X-Message-Number: 698
From: Henson/Darwin
Subject: Neurosuspension of Patient A-1260 (Part 3 of 3)
Although the intent was for Hugh and Keith to do the femoral cutdown,
their inexperience with the prep and drape phase (inadequately practiced
on pigs) slowed them down so much that they turned it over to Mike. Mike
went on to do the femoral cutdown with Hugh assisting and Keith handing
off instruments. (The first thing they ran into was a set of arterial
branches gnarled like tree roots.) Several sessions working with pigs
made it possible for Keith to anticipate when instruments, suture or
heparinized saline would be needed next, and had also sharpened up Hugh's
surgical skills. From arrest to going on bypass required 80 minutes, not
as fast we'd like, but better than last time (105 minutes) and the record
so far. Oxygenation and perfusion during HLR support was excellent, and
the patient had a strong femoral (groin) pulse which made it easier to do
the cutdown. The patient's temperature was 22.3 C at the time bypass on
the MALSS was started. This works out to a drop in temperature of 0.18 C
per minute - excellent for HLR-supported surface cooling, though this is
largely a function of patient mass/surface ratio.
Cooling to washout temperature went both smoothly and rapidly. Mike
had installed an extra heat exchanger in the bypass circuit (in addition
to the one on the Bentley hollow fiber oxygenator) and switched to a
higher output pump for delivering the ice water to the heat exchangers.
This resulted in a cooling rate of 0.47 C/min. When Nick's temperature
reached 10 C, washout with Viaspan began. This procedure took about 7
minutes and (with large bore lines this time) went very smoothly. Blood
washout was deemed excellent in the field and confirmed upon arrival at
the Alcor facility: Nick's hematocrit was 1%, indicating that about 98%
of his blood had been washed out.
At 5:01 a.m. we shut down the pump/oxygenator on the MALSS in order
to safely load it and Nick into the ambulance. At that time Nick's
esophageal temperature was 3.5 C (he could have been kept off bypass
safely for hours) and he had cooled approximately 34 C in 3 hours and 20
minutes - a powerful testimony to the effectiveness of the portable ice
bath and MALSS-supported cooling. Within a few minutes after Nick was
loaded in the ambulance, clean-up in the garage was completed, all the
support gear was loaded into the Cryovita van and assorted personal
vehicles, and transport to Riverside was begun. The ambulance arrived at
the lab about 7 a.m. Keith and Arel (who had dropped off Max and picked
up breakfast) made it by about 8 a.m.
Since there was at least a six-hour gap before the contract surgeon
could get there, most of the team headed off to get some badly needed
sleep. Even though Keith had not slept at all the previous night, he did
not feel like trying to sleep, so he remained awake to monitor and
operate the MALSS. By that time Nick was on intermittent (10 minutes on,
20 minutes off) low-flow bypass to minimize the risk of cold-perfusion-
associated-edema. Intermittent circulation of the Viaspan has been found
to be important to supply tissues with needed oxygen and glucose, remove
wastes and control pH. Initially Hugh was going to operate and monitor
the MALSS cart, but he was in worse shape than Keith, so he headed for
bed. This was Hugh's first transport-team leadership, and he had gotten
little sleep since days before it started from worrying about all the
things were needed and which can go wrong.
Mike left Keith with instructions to check pH once an hour and adjust
with bicarbonate as required. Keith decided to check glucose as well,
located a test kit, found the level to be low, and (following the
directions in the transport manual) adjusted it with glucose. This was
keeping Keith as busy as a one-armed paper hanger, so it was a great
relief to him when Paul came back in to help after a quick trip home for
a wake up shower. About the time Paul came in, Keith stuck a clamp on
the wrong line (no harm to the patient, thank goodness) opened a seam on
the oxygenator, and sprayed a couple of hundred ccs of perfusate on the
floor. Arel later made a suggestion of taping the lines with stripes of
narrow-gauge tape: red for arterial, blue for venous, and green for the
bypass line. It might not prevent all accidents, but it would sure help
dead-tired people. After cleaning up the mess, Paul and Keith checked
each other when they changed the clamps.
Paul and Keith had problems with both measurements and keeping the
ice water flow really at ice cold temperature. Near the end of the MALSS
support they moved the esophageal probe, and the reading dropped from 2.2
to 1.5 degrees, more likely representing the patient's core temperature.
The arterial probe must have been off by about 5 degrees, because the
arterial temperature (after going through the heat exchanger) had to be
lower than the patient's core temperature. The readings were still very
useful: they could see small rises in arterial temperature and take
steps to correct it. The heat-exchanger water flow kept channeling
between the pump and the return line, and required constant stirring and
fiddling to keep the right level of water and enough ice in the cooler
chest they were using. They kept at it for about 6 hours, until the rest
of the crew returned, both rested and fed, and the contract surgeon
showed up.
Three problems should be mentioned. First, the glucose test kit was
missing the calibration strip for the meter, so the test strips had to be
roughly read by hand. Due to unfamiliarity with procedures, and a
failure of communication (side effect of a lack of sleep) no analysis
samples were taken during the long period of low flow. Last, we run one
oxygen cylinder out. While it did not hurt the patient, it was not
noticed for some tens of minutes. Oxygen flow should be read with each
temperature.
Nick was moved from the MALSS to the operating room table. With Hugh
assisting, surgery to access the heart was seemingly uneventful.
