This MSNBC story (linked to by Instapundit) details how researchers are starting to learn, at a cellular level, what happens when people die. And, unsurprisingly, the conventional wisdom was wrong. Everyone figured, enough time without oxygen, and cells start dying. Despite "wanting" to continue living, their fundamental chemical processes stop functioning - "like a candle flickering out when you cover it with a glass" - and that, what's most important is to get more oxygen to the cells as quickly as possible. That's why, when you have a heart attack, they work hard to try to keep your heart and lungs working as much as possible (via CPR). The theory was, that extra bit of oxygen would keep your cells alive, much as a smoldering fire might be kept going with insufficient air, but a completely oxygen-starved fire will extinguish. One has to wonder to what extent centuries-old metaphors between life and fire influenced this view?
Now that they're actually beginning to research the particulars, though, the reality is much different. It turns out, if you starve cells for oxygen, they live fine, for at least an hour. In fact, Dr. Lance Becker, who was conducting the research, was so surprised by this that he noted, "we thought we'd done something wrong." As Asimov said, "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I've found it!), but 'That's funny...'" So many discoveries are made by scientists who do something, knowing full well what the result will be, who then end up spending a lot of time verifying their methods when the result is unexpected. Most of the time, the methodology is to blame, but sometimes, sometimes...
The best theory now is that the cells are fine without any oxygen, for quite some time. However, the mitochondria in the cells are confusing the jolt of oxygen after resuscitation with some sort of cancer event, and are causing the cells to undergo apoptosis (programmed cell death)* when oxygen is resumed. Those cells then die. In other words, other than being dead, you're fine at a cellular level while you're getting CPR, traveling in the ambulance, and arriving at the hospital. It's when they defibrillate you at the hospital and jolt you with oxygen that your cells then spontaneously undergo apoptosis, and your death becomes permanent.
It would seem, then, that recent research indicating that fast defibrillation is the key to heart attack survival has more to do with avoiding that later flooding of "dead" cells with oxygen than with any inherent short time limit. It may be that, in fact, if we can come up with some slower techniques, heart attack victims can be revived tens (or maybe even hundreds) of minutes after they "die" without serious long-term effects. In this view, the inevitable brain damage from long-term "oxygen starvation" during death is really caused by sudden oxygen resumption after resuscitation.
Dr. Becker also thinks this is all tangled up in hypothermia, too - the fact that people (especially young people) who drown in very cold conditions (e.g., by falling through thin ice on a pond) can sometimes be resuscitated hours later with no ill effects. Perhaps the cold retards whatever initial chemical "priming" is setting up the later apoptosis triggered by the resumption of oxygen?
In any event, all of this is very exciting stuff. It will no doubt take at least a decade before new techniques can be perfected, tried, and become mainstream practice. For the first time, though, we have a view to how death from sudden heart attack can be prevented, and the beginnings of an understanding of how death works at the cellular level.