Determinants of systemic hydraulic power in unanesthetized dogs.

COX, ROBERT. H., Determinants of systemic hydraulic power in unawsthetizcd dogs. Am. J. Physiol. 226(3) : 579-587. 1974.-The characteristics of hydraulic power delivery to the systemic circulation by the left ventricle were studied in 16 trained, unanesthetized, chronically instrumented dogs. Measurements of ascending aorta flow, and ascending aorta, left ventricular, and central venous pressures were made under control conditions and during the injection of various neurohumoral agents. Cardiac output averaged 132 ml/min per kg at a mean arterial pressure of 98 mmHg and an average heart rate of 96 beats/min under control conditions. Total systemic hydraulic power averaged 7 13 mW with oscillatory power averaging 2Ooj, of the total. Norepinephrine increased total power to 935 mW with oscillatory power averaging 19%. Angiotensin produced no significant change in total power, but oscillatory power averaged 1 4y0. Isoproterenol increased total power to 1,129 mW with oscillatory power averaging 32 7& The oscillatory power fraction of total power was a strong function of heart rate under all conditions. Values of hydraulic fluid impedance for the ascending aorta were also calculated. Similarities of the impedance spectra for the various conditions were observed. The hydraulic power delivered to the systemic circulation as well as its components were found to depend on a) heart rate, b) left ventricular afterload (arterial pressure), and c) the inotropic state of the left ventricle.