Researchers from Yale University revived brain cells belonging to pigs four hours after their death, according to a study published in the journal Nature that raises serious ethical questions over what it means to be dead.
The study was done on pigs, but it has implications for humans—mainly that the brain is much more resilient than previously thought.
“The assumptions have always been that after a couple minutes of anoxia, or no oxygen, the brain is ‘dead,'” says Stuart Youngner, M.D., who co-authored a commentary accompanying the study with Insoo Hyun, Ph.D., both professors at Case Western Reserve University School of Medicine. “The system used by the researchers begs the question: How long should we try to save people?”
For the experiment, researchers used 32 freshly slaughtered pigs heads from a nearby USDA processing facility. They removed the brains from the pig heads and flooded them with artificial blood to help them maintain their structure and a chemical solution that allowed them to track its flow and brought oxygen to brain cells. They called the process BrainEx. When they compared the brains of pigs left alone to decompose to those flooded with the chemical, they found that the pig brains receiving BrainEx showed signs that cellular activity was restored.
To be clear, the brains did not regain full function or consciousness. But it did call into question our practice of declaring a person brain dead when resuscitative efforts like CPR do not work.
Currently, standards for resuscitative efforts are varied. “It varies by country, emergency medical team, and hospital,” Youngner said.
These results make it difficult to say when exactly an emergency team should switch from trying to save a patient to trying to save the patient’s organs to give them to someone else in need.
If the results from the pig experiment could be adapted for humans (which Youngner and Hyun warn are a long way off in their accompanying editorial), it could be a game changer for people who are declared brain dead.
“As we get better at resuscitating the brain, we need to decide when are we going to save a patient, and when are we going to declare them dead—and save five or more who might benefit from an organ,” said Youngner.
But it’s not going to be simple. Doing so could potentially increase the number of people with extreme disabilities and divert much-needed resources, noted the editorial. “This study is likely to raise a lot of public concerns. We hoped to get ahead of the hype and offer an early, reasoned response to this scientific advance,” said Youngner.
While there was no evidence of neural activity that signaled consciousness—in fact, scientists took extra precautions to ensure that consciousness could not be regained—the experiment has implications for research on the brain, including for drug development for dementia, an area where science has made little progress for decades. Reviving brains could allow researchers to test drugs much more effectively.
“Pig brains are similar in many ways to human brains, which makes this study so compelling,” Hyun said. “We urge policymakers to think proactively about what this line of research might mean for ongoing debates around organ donation and end of life care.”
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