Brain Death and Disorders of Consciousness (Advances in Experimental Medicine and Biology)

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Human death is a single phenomenon. Human death is a single phenomenon occurring gradually as a process over time. There is a gradual loss of capacity for somatic integration of the whole body because of an irreversible cessation of all vital and biological functions including circulation, respiration controlled by the brain stem , and consciousness. The irreversibility of cessation of circulatory and respiratory functions is inter-linked to the onset of whole brain necrosis.

Arbitrary neurological criteria and circulatory criterion redefining human death in states of impaired consciousness enable heart-beating and non-heart-beating procurement of transplantable organs, respectively. Although brain-dead patients have no intracranial circulation and by definition only irreversible loss of spontaneous respiratory drive and consciousness, the heart and whole body circulation continue to function spontaneously in these patients, i.

Spontaneous circulation maintains many integrated biological functions in brain-dead patients that are indistinguishable from living human beings, and in some cases these patients can survive on mechanical ventilation for years Shewmon Some of the biological functions include wound healing, body temperature regulation, growth to puberty, reproduction, successful completion of pregnancies and delivery of healthy infants Truog Therefore, the concept of death based on only neurological criteria—i.

In the absence of sufficient empirical evidence for the concept of brain death, to salvage the concept of brain death and to continue support of the current practice of procuring organs from heart-beating donors, the Council proposes to ground this concept in a completely new philosophical rationale.

This rationale has not yet been the subject of public debate. However, some Council members have expressed dissent personal statements published in the white paper pp. In a separate commentary, Shewmon challenges the validity of the critical role of spontaneous breathing in defining living organisms Shewmon Therefore, brain death as a state of impaired consciousness and apnea continues to be challenged as a valid concept of human death because of continued insufficient scientific evidence and a less than convincing philosophical rationale.

Instead, as critics have postulated, the moment when a living organism is dead, and hence no longer alive is, conceptually, the moment when there is an irreversible cessation of integrative unity of the whole living organism Byrne and Weaver ; Joffe a ; Maruya et al. Defining death by neurological criteria has additional conceptual implications.

The reduction of any definition of death to exclusively neurological terms ignores the anthropologic, cultural, and religious dimensions that many people value highly. Cultural and religious traditions and beliefs about the treatment of the dead body, beliefs about life after death, and fears of mutilation can also influence decisions about organ donation p. Policies and practices for procurement of organs must be compatible with conditions deeply rooted in cultural, religious, and legal traditions p.

These traditions, however, greatly vary among global communities and pluralistic societies. Reduction of the definition of death to brain-based criteria ignores that the concept of death is not simply bioethical or biomedical in nature but fundamentally shaped and driven by a series of important sociologic influences Kellehear To the contrary, for many health care professionals and the general public, the concept of brain death is becoming increasingly abstract and socially disconnected from the nature of death Kellehear This paradoxical death, a brain-based determination of death with the physical image of a normally functioning body, creates emotional and cognitive conflicts for many health care professionals and family members Long et al.

Brain Death and Disorders of Consciousness : Calixto Machado :

What has actually happened in the history of this topic is [that] in we start with the practice. Then there is a revision of statutory laws. Then there is an attempt to come up with diagnostic standards. Then there is a scramble to find rationales for the statutory laws, and there is incoherence and lack of consensus about why destruction or total brain failure, whatever you want to call it, should be death. And so the actual history of brain death has followed exactly the opposite sequence of events that ought to characterize an ideal major socio-legal medical change.

The concept of brain death has been defined as an irreversible state of impaired consciousness diagnosed by universally approved criteria. Proponents also point out, what makes the determination of death accurate is the accuracy of following the rules: the practice guidelines that professional associations established for determining brain death Ivan and with contributions by Melrose In , The American Academy of Neurology published clinical guidelines for the clinical determination of brain death.

However, over the past decade, critics have increasingly scrutinized the scientific validity of these clinical guidelines for demonstrating that all brain functions have ceased irreversibly Joffe b , ; Karakatsanis ; Karakatsanis and Tsanakas ; Shewmon Clinical and histopathologic observations support that there are serious flaws in the clinical criteria used to declare brain death for heart-beating organ donation.

Several critical brain structures remain viable and continue integrated neurological functioning after clinically determined brain death. First, clinical observations suggest that heart-beating organ donors have residual brain functions, including hormonal and neural responses to nociception and pain during the procurement process Joffe b.

Surgical procurement, which is performed on donors without general anesthesia Keep , induces hemodynamic responses in donors that are similar to the responses of living organisms in distress Young and Matta The likelihood of incorrect declaration of brain death increases when the timeline necessary for determining irreversible cessation of critical brain functions is shortened because of early organ procurement.

