Cardiovascular Effects of Infusions of Epinephrine and Angiotensin Singly and in Combination

Angiotensin infused at 0.05 mcg/kg per min for 30 minutes into anesthetized dogs reduces cardiac output, raises arterial blood pressure, increases total peripheral resistance, but does not raise right ventricular pressure nor change left ventricular stroke work. It is suggested that this infusion rate may be comparable to the rate of production under certain conditions.The cardiovascular action of epinephrine given at rates similar to those occurring under stress, namely 0.1 mcg/kg per min and 0.2 mcg/kg per min for 30 minutes, are discussed. In the former dose no cardiovascular effects are seen, but with the latter dose the usual cardiovascular effects were observed.A transient augmentation of effect on cardiac output and stroke work is noted with a combination of epinephrine 0.1 mcg/kg per min and angiotensin 0.05 mcg/kg per min, and of stroke work alone when the dose of each is doubled. It is suggested that the physiological importance of this interaction may be limited to the initial phases of certain stresses in which both these substances are released. The mechanism of this effect is not clear, but may be the result of the interaction of epinephrine, angiotensin and aldosterone.