X-Message-Number: 33373
From:
Date: Mon, 28 Feb 2011 01:51:43 EST
Subject: Melody Maxim's Distorted Reality 8
I think it likely that the above quote will stun both Boon and Melody. I
am long past that point. If you are an Alcor patient receiving
extracorporeal support you have (based on this woman's past performance) a ~ 1
in 5
chance of being perfused with massive amounts of air at some point during your
care (either in the field or in the facility). This does not include
microbubble embolization, which happens during every case, and which they
neither
check for, nor apparently are sensitive to as a problem
Not stated in the quote above, or the case summary it came from, was that
this patient was massively edematous and was unrecognizable at the end of
CPA perfusion (described by one person present as looking like the Michelin
tire man).
Paradoxically, some of Alcor's in-field coordinators are far better at CPB
than are Alcor central staff. They are much more afraid and concerned
about their limitations, and thus more cautious and vigilant.
Having said that, none of these people have ever pumped a survival case on
either an animal or a human, and the enormous mass of acquired knowledge
and experience which both of you (Melody and Boon) have, is completely
absent. Both of you are aware of basic things such as the effect of tubing
diameter on flow and pressure. You know the safe levels required for the
reservoir you use and you are intimately aware of your response time versus
flow
and reservoir volume. I could easily write a textbook about all the things
you know, and know viscerally, leaving aside things like pharmacology,
acid-base balance, and basic physiology all which act to make you safe and
competent perfusionists.
I am writing this to give you a perspective that this will not be the case
with SA, Alcor, or other cryonics organization perfusionists who will
operate the ATP in the field. No matter how thoroughly these sincere people
master didactic training, they will not have any real clinical experience, and
will not have the instincts and embedded hand knowledge that even a
marginally competent perfusionist will have. This reality trumps all other
considerations in circuit design. These people will necessarily be like a
person
who has been taught the basics of operating an automobile on a closed
course. They can drive it forward and avoid hitting the walls at low speeds.
However, they have no crash avoidance skills, will freeze up at intersections,
will often reach for and activate the wrong control, have no instinctive
feel for the vehicle or its control console, and will be unable to backup,
let alone parallel park. No one with even vestiges of sanity would put such
a person into a high performance racecar and turn them loose in a NASCAR
race, let alone Indycar racing!
The obvious solution to this would be to hire a professional perfusionist.
This is simply not economically possible nor is it really practical given
the low volume of cases (less than 20 a year) even at Alcor, or even in
cryonics worldwide (less than 40 a year). And remember, of these cases, many
will not be perfusable due to delay, autopsy, sudden death, financial
constraints, or geographical remoteness.
The next best thing is to train appropriately skilled and motivated people
in an animal research environment where they can pump survival animals
(typically dogs) and gain the enormous array of both intellectual and manual
skills required to be a safe, competent, and flexible perfusionist. Alas,
this kind of training stopped some years ago and has been repeatedly rejected
as an option for SA personnel. Only such extensive in-house training on
relevant models will do the job. This is not going to happen. Please
integrate this fact into your thinking.
Hardshell vs. Bags
First, a caveat: I may be seen as biased since the current Alcor ATP was
reconfigured by me prior to its clinical implementation. The basic platform
was designed by Alcor and I want to make clear that most of the credit for
this system, including the critical idea of modularizing it in a Pelican
case, is the work of Steve van Sickle and Hugh Hixon at Alcor.
Given logistic constraints, and lack of training of personnel,
recirculating in-field CPB will be a relatively rare thing and, frankly,
something I
would rather not see done solely due to skills issues. A patient who has
been safely washed out and cooled is vastly better off than a patient who has
been embolized with macro air in an attempt to cool a few more degrees or
provide metabolic support in ultraprofound hypothermia.
To this end, I configured the system to have almost no potential for
administering macro air. This was done by drawing from a collapsible perfusate
reservoir (Alcors' idea) and using a collapsible venous reservoir which was
to be kept largely purged of air. Since the ATP cannot be moved there is
always a sharp time constraint on how long a patient can be maintained on
CPB. This is so for at least the following reasons:
1) Most cryopatients have major compromise to systemic capillary
integrity. In particular, most patients will have experienced massive pulmonary
edema and alveolar flooding. Many patients will have active GI bleeds due to
erosion of the gastric mucosa by hydrochloric acid during agonal
hypoperfusion (shock). Gastric blood flow is negligible in many patients during
the
last few hours of agonal hypotension. The effect of this is that perfusate
rapidly leaves the extracorporeal circuit either as pulmonary transudate or
via hemorrhage of compromised gastric mucosa. Even if gastro-protection has
been undertaken prior to cardiac arrest, there is usually massive pulmonary
transudation of perfusate, including the colloid. You will see this in the
intubated patient as a steady flow of blood-tinged perfusate existing the
ET tube at a rate of up to 20 ml/min. This will limit the time on the pump
unless a reserve of 10 to 20 liters of perfusate has been provided to make
up for this loss. Contemporary cryonics personnel are oblivious to this as a
problem and assume that, the patient is bleeding internally. If a reserve
of perfusate is on hand and MAP is kept to ~35 mm Hg it is possible to
perfuse such patients continuously for over 12 hours (Ive done it). It is also
physiologically desirable given the limitations of the current perfusate
(MHP-2).
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