Plasma catecholamine levels and hemodynamic responses of severely acidotic dogs to dopamine infusion.

Changes in plasma catecholamine (CA) levels and hemodynamic responses after a dopamine (DA) infusion of 20 micrograms/kg body weight per min were studied in dogs with a normal acid-base state (pH 7.4, PaCO2 40 torr) and in the same animals after induction of severe metabolic acidosis (pH 7.0, PaCO2 40 torr). DA increased plasma norepinephrine (NE) levels from .487 +/- .109 ng/ml to 3.077 +/- 0.357 ng/ml in the normal acid-base state, and from 1.762 +/- .521 ng/ml to 9.533 +/- 1.403 ng/ml in acidosis. Plasma epinephrine (E) levels in normal and acidotic states were also increased by DA infusion. In the normal acid-base state DA increased myocardial contractility and cardiac index (CI). DA also increased myocardial contractility during acidosis, but the response of CI to DA was abolished. DA significantly decreased systemic vascular resistance index (SVRI) in the normal acid-base state and significantly increased SVRI in acidosis. Acidosis appears to enhance the rate of conversion of DA to NE and E. The failure of DA to increase CI in acidosis may be a result of the increased afterload on the left ventricle.