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825 
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DISCUSSION 
Perry L. Blackshear, University of Minne- 
sota, Minneapolis : Did you have any rings that 
remained clean, or that left the kidneys clean? 
Dr. Kusserow: Yes. 
Dr. Blackshear: So this is reasonably good 
evidence that by squeezing the outside of the 
aorta enough tissue juice was not produced to 
incite some sort of rapid clotting phenomena? 
Dr. Kusserow: Yes, we think that his so- 
called "ring end phenomena" to which you refer 
can be a real problem under two circumstances. 
One is any sort of traumatic insertion of the 
ring. This is something of which one must be 
very careful when the ring is inserted. One can 
do no better than to use his best surgical judg- 
ment and technique and be careful not to injure 
the endothelial surface. The second thing that 
can be done to reduce this possibility, is to 
do away with the trauma which may result 
from aortic pulsation against the edges of the 
ring implant. This is the reason that we 
have used the wrapping. Interestingly enough, 
Dr. Blackshear, the rings which have remained 
clear have generally been very smooth. I don't 
know whether there is anything fundamental 
behind this or whether the material tends to 
slide off more easily. 
Dr. Blackshear : What materials were those 
that remained clear without embolizing? 
Dr. Kusserow: No material tested to date 
has yielded both a thrombus free ring and in- 
farct free kidneys during a single implantation 
procedure. 
Jeffrey L. Peters, University of Utah, Salt 
Lake City : Dr. Kusserow, I enjoyed your paper. 
I want to ask you two questions. One, have you 
been able to characterize the different types of 
thrombi as a function of material? Is this the 
next stage, or will you be doing this? Secondly, 
do you have a problem with sepsis with these 
experiments? Do you have bacteremia some- 
times ? 
Dr. Kusserow : In answer to your first ques- 
tion, we have not been able to find consistent 
differences which are a function of the type of 
material, i.e., consistent differences in the com- 
position of the thrombus. They are all rich in 
platelets. There are also varying amounts of 
