Kenneth Glad
A presentation at a leading scientific conference is reigniting debate over one of medicine’s most fundamental definitions. Doctors and researchers are now taking a closer look at how the end of life is determined in modern hospitals.
In a carpeted breakout room at the American Association for the Advancement of Science (AAAS) annual meeting, a session on resuscitation science drew a steady crowd, reports LadBible. The topic was clinical: What happens in the brain after the heart stops.
According to research presented at the conference, neurological shutdown may not be instantaneous. Anna Fowler, a student researcher at Arizona State University, told conference attendees that emerging evidence suggests that “biological and neural functions do not cease abruptly,” but instead taper off over minutes — and in some cases longer.
Her presentation drew on peer-reviewed cardiac arrest research published over the past decade, including findings from the AWARE (AWAreness during REsuscitation) studies led by Dr. Sam Parnia and colleagues.
A decade of Research
Results reported in journals such as Resuscitation and The Lancet between 2014 and 2023 found that roughly 15 to 20 percent of successfully resuscitated cardiac arrest patients described some form of conscious experience while undergoing CPR.
In several of those cases, patients showed no outward responsiveness and had low or flat readings on electroencephalograms (EEGs) — a test that measures electrical activity in the brain using sensors placed on the scalp.
Standard bedside monitors did, writes LadBile, not detect organised patterns typically associated with wakefulness. Fowler emphasised that she was synthesising published clinical findings rather than presenting new trial data.
As Fowler told attendees, these reports suggest “elements of consciousness may briefly exist beyond the measurable signals we typically rely on.” She added that limitations in current monitoring technology make interpretation difficult.
Then the questioning began.
One audience member asked whether surface EEG recordings can miss deeper brain activity. Another raised the issue of how memory might form during periods of severely reduced blood flow.
Other neurologists have urged restraint. Dr. Steven Laureys, of the University of Liège, has previously noted that EEG has blind spots and may not capture every type of neural signal.
At the same time, he has cautioned that recollections reported after resuscitation do not prove awareness during complete electrical inactivity. Oxygen deprivation followed by restoration of circulation can trigger chemical and metabolic changes in the brain that affect perception and memory formation.
Under current law, death is defined in most countries as either the irreversible cessation of circulatory and respiratory function or the irreversible cessation of all brain function. Those standards guide decisions about ending resuscitation efforts and beginning organ donation procedures.
Speaking previously to the New York Academy of Sciences in 2019, Parnia said that older assumptions about rapid brain cell death have been revised. Rather than immediate destruction, he described a chain reaction: Loss of oxygen disrupts energy production, which can set off inflammation and delayed cell death over hours.
For hospitals, the issue is practical. Resuscitation timelines, transplant protocols and reviews by hospital ethics boards all depend on clear definitions. Current guidelines have not changed, but ongoing research into post-arrest brain activity could inform how those standards are applied in the future.
Sources: LadBible, AWARE study publications in Resuscitation and The Lancet (2014–2023); remarks by Dr. Sam Parnia at the New York Academy of Sciences (2019).
