Advances in stem cell research, neuroscience, and resuscitation science have enabled scientific insights into what happens to the human brain in relation to death. Brain cells are more resilient to anoxia than previously assumed, becoming irreversibly damaged over hours to days postmortem. Resuscitation science has restored life to millions after cardiac arrest, and survivors describe a universal set of recollections related to death. This review examines death, recalled experiences during cardiac arrest, post-intensive care syndrome, and related phenomena, discussing potential mechanisms, ethical implications, and methodological considerations. It also addresses controversies in studying consciousness and recalled experiences of cardiac arrest and death in comatose subjects to standardize future research.
A spectrum of consciousness and awareness, including signs of implicit learning and electrocortical biomarkers, may be present during deep hypothermic circulatory arrest (DHCA), despite the absence of visible signs of consciousness. In a prospective study across 10 hospitals with 36 DHCA patients, 29 had a tablet set up to deliver audiovisual stimuli. All had EEG and NIRS monitoring, but only 9 had usable EEG data. Delta EEG waves were observed during circulatory arrest in 3 of those 9 patients. None had explicit recall of the three fruit names, but 3 of 36 correctly guessed them, suggesting implicit learning, and 3 recalled other memories, including themes of a death experience. This may help explain negative psychological outcomes in cardiac arrest survivors.