Meaning of the cardiac output-blood volume relationship in essential hypertension

This study interprets the cardiac output-blood volume relationship in essential hypertension. Previous reports indicated that the chronic volume-flow slope (i.e., the regression coefficient alpha, cardiac output = alpha blood volume + beta, obtained from steady-state volume and flow) and the transient volume-flow slope observed during a dextran infusion were both steeper in essential hypertensives than in normotensives. By applying the Guyton-Coleman circulatory model to essential hypertension, this reports demonstrates that: 1) several alterations of the circulatory system may theoretically change the steady state of volume and flow and generate a chronic volume-flow relationship. However, only alterations of the kidney function and of the autonomic nervous system may produce a volume-flow curve compatible with the available data. 2) As hypertension develops, vascular resistance and compliance have the greatest influence on the slope of the chronic volume-flow curve. 3) To account for the observed increase of this slope in the transition from normotension to essential hypertension, not only must resistance be increased but also compliance must be reduced in essential hypertension. The same conclusions are drawn from the study of the transient volume-flow relationship observed during the dextran infusion.