Dr. Sam Parnia, director of critical care and resuscitation research at NYU Langone School of Medicine, revealed that the human brain may remain active after cardiac arrest.
In the minutes following the cessation of cardiopulmonary resuscitation (CPR), Parnia said the deceased may hear doctors pronounce him dead before all signs of life have faded away.
Parnia did not just study what happens to the brain at the time of death, but also conducted interviews with patients who survived near-death experiences. The research revealed numerous cases of patients who were clinically dead – that is, their hearts had stopped beating – and were later revived, and they described with astonishing accuracy the conversations and events that took place in their rooms during their death.
Doctors typically focus on the heart when determining the time of death because it's the moment blood flow to the brain ceases. However, Parnia's study revealed spikes in brain waves associated with higher cognitive functions that persist for up to an hour after CPR begins.
This means that the brain is able to "wake up" and resume functioning in a manner resembling normal thinking and consciousness, even while doctors continue to perform resuscitation on a stopped heart.
Electroencephalography (EEG) analyses during near-death experiences showed that patients were in a dream-like state of consciousness, allowing them to hear others and interact with what was happening around them.
Parnia said: "Although doctors have long believed that the brain suffers permanent damage about 10 minutes after the heart stops supplying it with oxygen, our study found that the brain can show signs of electrical recovery for a period while resuscitation continues."
Parnia’s study focused on tracking what happens to people’s brains during cardiac arrest in 25 hospitals in the United States and the United Kingdom, by monitoring brain electrical activity, measuring oxygen levels, and interviewing survivors about what they remembered during their clinical death.
The team examined 567 people who suffered cardiac arrest in the hospital and received resuscitation, and discovered that one in five survivors reported vivid, dreamlike experiences, such as feeling detached from their body, seeing events in the room, or watching memories of their lives fade away before their eyes.
The study, published in the journal Resuscitation, showed spikes in brain waves, including gamma, alpha and beta waves associated with thinking, memory and consciousness, appearing 35 to 60 minutes after cardiac arrest.
When blood flow to the brain stops, brain cells rapidly lose oxygen, but they don't shut down completely. Instead, they emit powerful signals and communicate in new ways for a short period. Researchers believe this activity creates a state of heightened alertness and intense focus, which explains why some people can hear their surroundings even after the rest of their bodies have ceased functioning.
Parnia explained that this surge of brain energy allows patients to access everything in their minds at once. He said, "With the brain shutting down due to a lack of blood flow, the natural inhibition systems are removed, a phenomenon known as loss of inhibition, which allows people full access to their consciousness—all their thoughts, memories, feelings, and everything they have experienced in their lives from a moral and ethical perspective."
He noted that this discovery opens up prospects forstudying patient care, including developing new ways to restart the heart or prevent brain injuries during cardiac arrest, and that improved technologies and drugs could help protect the brain during cardiopulmonary resuscitation.
