A study of cardiac arrest survivors found that about a third reported memories and perceptions during this period, indicating consciousness. Some reported regaining consciousness during or after resuscitation, while others described dream-like or transcendent experiences associated with death. Importantly, the research team also found that the brain can show signs of activity even after the heart has stopped beating. The research was published in Resuscitation.
Cardiac arrest is when the heart suddenly stops beating. It is usually caused by an electrical disturbance in the heart that disrupts its normal pumping rhythm. When this happens, blood flow to vital organs, including the brain, stops. If not treated immediately, it can lead to unconsciousness and death. Cardiac arrest is different from a heart attack, which is caused by a blockage in the arteries that supply blood to the heart muscle.
In the United States, between 350,000 and 750,000 people suffer cardiac arrest each year, with only about 10% surviving. Although persons in cardiac arrest typically appear unconscious, approximately one-third of survivors report conscious experiences during this period. Previous studies have been inconclusive in determining whether these experiences reflect actual awareness of their environment.
Study authors Sam Parnia and his colleagues wanted to investigate the cognitive experiences of cardiac arrest survivors. They wanted to categorize the types of experiences reported, but also establish electroencephalographic biomarkers that would show if and when a person in cardiac arrest wakes from a coma and regains consciousness. The authors of this study hoped this would help them determine when such a person is also experiencing lucid cognitive activity.
The research team identified 567 patients with cardiac arrest in 25 hospitals. During resuscitation, they placed a tablet computer and headphones on the patients, displaying images and playing sounds (e.g., words for fruits like apple, pear, and banana), to test for post-arrest memory recall.
Of these individuals, medical staff were able to restore circulation to 213 of them, but only 53, or just over 9%, survived long enough to be discharged from the hospital. Cardiac arrest survivors were more likely to be men than women and younger. Cardiopulmonary resuscitation lasted an average of 26 minutes, but individual duration varied widely.
Interviews were conducted with 28 survivors about their conscious experiences during cardiac arrest. Eleven reported memories and perceptions indicative of consciousness, despite showing no external signs of consciousness such as moaning or moving. These experiences include awakening from a coma during or after resuscitation, and dream-like or transcendental experiences.
The experiences reported by these eleven individuals can be grouped into four categories: 1.) coming out of a coma during or 2.) after resuscitation, 3.) dream-like experiences, and 4.) memories of death. A further 126 survivors were interviewed, revealing similar experiences, plus misleading misinterpretations of medical events. For example, the feeling of an intravenous line was misinterpreted as burning in hell.
Participants who emerged from a coma during resuscitation typically described the impact of the procedure on their bodies. They talked about feeling electrodes, pain, pressure, bouncing from chest compressions or hearing doctors’ conversations during this period. Those who emerged from a coma after resuscitation typically spoke of memories of intensive care.
Individuals who recalled experiences of death spoke of perceptions of separation from the body, often with the recognition that they had died, with a visual awareness of the situation from the perspective of people performing the resuscitation, a purposeful and educational reevaluation of carried out their lives and returned. to a place like home. These experiences usually ended with a decision to return to their bodies.
Dreamlike experiences include visions of rainbows, fish, igloos, humanoid creatures, wooden houses and other themes. However, researchers were unable to identify any similarities in these experiences and they did not appear to follow a storyline.
The researchers also conducted a substudy that used brain monitoring using EEG, or electroencephalography, a method used to record the brain’s electrical activity. EEG data were collected from 85 subjects during CPR, but only 53 of these had interpretable EEG data due to issues such as electrical interference and motion artifacts.
The EEG data showed several patterns. There was a predominant absence of cortical brain activity (suppressed EEG) in 47% of the data/images. Seizure-like (epileptiform) activity was observed in approximately 5% of the data/images. Importantly, signs of near-normal or physiological EEG activity consistent with consciousness were also observed, including delta and theta activity in 22% and 12% of the data/images, respectively, alpha activity in 6% and beta activity in 1%.
In a subset of patients, brain activity returned to normal or near normal from a flat state during resuscitation, as evidenced by the presence of gamma, delta, theta, alpha, and beta waves associated with better mental functioning. This occurred in almost 40% of patients and was observed up to 35-60 minutes after resuscitation. This is the first report of such biomarkers of consciousness during cardiac arrest and resuscitation.
“Although unrecognized, people undergoing cardiac arrest may have awareness, awareness and cognitive experiences despite the lack of visible signs of consciousness. Although systematic investigations have failed to absolutely prove the reality or meaning of patients’ experiences and claims regarding death, it has also been impossible to deny them. The remembered experience surrounding death now deserves further genuine empirical investigation without bias,” the study authors concluded.
The study sheds light on possible conscious experiences of individuals undergoing cardiac arrest. However, it should be noted that the results are based only on experiences of individuals who survived cardiac arrest while in good enough health to give interviews. Furthermore, none of the 28 survivors interviewed remembered the images presented during cardiac arrest, and only one remembered the sounds.
The article, “AWAreness during REsuscitation – II: A multicenter study of consciousness and awareness in cardiac arrest,” was written by Sam Parnia, Tara Keshavarz Shirazi, Jignesh Patel, Linh Tran, Niraj Sinha, Caitlin O’Neill, Emma Roellke, Amanda Mengotto , Shannon Findlay, Michael McBrine, Rebecca Spiegel, Thaddeus Tarpey, Elise Huppert, Ian Jaffe, Anelly M. Gonzales, Jing Xu, Emmeline Koopman, Gavin D. Perkins, Alain Vuylsteke, Benjamin M. Bloom, Heather Jarman, Hiu Nam Tong , Louisa Chan, Michael Lyaker, Matthew Thomas, Veselin Velchev, Charles B. Cairns, Rahul Sharma, Erik Kulstad, Elizabeth Scherer, Terence O’Keeffe, Mahtab Foroozesh, Olumayowa Abe, Chinwe Ogedegbe, Amira Girgis, Deepak Pradhan and Charles D Deakin.