K. T. WEBER, J. S. JANICKI, A. A. WALKER AND B. H. DENNISON 
1261 
chiocephalic artery) for arterial pressure moni- 
toring, (b) A pressure transducer* ** was im- 
planted into the left ventricular chamber via 
either the apex or through an avascular area of 
the anterior epicardial surface (posterior to the 
anterior papillary muscle) and secured in place 
with a purse-string suture. With the apical ap- 
proach, the transducer and a one-inch segment 
of the lead wire floated freely within the left 
ventricular chamber, whereas with the higher 
approach, the transducer was placed flush 
against the endocardial surface to minimize 
possible papillary muscle artifact, (e) An elec- 
tromagnetic flow probe* ** was placed around 
the aortic root (20-26mm diameter), (d) Epi- 
cardial ECG leads were sewn to the heart using 
stainless steel suture. These may also be used 
for pacing. Direct myocardial leads were chosen 
because of the difficulty in using and securing 
limb leads in the conscious animal, (e) For cor- 
onary sinus blood sampling, the sinus was can- 
nulated via the hemiazygous vein which, in the 
calf, joins the coronary sinus approximately 
5cm proximal to its termination into the right 
atrium. The hemiazygous may be ligated with- 
out side effects, (f ) Other devices representing 
particular needs of the protocol have also been 
utilized. The latter include vascular occlu- 
ders*** positioned around the coronary arter- 
ies, an intra-aortic balloon (Tecna Corporation, 
Emeryville, Calif.) inserted into the descending 
thoracic aorta via the femoral artery, and other 
assist devices which have been previously re- 
ported.^ The surgical instrumentation necessary 
for these procedures is, in large measure, sim- 
ilar to those available in most laboratories using 
dogs. 
Following instrumentation, the chest cavity 
was thoroughly rinsed with warmed saline con- 
taining 10 million units of penicillin and aspir- 
ated. Each lead wire was brought out, in a stag- 
gered fashion, through the original incision, 
and secured in place with a purse-string suture. 
Divided muscle is carefully approximated and 
closed with continuous suture. Skin is closed 
with mattress suture (00 silk) to prevent wound 
* Konigsberg Institute, Pasadena, California. 
♦* DynaSciences, Pasadena, California. 
* In Vivo Metrics, Redwood Valley, California. 
** Biotronex Laboratory, Inc., Bethesda, Maryland. 
*** Rhodes Medical Instruments, Woodland Hills, California. 
dehiscence. Lead wires were secured in place 
externally with skin suture. All catheters were 
capped with Luer locks, filled with pure heparin 
and patency checked daily. Systemic anticoagu- 
lation was only needed 24-48 hours following 
surgery with this technique. A loose cloth 
binder is placed around the thorax to prevent 
damage to instrument leads. A chest tube for 
fluid drainage was placed in the seventh inter- 
costal space and withdrawn 24 hours post-oper- 
atively. Vacuum on the chest line was kept at 10 
cm H2O or less negative pressure. Fluid loss 
(primarily serous) during this period was ap- 
proximately one liter. 
Post-Operative Care 
The animals were maintained on intramuscu- 
lar penicillin (1.2 million units, two to four 
times daily) for fourteen days regardless of 
body temperature (rectal temperature of 101- 
102° may be considered in the normal range). 
Intravenous fluids were continued as needed; 
however, this has not usually been necessary be- 
yond the first 24 hours post-operatively. Elec- 
trolyte abnormalities were a rarity. Food and 
water were provided ad libetum post-opera- 
tively; however, no more than one-half bucket 
of grain for the first 24 hours should be pro- 
vided to avoid bloating, thus compromising ven- 
tilatory exchange. The animals were generally 
standing within two hours following surgery 
(ketamine anesthesia) , although their condition 
was still quite weak. Viral pneumonias are occa- 
sionally seen during the post-operative period 
and have been unsuccessfully treated with pres- 
ently available antibiotic regimens. The incid- 
ence of pneumonia appears to be higher in 
animals obtained through auctions, where expo- 
sure to a larger number and variety of patho- 
gens occur. All post-operative calves were kept 
in a separate room in an attempt to minimize 
wound infections. Subcutaneous infections 
which do occur are generally well loculated and 
tolerated by the animal. However, as an adjunct 
to treatment, Streptokinase-streptodornase 
(Varidase) * and drainage are occasionally used. 
The room and interfacing with the data acquisi- 
tion system will be described later. Ultimate 
* Lederle Laboratories, Pearl River, New York. 
