F. T. GALYSH AND R. F. WALLIN 
1039 
PERFUSION TECHNIQUES AND PROBLEMS 
We have performed cardiopulmonary bypass 
in our laboratories in more than 100 calves 
varying in size from 65 to 130 kg for periods 
ranging from sixty minutes to more than three 
hours. These studies have in part related to 
standardizing a bypass technique for the im- 
plantation of heart valves and total artificial re- 
j placement hearts. With careful attention to de- 
tail, cardiopulmonary bypass is now carried out 
routinely with maintenance of acceptable perfu- 
sion flows and pressures, blood pH, PCO2 and 
PO2 values. 
The extracorporeal apparatus employed in 
these operations incorporates a 25 inch Kay- 
Cross disc oxygenator,'^ a Travenol Miniprime 
6LFP or a Bentley Q-lOO*^ bubble oxygenator 
I and critically occluded double roller pumps. A 
Sarns arterial line, or more recently, a Travenol 
venous line heat exchanger^ effectively main- 
tained normothermia with water bath tempera- 
tures of 40 to 42 °C in the Sarns normothermia 
module.^ Venous return reservoirs, arterial 
bubble traps and arterial filters were often 
added to the circuit. The reservoir serves to fa- 
cilitate storage and rapid administration of ex- 
cess blood and administration of fluids and the 
filter to remove fibrin and other debris that 
might otherwise find itself into the vascular 
system of the animal.^^ 
In some bypass procedures the carotid artery 
was also perfused separately with an additional 
pump to simulate those conditions in which 
prosthetic devices might be sutured to the aor- 
tic root. To gain space for such prostheses in 
the calf, the brachiocephalic trunk and aortic 
arch may be clamped during bypass. In this cir- 
cumstance, separate perfusion of the head is 
mandatory. 
In calves above 110 kg, perfusion flows may 
exceed 6 liters per minute. In these cases we 
have perfused both femoral arteries utilizing 
two separate roller pumps. Dual return sites re- 
duce resistance to pumping at such high perfu- 
sion flows and thus minimize potential cavita- 
tion effects as a source of gas embolization, 
which has occasionally been observed in the cer- 
ebral arteries (Figure 3) . 
Oxygenator priming requirements varied be- 
tween 2,500 and 4,000 ml depending upon the 
equipment and approach used. Our standard 
priming solution is a mixture of two parts lac- 
tated Ringer's solution to one part freshly 
drawn heparinized whole blood. Earlier use of 
an acellular priming solution led to poor venous 
return and generally poor perfusion. A 6% solu- 
tion of dextran-70 in 0.9% sodium chloride 
solution used as a component of oxygenator 
priming solutions, was found to produce un- 
acceptable post-operative bleeding. The prim- 
ing fluid now employed allows reproducible 
blood flows in the range of 4-6 liters per 
minute for periods of two hours or longer. 
Perfusion pressures are easily maintained in 
the range of 80-100 mm Hg by addition of 
blood or by slight occlusion of venous return 
lines in those cases where flows are adequate. 
Donawick^ has reported some difficulty in 
maintaining Pa02 values above 70-80 mm Hg 
during cardiopulmonary bypass in calves. How- 
ever, in a series of ten calves having a mean 
body weight ± S.E. of 132.7 ± 2.1 kg perfused 
by us with a disc oxygenator at mean perfusion 
flows ±S.E. of 4.90 ± 0.23 liters/min., PaOa 
± S.E. was was 115 ± 11.3 mm Hg, PaC02 ± 
S.E. was 34.9 + 1.63 mm Hg and pH ± S. E. 
was 7.301 ± 0.022. These values were deemed 
to be quite acceptable for the large calves used in 
" Pemco, Incorporated, 5635 Brecksville Road, Cleveland, Ohio 
44131 
^ Travenol Laboratories Incorporated, Morton Grove, Ulinoia 
60053 
" Bentley Laboratories Incorporated, Santa Ana, California 92707 
Figure 3. — Gas emboli (arrow) in cerebral artery 
branches, of the calf. 
■I 
