How late is too late to revive a brain? Pig brain study raises questions

The news two weeks ago that scientists at Yale University developed technology to partially restore brain activity in pigs 10 hours after they were decapitated at a slaughterhouse is still reverberating in the scientific community, and researchers are now engaging with the many bioethical concerns the work raises.

Perhaps the biggest issue is a profound change in our understanding of limits of when a brain can be revived after what we ordinarily consider the threshold of death.  

Nenad Sestan, a professor of neuroscience at Yale University was the senior author of the study published in the journal Nature. He stressed in a call to reporters after his findings were announced that "this is not a living brain, but it is a cellularly active brain."

He added, "These findings lay the groundwork for novel approaches to studying the post-mortem brain and potentially restoring the function of damaged cells within the diseased brain."

How they partially revived the pig brains

The scientists achieved this feat with the help of technology they developed called BrainEx. It used a computerized network of pumps, heaters and filters to pump artificial blood through the pigs brains in a process known as "perfusion."

The scientists began their procedure four hours after the pigs were decapitated. They perfused the brains for six hours, after which they discovered a partial restoration of brain activity.

This is not a living brain, but it is a cellularly active brain.- Prof. Nenad Sestan, Yale University

"I want to make clear that the organized electrical activity that would be correlated with any kind of consciousness was never detected in the course of the research," said Steven Latham, the bioethicist on the Yale team who added that inducing consciousness was never their goal.

To make sure the 32 pig brains didn't entirely reboot, the scientists added a neuronal activity blocker to the artificial blood. They were also standing by with anesthesia in case they detected any signs of organized global electrical activity in the brain, which could indicate a return to consciousness in pigs.

Blurring the line between life and death

"The main implication of this finding is that the cell death in the brain occurs across a longer time window that we previously thought," said Sestan who added that they showed cell death in the pigs' brains is a gradual process that "can be either postponed preserved or even reversed."

The fact it's possible to bring back a person from death after their heart stops wasn't a surprise to Dr. Sam Parnia, a resuscitation specialist and professor at the New York University School of Medicine.

"We've seen now for the past few decades that there have been remarkable cases of people who've died — and typically become cold after they died — and then brought back to life many hours after they've crossed the threshold into death," said Dr. Parnia in conversation with Quirks & Quarks host Bob McDonald. 

It might be that if the [Yale] team had prolonged their work for longer than six to 10 hours, which is what they did, that they may well have seen evidence of electrical activity resuming that could have correlated with consciousness in those [pig] brains.- Prof. Sam Parnia, New York University School of Medicine

"When we try to bring people back, often many clinicians have a perception that they only have five or 10 minutes before people end up with permanent brain damage," said Dr. Parnia. "And as a consequence of that, they don't try for long enough because they feel that if they were to try, they're going to bring back patients who will end up either severely disabled or even possibly in a persistent vegetative state."

But this study reviving pig brains suggests the window for resuscitation is a great deal longer. 

A host of bioethical implications

The very thought that we could potentially extend that window between when the heart stops and brain dies brings up a host of complex ethical issues.

When Hank Greely, a professor of law from Stanford University and president of the International Neuroethics Society, heard about this work he was shocked and surprised. 

He said if this research can be replicated, proven, and adapted to humans, it could have "huge implications for questions like: When do we decide whether people are dead? Or, when can we do transplants of hearts from people? These are going to be big questions that we're going to have to deal with."

I could imagine somebody somewhere — and I hope not in the United States or Canada — telling dying people, 'Give me $100,000 and I'll cut off your head and we'll hook you up to this pump and you'll continue to live.' I think, that to me, is the biggest short-term nightmare.- Prof. Hank Greely, Stanford University

Greely said his biggest fear is that quacks will try to fleece desperate people who hope to prolong their lives by any possible means.

"I could imagine somebody somewhere — and I hope not in the United States or Canada — telling dying people, 'Give me $100,000 and I'll cut off your head and we'll hook you up to this pump and you'll continue to live.' I think, that to me, is the biggest short-term nightmare."

He added this BrainEx study also brings up questions about research ethics involving animals.

"I don't want a pig brain waking up with no body around it and wondering where is it and what's going on," said Greely. "Those pig brains are in limbo. They're not laboratory animals. They're dead. There are no real ethical rules about how you deal with the tissues of dead laboratory animals."