X-Message-Number: 33158
Date: Wed, 29 Dec 2010 11:21:21 -0800
Subject: Cryopreservation since 1990
From: Brian Wowk <>

   Mike Darwin wrote:

> Finally, the quality of cryopreservation most patients  are now receiving
is dismal and has, on average, deteriorated since 1990.

    While personnel presently doing cryonics field work may not have
the same background as Jerry Leaf and Mike Darwin in the 1980s, this
statement is not supportable.  The single greatest change that has
occurred in cryonics since the 1990s is the switch to higher
concentrations of cryoprotectants, which has a dramatic effect on
structural preservation as shown at the bottom of this page

http://www.alcor.org/AboutCryonics/index.html

Acknowledgments go to Mike himself for one of the studies in the 1990s
that showed this.

http://www.alcor.org/Library/html/braincryopreservation1.html

This suppression of ice formation is so beneficial to structural
preservation that it overwhelms any other change in cryonics care that
could have conceivably occurred since that time.  For any change in
field stabilization procedures since 1990 to be so bad that it
counteracts the benefits of these improved cryoprotectant solutions,
it would have to cause the *whole brain* to be perfused with a
cryoprotectant concentration equivalent to less than 3 Molar glycerol.
 By the metrics of observed brain dehydration and venous effluent
concentration, there is no evidence for that in most patients who
receive cryoprotectant perfusion with a vitrification solution.

     Nor are the effects of incomplete perfusion with vitrification
solution as bad as Mike fears.  Attempting to vitrify small tissue
pieces with sub-vitrifiable concentrations of cryoprotectant is very
bad because rapid cooling can cause them to freeze intracellularly.
However human heads are so much larger than tissue pieces that even
when cooling a head at the maximum possible rate, that rate in the
brain is not much faster than the canonical 1 degC per minute that
allows an average cell to dehydrate in response to growing
extracellular ice and thereby avoid intracellular freezing.  In other
words, it appears plausible if not probable that the effect of poor
perfusion or incomplete equilibration with vitrification solution in
human cryopatients is freezing of those tissues in a manner similar to
that seen with low concentration glycerol in the 1980s.  While an
ideal vitrification protocol is equilibration with a vitrifiable
concentration of cryoprotectant followed by cooling as rapidly as
possible to near or below Tg, departures from this in large tissue
masses have less severe consequences than in small ones.

    Cryonics may indeed be "dismal" compared to what it could be if it
were supported by mainstream medicine with all attendant
infrastructure, personnel, and cooperation.  However the quality of
cryopreservation has certainly not deteriorated since 1990, not for
patients recovered sufficiently quickly to receive perfusion with
modern cryoprotectant solutions.

---BW

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