Studies have found that hypothermia seems to protect the brain by decreasing its need for oxygen and aborting activated cell death pathways. Still, there are limits — although body-cooling techniques have improved recovery in many patients after cardiac arrest, there will be a moment when the damage is too much and it’s too late to come back, the experts said.

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.