Effects of changes of pH and of carbon dioxide tension on left ventricular performance

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Abstract
In canine, paced, isovolumetric, left ventricle preparations, the influence of acidosis and alkalosis and of changes in PaCO2 on left ventricular systolic pressure (LVSP) was investigated. Divergent changes in the pH and PaCO2 of the coronary arterial blood were produced either by changing the CO2 content of the insufflating gas mixture in the oxygenator or by the brief addition of tris (hydroxymethyl) amino methane to the perfusing blood. There was a consistent reduction in LVSP when coronary blood pH fell and PaCO2 rose, and an increase in LVSP when pH rose and PaCO2 fell. A transient increase in both pH and PaCO2 by the addition of NaHCO3 to the perfusing blood caused a marked reduction in LVSP. When the blood pH was maintained constant by means of an automatic titrator, PaCO2 could be varied over a wide range of values with no significant effect upon LVSP. The most plausible explanation for the changes in LVSP induced by these various interventions appears to be that the intracellular pH is the critical determinant of myocardial performance during derangements of acid-base balance.