond A. Moody Jr. in Life after Life: The Investigation of a Phenomenon—Survival of Bodily Death (1976), a compilation of interviews with people who claimed to have come back from the dead. A decade earlier, Elisabeth K¨bler-Ross investigated out-of-body episodes recounted by her patients.
The near-death experience is not a phenomenon limited to modern times. It has been recounted in various forms of mysticism, as well as by well-known historical figures such as the Greek philosopher Plato (428–348 B.C.) and the Benedictine historian and theologian St. Bede (673–735). It appears, however, that the development and administration of emergency resuscitation has contributed to widespread reports of near-death experiences.
Some people who were revived after having been declared clinically dead have recounted remarkably similar patterns of experiences. They report leaving their body and watching, in a detached manner, while others tried to save their life. They felt no pain and experienced complete serenity. After traveling through a tunnel, they encountered a radiant light. Some claim they met friends and relatives who have died; many attest to seeing their whole life replayed and of ultimately being given either a choice or a command to return to their body.
Many people who have had a near-death experience believe they have undergone a spiritual event of great importance. For example, they may believe that they saw, or even entered, the afterlife. Studies conducted during the 1990s indicated that the near-death experience might be related to one or more physical changes in the brain. These changes include the gradual onset of anoxia in the brain; residual electrical activity in the brain; the release of endorphins in response to stress; or drug-induced hallucinations produced by drug therapies used during resuscitation attempts or resulting from previous drug abuse.
Not everyone who has been close to death has had a near-death experience. These experiences are atypical reactions to trauma, and the involvement of the temporal lobes of the brain in these experiences has been explored by researchers for decades. In “Near-Death Experiences and the Temporal Lobe” (Psychological Science, vol. 15, no. 4, April 2004), Willoughby Britton and Richard Bootzin discuss the results of their study of temporal lobe functioning in forty-three individuals who had experienced life-threatening events. Of these forty-three participants, twenty-three reported having had near-death experiences during these events. The researchers find that people who reported near-death experiences had more of certain types of temporal lobe activity than those who did not have such experiences. The researchers conclude that “altered temporal lobe functioning may be involved in the near-death experience and that individuals who have had such experiences are physiologically distinct from the general population.”