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SURGERY AND TRANSPLANTATION 
bypass is employed with the calf, perfusion 
and blood pressure are inadequate and pressor 
agents have to be employed. 
Deep Hypothermia 
Dr. Jun Kawai introduced deep hypothermia 
in our laboratory as a method of implanting 
the artificial heart.^'^ 
The fasted, pre-conditioned calf is induced 
with scopolamine (0.015 mg/kg) and brevane 
(5 mg/kg), intubated and placed on a Bird 
Respirator (Mark 14), with halothane gaseous 
anesthesia. The calf is then instrumented with 
ECG electrodes, femoral arterial blood pressure 
catheter, external jugular vein catheter (for 
Ringer's lactate solution infusion) and a rectal 
temperature probe. The calf is placed in an ice 
bath and cooled to a rectal temperature of 24° C 
(range 22.5°— 25° C). Figure 4 illustrates the 
changes in heart rate and blood pressure during 
cooling. On the operating table, cooling is main- 
tained by ice bags on the head, neck and groin. 
The chest is opened by a midsternal split and 
the great vessels dissected and ligated after 
heparin (1 mg/kg) is given. Once the rectal 
temperature has decreased to 21° C, blood is 
expelled from the natural heart and with hyper- 
ventilation, from the pulmonary circulation. 
Both circulatory and respiratory arrest are 
maintained during the implantation of the arti- 
ficial heart which usually takes 45 minutes. 
The artificial heart is pumped slowly at first 
and at low pressures in order to detect and 
repair blood leaks and to prevent the pulmonary 
and systemic circulation from being exposed to 
sudden high pressures and flows. Protamine 
sulfate is administered (1.5 mg/kg), four chest 
drainage tubes are inserted and the chest is 
closed. The calf is then placed in a warm water 
bath (40° C) until the rectal temperature 
reaches approximately 34° C (see Figure 4 for 
blood pressure changes during rewarming) , 
after which the calf is placed in a specially 
(HZ 
^_ RECTAL TEMP i 
_ HEART RATE | 
rnin blood pres. 
HRS. 
Figure 4. — Utilization of deep hypothermia to implant the artificial heart. Calf is cooled to approximately 20° rectal 
temperature at which temperature the natural heart is excised and replaced with an artificial heart during 
circulatory and respiratory arrest. 
