Physiologic effects of simulated + Gx orbital reentry in primate models of hemorrhagic shock.
BACKGROUND
While the physiologic effects of space travel are documented in healthy individuals, little is known about its impact on medically ill or injured persons. In this study, hemorrhagic shock in primates was used to model a potentially common pathophysiologic condition during exposure to gravitational forces simulating return from Earth orbit. This experiment did not model the effects of cardiovascular deconditioning that normally occur during spaceflight.


METHODS
Using invasive hemodynamic monitoring, serial cardiovascular and laboratory parameters in baboons (Papio papio) were studied. Subjects were centrifuged at either a low +Gx (3.3 G maximum) or high +Gx (7.8 G maximum) acceleration reentry profile before and after being subjected to either class II (20% volume loss) or class IV (40% volume loss) hemorrhagic shock.


RESULTS
Significant alterations in cardiovascular and laboratory parameters occurred during shock and exposure to high and low +Gx acceleration. Shock classification was the primary determinant of change in cardiovascular function. During the experimental protocol, 31 of 32 animals survived (97% survival). After a 1-wk post-protocol observation period, 28 of 32 subjects survived (88% survival).


CONCLUSIONS
This preliminary study presents data that suggest that the emergent return of a medically compromised individual without resuscitation may be potentially survivable. However, medical stabilization with volume resuscitation, supplemental oxygen, and noninvasive monitoring would likely optimize clinical outcomes in the event of significant hemorrhagic shock states necessitating emergent deorbit.
Stepaniak
Philip C
PC
Department of Emergency Medicine, Wright State University, Kettering, OH, USA. philip.stepaniak-1@nasa.gov
Hamilton
Glenn C
GC
Olson
James E
JE
Gilmore
Stevan M
SM
Stizza
Denis M
DM
Beck
Bradley
B
D000054:Acceleration / Q000009:adverse effects; D000337:Aerospace Medicine; D000818:Animals; D002319:Cardiovascular System; D002498:Centrifugation / Q000009:adverse effects*; D003198:Computer Simulation; D018471:Hypergravity / Q000009:adverse effects*; D008297:Male; D023421:Models, Animal; D010215:Papio / Q000502:physiology*; D012307:Risk Factors; D012771:Shock, Hemorrhagic / Q000209:etiology* / Q000401:mortality