596 
HEMODYNAMICS 
or basal portions of the left pleural space when 
using units containing more than three pres- 
sure cells. The pre- and post-operative proce- 
dures for implanting these devices has been pre- 
viously described.18 All animals in Group I 
were additionally instrumented with electro- 
magnetic flow meters placed on the ascending 
aorta; these were replaced with Doppler ultra- 
sonic trandsucers in Group 11 animals. Group I 
animals were additionally studied by Doppler 
flow meters placed on the common carotid and 
subclavian arteries as previously described.^^ 
Lead wires from all flow transducers were bur- 
ied beneath the skin in the vicinity of the origi- 
nal thoracotomy incision and exteriorized fol- 
lowing anesthesia at the time of subsequent 
studies. 
Four animals were actually instrumented in 
the Group I study but two died 18 and 37 days 
post-operatively from pneumonia. The third an- 
imal in this group succumbed from an empyema 
and sepsis subsequent to replacement of the im- 
planted battery pack 3 months after surgery. 
Change in antibiotic regime has subsequently 
remedied this situation. The last animal has 
survived without complications and is now 23 
months post-surgery and has gained 25 pounds 
during this period. The implanted units oper- 
ated for only two weeks in each animal in 
Group I, Examination of the units subsequent 
to removal at post-mortem revealed leakage of 
body fluids into the site of union of transducer 
leads with the transmitter and corrosion of sol- 
der joints in that area. 
All animals in Group I (two instrumented, 
two uninstrumented) were studied only after 
intramuscular anesthesia using 0.8 mgm/kgm 
of phencyclidine HCl (sernylan). Four animals 
were also instrumented in the Group II study. 
One animal died from aortic rupture due to the 
Doppler flow transducer three weeks post-sur- 
gery. One animal was sacrificed 75 days post- 
operatively after suffering a cerebral infarction 
and early gangrene of the lower right leg aris- 
ing from complications following cardiac cath- 
eterization and angiocardiographic studies. The 
last two amimals remain alive and well at the 
present time. The telemetry units have operated 
well in all Group II animals. The unit implanted 
in one of the surviving animals in Group II con- 
tinues to operate well eleven months post-opera- 
tively (Figure 3). The transmitter remains 
functional in the last animal but no useful phys- 
iologic signals have been obtained for the last 
two months. Data from these last three animals 
are included as Group II data in this study and 
were obtained both awake and following anes- 
thesia. 
Direct measurement of right and left sided 
pressures were made using Statham P23Gb 
gages from catheters inserted through the right 
and left femoral vessels using standard clinical 
catheterization techniques. 6F catheters were 
placed under fluoroscopic control in the right 
atrium for indicator dilution injection and infu- 
sion of sympathomimetic amines. Catheters 
were placed in the arterial system for indicator 
dilution sampling and measurement of arterial 
and left ventricular pressures. Reported levels 
of pressure represent average values before and 
after determination of indicator dilution car- 
diac outputs. 
Cardiac output was measured in all animals 
by means of cardio-green indicator dilution 
methods with injection of 1.0 cc of dye into the 
right atrium and sampling in the aortic arch by 
an 8F fiber optic catheter system inserted by 
cutdown through the left femoral artery.^^ 
Pressure and fiow responses of the central cir- 
culation were studied during constant infusions 
of standard sympathomimetic drugs into the 
right atrium using a Harvard syringe (Figures 
4 and 5). Such studies were conducted 6 weeks 
post-surgery in Group I animals and 8 weeks 
post-surgery in Group II animals. Infusion of 
each drug concentration was maintained for a 
period of five minutes, hemodynamic measure- 
ments were made after three minutes of infu- 
sion during each period. Fifteen-minute recov- 
ery period was allowed between isoproterenol 
and norepinephrine infusions. 
RESULTS 
Figure 6 demonstrates the course and magni- 
tude of heart rate and peak systolic right and 
left ventricular pressures for all Group II ani- 
mals for a period from the day of operation to 
150 days post-surgery. Figure 3 shows a de- 
tailed tracing obtained by telemetry in Chim- 
