X-Message-Number: 33374
From:
Date: Mon, 28 Feb 2011 01:54:23 EST
Subject: Melody Maxim's Distorted Reality 9
2) Many mortuaries that cooperate with cryonics organizations specialize
in embalming for air shipment, or are otherwise busy with their usual case
load. They cannot afford to have the prep-room tied up for long periods of
time and frequently balk at the time constraints imposed by even a simple
blood washout. While not always the case, the mortuary frequently wants the
cryonics personnel out of there, if for no other reason than to free up their
personnel. A cryonics case requires more total personnel time than a
regular embalming, including application of cosmetics and clothes. Further,
their personnel are a limited resource and if they use them extensively on a
cryonics case they may be unwilling to handle a case from the community on a
timely basis and/or charge overtime.
3) It is usually imperative to catch the next available commercial flight
and this means that the patient must be prepared for transport as soon as
possible. Since the ATP cannot be moved the patient must be disconnected from
extracorporeal support. Typical air transport of a cryopatient is shown
below:
The solution to this problem for local (within 4 hours drive time) cases
was to develop a mobile CPS platform that included ECMO capability:
Note (below) the CDI on the right and the Tektronix monitor under the lamp
(on the left) for invasive monitoring of MAP and CVP:
This system allowed for continuous perfusion and metabolic support of
patients. However, it requires several skilled personnel to use this kind of
equipment and, at its core, a skilled perfususionist (professional or
otherwise) who is familiar with the peculiarities of asanguineous perfusion in
the
patient with MSOF and fulminating pulmonary edema. For the time being this
system is not being used by SA and is only used by Alcor for acute blood
washout.
Which brings us back to the SA ATP as it was configured by Alcor: the ATP
is very hard to pump macro air with. If you empty the bulk perfusate
reservoir bag and then accidentally empty the patient (venous) reservoir bag,
even if the venous reservoir has 500 cc of air, none of it will reach the
patient before the pump begins to make that unmistakable thuwmp, thwump, thwump,
sound that indicates that it is pulling a vacuum on the inlet side of the
pump shoe. Flow drops off to nil and the bleed-line on the arterial filter
provides additional protection. If this happens it means that all perfusate
in the reservoir bag has been expended (the patient has been successfully
washed out) or there is a kink in the feed line to the venous reservoir.
There is thus no infinite reservoir of atmospheric air to draw upon.
I was careful to specify arterial tubing lengths and filter volume such
that even if the venous reservoir had 500 cc of air in it, it would not reach
the patient (this in addition to using an air separating filter). This is
the reverse of what is done clinically (and especially in dog work) where
every centimeter of tubing is a curse of hemodilution which may have to be
overcome by transfusion on the pump (a major problem in the dog because we do
not have in-house blood banks).
Thus, until skill level improves dramatically and consistently in
personnel who operate the ATP, I am unalterably opposed to hard-shell or
otherwise
open venous reservoirs. The changes I wish to see made the most are the
addition of an ultrasonic macro/micro air bubble detector to the arterial line
between the oxygenator and the filter, and high pressure (arterial and
venous) alarms which will shut the pump down and clamp the arterial line. The
presence of a closed venous reservoir will also prevent venous return in a
no-(arterial) flow situation from over-topping the hardshell reservoir
something that happened at least once after I left Alcor and which air-locked
the hardshell oxygenator (something which they had no idea what to do about).
My specific comments are below: (see Judge For Yourselves - Part 2)
Mike Darwin Mike Darwin
(Login mgdarwin)
Veteran Member
Judge for Yourselves - Part 2 February 3 2009, 11:23 PM
Changes to Suspended Animations Perfusion Circuit,
As of May 29, 2006, Melody Maxim
Melody Maxim: 1. Replaced bag with hardshell reservoir.
Melody Maxim: A hardshell reservoir offers many advantages over a soft bag
reservoir, including less resistance to venous return, higher volume
capacity and better air handling.
Mathew Sullivan: Can you provide more information on better air handling?
Boon: The venous reservoir serves as a high-capacitance (i.e.,
low-pressure) receiving chamber for venous return, facilitates gravity drainage,
is a
venous bubble trap, provides a convenient place to add drugs, fluids, or
blood, and adds storage capacity for the perfusion system. As much as 1 to 3 L
of blood may be translocated from patient to circuit when full CPB is
initiated. The venous reservoir also provides several seconds of reaction time
if venous return is suddenly decreased or stopped during perfusion.
Reservoirs may be rigid (hard) plastic canisters ("open" types) or soft,
collapsible plastic bags ("closed" types). The rigid canisters facilitate
volume measurements and management of venous air, often have larger capacity,
are easier to prime, permit suction for vacuum-assisted venous drainage,
and may be less expensive. Some hard-shell venous reservoirs incorporate
macrofilters and microfilters and can serve as cardiotomy reservoirs and to
receive vented blood.
Air handling of hardshell reservoirs is better than the softshell bags for
the fact that the rigid plastic canisters are open types, or what we call
an open system vs. the closed system of the collapsible plastic bags. When
you have lots of air entering the softshell bag, you will need to manually
purge the air out the top of the bag whereas air in the hardshell reservoir
is vented out automatically without your interventions. Hence, in this
sense, we say hardshell reservoirs can handle air better than the softshell
bags.
It also provides for filtering of the venous return, a feature that should
be highly desirable compared to the non-filtered bag reservoir, as the
presence of clots in the venous return during a cryonics procedure is likely.
Content-Type: text/html; charset="US-ASCII"
[ AUTOMATICALLY SKIPPING HTML ENCODING! ]
Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=33374
Warning: This message was filtered from the daily CryoNet digest
because the poster sent too many messages per digest.
It thus may need to be rated.