2023-09-22 19:22:13
MONTREAL — Even though it no longer showed any signs of activity, the brains of patients in cardiac arrest suddenly “woke up” up to an hour after the start of resuscitation maneuvers, reports a new study.
The activity that reappeared in the brain corresponded to that which we normally associate with consciousness, specify the authors in the pages of the medical journal Resuscitation.
Consciousness, write the authors of the study, could therefore be “present despite clinically undetectable consciousness (in particular) under anesthesia (…) and in patients supposed to be in a persistent vegetative state”.
The authors of the new research studied 567 patients in cardiac arrest between May 2017 and March 2020. Data regarding brain oxygenation and organ activity could be collected from 53 of them. The brains of most of these patients showed no signs of activity during an electroencephalogram (their brains had “flatlined,” to use an English term that has no obvious translation into French).
But in about 40% of cases, normal or near-normal brain activity returned during cardiopulmonary resuscitation maneuvers, sometimes up to sixty minutes after they were initiated.
Twenty-eight survivors were interviewed by the researchers. Nearly 40% of them had a vague memory of the event, nothing more, and 20% seemed to remember their death ― but these are stories that should be taken with a grain of salt, warned Professor Florin Amzica, from the neuroscience department of the University of Montreal.
We have thus observed over time that people who are asked, for example, to recount their oldest childhood memory will often recount, and in complete honesty, not a memory that they actually remember, but rather something that was reported to them.
We therefore have no guarantee that people who report a near-death experience are not instead repeating something they read or heard somewhere.
“They went through an extremely traumatic experience psychologically, but also physically, physiologically, on the brain,” he said. And then we ask them, what did you feel? There is no assurance anywhere that what they are saying is not something they have known about before and imagine they experienced during those times.”
Oxygenation of the brain
The goal of resuscitation maneuvers, recalled Dr. Sam Shemie, a MUHC expert whose team recently published new guidelines to clarify the concept of brain death, is to supply the organs with oxygen after a cardiac arrest, and particularly the brain.
So, he said, “if you look at the brain as an organ that depends on the delivery of oxygen,” and if resuscitation maneuvers are effective, “it’s certain that we’re going to have patients who will have consciousness during resuscitation and who will be able to have memories afterwards.
A patient whose brain is sufficiently well oxygenated during resuscitation maneuvers will therefore be able to keep a memory of them, he stressed.
This experience had a huge impact on some patients who, the study authors say, emerged with “a sense of heightened awareness, with paradoxical lucidity – a meaningful, voluntary examination and moral re-evaluation of thoughts, intentions and actions towards others, perceptions of death and of a different and ineffable reality”.
“It’s very appealing to interpret the results (of the new study) as having had a spiritual or religious effect,” Dr. Shemie said. But from a scientific point of view, brain function depends on the level of oxygen delivery and circulation.”
Fluctuations in brain function can express themselves in different ways, he added, from hallucinations to delusions to distorted interpretations of reality.
The study is far from perfect from a scientific point of view, Professor Amzica said, although the researchers did their best under the circumstances. We can hardly blame them, for example, for having only interviewed patients who survived (which is inevitable) and the same study would be impossible to carry out in animals.
A flat electroencephalogram does not mean that nothing is happening in the brain either, he points out, since the device only measures activity that occurs on the surface (in the cortex) and not in depth.
Professor Amzica and his colleagues had also revealed, in a study published ten years ago, the existence of a hitherto unknown activity in a brain plunged into a very deep coma.
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