Effects of acute lactic acidosis on left ventricular performance

Abstract

Responses of the chloralose-anesthetized dog''s left ventricle to rapidly infused lactic acid were examined under conditions of constant heart rate, aortic pressure, and flow. Significant depressions in ventricular contractilily were apparent at pH 7.1 and pH 6.8, but the depressions were preceded by transient positive inotropic changes. Dogs pretreated with propranol-ol showed no positive effects, and their final decreases in left ventricular function were more severe. Dogs pretreated with reserpine or pentolini-um retained the biphasic response. THAM [tris (hydroxymethyl) amino-methane] infusions returned pH to control levels and increased contractility in all dogs, fii additional reserplnized dogs, acidosis reduced the inotropic response of the heart ot constant infusions of no repine phrine. Acute lactic acidosis may affect venticular function through direct depression, catecholamine release, and reduction of ventricular responsiveness to catecholamines. Deomonstration that inotropic changes may be interpreted as positive, negative, or no change, depending on sympa-thoadrenal function and on time of observation may provide a basis for reconciliation of previous conflicting reports on the inotropic effect of acidosis.