We held our alpha test of the new ATP and the whole-body vitrification system this month using a swine as test subject. Given that this was our first large animal operation in many years,
we had something of a learning curve with regard to animal handling and
the specific surgical procedures necessary for performing bypass. We
chose to cannulate the carotid artery and internal jugular vein for the
procedure. I performed the cannulation and Regina Pancake assisted, and
the surgery went quite smoothly. We had the animal on bypass in 45
minutes, which our observing veterinarian considered quite successful.
We began our equipment testing with the new transport perfusion system.
We needed a mere five minutes to prepare and prime the system prior
to cannulation, but this figure was artificially high because the two
people preparing the system had to refresh their memories about how to
hang the perfusate bag. A time of less than two minutes to prepare the
system is the benchmark for our next test. All of the new elements
worked well, and we had no problems at all with the new ATP. We did not
test it fully on a closed circuit, only for open flush of the swine, in
order to start testing the whole body system.
Our whole body system consists of two parts that we tested: the
patient enclosure and the computer-controlled perfusion. The patient
enclosure involves an operating stage that cools the patient using
liquid nitrogen injected into a plenum underneath the patient, fans to
circulate nitrogen around the patient, a transparent – but internally
lighted – cover for the patient, and enough seals to keep the nitrogen
– both vapor and liquid – precisely where they should be.
The cooling stage cooled quite rapidly to the set temperature. We
added controllers for that only recently, because we were still
modifying the enclosure based on previous test results. The temperature
controllers need to be adjusted slightly by modifying how the cooling
curve is handled, but it took less than ten minutes to cool the stage
to three degrees C. We were quite pleased with the even nature of the
temperature, and Randal Fry is to be commended for his efforts to
adjust the nitrogen spray to accomplish this result. The table itself
is also at a more comfortable height for performing surgeries.
The perfusion system itself was the biggest unknown. Of course, the
programmer knew precisely how the system would respond to our tests;
because it was doing everything he told it to do. The calibrations of
the system went well, as did the system initialization. Our
cryoprotectant ramp control handled itself very well. Pressure control
did not go well, and this was because we had been using the pressure
control in a way that worked with an unloaded system (there was no body
in the loop). This made a big difference, and we will be adjusting that
portion of the program accordingly.
Our alarm functionality worked quite well. A clamp on a line that
causes the pressure to spike resulted in immediate shut off the main
pump. Level indicators worked well, and all the pumps in the system
responded appropriately. Both manual and automatic control of all
parameters functioned as intended. We have some minor tweaks to make to
the user interface, but those are primarily cosmetic.
Elements that were not quite ready for the test included the full
reporting functionality, though the pure data collection elements are
all working well; the bubble alarms are not installed; and neither is
the emergency stop button we intend to place on the patient enclosure
(in case the surgeon sees something requiring immediate cessation of
perfusion). We will be performing additional tests on the system’s
memory requirements, to ensure that we will not have any problems
during a long case. Once we tested the perfusion system to that extent,
we tested the final element of the patient enclosure: the ability of
the system to perform first-stage cooling.
This is the step where we plunge the patient’s temperature to just
above the glass transition point for M22, -110 degrees C. The table
itself cooled to -110 in eleven minutes, though of course, it took
longer for the swine to reach that stage. Using an animal that was not
vitrified caused the temperature to be reduced more slowly because of
the heat requirements for the ice formation, but the swine passed the
freezing point in 3.5 hours. We considered this acceptable under the
test conditions. The swine’s temperature continued to drop until it
reached -95 degrees C, at which point we discontinued the test. That
drop took approximately 18 hours. This time is good, given that not all
elements of the system worked exactly as intended, and we expect faster
times as adjustments are made. We did find it took a considerable
amount of nitrogen to reach that stage, but part of this is because our
environmental fans failed. We will be looking into different fans for
the next test and other improvements to reduce nitrogen consumption.
Overall, everyone was quite pleased with the results, and we expect
to make the necessary modifications quickly and are planning our second
test for later this week.
This work was done under the supervision of the Alcor Institutional
Animal Care and Use Committee under Alcor’s USDA registration as an
animal research facility, and was fully compliant with the requirements
and standards of the Animal Welfare Act. The animals used in these
tests were procured from a USDA-registered laboratory animal breeder.
I would like to thank the team who participated in this equipment
test, including: Dr. Craig Woods, Joel Anderson, Stephen Van Sickle,
Hugh Hixon, Randal Fry and Regina Pancake. We would also like to thank
all of the donors who made pursuing this project possible.
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