Transplant advocates have recommended against performing confirmatory tests when declaring brain death in order to avoid a delay or deferral of organ donation Greer et al. Not performing confirmatory tests may also lead to catastrophic errors in the clinical determination of brain death. The absence of neuropathologic findings of profound brain stem ischemia can suggest reversible causes of coma or perhaps retained neurological activity undetected by clinical examination Walker More than one-third of the neurosurgeons surveyed also considered that some blood flow to the brain or a brain stem with minimal microscopic damage is incompatible with a clinical determination of brain death.

Accepting questionable clinical guidelines as the medical standard for early declaration of brain death and organ donation can have fatal consequences when patients whose condition may be salvageable, i. It is commonly claimed that, despite unresolved and debated issues about clinical determination of brain death, both the concept and the practice of declaring brain death for organ donation and transplantation have gained wide acceptance in most parts of the world.

The development of and adherence to practice guidelines to determine brain death are believed to have elicited universal compliance Ivan and with contributions by Melrose Recently, the inconsistency of the medical standard for the clinical determination of brain death for organ donation has been highlighted at leading US neurological hospitals Laureys and Fins This inconsistency has opened the door not only for loosening the accepted medical standard for the determination of brain death, but also for potentially sacrificing neurologically salvageable individuals for the sole purpose of organ procurement.

In a study by Mathur et al. Therefore, in this study, a significant proportion of donors may have been incorrectly declared as brain dead. Similar observations have been noted among adult donors as well; more than two-thirds of leading US neurological hospitals vary widely in their compliance with clinical guidelines for determining brain death before organ donation Greer et al. With the growing need for transplantable organs far exceeding the number of organs procured from brain-dead donors, an alternative criterion to declare death based on cessation of circulation was incorporated in the Pittsburgh NHBOD protocol DeVita and Snyder The circulatory criterion to declare death can be used for procuring transplantable organs from patients with other clinical states of impaired consciousness but who cannot be declared clinically brain dead Fig.

Circulatory arrest is determined by the loss of arterial pulse.

Is brain death a coherent and justified concept for determining death?

Nathan-Medscape Transplantation Ongoing debates indicate that not only the scientific validity of the circulatory criterion is questionable Joffe a but also that brain-based criteria of death contribute little, if anything, to defining the exact moment of death in NHBOD Shemie Coronary perfusion pressure is the gradient between asystolic diastolic arterial and central venous pressure subtracted from the intrapericardial pressure.

Autoresuscitation i. The presence of coronary and cerebral perfusion pressures after circulatory arrest can explain the Lazarus phenomenon and autoresuscitation in some of the reported cases. This observation is relevant not only because coronary and cerebral perfusion pressures are related to systemic blood flow, but it is also independently controlled by selective arterial and venous vasomotor tones vascular smooth muscles contraction and intrapericardial and intracranial pressures surrounding the heart and brain, respectively Rady et al.

Neuropathologic features of ischemia or necrosis of the whole brain and brain stem become integral observations to establish, with clinical certainty, irreversible apnea and unconsciousness when determining death by the circulatory criterion in NHBOD. From a legal perspective on determining death with cardiorespiratory criteria, the irreversibility of cessation of circulatory function is interlinked with the irreversibility of cessation of respiratory function of the brain stem National Conference of Commissioners on Uniform State Laws This point must be emphasized because the UDDA considers human death as a single phenomenon whether determined by neurological criteria or by cardiorespiratory criteria.

Considering death to be the total cessation of life processes characteristic of living organisms throws the practice of applying either circulatory or neurological criteria for declaring death for organ donation into question Fig. The exact moment when loss of circulation and loss of somatic integration occur is not known and, therefore, the concept of brain death adds little, if any, relevant information about how to determine the precise moment of death in human beings. Other states of impaired consciousness, besides brain death, include coma, akinetic mutism locked-in syndrome , minimally conscious state, and vegetative state.

Since , pressure has been growing to expand the recovery of transplantable organs from patients with other states of impaired consciousness, such as those in a vegetative state Hoffenberg et al. In August , a perspective roundtable discussion of organ procurement for transplantation echoed similar interest to abandon traditional neurological criteria for determining death The New England Journal of Medicine online ; Truog and Miller As highlighted in previous sections of this paper, several shortfalls exist regarding the scientific validity of the concept of brain death.

