422 SURGERY AND TRANSPLANTATION 
Table I. — Considerations In Selecting Species for Experimental cardiovascular Surgery : Relative Comparison 
Primate 
Dog 
Pig 
Pony 
Goat 
Sheep 
Calf 
Cost/Availability .. 
— 
+++ 
++ 
++ 
++ 
++ 
++ 
Husbandry 
+++ 
++ 
++ 
-H- 
++ 
+ 
Size/Maturity 
-t— r+ 
1 -1- 
+— 
1 1 1 
1 1 1 
I 1 1 
1 1 1 
1 1 1 
Anesthesia- 
++ 
1 1 1 
+± 
++ 
++ 
++ 
++ 
Thoracic Exposure 
+++ 
+++ 
+ 
++ 
+ 
++ 
CV-Human Simijaritles 
++++ 
++ 
+++ 
+± 
+± 
+± 
CPBP Tolerance 
+++ 
+ 
+ •>. 
+ 
+++ 
CV-Tissue Tolerance 
++ 
+ 
+++ 
++ 
+ 
+++ 
Postop Management 
+± 
± 
+ 
+ 
++ 
Instrumentation Tolerance 
+ 
+ 
+++ 
++ 
++ 
-H-+ 
Chronic MCA Tolerance 
±: 
? 
+ 
++ 
+++ 
References 
11-13, 
14-38, 
39-48, 
49-58, 
10, 59, 
61, 63-71, 
7-9, 72, 91, 
111-131 
95, 97, 98 
95, 96, 100 
99-105 
62 
101, 104 
92, 94, 102, 
— = Poor, ? = insufficient information, +(s) = degree of acceptability 109, 110 
of approximately 70 kg primates. While the 
other species are relatively easy to care for, 
special facilities are necessary to meet the hus- 
bandry requirements of each. 
The importance of establishing rigorous pro- 
cedures and adequate facilities for the procure- 
ment and preoperative conditioning of animals 
prior to attempting extensive experimental 
cardiovascular surgery cannot be overempha- 
sized. It is imperative in most experiments that 
sound, healthy animals be used in order to 
minimize the variability of the experimental 
results and to maximize tolerance to anesthesia 
and surgical trauma. Spontaneous disease prob- 
lems occur in all species of laboratory animals 
and necessitate constant surveillance. For ex- 
ample, screening for heartworm disease is nec- 
essary in randomly-procured dogs, particularly 
in the coastal areas where Dirofilaria immitis 
is endemic. The frequency of this disease is a 
deterrent to the use of the canine in many 
cardiovascular studies. The problems of res- 
piratory disease in calves has been noted by 
many investigators. Our laboratory has 
largely solved this problem by culling and con- 
ditioning these animals as previously described. 
If animals of approximately 70 kg are re- 
quired, their maturity at this vs^eight may be an 
important consideration. Relative to the other 
species, the calf is less mature for a given 
weight and gains approximately 1 lb per day. 
This can be a disadvantage in studies involving 
long term observation of implanted prostheses, 
e.g., following prosthetic valve implantation, 
relative valvular stenosis results.^ 
While a number of difficulties have been en- 
countered in the anesthetic management of each 
of the above sub-human mammals, most prob- 
lems can and have been overcome with experi- 
ence. Anesthetic induction has been a problem 
in the pig because of the small size of the ac- 
cessible vessels.^^ In addition, perilaryngeal 
anatomy of pigs has rendered tracheal intuba- 
tion difficult in the hands of some investiga- 
tors.3^ The anesthetic management of calves 
has also been variably reported. While 
some investigators have had good success with 
barbiturate anesthesia in calves others,'^ 
including the authors, have noted that the use 
of barbiturates is accompanied by prolonged 
recovery periods. Inhalation anesthesia, par- 
ticularly with halothane and methoxyflurane, 
has more recently been used in most of the 
species."'i^'*2.49.59,64,86 Incorporating nitrous ox- 
ide into the gaseous mixture allows one to re- 
duce the concentration of the primary anes- 
thetic agent. 
The depressing effects of halothane on myo- 
cardial function have been documented in a 
number of species. Prolonged pre-ejection pe- 
riods in calves have been observed by the au- 
thors and are being reported elsewhere, further 
supporting the depressing effects of halothane 
on myocardial contractility. 
The relative ease of gaining access to the 
chest through fat, muscle and ribs, as well as 
the relative accessibility of the heart and great 
vessels once the thorax is entered, is of im- 
portance when considering an animal species 
for experimental surgery. The pig has a par- 
