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Paolo Rossi Castelli05 Oct 20233 min read

Brain activity, even during cardiac arrest

Surprise results from a study conducted in 25 U.S. and British hospitals. Several patients who were in a state of cardiac arrest for up to an hour showed signs of brain activity while the doctors were attempting to resuscitate them.

What happens to a person's brain when they go into cardiac arrest?

We have been asking ourselves this question since time immemorial, because the stages between the moment when the heart stops beating and brain death are still, in part, a mystery, one which we have not yet completely unravelled. Until now, it had always been thought that, when the blood in the body stopped circulating, brain death was inevitable after five to ten minutes at the most. However, a study published in the journal Resuscitation suggests that, on the contrary, in some cases the time that passes between cardiac arrest and the cessation of all brain activity can be longer.
The study, called AWAreness during REsuscitation (AWARE)-II, was conducted across 25 British and U.S. research centres and coordinated by resuscitation specialists at the New York University Grossman School of Medicine. The researchers focused their attention on 567 patients who had experienced cardiac arrest and undergone cardiopulmonary resuscitation (CPR), performed using identical procedures (chest compressions, artificial ventilation and a defibrillator) for the purpose of collecting uniform data.

Less than 10% of the patients survived. However, of those, approximately four out of ten reported having lucid recall of much more than what the doctors had expected—this despite the fact that the normal equipment had not picked up any brain activity whatsoever. Furthermore, some of the patients were subjected to more in-depth testing even while undergoing CPR; of these, 40% had electroencephalogram readings that showed a number of spikes in their gamma, delta, theta and alpha waves (which indicate higher mental function) up to an hour after cardiac arrest—and therefore well beyond the ten minutes traditionally accepted as the maximum amount of time the brain can remain without blood supply.

Between life and death: a different state of consciousness

In terms of their first-hand accounts, these patients, like others before them, described a state of conciousness entirely different from the hallucinations, dreams, visual distortions or temporary returns of consciousness which are sometimes induced by CPR. Rather, they understood on a rational level what was happening to them during resuscitation and felt no pain, but only a sensation of detachment from their own bodies.
The researchers believe that what is happening could be caused by the inhibitory systems present in the brain temporarily ceasing to function (a state that is in fact called disinhibition), similar to what occurs when a person uses a substance, such as a psychedelic drug, that causes dissociation. Deprived of its filters, the brain taps into a different, broader vision of reality, one which also opens access to very early memories—such as those from childhood, which, while buried, have always been present—or to spiritual sensations or dreamlike states. We discussed in depth what happens to the brain in the stage between life and death in one of our recent articles

Should we change the rules for transplants?

The discovery of this peculiar persistence of brain activity in a small number of people for up to an hour following cardiac arrest merits further study, including because of how it could affect our standard time-frames for declaring brain death and removing organs for transplant. Moreover, this new information could be incorporated into CPR protocols to prevent further brain injuries. Human consciousness never ceases to amaze and it is clearly evident that there is still much more to be explored.


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Paolo Rossi Castelli

Journalist since 1983, Paolo has been dealing with scientific divulgation for years, especially in the fields of medicine and biology. He is the creator of Sportello Cancro, the site created by on oncology in collaboration with the Umberto Veronesi Foundation. He collaborated with the pages of the Science of Corriere della Sera for several years. He is the founder and director of PRC-Comunicare la scienza.