The unassailability of the clinical guidelines for the determination of not only brain death but also that of vegetative state has also been called into question. The American Academy of Neurology has described vegetative state with the following criteria: 1 no evidence of awareness of self or environment and an inability to interact with others; 2 no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli; 3 no evidence of language comprehension or expression; 4 intermittent wakefulness manifested by the presence of sleep-wake cycles; 5 sufficiently preserved hypothalamic and brain stem autonomic functions to permit survival with medical and nursing care; 6 bowel and bladder incontinence; and 7 variably preserved cranial nerves pupillary, oculocephalic, corneal, vestibulo-ocular, gag and spinal reflexes Report of the Quality Standards Subcommittee of the American Academy of Neurology Both brain death and PVS are possible outcomes of the comatose state, but, in PVS, the brain stem, which sustains functions such as respiration and circulation, has been spared injury.

Disorders of Consciousness Program

Because these patients may be allowed to die, they may be considered for organ donation; however, unless physician-assisted death is legalized, patients in PVS are ineligible to become organ donors Detry et al. Although some have advocated the acceptance of the concept of higher brain death so that organs from patients in permanent vegetative state can be used for transplantation Hoffenberg et al.

It is often postulated that patients in PVS are devoid of conscious content and cognitive and affective functions and that they have no behavioral evidence of awareness of their external environment Ivan and with contributions by Melrose A neurophysiologic explanation of impaired consciousness in PVS underpins this premise, although scientific observations and theory may not be capable of providing a complete account of consciousness Zeman Critics have countered, however, that the evidence from human brain imaging studies as well as neurological damage in animals and humans suggests that some form of consciousness can survive the brain damage that commonly causes vegetative state Panksepp et al.

Neuroscientific evidence indicates that raw emotional or affective feelings primary-process affects can exist without cognitive awareness of those feelings. The fact that patients in a PVS can have the capacity to experience affective feelings in the absence of any reflective awareness represents a diametrically opposite position to the one claiming that these patients are devoid of conscious content and cognitive and affective functions.

Brain Injury: Neuroscience and Neuroethics

Many aspects of human cognition can go on in the absence of reflective awareness. Functional neuroimaging methods have demonstrated that aspects of speech perception, emotional processing, language comprehension, and even conscious awareness might be retained in some patients who behaviorally meet all of the criteria that define PVS Owen and Coleman The diagnosis of PVS is made primarily based on clinical judgment and without performing static and functional neuroimaging and electrodiagnostic studies to confirm this diagnosis with certainty Wijdicks and Cranford When diagnosing vegetative state, clinicians may not be as meticulous in their thought processes as they should be, particularly because the need for transplantable organs has risen to the level of what has been called a national health crisis.

The risk of misdiagnosing another reversible condition as vegetative state is greater because the vegetative state is not as common as are other prolonged states of impaired consciousness. The clinical criteria for the diagnosis of vegetative state cannot be proven to be valid beyond doubt. The accurate determination of PVS requires, among other criteria, clear and robust standards that can be followed in a consistent fashion by the medical community Rifkinson-Mann Currently, there is neither consensus on the criteria that encompass the spectrum of PVS nor agreement on the criteria that distinguish this diagnosis from other states of impaired consciousness Cusack et al.

All of these open-ended questions and uncertainties surrounding the diagnosis of PVS The House of Representatives of the th General Assembly of the State of Delaware , as with brain-dead, indeed make it medically, ethically, and legally impossible to procure organs by following heart-beating procurement procedures in patients who are in a vegetative state.

Neuroscience and Brain Death Controversies: The Elephant in the Room

The scientific validity and accuracy of clinical guidelines declaring other states of impaired consciousness as unrecoverable within a few days after non-traumatic brain injury have also been called into question. The predictive accuracy of the American Academy of Neurology practice parameters have not been prospectively validated in either multicenter or multinational studies. Nevertheless, the practice parameters and clinical guidelines declaring states of impaired consciousness or coma unrecoverable within days have become essential prerequisites to facilitate early recovery of transplantable organs Fig.

It is commonly stated that all religions approve of organ donation Ivan and with contributions by Melrose ; Woien et al.

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It is commonly assumed, without further formal discussion among religious leaders, that the justification of the more recent protocols of organ procurement in NHBOD, including in other states of impaired consciousness, can be derived from the agreement, on principle, that organ donation is a genuine act of beneficence. However, recent events and developments in organ procurement procedures have triggered a response from religious institutions.

Scholars from diverse religious affiliations have revisited the opinions on brain death in light of contemporary medical knowledge Brown ; Diamond ; Kunin ; Shea The report recognizes that several major religious groups as well as some individuals with no faith group affiliation had major reservations about the concept of brain death and opposed organ donation from donors whose death has been defined solely on the basis of brain death. Several diverse religious groups oppose organ donation because of a fundamental belief that the human body is a trust that has been given and owned by God and, therefore, should not be physically violated by removing organs.