While it is true that a very few individuals have come back after years
of coma, they did show some brain activity.  One of the most important
determinations is brainstem evoked potential, which will determine if
your brain is sensing light or sound.

As a general rule of thumb, I'd say to give up after 3 weeks, unless the
comatose state is due to one of the various things that could protect
the brain.  One rule of emergency medicine, for example, is "you're not
dead until you're warm and dead," meaning prolonged hypothermia can
protect the brain.  If the patient had been hypothermic or in induced
barbiturate coma, there's a slightly better chance that they might come
out of it.

It's a difficult situation to try to predict everything, because your
advanced directive may simply not cover a new and relevant technique
with a chance of returning function.  In the final analysis, I think
it's a matter of providing enough examples that the clinical teams know
that you understand the scope of "no heroics", that you do consider
quality of life as well as brain death, and you are aware of the
consequences of your directive.

My sister died of breast cancer that had spread to her
liver. That morphine business is what they tried to do
with her, but she would not permit the morphine. From
what our relatives told me, she didn't appear to be in
awful pain.....liver just shut down eventually and she got
weaker and weaker; she wanted to be awake and aware
at the moment of leaving, and she was. Some cancer is
not agonizing, we learned.

Ditto, to what both of you have said.  I just hope BOTH my brain and body
die at the same time, when it's time for me to check out of the Hotel de
Vie. Or failing that, I hope that no grandstanding congress person EVER
takes on keeping me 'alive' as their personal cause.

What makes me maddest in this I guess, is that in August 2001, when he got
the memo that Bin Laden was determined to strike at the U.S. Bush stayed
down on the ranch and went fishing, when his presence in Washington D.C.
might have actually been prudent.  BUt he'll come running back to Washington
to sign a special bill to keep Terry Shiavo alive.

ARRRRRG!

Melissa

There are times to be aggressive in life support. The national
statistics on, for example, cardiopulmonary resuscitation simply don't
lend themselves to a single number.  IIRC, the national figure on people
with cardiac arrest that walk out of the hospital, with no neurological
impairment, is probably around 10%.

That number, however, tends to include people that had disease otherwise
incompatible with life, or where there was too long a delay to start
even basic life support, and especially defibrillation. More and more
states are allowing paramedics to declare death in the field, under
quite well-defined circumstances. For example, if someone is found
pulseless after blunt chest trauma (e.g., crash against the steering
wheel), they aren't going to come back. Penetrating chest wounds where
the heart stops have a slightly better prognosis, but still dismal.

At the same time, I've been an observer in the ER where a woman was
pulseless from blood loss from a savage slashing attack, but nothing
vital was hit. She recovered -- needed a lot of plastic surgery, but had
no residual systemic effects.  Now, her heart stopped when she was
already in a trauma room and getting intensive support -- and this was
1966, when we had a lot less resusciative technology.

Children are more likely to go down from respiratory than cardiac
failure -- sometimes a few rescue breaths are all they need to restore a
pulse.  The extreme example of when resuscitation should go absolutely
all out is a child that drowned in cold water. Deliberate hypothermia is
used in cardiac surgery, and hypothermia can so slow body functions that
you can get full recovery after hours.

As I've mentioned, some injuries are incompatible with life. There's an
old story of a lawyer cross-examining a physician, demanding how he knew
the victim was dead.  The physician opined that decapitation tended to
be fairly definitive.

The lawyer sneered, "Oh, is that so?"

And the physician corrected himself. "Well, he could have been a lawyer.
I recently had convincing evidence one could function without a brain."

I'm rather fond of "Thank God and Greyhound you're gone..."