Journal of Applied Physiology, Vol 56, Issue 6 1526-1532, Copyright © 1984 by American Physiological Society
Performance of hypothermic isolated rat heart at various levels of blood acid-base status
M. Sinet, M. Muffat-Joly, D. Henzel, G. Renault and J. J. Pocidalo
The effects of respiratory-induced pH variation on mechanical function and
myocardial oxygenation of isolated, blood-perfused working rat hearts were
studied in hypothermia (26 degrees C) and compared with control values (37
degrees C). In these experiments, the change of plasma pH during
hypothermia was parallel to the change in pH of neutral water. At 37
degrees C, pH was varied from 7.15 to 7.62; heart rate increased with pH,
both cardiac output and external work remaining unaltered. An increase in
pH induced a decrease in coronary flow and an increase in the O2
arteriovenous difference. In hypothermia, hemodynamic performance and
myocardial O2 consumption decreased proportionately with no change in
cardiac efficiency. At 26 degrees C, the cardiac capacity to react to
acid-base variations (pH from 7.34 to 7.86) was preserved, i.e., heart rate
increased with pH. As at 37 degrees C, regulation of both coronary flow and
myocardial oxygenation was maintained. The present data suggest that the
myocardial function of a working isolated rat heart undergoing hypothermia
was also preserved. Moderate variations in extracellular acid-base status
during hypothermia did not impair either myocardial function or the O2
supply-to-demand ratio.
