TOTAL CARDIOPULMONARY BYPASS WITH A 
MEMBRANE OXYGENATOR IN CALVES 
M. P. Kaye and J. B. Pace' 
Thirty-five Holstein calves weighing 65 to 110 kg 
were subjected to total cardiopulmonary bypass for pe- 
riods up to 4 hours. Twenty-five underwent bypass with 
the Dow capillary membrane oxygenator. In ten of 
these animals, a filter was used on the oxygenator inlet. 
The remaining ten animals were subjected to bypass 
utilizing a bubble oxygenator. Anticoagulation was ac- 
complished with an initial heparin dose of 4 mg/kg and 
an hourly dose of 1 mg/kg. Pressure drop across the 
oxygenators was measured for the Dow units. Blood 
samples were obtained at hourly intervals during bypass 
from the venous and arterial lines for pH, pOs, pCOj, 
hemoglobins and oxygen saturations. All animals had 
pre-operative biochemical and hematological surveys 
which were repeated on post-operative days 1, 3, 7 and 
10. All were subjected to complete autopsies. 
Our data indicate that two 3-liter Dow oxygenator 
units when used in parallel are capable of supporting a 
calf on total cardiopulmonary bypass when a filter is 
placed on the inlet end of the oxygenator. Use of the 
oxygenator without a filter resulted in formation of 
platelet aggregates on the oxygenator inlet tubesheet. 
Oxygen transfer rates at flows ranging from 2,500 cc to 
5,000 cc per minute were comparable for Dow units 
with filters and bubble oxygenators. No significant al- 
terations in hematology or biochemistry was noted con- 
sequent to perfusion with the membrane oxygenator. 
All animals perfused with the membrane oxygenator 
utilizing filters survived perfusion. Because of respira- 
tory distress due to pneumonia, one animal was sacri- 
ficed on the first post-operative day. Nine animals had 
uneventful post-operative courses and were sacrificed 
on the tenth post-operative day. Four of ten animals 
subjected to perfusion with the bubble oxygenator ex- 
pired during the course of bypass. An additional animal 
was sacrificed on the sixth post-operative day because 
of pulmonary complications. It is concluded that the 
hollow fiber oxygenator when used with a filter is capa- 
ble of adequately supporting calves for four hours of 
total cardiopulmonary bypass. 
INTRODUCTION 
The work reported in this paper is based on 
the testing of a hollow fiber membrane oxygena- 
tor developed by Dow Chemical Corporation 
under direction of the Medical Devices Applica- 
* T & E Facility, MDAP, IIT Research Institute Chicago, Illinois. 
tion Program, National Heart and Lung Insti- 
tute. 
In recent years numerous papers have de- 
scribed the advantages of membrane oxygena- 
tors over other oxygenators which function 
through a direct blood-oxygen interface.^ The 
design and functional concept of the hollow 
fiber membrane oxygenator has been previously 
reported and has been shown to perform satis- 
factorily during partial bypass studies in 
dogs.^ However, no information exists concern- 
ing the efficacy of this type of oxygenator in 
procedures requiring total cardiopulmonary by- 
pass for periods approaching four hours. This 
manuscript describes the use of a disposable 
hollow fiber capillary membrane oxygenator for 
total cardiopulmonary bypass of four hours du- 
ration in calves and compares the long-term 
effectiveness of the hollow fiber device to a com- 
monly used bubble oxygenator. 
This study was designed to permit compari- 
son of the gas transfer characteristics of the 
membrane oxygenator with data derived in an 
identical manner utilizing a standard bubble ox- 
ygenator in the perfusion circuit. In addition, 
the effects on blood constituents and animal 
survival of four hours of perfusion with both 
bubble and membrane oxygenators are com- 
pared. 
METHODS 
The hollow fiber membrane oxygenator used 
in these experiments (Figure 1) consisted of a 
bundle of 48,000 fibers spun from a siloxane-pol- 
ycarbonate copolymer. At each end of the fiber 
bundle, the area between the fibers is filled with 
a potting material of silastic to form a tube- 
sheet of approximately 2 centimeters in thick- 
ness. The sealed fiber bundle is surrounded by a 
lucite jacket which encloses the gas phase of the 
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