AJP - Heart and Circulatory Physiology, Vol 246, Issue 3 344-H350, Copyright © 1984 by American Physiological Society
Cardiopulmonary response of the rat to gram-negative bacteremia
L. J. Pass, P. R. Schloerb, F. J. Pearce and W. R. Drucker
Hemodynamic and respiratory effects of a continuous 5-h intravenous
infusion of live Escherichia coli were studied in rats. Control animals
were infused with saline. Rats infused with 1.8 +/- 0.4 X 10(10) bacteria/h
did not survive a 5-h infusion. These animals developed early hypotension
and reduced cardiac output (CO) measured by thermal dilution technique.
Rats infused with 8.0 +/- 0.4 X 10(9) bacteria/h survived a 5-h infusion
with hypotension and reduced CO occurring later in the course of
bacteremia. Heart rate was markedly elevated in both septic groups.
Arterial blood gas measurements revealed that partial pressure of O2 was
not affected by bacteremia, but partial pressure of CO2 was significantly
decreased. Arterial pH remained within the normal range indicating
respiratory compensation of a metabolic acidosis. Since hypotension and
reduced CO were accompanied by a fall in right atrial pressure (RAP) during
bacteremia, a third septic group was studied to evaluate cardiac
performance during volume loading. After 3-5 h of bacteremia, a 40%
reduction in CO was associated with a significant drop in arterial pressure
and RAP. Despite volume loading, ventricular stroke work and arterial
pressure were significantly reduced compared with control animals. The
results indicate that severe gram-negative bacteremia produces myocardial
depression in the rat. This model can be useful for further studies of
cardiac dysfunction during sepsis.
