The Circle of Willis in Cryonics Perfusion

The Circle of Willis in Cryonics
Perfusion
by Ben Best
Blood flows into the brain primarily via the carotid arteries
and the vertebral arteries. The Circle of Willis is a circular
arterial structure in the brain that connects blood
flowing in from the carotid arteries with blood flowing in
from the basilar artery (which is fed by the vertebral arteries).
Blood flows from the Circle of Willis into brain tissue
via the anterior, middle, and posterior cerebral arteries
Many studies have shown that the Circle of Willis is incomplete
in most people. A 1998 study of 150 healthy
adult volunteers showed a complete Circle of Willis in
only 42% of cases — more often complete in younger
persons and females [RADIOLOGY; Krabbe-
Hartkamp,MJ; 207(1):103-111 (1998)]. A slightly more
encouraging 2002 study of 118 healthy volunteers in the
65-68 age group, showed 47% had a complete Circle of
Willis [THE JOURNAL OF CARDIOVASCULAR SUR-
GERY; Macchi,C; 43(6):887-890 (2002)]
For cryonics purposes, it has been believed that perfusion
into the carotid arteries, but not into the vertebral arteries
will result in incomplete perfusion of the brain if the Cir-
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cle of Willis is not complete. In particular, if both posterior
communicating arteries are missing, then perfusing only
through the carotid arteries will result in no blood getting
to parts of the brain supplied by the posterior cerebral arteries.
Both posterior communicating arteries were missing
in 11% of those in the 1998 study and in 14% of those in
the 2002 study cited above.
Nonetheless, a 2008 study showing Circle of Willis complete
in only 40% of 99 patients found no case of insufficient
perfusion in functional tests of patients given unilateral
cerebral perfusion. The authors concluded that
“extracranial collateral circulation” provides an alternative
pathway to the Circle of Willis for cerebral crossperfusion
[EUROPEAN JOURNAL OF CARDIO-
THORACIC SURGERY; Urbanski,PP; 33(3):402-408
(2008)]. Although persons with missing posterior communicating
arteries could easily have pathways to opposite
sides of the brain, other variants of Circle of Willis incompleteness
would be expected to prevent perfusion across
hemispheres.
When the cryonics organization Alcor does a cephalic isolation
(“neuro”) perfusion, the carotid arteries are initially
cannulated and the vertebrals are not cannulated. Only if
when the patient is being perfused into the carotid arteries
no flow is seen coming from the vertebral arteries are the
vertebral arteries to be cannulated and the patient is to be
perfused through both the carotids and the vertebrals. If,
on the other hand, flow is seen coming from one of the
vertebral arteries after perfusion of the carotids has begun,
it is assumed that the Circle of Willis is complete and the
vertebral arteries are clamped for the rest of the perfusion.
Flow only needs to be seen in one of the vertebrals to confirm
that the Circle of Willis is complete, because the vertebrals
unite in the basilar artery before connecting to the
Circle of Willis.
One Alcor employee has informed me that of 15-20 neuro
patients perfused by this cephalic isolation method, not
once has there been an absence of flow from the vertebrals
and not once has Alcor perfused a cephalic isolation patient
through the vertebral arteries. This would be slightly
improbable, based on a 10-15% expected rate of incomplete
communicating posterior arteries on both sides. But
another Alcor employee remembers one or two cases
where vertebral artery perfusion was done (which would
match expectations).
When both posterior communicating arteries are not missing,
there is another potential problem with perfusing only
into the carotids and not the vertebrals — namely, loss of
perfusion pressure. Perfusate entering the Circle of Willis

could exit through the basilar artery (the vertebrals) instead
of through the cerebral arteries. Vascular resistance
in the body is reportedly only one quarter what it is in the
brain. Clamping the vertebral arteries (as is done during
Alcor neuro perfusions) could prevent this problem.
Blood flowing into the basilar artery need not be pushing
all of the blood in the body, however, because arteries —
and especially veins — have a large reserve capacity (a
balloon-like ability to expand).
Possibly the reserve capacity of the brain would allow
blood to flow into the brain as readily as into the body.
Blood has about three times the viscosity of water, and
vitrification solution has about twice the viscosity of
blood. Viscosity will increase vascular resistance in all
blood vessels, but the effect would be greater in the brain.
The “no reflow” phenomenon would also create resistance
in the blood vessels, which again might be greater
in the brain than in the body.
Prior to the use of vitrification solution, the Cryonics Institute
only perfused cryonics patients through the carotid
arteries — there was no attempt to perfuse into the vertebral
arteries. Nonetheless, dehydration was seen in the
patients, and adequate effluent flow was seen from the
jugular veins. Perfusion pressures were reportedly not
excessive.
Currently, CI’s funeral director has been opening the
chest (median sternotomy), and attempting to clamp the
subclavian arteries, as well as the descending aorta, to
perfuse into the ascending aorta. In several cases the ascending
aorta has been perforated, forcing higher cannulations
or the subclavians have been difficult to cannulate
after having opened the chest. Our funeral director refused
to open the chest at all for a known case of Methacillin-
Resistant Staphylococcus Aureas (MRSA).
It would be preferable if a case could be made for perfusing
all CI patients only through the carotids. Carotid-only
has been recommended for vitrification perfusions overseas,
as well as for glycerol perfusions in post-mortem
sign-ups. Whether vitrification solution perfusion into the
carotids can acheive adequate perfusion pressure in the
brain — and whether adequate perfusion pressure can be
verified by the observation of effluent from the jugular
veins remains unresolved.
It should not be too difficult to clamp the vertebral arteries by
cutting near the clavicle, as CI’s funeral director did when CI
began the attempt to perfuse the vertebrals as well as the carotid
arteries. Nonetheless, this would result in failure to perfuse portions
of the brain supplied by the posterior cerebral arteries in
the 10-15% of patients who are missing both posterior communicating
arteries.
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HOW TO STAY YOUNG
1. Throw out nonessential numbers. This includes
age, weight and height. Let the doctors worry about
them. That is why you pay 'them'
2. Keep only cheerful friends. The grouches pull you
down
3. Keep learning. Learn more about the computer,
crafts, gardening, whatever. Never let the brain idle.
'An idle mind is the devil's workshop.'
4. Enjoy the simple things
5. Laugh often, long and loud. Laugh until you gasp
for breath.
6. The tears happen. Endure, grieve, and move on.
The only person, who is with us our entire life, is
ourselves. Be ALIVE while you are alive.
7. Surround yourself with what you love , whether
it's family, pets, keepsakes, music, plants, hobbies,
whatever. Your home is your refuge.
8. Cherish your health: If it is good, preserve it. If it
is unstable, improve it. If it is beyond what you can
improve, get help.
9. Don't take guilt trips. Take a trip to the mall, even
to the next county; to a foreign country but NOT
to where the guilt is.
10. Tell the people you love that you love them, at
every opportunity.
AND ALWAYS REMEMBER :
Life is not measured by the number of breaths we
take, but by the moments that take our breath away.
And if you don't send this to at least 8 people - who
cares! But do share this with someone. We all need
to live life to its fullest each day!! Worry about nothing,
pray about everything--Submitted by Debbie
Fleming