X-Message-Number: 1926
Date: 09 Mar 93 23:34:17 EST
From: Mike Darwin <>
Subject: CRYONICS Letter to Ettinger
Michael Darwin
Cryovita Laboratories
1220 E. Washington St. #24
Colton, CA 92324
9 March, 1993
Robert Ettinger
Cryonics Institute
2443 Roanoke
Oak Park, Michigan 48237
Dear Bob,
I have spoken with Greg and he will hopefully respond to you
directly. He informs me that he has been able to cool 500 cc
quantities of material to about 25 degrees below TG if he cools VERY
slowly and if he allows annealing time at or near TG. He said he
has been able to cool smaller samples (i.e., 100 cc) to as low as -
160*C. He feels that very slow cooling to within 20 degrees below
TG ought to work. However, he has done only one experiment and
clearly more are needed.
This is an area where CI might be able to make great progress
for all involved: would you be willing to carry out carefully
designed experiments cooling bulk solutions to below TG and
determine their fracture points, stability, etc. I am sure Greg
could design some experiments that would help to clarify matters
considerably, and perhaps help to advance his own organ preservation
work as well (since it also relies on fracture-free storage of
vitreous materials).
Further, I should be able to provide you with uniformly
glycerolized animals (dogs or pigs) which could be shipped to you at
dry ice temperature and subjected to further slow, controlled
cooling to a temperature deemed safe. It is possible that tissue
will behave either better or worse than bulk solutions. I say this
because I observed far less fracturing in the fiber reinforced
tissue areas of glycerolized animals which fractured on cooling. By
contrast the lungs, brain, and spinal cord were very hard hit.
Structures like the spinal cord and nerves which extend through
small openings and snake over long distances may be far more
vulnerable to fracturing than a relatively homogenous mass of
solution.
Yes, you are quite right about the variation in concentration
from area to area of the body. As no doubt you yourself have
observed, perfusion is often very poor in the lower extremities in
ischemic patients. What we will probably have to content ourselves
with here is protecting the brain.
You raise the larger issue of the importance of eliminating the
fracturing from an ultimate benefit standpoint. This is a much
tougher question and one for which I have no hard and fast answers.
If fracturing can be eliminated with a modest exertion of effort and
a modest (or no) increase in cost then I think we are all agreed it
should be eliminated. How important this will be to the typical
patient today I can't say. However, if the cost is likely to be
very high, then it probably should not be an immediate issue for
concern. In any event, if it is do-able and people can make an
informed choice, I think that the option should be available. I
would not propose that cheaper, fracture-free LN2 storage be
eliminated if it will exclude patients -- not unless it can be
demonstrated with a reasonable degree of confidence that fracturing
is causing serious information loss.
What are your concerns about ethyl chloride? It would be
containerized and not in direct contact with the patient.
Regarding your comments with respect to the hypothermic phase
of the procedure I wish I could be more sanguine. Unfortunately,
cold water drowning is not really comparable to what happens to the
typical cryonics patient. I believe that very serious injury is
occurring during ischemia and reperfusion. I believe that some of
this injury results in immediate and serious destruction of
ultrastructure. Other injury is secondary to loss of capillary
integrity, leukocyte plugging of capillaries, and other problems
which compromise subsequent cryoprotective perfusion.
This has been borne out by both ultrastructural and
histological studies conducted in-house -- as well as by the
response of human patients to various transport scenarios. How
significant this injury is to the ultimate recovery of the patient
remains an unknown since we do not know the full extent of the
damage, the structures which encode memory and personality, and so
on. Indeed, as the pages of THE IMMORTALIST attest, there is even
now wide debate and little consensus about the very nature of what
we seek to preserve (human identity).
I have great respect for cerebral ischemia as I have tried
several times to reverse it (11 minutes) using every pharmacologic
and other tool at my disposal (including external cooling of the
dog's head). In this I have failed dismally each and every time but
the last time. Every organ system would recover fine but one: the
brain.
What I do know is that there truly is no comparison between
patients who have long ischemic episodes and those who are
transported under good conditions. And this bears directly on how
well or poorly the patient equlibrates with cryoprotectant.
However, as you point out, in the final analysis the decision
belongs with the member. It is his or her pocketbook and his or her
chances. Ultimately, it should be his or her decision.
Sincerely,
Mike Darwin
Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=1926