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."
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.