X-Message-Number: 4959
From: Brian Wowk <>
Date: Tue, 10 Oct 1995 23:40:54 -0500
Subject: Dendritic spines

        Mike Perry's article about the loss of dendritic spines
during long intervals of cold ischemia is very interesting, and
is indeed a cause for concern for some cryonics patients.  However 
I want to emphasize that the experiment cited is NOT relevant to 
all cryonics patients who experience cold ischemia.  Mike 
acknowledges this when he states that the results do not apply 
when metabolic support or perfusion is implemented, but this point 
deserves further amplification.
 
        The majority of cryonics patients who make advance
arrangements are cryopreserved under controlled conditions
with a cryonics team standing by when their heart stops.
Circulation is then artificially resumed, cooling is begun,
and their BLOOD IS SUBSTITUED BY A PERFUSATE SPECIFICALLY
DESIGNED TO MAINTAIN TISSUE VIABILITY DURING COLD ISCHEMIA.
They are then transported on ice to a cryonics facility for
subsequent cryoprotective perfusion and freezing.  
 
        This transport phase can subject the patient to many
hours of cold ischemia-- but not the same kind of ischemia 
that exists when ordinary blood remains in the tissue.  The
experimental evidence documenting the protective effects of
a good perfusate during cold ischemia is some of the most
dramatic in all of cryonics.  Mike Darwin and Jerry Leaf at
Alcor were able to recover dogs after more than FOUR HOURS
of cold ischemia with no neurological deficits.  Mike and
his associates at 21st Century Medicine have since extended
this time beyond SEVEN HOURS.  The guinea pig study cited by  
Doug Skrecky and Mike Perry would have predicted these brains
would be Alzheimhers-like mush after this length of cold
ischemia.
 
        In summary, the reported loss of dendritic spines is
a concern for "bad scenario" cryonics cases where cardiac
arrest occurs without a cryonics team nearby.  However it
doesn't seem to be a concern for most cryonics cases where
advance arrangements have been made.
 
---Brian Wowk


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