There
are obviously several factors involved and we have been badly misinformed until
recently. That is fortunately
changing. The take home remains exactly
the same. Apply CPR in the form of heart
compressions to maintain active blood while help arrives. It does work and prospects are far better
than has been assumed.
What
has been broken is the assumption of a low threshold death that has informed
emergency room personnel for years.
This
is all good and perhaps we can claw back the awful death rate associated with
heart attacks.
Scientists looking closer at what happens when body
dies; edge closer to new understanding
Lee Bowman, Scripps
Howard News Service
Dec 18, 2013
Scientists are stretching the boundaries of
understanding what happens as the body dies - and learning more about ways to
perhaps interrupt the process, which takes longer than we might suppose.
Death is the final outcome for 100 percent
of patients. But there's growing evidence that revival is possible for at
least some patients whose hearts and lungs have stopped working for many
minutes, even hours. And brain death - when the brain irreversibly ceases
function -- is also proving less open and shut.
For decades, doctors have recorded cases
where people immersed in very cold water have been revived after hours have gone
by. Normally, brain cells start dying within a few minutes after the heart
stops pumping oxygen.
Many studies have found that hypothermia
protects the brain by decreasing its need for oxygen and staving off cell
death. Body cooling has become common for many patients after cardiac arrest.
However, cooling more a few degrees below
normal temperature can also cause cell damage.
Cardiologists are still tinkering to find
the best approach. Two recent studies presented at the American Heart
Association's scientific meeting in Dallas in November tried to see whether
early cooling by paramedics after they get a heart restarted is helpful (it
didn't seem affect survival or brain damage) or whether cooling to 91.4 degrees
Fahrenheit or 96.8 degrees during the first day in the hospital brings better
results (again, not much difference).
Then there's the issue of how long to
perform CPR. One 2012 study found the median duration in hospitals was 20
minutes for patients that didn't survive; 12 minutes for those who did. The AHA
recommends bystanders keep performing CPR until emergency medical services
arrive.
A Japanese study presented at the AHA
meeting, based on six years of data on cardiac arrest survival across Japan, concluded
it is worthwhile to continue CPR for 38 minutes or longer and still have a
chance to avoid major brain damage.
Defining brain death is becoming more
complex as researchers find signs of activity in both human and animal subjects
whose brain waves at first show they've "flat-lined" to the point
that there is no brain function. While some doctors use the EEG as a final
check for signs of life in the brain, most rely on a series of reflex and
respiration tests given over several hours to determine brain death.
Scientists at the University of Montreal
reported in September on the case of one Romanian patient who was in an extreme
deep coma after treatment with a powerful anti-epileptic drug. Although the
electroencephalogram (EEG) showed no activity in the man's cortex (the master
processor of the brain), there was activity in the hippocampus, the
region responsible for memory and learning.
The Montreal team, which reported their
findings in the journal PLOS One, recreated the same coma state in 26 cats, and
observed the same type of oscillations being generated in the hippocampus of
each one.
Although the clinical determination of
brain death in a hospital relies on more than a flat EEG, the Montreal study is
one of many that suggest the criteria may need to be changed. And it points to
the possibility that greater use of medically-induced deep coma to help
brain-injured people recover may be possible.
Just how conscious the brain remains after
cardiac arrest is frequently debated and researched. Various studies of cardiac
arrest survivors shows many experience profound mental or emotional change.
About 20 percent of survivors say they heard or saw something while they were
clinically dead.
During the AHA meeting, Dr. Sam Parnia,
head of intensive care at Stony Brook University Hospital in New York, reported
early results of a 25-hospital study of how frequently cardiac arrest survivors
see or hear things while their hearts are stopped. Of 152 survivors
interviewed, 37 percent said they had recollections from the unconscious
period. Only two recalled actually seeing events and one described any events
that could be verified. None saw images mounted in the treatment room as part
of the experiment.
Still, there's evidence that dying brains
can remain active. In August, researchers at the University of Michigan
reported on brain studies of rats dying from induced cardiac arrest and
suffocation. They found that within the first 30 seconds after death, all the
rats displayed a surge of brain activity. The rodents' brains showed
consciousness that exceeded levels normally found in the animals when they're
awake.
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