A recent study conducted in dying patients, published in the journal Philosophy, Ethics, and Humanities in Medicine (1), was able to demonstrate how the global cerebral hypoxia that occurs in these patients after withdrawal of their ventilatory support markedly stimulated the brain activity recorded on an electroencephalogram (gamma activity) in some individuals. As the study authors highlight, this finding suggests that a patient’s brain may still be very active during the dying process. The conclusions of this study also suggest the need to reevaluate the role of the brain during cardiac arrest.

The aforementioned gamma activity recorded on electroencephalogram (a pattern of brain waves found in the frequency of around 30 to 100 hertz) is not a manifestation of residual brain activity; on the contrary, these gamma waves are high-frequency and are commonly associated with higher cognitive processes, such as sensory perception, memory, attention, and information processing. Gamma activity in healthy people is particularly noticeable during situations where increased mental activity is required, such as learning, problem solving, and intense concentration. It has been observed that the synchronization of gamma activity in different regions of the brain is related to information integration and the coordination of cognitive functions.

This and other similar studies confirm the erroneous belief that neuronal activity decreases during the near-death stages in all patients. Experimental animal studies have found that phase coupling between gamma brainwaves and alpha and theta brainwaves occurs in the first 30 seconds after cardiac arrest and is accompanied by an increase in gamma brainwaves. Similar increases in brainwave activity have also been observed during asphyxia and hypercapnia events.

The discovery of these electrical brain phenomena forces us to make several considerations of the dying process, including:

How should we interpret the fact that brain activity increases during the dying process in humans?

How long should we wait to establish a diagnosis of death after cardiac arrest?

Do patients in whom asystolic organ donation is performed present the same brain phenomena described in other dying patients?

Is it ethically correct to make the diagnosis of death if brain activity still persists during the period of aystole?

There is a majority agreement — clinical and legal — that death of the human being can be established, from an organic point of view, when there is complete and irreversible cessation of brain functions. The diagnosis of death through verification of the irreversible absence of brain activity (brain death) has been accepted for decades as death of the person. However, it should not be forgotten that lack of cardiac activity is not synonymous with death, since the cessation of heart activity is not necessarily accompanied by the immediate cessation of brain activity. Moreover, the efficacy of cardiopulmonary resuscitation performed after cardiac arrest has been demonstrated, finding that it may not only reverse it, but, in a considerable percentage of patients, achieve restitutio ad integrum (complete recovery) of brain functions. Although there is ample experimental and clinical evidence showing that cardiac and respiratory arrest, the main mechanisms that trigger death, cause complex time-dependent changes in neuronal activity that sometimes lead to brain death, it is also true that brain damage can be reversed with successful resuscitation.

Based on the foregoing, it should be inferred that cardiac arrest should only be considered a sign of death when the cessation of cardiac activity is irreversible and is also accompanied by irreversible cessation of brain activity. Therefore, after a cardiac arrest, with no intent to resuscitate, the diagnosis of death of the person can be established after sufficient time has elapsed for the cessation of circulatory activity to be accompanied by the cessation of brain electrical activity. However, the aforementioned electroencephalographic studies suggest that some time must elapse after cardiac arrest to establish the diagnosis of death (enough for integrated neuronal activity to cease).

The fact that there are discrepancies between different authors on how much time is needed after the cessation of cardiac activity to determine that the cessation of brain activity is irreversible may lead us to conclude that the establishment of particularly short times (such as those established by some legal frameworks) could lead to the diagnosis of death being established in patients in whom brain activity not only persists, but may also potentially fully recover.

Evidence of the discrepancies for establishment of the diagnosis of death after cardiac arrest is the fact that there are significant disagreements in the temporal criteria required for the diagnosis of death in so-called “non-heart-beating donors” (2). While this type of donation is prohibited in some countries, such as Germany, in those where it is legislated, the “no-touch time” (time from the complete cessation of cardiac activity until the steps for organ harvesting can be initiated) shows extreme variations. Thus, some countries consider that only 2 minutes of asystole are needed for death to be declared, 5 minutes are required in Spain, and 10 minutes in Switzerland, Austria and the Czech Republic, while in Italy the mandatory time is 20 minutes.

Philosophically, death is the irreversible state where the integrative unity of the body as a whole has been lost; the body is no longer more than the sum of its parts, and irreversibly cannot resist the disintegration entailed by the forces of entropy. When we talk about death, it is useful to review the models used to explain it: death is a biological/ontological event that cannot be changed. According to J.L. Bernat, death is the event that separates the process of dying (one is still alive, although death is imminent) from bodily disintegration (3). The same author argues that death is a univocal state of an organism, and irreversible (“if the event of death were reversible it would not be death but rather part of the process of dying that [was] interrupted and reversed”) (4).

It is important to take into consideration the ordinary meaning of the term “irreversible”, which is “not capable of being reversed” and “depends on what physically can or cannot be done”. The clear meaning is that “no known intervention could have eliminated it”.

In the case of patients in whom cardiac activity has ceased, with persistence of brain activity, we can consider that it is a “reversible” situation (“capable of being reversed”), and given the possibility of reversibility, this situation could not be considered permanent.

The main advocates of non-heart-beating donation have argued that death is not primarily an ontological or moral issue, but rather “fundamentally a medical practice issue” (2). In addition, they argue that when doctors usually declare death based on cardiocirculatory criteria, they declare it based on the cessation of cardiac activity, without a waiting period.

These claims are misleading and inaccurate. Death of the person is an ontological concept, with physiological bases and moral extension. Moreover, it is important to establish whether the patient “is dying” or “is dead.” The process of dying is not synonymous with death. It is therefore important to establish not only the permanence of the situation, but also its irreversibility, where irreversibility means “not capable of being reversed” and not “that there is no intent to reverse”.

When a situation is not reversed it is considered “permanent”, but if a condition can never be reversed, it is considered “irreversible”. In other words, irreversibility entails permanence; permanence does not entail irreversibility.

The consensus on the moral acceptability of non-heart-beating donation sustains the weak construal of the equivalence of “irreversibility” and “permanence.”

The existence of brain activity during the early stages after cardiac arrest demonstrated in numerous studies (such as the one cited at the beginning of this article) should not only lead us to consider the importance of the persistence of characteristics of persons in the human corporeality — and consequently the incompatibility with the diagnosis of death — but also leads us to consider this stage of the dying process as an important period of life that must be accompanied from a medical, as well as a spiritual, perspective.

José María Domínguez

Bioethics Observatory- Institute of Life Sciences

Catholic University of Valencia


  1. Xu G, Mihaylova T, Li D, Tian F, Farrehi PM, Parent JM, et al. Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain. Proc Natl Acad Sci U S A. 2023;120(19):e2216268120.
  2. Joffe AR, Carcillo J, Anton N, deCaen A, Han YY, Bell MJ, et al. Donation after cardiocirculatory death: a call for a moratorium pending full public disclosure and fully informed consent. Philos Ethics Humanit Med. 2011;6:17.
  3. Bernat JL. Are organ donors after cardiac death really dead? J Clin Ethics. 2006;17(2):122-32.
  4. Bernat JL. How the distinction between «irreversible» and «permanent» illuminates circulatory-respiratory death determination. J Med Philos. 2010;35(3):242-55.


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