Consider someone who has just died of a heart attack. His organs are intact, he hasn't lost blood. All that's happened is his heart has stopped beating -- the definition of "clinical death" -- and his brain has shut down to conserve oxygen. But what has actually died? "After one hour, we couldn't see evidence the cells had died. We thought we'd done something wrong." In fact, cells cut off from their blood supply died only hours later.
But if the cells are still alive, why can't doctors revive someone who has been dead for an hour? Because once the cells have been without oxygen for more than five minutes, they die when their oxygen supply is resumed.
Mitochondria control the process known as apoptosis, the programmed death of abnormal cells that is the body's primary defense against cancer. "It looks to us," says Becker, "as if the cellular surveillance mechanism cannot tell the difference between a cancer cell and a cell being reperfused with oxygen. Something throws the switch that makes the cell die."
With this realization came another: that standard emergency-room procedure has it exactly backward. [...] "We give them oxygen," Becker says. "We jolt the heart with the paddles, we pump in epinephrine to force it to beat, so it's taking up more oxygen." Blood-starved heart muscle is suddenly flooded with oxygen, precisely the situation that leads to cell death. Instead, Becker says, we should aim to reduce oxygen uptake, slow metabolism and adjust the blood chemistry for gradual and safe reperfusion.
A study at four hospitals showed a remarkable rate of success in treating sudden cardiac arrest with an approach that involved, among other things, a "cardioplegic" blood infusion to keep the heart in a state of suspended animation. The study involved just 34 patients, but 80 percent of them were discharged from the hospital alive. In one study of traditional methods, the figure was about 15 percent.
(Via jwz's blog.)