“These recalled experiences and brain wave changes may be the first signs of the so-called ‘near-death’ experience, and we have captured them for the first time in a large study,” lead investigator Sam Parnia, MD, PhD, with NYU Langone Health, said in a news release.
Identifying measurable electrical signs of lucid and heightened brain activity during CPR, coupled with stories of recalled near-death experiences, suggests that the human sense of self and consciousness, much like other biological body functions, may not stop completely around the time of death, Dr. Parnia added.
He presented the findings Nov. 6 at a resuscitation science symposium at the American Heart Association scientific sessions.
The AWARE II study
“For years, some people in cardiac arrest have reported being lucid, often with a heightened sense of consciousness, while seemingly unconscious and on the brink of death,” Dr. Parnia noted in an interview.
“Yet, no one’s ever be able to prove it and a lot of people have dismissed these experiences, thinking it’s all just a trick on the brain,” Dr. Parnia said.
In a first-of-its-kind study, Dr. Parnia and colleagues examined consciousness and its underlying electrocortical biomarkers during CPR for in-hospital cardiac arrest (IHCA).
They incorporated independent audiovisual testing of awareness with continuous real-time EEG and cerebral oxygenation (rSO2) monitoring into CPR.
Only 53 of the 567 IHCA patients survived (9.3%). Among the 28 (52.8%) IHCA survivors who completed interviews, 11 (39.3%) reported unique, lucid experiences during resuscitation.
These experiences included a perception of separation from one’s body, observing events without pain or distress, and an awareness and meaningful evaluation of life, including of their actions, intentions, and thoughts toward others.
“These lucid experiences of death are not hallucinations or delusions. They cannot be considered a trick of a disordered or dying brain, but rather a unique human experience that emerges on the brink of death,” Dr. Parnia said.
And what’s “fascinating,” he added, is that despite marked cerebral ischemia (mean regional oxygen saturation [rSO2] 43%), near-normal/physiologic EEG activity (gamma, delta, theta, alpha, and beta rhythms) consistent with consciousness and a possible resumption of a network-level of cognitive and neuronal activity emerged for as long as 35-60 minutes into CPR.
Some of these brain waves normally occur when people are conscious and performing higher mental functions, including thinking, memory retrieval, and conscious perception, he said.
‘Seismic shift’ in understanding of death
This is the first time such biomarkers of consciousness have been identified during cardiac arrest and CPR, Dr. Parnia said.
He said further study is needed to more precisely define biomarkers of what is considered to be clinical consciousness and the recalled experience of death, and to monitor the long-term psychological effects of resuscitation after cardiac arrest.
“Our understanding of death has gone through a seismic shift in the last few years,” he said.
“The biological discoveries around death and the postmortem period are completely different to the social conventions that we have about death. That is, we perceive of death as being the end, but actually what we’re finding is that brain cells don’t die immediately. They die very slowly over many hours of time,” Dr. Parnia noted.
Reached for comment, Ajmal Zemmar, MD, PhD, of University of Louisville (Ky.), noted that several studies, including this one, “challenge the traditional way that we think of death – that when the heart stops beating that’s when we die.”
The observation that during cardiac arrest and CPR, the brain waves are still normal for up to an hour is “fairly remarkable,” Dr. Zemmar told this news organization.
“However, whether there is conscious perception or not is very hard to answer,” he cautioned.
“This type of research tries to bridge the objective EEG recordings with the subjective description you get from the patient, but it’s hard to know when conscious perception stops,” he said.
Funding and support for the study were provided by NYU Langone Health, The John Templeton Foundation, and the UK Resuscitation Council, and National Institutes for Health Research. Dr. Parnia and Dr. Zemmar reported no relevant financial relationships.
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