Some Cardiac Arrest Survivors Can Report Clear Memories of Death

A first-of-its-kind study has explored consciousness and brain activity in patients during cardiopulmonary resuscitation (CPR) after a cardiac arrest (CA). The data show that some patients demonstrate brain wave patterns that are associated with conscious thought up to one hour after their heart stops beating.

The blurred lines between life and death

During a CA, the heart stops beating and blood flow to the brain ceases. Should immediate medical attention be available, survival is possible. CPR can revive people many minutes after their heart stops, with approximately 10% of cardiac arrest patients surviving the ordeal. This statistic, however, is highly dependent on whether the arrest occurs inside a hospital environment. For many, when their heart stops beating, their life ultimately reaches its end.

When the human body teeters on the precipice of life and death, what happens to our brain? Survivors of a CA often report different experiences. For some patients, depression or post-traumatic stress disorder is a side effect of near-death. Others report transcendental experiences, the outcome of which is a transformative evaluation of their life, actions and relationships.

The AWAreness during REsuscitation (AWARE)-II study, led by Dr. Sam Parnia, MD and associate professor in the Department of Medicine at New York University Langone Health, is a first-of-its kind study that sought to understand the diversity of experiences reported by CA survivors.

The largest study examining what happens to the human brain and mind in death

“The AWARE-II study was the world’s largest and most comprehensive study examining what happens to the human brain, mind and consciousness as people transition from life to death when they’re going through CA resuscitation,” says Parnia.

The research team analyzed data from 567 individuals that experienced a CA and underwent CPR while in hospital throughout the period of May 2017–March 2020. The study was conducted across 25 hospitals, mostly in the United States and the United Kingdom.

The researchers aimed to gather data including audiovisual testing of awareness, electroencephalography (EEG) and cerebral oxygen reporting and interviews from all patients recruited to the study. Ultimately, 85 participants were monitored via EEG and 53 patients survived the CA, meaning they could be interviewed when they recovered. The researchers also gathered testimony from an additional 126 survivors of cardiac arrest to analyze their self-reported experiences of death in relation to the experiences reported in the current study.

The recalled experience surrounding death should be studied without prejudice

Some patients who were successfully revived by CPR, even up to an hour after their hearts had ceased beating, could report vivid memories of experiencing death. During their unconscious state, these individuals showed electrical brain patterns associated with cognitive processes and memory, revealing new insights into the intriguing relationship between moments of clinical death and consciousness.

“The study was able to show, for the first time, that the experiences that people have been describing about having a lucid hyperconscious experience, where they can reevaluate their entire life – every memory, every thought and every intention – is real, and is different to hallucinations, to dreams and to other imaginary experiences,” says Parnia. “We were also able to show, for the first time, the brain markers of these hyperconscious, hyperlucid experiences that are occurring in the brain.”

“We were also able to identify the mechanism by which this experience occurs […] as the brain shuts down because of a lack of blood flow in death, the normal braking systems in the brain are removed – known as disinhibition. This enables people to have access to their entire consciousness; all their thoughts, memories, all their emotional states – everything they have ever done – which they relive through the perspective of morality and ethics,” adds Parnia.

While the researchers acknowledge limitations to the work in the paper, including that the survivor pool is small and attaching brain monitoring devices during CPR is challenging, they believe the study has several important implications.

“Although doctors have long thought that the brain suffers permanent damage about 10 minutes after the heart stops supplying it with oxygen, our work found that the brain can show signs of electrical recovery long into ongoing CPR,” says Parnia. He emphasizes that this creates new avenues of research in the pursuit of treatments to preserve the brain and restore life and consciousness.

In his opinion, the research also helps us to understand what happens to the human mind as people are experiencing life and death, with ramifications for end-of-life care and organ transplantation.

"Although systematic studies have not been able to absolutely prove the reality or meaning of patients’ experiences and claims of awareness in relation to death, it has been impossible to disclaim them either. The recalled experience surrounding death now merits further genuine empirical investigation without prejudice,” the study authors conclude.

Reference: Parnia S, Keshavarz Shirazi T, Patel J, et al. AWAreness during REsuscitation - II: A multi-center study of consciousness and awareness in cardiac arrest. Resuscitation. 2023. doi: 10.1016/j.resuscitation.2023.109903

This article is a rework of a press release issued by [name of institute]. Material has been edited for length and content.