They call it resuscitation science. It's a new area of research at the University of Pennsylvania, where a Center for Resuscitation Science opened less than a year ago, and where the line between life and death is shifting.
Historically, doctors have defined clinical death as the point at which either the heart irreversibly stops beating or the brain shows no signs of activity according to Dr. Benjamin Abella, the center's clinical research director.
"But researchers … now believe there's a third state of being that hovers somewhere between life and death -- a place where most of the body's cells are still alive, but neither of these two classical signs of life are present," Dr. Abella said.
How can medicine bring patients back from that state without causing irreversible damage to the cells?
"It used to be thought that getting someone back as quickly as possible with CPR, defibrillation and warming … was the best approach," said Dr. Abella. "Where that may in part be true, many initial survivors from cardiac arrest go on to suffer severe debilitating brain injury and sometimes don't live to leave the hospital alive."
Restarting the heart while protecting the brain is where the key to successful resuscitation lies. It is dramatically demonstrated in the National Geographic Channel documentary "I Came Back from the Dead," airing Jan. 29.
Through a cooperative arrangement with the National Geographic Channel, ABC News has looked into two of the cases featured in the documentary, studying how the lessons learned from them have contributed to the knowledge of how people can be brought back from clinical death.
'He Looked Like a Cadaver'
Ward Krenz, now of Sioux Falls, S.D., survived after being submerged for an hour in an icy lake.
"He certainly came back from the appearance of death from all the clinical criteria for death," said cardiovascular surgeon Dr. Dan Waters of Clear Lake, Iowa. "I don't think it's a big stretch to say he came back from the dead."
Today Krenz is active and healthy and works for a railway company in Sioux Falls. In 1993, he was presumed dead when his body was pulled from a frozen lake he fell into after his snowmobile careered onto an open patch of water in Clear Lake.
"That's when you are in panic mode," Krenz said. His companions heard him cry for help but were unable to reach him.
Krenz treaded water. "I believe it was for about five to 10 minutes," he said.
Then Krenz lost consciousness and slipped beneath the surface. Rescuers discovered his body, with only the helmet still floating above the surface, roughly an hour after the accident. His father was told his son had died.
"So on his way to the hospital," said Krenz, "for three hours he was planning my funeral."
"When [Krenz] came to the emergency room he looked like a cadaver," Waters said. "He was stiff, ice-blue, horribly cold to the touch, and he just looked like somebody who had been dead for a long time."
Krenz had flat-lined.
Nevertheless, an estimated two hours after he plunged through the hole in the ice, he was hooked up to a heart-lung machine. Doctors were able to restore a heartbeat, but the prospects, if he survived, were troubling.
"There was at least, I thought, a statistically significant chance we would not get the person he was before back," Waters said. "That he would suffer severe, irreversible brain damage, and still … persist in a vegetative state. So that was my biggest concern."
But in the icy lake, Krenz's body had reacted with incredible, evolutionary defenses: capillaries constricted, sending blood to his vital organs, which needed the oxygen, and away from the skin to reduce heat loss. Had he been warmed too quickly before being placed on the heart-lung machine it could have been the worst thing for him.
According to Abella, research shows that cooling a patient, as Ward Krenz was cooled by the lake, can also slow the clock that counts the seconds of remaining life.
"Hypothermia, or keeping someone cool, seems to add minutes to that clock," Abella said. "So it seems we can push back that envelope and actually affect the transition point between life and death."
In addition, Krenz's lungs never flooded with water because the shock of the cold caused a spasm that closed his windpipe.
The cold also protected his brain.
"He was fully immersed," said Waters. "So not only did his body cool evenly, but his head was underwater and his brain actually was physically cooled by the water as well."
"It turns out when you lower the core body temperature, you slow metabolism," Abella said. "And it seems to have protective effects on the brain, the heart and other organs."
The cold may have been lethal but it also saved Krenz. A sudden warming and uncontrolled return of blood flow to his body could have damaged or killed him. Researchers are now working on understanding why. It's the type of case that has changed conventional thinking about how to revive patients from clinical death.
"When the heart is stopped, that's clearly a bad thing," said Abella. "But when we get blood flow back, a whole new set of injuries kick in at that very moment."
That damage appears to be slowed and lessened by hypothermia.
"I've cared for many patients after cardiac arrest who I thought would never leave the hospital, and I thought would be brain damaged," Abella said. "And what I've seen is that hypothermia brings them back."
First Death, Then Surgery
As the science of resuscitating people advances, it also means that surgeries can be attempted on some conditions that would otherwise be untreatable -- first by killing the patient; then by bringing the patient back. That was what was necessary to operate on a painful and potentially fatal aneurysm in the brain of Atlanta musician Pam Reynolds.
"It was difficult to eat, it was difficult to sleep," said Reynolds. "And it's the kind of pain that no medication helps."
Reynolds went to Phoenix neurosurgeon Robert Spetzler.
"When an aneurysm blows, half the patients die," said Spetzler. "And those that survive, half of them never return to being normal. So it's a real, real threat."
To remove that threat, Reynolds had to be placed in a state of clinical death. Her body was cooled by a heart-lung machine until her heart was at a standstill; then it was stopped completely by an injection of potassium chloride, the same chemical used in death row executions.
Spetzler and his team repaired the aneurysm. During her clinical death, Reynolds experienced something that is reported by around 20 percent of cardiac arrest victims -- a phenomenon commonly termed a near-death experience. She had the sensation of having watched her surgery from above the table, and what surprised her doctors was that she could recount specific details of the operation, including parts of the operating room conversation.
"I heard a female voice say, 'We have a problem, her arteries are too small,'" Reynolds said.
The conversation and other details she recounted were in the surgical records.
Dr. Karl Greene, who was on the team of surgeons, asked, "Why would she have this kind of information if she was so deeply under a barbiturate infusion of medications that should be shutting down her brain?"
In the absence of facts, some partial theories have been proposed. The body may have a self-defense mechanism that produces endorphins to create a sense of well-being in anticipation of death. Because cells never stop working all at once, Reynolds' brain might have continued to function after it had flat-lined, absorbing or envisioning details.
Reynolds, however, believes it was a distinct memory.
"It was just too in the pocket to make it up," she said.
"Whether that image came from somewhere else that she then internalized somehow, I don't think there is any way to tell," said Spetzler. "But it was sort of intriguing how well she described what she shouldn't have been able to see."
As the science of resuscitation improves and tackles unanswered questions, doctors are not only redefining what we mean by the term "clinical death," they are re-engineering the ways they can resuscitate those who have experienced it.
"I don't think you want to live at those limits, but at least you know that there is maybe a little maneuvering room out there," Waters said.