Moreover, scientists have learned that successful recovery depends on how the patient is treated after the heart is restarted and how the body is warmed after hypothermia.
"What we are learning is counterintuitive, because what we were all taught, if somebody's oxygen is low, I should give them oxygen, if their blood pressure is down, I should crank their blood pressure up," Becker said. [The Science of Death: 10 Tales from the Crypt & Beyond]
In reality, however, if a patient responds to initial care and his heart is restarted, a sudden rush of blood and too much oxygen to the brain could actually worsen the neurological damage. Instead, moderating the amount of oxygen delivered to the brain may be crucial in resuscitation.
The idea of cooling the body after cardiac arrest has been around for a few decades, but scientists were not certain if it truly was beneficial to patients.
In recent years, however, studies have provided evidence that hypothermia improves patient's survival and recovery, and professional societies such as the American Heart Association recommend considering hypothermia after patient's blood circulation is restored.
Nevertheless, not all hospitals have implemented hypothermia as part of their critical care protocol.
"What is sad is that this knowledge out there, the system is available but is not implemented," Parnia said. Less than 10 percent of people in the United States who might benefit from cooling therapy actually receive it, he said.
In an ideal world, resuscitation protocols would use machines instead of people to deliver chest compressions as long as needed, and to ensure right amounts of oxygen and blood are getting to the brain, Parnia said. Cooling and reducing oxygen after the heart is restarted are among factors that should increase people chances of coming back without brain damage, he said.
The conventional wisdom in medical practice is to not revive a patient who has suffered extensive brain damage and would only survive in an unending coma. Attempting to bring back a patient hours after cardiac arrest may even pose higher risks of brain injury, raising an ethical question for those who support a more comprehensive resuscitation protocol.
However, Mayer argued that our knowledge of brain damage and dying is incomplete, and it's not always clear how much injury one has endured, and whether it's reversible.
"What we've come to learn is that those notions of irreversibility of brain damage are dead wrong," Mayer said. "If you make those judgments too soon without going fully all the way, you may be actually writing people off."
Becker said while extending life artificially may not be appropriate in every case, doctors should apply all available methods if they decide to resuscitate.
"If we are going to do anything, I don't know why we do less than everything we can to save a person. So the question is, why would you want to save a person half-way?" Becker said.
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