X-Message-Number: 33172
Date: Sat, 1 Jan 2011 10:55:10 -0800
Subject: Re: Cryopreservation since 1990
From: Brian Wowk <>

     Mike expressed the opinion that the quality of cryopreservations
have gone down since 1990 despite the use of better cryoprotectant
solutions because a lower percentage of people are being perfused with
the solutions.  Alcor did 10 cases in 2010.  One was a post-mortem
signup, one had cryopreservation blocked by relatives, and one was a
middle aged man who suffered sudden cardiac death.  The last two cases
required court action to gain access to remains.  The remaining seven,
Alcor's last seven cases, all received cryoprotective perfusion.  Six
of those received standbys.  That is as good as the Darwin/Leaf record
of 1980s, and at a much higher case density.  Three of these seven
cases occurred within a one month period.

     Mike expressed concern that ice blockers in modern vitrification
solution could worsen freezing injury in poorly-perfused areas by
delaying ice nulceation to very low temperatures where water would be
less mobile, and membranes less permeable to water.  However the high
molarity glycerol solutions used in cryonics in the 1990s were already
doing this.  The 7.4 molar glycerol solution in Mike's 1995 canine
study that showed excellent preservation would have had a melting
point near -50 degC, and would have likely supercooled tens of degrees
below that before starting to freeze as highly concentrated
cryoprotectant solutions tend to do.  An attempt was made at 21CM to
study what would happen to a brain cryopreserved and rewarmed after
perfusion with only 80% normal concentration of M22.  The experiment
failed to elucidate what happens to tissue that freezes due to
perfusion with sub-vitrifiable concentrations of M22 because even at
only 80% normal concentration, no freezing injury was observed.  It
may be that the concentration regime in which freezing differences
with and without ice blockers become most apparent is at dilute
concentrations, well below full concentration; concentrations at which
ice nulceation would normally occur near 0 degC, but becomes delayed
to low sub-zero temperatures by ice blockers.  The concern is valid in
theory, but there is no data, and as far as the brain is concerned it
would seem to only apply to a minority of patients when perfusion goes
poorly.  I remember speculating years ago that if a perfusion were
going poorly it might be theoretically beneficial to add ice
nucleators to the perfusion solution.  However it would be a difficult
call to make, and there is no data to support to it.


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