X-Message-Number: 20702
Date: Mon, 23 Dec 2002 23:49:06 -0800 (PST)
From: Michael Hartl <>
Subject: Stepdad's argument

Toby Christensen wrote:
> My stepdad's argument, succinctly
> Is this:
>
> That after 7 minutes without oxygen a person is 
> brain-dead and that the idea that someone will 
> develop the technology to revive brain dead  people 
> one day is mysticism. 

Hi Toby,

Your stepdad's argument is important and deserves a
detailed rebuttal.  Steven Harris is probably the best
person for that, but I can give you the short version.
Most "damage" done by oxygen deprivation to the brain
is in fact only *potential* damage.  The body reacts
to brain trauma through an autoimmune cascade, the
strength of which depends on the level of trauma.  The
damage can largely be prevented through cooling, which
 is why we ice sprained ankles.  The current record
for resuscitation without damage in canines is 15
minutes at flatline, but only with subsequent cooling
to  minimize damage.  Without cooling, even 5 minutes
can be fatal.

The key point for cryonics is that the most of the
damage from oxygen deprivation is realized only after
the autoimmune response begins, after circulation is 
restored in the patient.  If a patient is rapidly 
cooled, this damage can be minimized upon re-warming
(and in fact cooling heart attack victims will likely
become standard emergency medical practice soon), but 
in cryonics the patient is not re-warmed: he is cooled
right down to liquid nitrogen temperatures without the
autoimmune cascade ever having a chance to do its
damage. By the time technology can reverse the damage
from the suspension, the question will be moot:
suppressing the autoimmune reaction is trivial
compared to the cellular repair needed for a
successful resuscitation.

I suspect that the damage is realized late enough that
the upper limit on time spent at flatline is quite
high, maybe even on the order of hours, as long as the
patient is cooled all the way down to cryogenic
temperatures after that point so that little or no
autoimmune damage occurs.  This is speculation,
though, and determining exactly when oxygen
deprivation damage is realized -- and how severe it is
-- is an important research problem.

In any case, if cool-down happens soon after the
pronouncement of legal death, the damage due to oxygen
deprivation is minimal, and the prospect for eventual
revival is excellent.

Cheers,

Michael

--
Michael Hartl
http://www.michaelhartl.com/

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