For up to an hour after their hearts had stopped, some patients revived by CPR had clear memories afterwards of experiencing death, and had brain patterns while unconscious that were linked to thought and memory, investigators have reported.
In a study led by researchers at NYU Grossman School of Medicine, in co-operation with 25 mostly US and British hospitals – and published in the journal Resuscitation – some survivors of cardiac arrest described lucid death experiences while they were seemingly unconscious.
Despite immediate treatment, fewer than 10% of the 567 patients studied, who received CPR in the hospital, recovered sufficiently to be discharged.
Four in 10 of the patients who survived, however, recalled some degree of consciousness during CPR not captured by standard measures.
The study also found that in a subset of these patients, who received brain monitoring, nearly 40% had brain activity that returned to normal, or nearly normal, from a “flatline” state, at points even an hour into CPR.
As captured by EEG, which records brain activity with electrodes, the patients saw spikes in the gamma, delta, theta, alpha, and beta waves associated with higher mental function.
Survivors have long reported having heightened awareness and powerful, lucid experiences, said the study authors. These have included a perception of separation from the body, observing events without pain or distress, and a meaningful evaluation of their actions and relationships.
This new work found these experiences of death to be different from hallucinations, delusions, illusions, dreams, or CPR-induced consciousness.
The study authors hypothesise that the “flatlined” dying brain removes natural inhibitory (braking) systems. These processes, known collectively as disinhibition, may open access to “new dimensions of reality”, they say, including lucid recall of all stored memories from early childhood to death, evaluated from the perspective of morality.
While no one knows the evolutionary purpose of this phenomenon, it “opens the door to a systematic exploration of what happens when a person dies”.
Senior study author Dr Sam Parnia, associate professor in the Department of Medicine at NYU Langone Health and director of critical care and resuscitation research at NYU Langone, said: “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. This is the first large study to show that these recollections and brain wave changes may be signs of universal, shared elements of so-called near-death experiences.”
These experiences, added Parnia, provide a glimpse into a real, yet little understood dimension of human consciousness that becomes uncovered with death.
“The findings may also guide the design of new ways to restart the heart or prevent brain injuries and hold implications for transplantation.”
Called the AWAreness during REsuscitation (AWARE)-II study – it followed 567 men and women who suffered cardiac arrest during hospital stays between May 2017 and March 2020 in the US and UK.
Only hospitalised patients were enrolled to standardise the CPR and resuscitation methods used, as well as recording methods for brain activity.
A subset of 85 patients received brain monitoring during CPR. Additional testimony from 126 community survivors of cardiac arrest with self-reported memories was also examined to provide greater understanding of the themes related to the recalled experience of death.
The authors conclude that research, to date, has neither proved nor disproved the reality or meaning of patients’ experiences and claims of awareness in relation to death.
They said the recalled experience surrounding death merits further empirical investigation, and they plan to conduct studies that more precisely define biomarkers of clinical consciousness and that monitor the long-term psychological effects of resuscitation after cardiac arrest.
Study details
Awareness during Resuscitation – II: A multi-centre study of consciousness and awareness in cardiac arrest
Sam Parnia, Tara Keshavarz Shirazi, Charles Deakin, et al.
Published in Resuscitation on 7 July 2023
Abstract
Introduction
Cognitive activity and awareness during cardiac arrest (CA) are reported but ill understood. This first of a kind study examined consciousness and its underlying electrocortical biomarkers during cardiopulmonary resuscitation (CPR).
Methods
In a prospective 25-site in-hospital study, we incorporated a) independent audiovisual testing of awareness, including explicit and implicit learning using a computer and headphones, with b) continuous real-time electroencephalography(EEG) and cerebral oxygenation(rSO2) monitoring into CPR during in-hospital CA (IHCA). Survivors underwent interviews to examine recall of awareness and cognitive experiences. A complementary cross-sectional community CA study provided added insights regarding survivors’ experiences.
Results
Of 567 IHCA, 53(9.3%) survived, 28 of these (52.8%) completed interviews, and 11(39.3%) reported CA memories/perceptions suggestive of consciousness. Four categories of experiences emerged: 1) emergence from coma during CPR (CPR-induced consciousness [CPRIC]) 2/28(7.1%), or 2) in the post-resuscitation period 2/28(7.1%), 3) dream-like experiences 3/28(10.7%), 4) transcendent recalled experience of death (RED) 6/28(21.4%). In the cross-sectional arm, 126 community CA survivors’ experiences reinforced these categories and identified another: delusions (misattribution of medical events). Low survival limited the ability to examine for implicit learning. Nobody identified the visual image, 1/28(3.5%) identified the auditory stimulus. Despite marked cerebral ischemia (Mean rSO2 = 43%) normal EEG activity (delta, theta and alpha) consistent with consciousness emerged as long as 35–60 minutes into CPR.
Conclusions
Consciousness, awareness and cognitive processes may occur during CA. The emergence of normal EEG may reflect a resumption of a network-level of cognitive activity, and a biomarker of consciousness, lucidity and RED (authentic “near-death” experiences).
See more from MedicalBrief archives:
Our lives might really flash before our eyes when we die – Vancouver brain study
Consensus review: Determination of brain death/death by neurologic criteria
Severe traumatic brain injury: Don’t be too hasty in pulling the plug