368 
SURGERY AND TRANSPLANTATION 
tion of these procured lungs was not evaluated 
immediately after their implantation. 
Hypothermia combined with hyperbaria, al- 
though apparently useful for short periods, has 
a time limitation providing a maximum effective 
storage period for kidneys of about 24 hours 
under ideal conditions.^^-^^ Clear cut evidence 
of successful storage of hearts by this method 
is not recorded.^^ In order to differentiate be- 
tween the physical effect of increased pressure 
and the increased oxygen saturation, kidneys 
were subjected to hyperbaria with either helium 
or oxygen by Samson and Murphy.^^ Kidneys 
exposed to helium demonstrated adequate crea- 
tinine and osmolar clearances. Deleterious ef- 
fects of oxygen were manifested by increased 
renal vascular resistance to perfusion, and im- 
pairment of cortical perfusion as measured by 
the xenon clearance technique. 
PERFUSION OF ORGANS 
Various devices designed for perfusion of 
isolated organs have now been used for almost 
a century by physiologists and pharmacologists. 
Much of our present knowledge of physiology 
and the action of drugs on individual organs is 
derived from the use of these techniques. With 
the development of interest in organ transplan- 
tation, organ perfusion studies have gained a 
new impetus, stimulating the publication of 
new books and numerous papers devoted to the 
subject. It must be noted, however, that little 
has been accomplished in improving the actual 
technology of perfusion since the late thirties. 
All perfusion apparatuses are still utilizing the 
constant perfusion pressure or volume flow 
principle, which does not allow for the physio- 
logical regulation of blood flow. This inevitably 
causes damage to the perfused organs. The rela- 
tively short survival time of isolated perfused 
organs, the repeated observation of increased 
vascular resistance to perfusion as perfusion is 
continued and the demonstrable spasm of the 
vessels in isolated organs indicates that the 
microvascular system is the primary target 
which sustains damage during perfusion. 
Several papers in which the results of various 
perfusion methods were compared, historical 
reviews given, and the various methods of per- 
fusion described have been published in recent 
years.^*-^^ Repetition of these efforts would 
serve little purpose. 
Consideration of perfusion literature makes 
it quite clear that, despite all atempts to re- 
create the normal physiologic environment even 
under the best of circumstances, all existing per- 
fusion systems are, in fact, unphysiologic. Most 
undesirable qualities of perfusion come both 
from the inflexibility of the delivery system and 
the deficiency of the perfusates. Blood cannot 
be used in most perfusion systems because of 
the inability of the erythrocytes and other cel- 
lular and non-cellular components to withstand 
mechanical injury and because of the clotting 
problems. This led to the utilization of blood 
components and the formulation of artificial 
chemically defined perfusion media. Among 
blood products, plasma was shown to be the 
most effective media by Humphries et al.^^ Cryo- 
precipitated and filtered plasma used by Bel- 
zer 3^ allowed him to maintain functional, trans- 
plantable kidneys for several days. In the 
non-blood product perfusion media category, 
the best results were obtained with various 
tissue culture type media.^^ 
When perfusion techniques are used for 
physiologic studies of isolated organs, the re- 
quirements are different from those of preserva- 
tion. The aim in physiological studies is to re- 
produce the in vivo environment as closely as 
possible and to elicit maximal physiological 
function of the organ subjected to study. There- 
fore, physiologic studies are usually conducted 
at normothermic temperatures. In preservation 
attempts, temperatures which assure the long- 
est survival of an organ are selected. Paradoxi- 
cally, perfusion of organs at temperatures close 
to the freezing point does not extend the life 
span of an organ. The longest periods of "sur- 
vival" of simian hearts perfused under identical 
conditions at different temperatures were ob- 
tained in the temperature range of 10-15 °C. At 
these temperatures the hearts resumed con- 
tracting on rewarming after an average perfu- 
sion time of nine days. The hearts perfused 
at 4-6 °C failed to contract on rewarming after 
12 hours. Hearts perfused at room temperatures 
(22-25°C) pulsated, on an average, for 48 
hours, while hearts perfused at normothermic 