Arterial and venous cannulas were placed, Mike did a bur hole using the
DuPuy pneumatic bur-hole tool. This time he did not open the dura.
Brain swelling or shrinking was assessed by depressing the dura with a
blunt instrument to "sound" the cortical surface, and observing the dura
in the bur-hole for being flaccid or bulging. It seems that the profuse
leaking of perfusate observed in previous well-supported cases was due to
cutting nearly invisible vessels in the dura, not (as Keith had
speculated) from the brain surface itself. This was the first time the
DuPuy was used in a suspension and it worked very well, making a small
hole in the skull in a fraction of the time it took to open a hole with a
conventional hand drill. Observations of intracranial pressure were
consistent with low injury patients: low pressure and some shrinkage of
the brain during perfusion.
While all this was going on, Arel made a food run. Later she and
Keith got busy cleaning out the MALSS cart. They used a lot of Clorox,
and this time the vacuum system got checked.
With surgery completed, Carlos took the surgeon back to the airport,
and Ralph started on the perfusion ramp. After a quick lesson Keith was
put on measuring perfusate refractive index--which converts to a
measurement of the level of cryoprotective agent going into and coming
out of the patient. From the start, the computer model and the measured
results were not agreeing. Dr. Perry was called over to see if anything
odd was going on with his program, but it seemed to be OK--reality was
out of adjustment. Early measurements indicated that the glycerol
concentration was not increasing as rapidly as predicted and that we
might not reach target. The reason for this was not apparent until the
conclusion of perfusion, and after cephalic isolation. At that time we
discovered that the umbilical tape (heavy duty surgical ties) the
contract surgeon had used to tie off the aorta (so that the body did not
perfuse) had not completely closed off flow--with the result that the
patient's body had partially perfused! This was a potentially very
serious problem. We now know better and in the future only metal
(Satinsky) occlusion clamps specially designed for closing large vessels
will be used for neurosuspension isolation.
Fortunately we came very close to the minimum target glycerol
concentration of 4.0 M (the final venous reading was 3.86 M or 27.84%).
We just reached this concentration with the last drop of glycerol. Hugh
was running blood gases, and we were pleased to see that Nick was using
oxygen (as determined by the arterial-to-venous oxygen differences) at
levels comparable to those observed in our (viable!) canine
total-body-washout animals cooled to similar temperatures.
About an hour before ending the cryoprotective ramp, a comment by
Mike led to the realization that nobody had been assigned to get dry ice.
The only source at that time in the night was two hours away, so Carlos
took off to get some. He made it back in time, but in the meantime Mike
and Leonard had rigged a way to get cooling with the Silcool oil started
using liquid nitrogen.
During our efforts to reach the target glycerol concentration another
problem surfaced, one which really requires an immediate fix. During
early cryonic suspensions it was discovered that when glycerol
concentrate is added to the recirculating system (the perfusate being
pumped through the patient) it tends to stratify, i.e. it sinks to the
bottom of the reservoir and ends up being pumped into the patient without
first being safely diluted. (Glycerol is the very best available
cryoprotective, but very high glycerol concentrations are used to
*dissolve* some tissues!) This problem was solved by continuous mixing
of the perfusate with a magnetic stirring bar. Unfortunately, if the
reservoir level drops too low, the stir bar creates a vortex--which sucks
in air and fills the perfusate with micro-bubbles. This happened during
Nick's perfusion, though--fortunately--the in-line arterial
filter/bubble trap caught the air. However, we cannot rely on this in
the future and several (patentable?) suggestions have been put forth on
how to eliminate this problem. A decision has also been made to acquire
(as soon as we can locate one) an air-bubble detector for use on the
circuit. Operating room perfusionists have had bubble detectors for so
long that few of them would willingly do without one.
Cephalic isolation has been greatly improved due to the introduction
of new tools by Keith and Mike. (Details on the procedure are available
to those who ask.) We now have this procedure down to a fraction of
Jerry Leaf`s best time. After trying umbilical tape (which proceeded to
untie itself), Mike found cable ties to be an efficient way to occlude
(tie off) the esophagus and trachea. This goes a long way to maintain a
clean surgical field during cephalic isolation.
Cooling to -79 C was started at about 11 p.m. After cooling was
started, the grueling and seemingly endless process of cleaning up began.
About this time Mark Connaughton came in and calibrated the blood-gas
machine so we could try to make better sense out of pH data that did not
agree between two machines. Cleanup was fairly well completed by about
2:30 a.m., though there was a lot of work left for the next few days,
restocking, re-ordering, and cooldown.
The final result of this suspension was close to or perhaps the very
best to date. It is fairly clear that the most serious problem (nearly
having the patient deanimate with us hours away) was the result of faulty
pre-suspension medical evaluation and had nothing to do with the cryonic
suspension aspects on which so much recent effort has been expended.
Organization and attention to detail need a lot more work, and we are
really going to have to train some of the suspension team members (in
addition to Mike) as backups to do the cardiac surgery. Emotionally
suspensions are about as rough on people as can be imagined, but there
was great (and effective) effort by all concerned to be more supportive
of each other. Sadly, we have to expect to be doing more HIV cases as
time goes on and Alcor grows. Mike Darwin wishes to add his thanks to
all involved for allowing his participation in the suspension, and his
special thanks to Arel Lucas for her constant and invaluable support and
to Paul and Maureen Genteman and Brenda Peters for their facilitation of
his participation. Keith adds that *he* is responsible for the harshest
presentation of our problems in this article.
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