Saturday, March 22, 2008

When it comes to treating heart attack victims, have we been getting it backwards?

This is the most interesting science news story I've read in quite a while. Simply put, this is a fascinating development.

When a person has a heart attack on the street, by the time he reaches the emergency room, his body has been deprived of oxygen for an average of 15 minutes. Doctors have always assumed that by this point, heart and brain cells and other cells in the body are past the point of resuscitation.

But it turns out not to be the case:
That dogma went unquestioned until researchers actually looked at oxygen-starved heart cells under a microscope. What they saw amazed them, according to Dr. Lance Becker, an authority on emergency medicine at the University of Pennsylvania. "After one hour," he says, "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.
The reason for this phenomenon has to do with a cell's "power plants," the mitochondria:
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."
The key to improving post-heart-attack survival, then, is not getting the victim oxygen as quickly as possible:
Instead, Becker says, we should aim to reduce oxygen uptake, slow metabolism and adjust the blood chemistry for gradual and safe reperfusion.


The mitochondrion, the cell's power plant.

—Mellow Monk


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