HEMODYNAMICS IN THE CHIMPANZEE: 
UNANESTHETIZED AND ANESTHETIZED 
H. L. Stone* and H. Sandler' 
The cardiovascular system of the chimpanzee has not 
been studied very extensively, and this animal's rela- 
tionship to human standards in this regard are not well 
known. The response of this animal to various common 
stimuli must be known in order to propose the chim- 
panzee as an analogue of man or for human disease in- 
volving the cardiovascular system. Seven chimpanzees 
weighing 23 to 32 kg were used in this study. A left 
thoracotomy was performed in the fourth intercostal 
space under sterile surgical conditions. A multichannel 
telemetry unit containing ECG electrodes and 3 to 6 
solid state pressure cells was implanted in each animal. 
Pressure cells were implanted in the right and left ven- 
tricular cavities and the left atrium. The remaining 
pressure cells were left in various locations in the 
thorax. An electromagnetic or Doppler ultrasonic flow 
probe was implanted around the ascending aorta. The 
chest was closed and evacuated. Telemetry signals were 
recorded periodically from the unrestrained caged ani- 
mals following surgery. The response of these animals 
was determined to anesthesia, norepinephrine and iso- 
proterenol. Results indicate that the chimpanzee has an 
elevated mean arterial pressure by human standards 
and that the response pattern to most conditions is me- 
diated by the sympathetic nervous system. 
INTRODUCTION*** 
Interest in the study of various non-human 
primates has increased over the past 15 years 
as demonstrations have been made that they 
may serve as realistic models for various phys- 
iologic processes in man. Such animals are 
phylogenetically and anthropomorphically close 
to man, have a near human posture and are 
highly intelligent. The chimpanzee of all non- 
human primates has been thought to be closest 
to man.^ Chimpanzees have been used exten- 
sively in neurophysiologies and social behav- 
ioral studies,^ are susceptible to a wide variety 
of human infections^ and were chosen by the 
Space Agency in the late 1950's as the best ani- 
♦ The Marine Biological Institute Galveston, Texas. 
•* NASA-Ames Research Center Moffett Field, California. 
•** Supported in part by NASA Contract No. NGR-44-088-002. 
mal model to simulate man prior to space 
flight.^ 
Although a chimpanzee's heart was used as 
donor for the first human heart transplantation,*' 
only a few cardiovascular studies and demon- 
strations of cardiovascular function have been 
reported in these animals. "^"^^ The first studies of 
the systemic and pulmonary circulations of the 
chimpanzee were reported by Weissler in 1963.^ 
These latter studies were conducted using stand- 
ard clinical catheterization techniques in awake 
but restrained animals. Heart rates and direct 
recordings of arterial pressures were signifi- 
cantly elevated by human standards. These 
findings correlated with previous observations 
reported by the Space Agency using similar ani- 
mal preparations as part of ground based obser- 
vations prior to space flight.^ On the basis of 
these previous findings and with the develop- 
ment and use of multichannel implantable telem- 
etry units in these laboratories, it was decided 
to obtain additional blood pressure recordings in 
the chimpanzee in an awake unrestrained state 
and to determine cardiovascular response to 
anesthesia and standard sympathomimetic 
drugs. 
METHODS 
Data were collected on 7 animals. All animals 
were obtained from the 6571st Aeromedical Re- 
search Laboratory, HoUoman Air Force Base, 
Allamagordo, New Mexico; five were used for 
purposes of chronic instrumentation. They con- 
sisted of 3 males and 2 females ranging in age 
from 5 years to 7 years. Two uninstrumented 
animals in this same age span were also in- 
cluded as controls. The smallest animal weighed 
23 kg and the largest weighed 32 kg with an av- 
erage weight of 28 kg. The study was conducted 
in two parts, separated by a year. Two animals 
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