X-Message-Number: 33376
From:
Date: Mon, 28 Feb 2011 01:58:22 EST
Subject: Melody Maxim's Distorted Reality 11
By the application of both reason and experience we identified which drugs
and devices could be used beyond expiry, and for how long. Ultimate
validation was in the animal lab and often we had help on this from other
investigators who were using outdated supplies: this was once the way most
research got done. This practice is now illegal, so a vast reservoir of data
shared between labs and by manufacturers is now no longer available.
Most hollow fiber oxygenators and dilyzers are good indefinitely if they
are stored under reasonable conditions. This is amazing. However, this is
most emphatically not the case for bubblers or for cardiotomy reservoirs, and
storage conditions are critical.
The urethane column in hardshell reservoirs is subject to oxidation and
disintegration over time. Some of you may have observed this effect with old
urethane bed pillows which have become crumbly and non-elastic. The urethane
foam column inside a reservoir stored under uncontrolled conditions or
past its expiry becomes a crumbly, embolizing mess. It begins to shed large
numbers of particles in 1 to 10 micron range long before this deterioration
is visible to the naked eye. High ambient temperature and humidity can
greatly accelerate this process (as does UV light, which not a consideration
here). It is important to remember that these reservoirs (ATPs) will be stored
under uncontrolled conditions; no guaranteed, monitored, ISO 900X
environments.
I have seen relatively stable in-field PVC items become sticky from
plasticizer elution due to long storage times, and especially due to storage
under uncontrolled conditions. Not surprisingly, Florida is where I have
observed this the most (there used to be a permanent Alcor perfusion facility in
FL which was established in the early 1980s and decommissioned in the late
1990s. I both implemented and decommissioned it). I am thus very wary of
components that fail catastrophically with extended storage.
I agree that the waste dump line should come before the venous return line
enters the cardiotomy reservoir. This not only guards against clots, but
also reduces contamination with red cells and with agglutinated RBCs.***
Boon: Disadvantages of hardshell reservoirs include the use of silicon
antifoam compounds, which may produce microemboli, risk of microembolism, and
increased activation of blood elements. Soft bag reservoirs eliminate the
blood-gas interface and by collapsing reduce the risk of pumping massive air
emboli. Because of the concerns on microemboli and increased activation of
blood elements, some perfusionists have switched back to using softshell
bags again.
Mike Darwin: ***See my commens above. I would also add that the current
(Alcor) ATP components retain their utility and safety even when stored under
extreme ambient conditions. I am reluctant to give this up. It has been
hard-won experience. I actually made a complete tubing pack of tubing and
connectors out of polymer that does not have plasticizers and should have had
an indefinite shelf life. This was packed for shipment to SA. I have no idea
whether it ever got there. It used polypropylene connectors and the tubing
was resistant to the solvents in the vitrification solutions.
[As an aside, I am very concerned about plasticizer leaching from PVC
tubing during CPA perfusion, especially with the addition of dimethylformamide.
Both DMSO and DMF raidly degrade PVC components at room temperature.
Contamination of perfusate with dissolved plastics and housing failure on
oxygenators under pressure seems quite possible; for example, the Sarns
oxygenator housings are a clamshell with a glue joint holding the two halves
together.]***
Melody Maxim: The reservoir currently available at SA is a cardiotomy
reservoir, rather than a venous reservoir, which would be more desirable. The
cardiotomy reservoir is designed for blood collection, such as that from
general suction lines that are used in the field. Hence, the cardiotomy r
eservoir has a very effective filter designed to remove debris. One undesirable
effect of this feature is reduced flow rate, due to the time it takes the
perfusate to traverse across the filter. (SAs existing cardiotomy reservoir
is rated at a maximum flow of 5LPM.) Another disadvantage of the cardiotomy
reservoir is that it does not have a 1/2" port for the venous return line,
therefore requiring a 1/2-3/8 reducer in the venous return line. Nor does
it provide for a venous luer lock for the sampling manifold, thus requiring
an additional luer lock connector to be placed in the venous line for this
purpose.***
Mathew Sullivan: I agree that we dont want to use a cardiotomy reservoir
because of the high flow rates, but the bottom connection is tapered and
will hold both a 3/8 and tubing. At Alcor we used to reduce the tubing down
to a , and ran the tubing coming from and going to the reservoir through a
pumphead, but changed this to a gravity drain with larger tubing to reduce
the amount of air being pumped into the mixing reservoir during
cryoprotection in hopes of avoiding pumping micro bubbles into the patient.
Boon: For your portable circuit (have never seen the actual circuit, just
some photos that Charles sent a while back) I dont know whether a hardshell
cardiotomy-venous reservoir will fit in the carrying-case or not.
Obviously the soft bag will have no issues.
Melody Maxim: Modifications will have to be made to accommodate SAs level
detection system, as discussed.
Mike Darwin: ***ANY decrease or restriction in diameter largely defeats
the advantage of using a larger line. In other words, if you are using a
line (as you should) to facilitate venous return and you put a 3/8 connector
in that line you have dramatically reduced your flow and increased your
resistance (and thus your CVP under high flow conditions).***
2. Melody Maxim: Moved oxygenator recirc line to top of reservoir.
Should air need to be evacuated from the oxygenator, (this should be
unlikely, provided a watchful eye is kept on the reservoir), the air is handled
without effort, unlike in the previous SA circuit where the removal of air
from the oxygenator would have led to filling the bag reservoir with air
that was somewhat difficult to expel.
Mathew Sullivan: I agree.
Boon: Thats the beauty of hardshell reservoirs, they handle air better
than the soft bags.
Mike Darwin: ***I cant comment on this change without seeing the circuit.
I will make comments via the pictures and Boons comments below.***
3. Melody Maxim: Deleted reservoir vent line to waste bag line.
No longer necessary. If volume is excessive, it can easily be diverted to
the waste bags via the Y-connector in the venous return line. Parallel
clamps have been placed on the branches of the venous line, past the
Y-connector, so they are easy to see and manipulate, while continuing to monitor
the
reservoir.
Mathew Sullivan: I agree the vent line is no longer necessary, but I may
need some clarification on the volume you speak of are we still talking
about air? Until I see the proposed reservoir, Im not sure to what extent this
might be an issue. With the cardiotomy reservoir as it stands now there is
more than enough capability to vent any amount of air we will likely see.
Boon: I dont think Melody is referring to air when she talks about
excessive volume. The volume shes talking about is fluids. I do agree with her
in
putting a Y-connector in the venous return line instead of having a vent
line from the cardiotomy reservoir connected to a waste bag.
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