Development of Hypertension in Renal Disease

Abstract

Central and peripheral hemodynamics, circulating blood volume and plasma renin activity (PRA) were investigated under resting conditions in 97 patients with chronic nonuremic renal parenchymatous disease and without anemia. For comparison a group of 17 healthy subjects was used. An initial abnormality appeared in 12 of 32 normotensive renal patients. It consisted of a markedly increased circulating blood volume, raised cardiac output, low total peripheral and forearm vascular resistance, hyperfusion of the forearm and increased venous distensibility. PRA was slightly (but significantly) higher in these hyperkinetic subjects with relaxed peripheral vessels than in the other 20 normotensive renal patients who did not differ hemodynamically from the control subjects. Of 47 renal patients with a mild or moderate hypertension, 15 were hyperkinetic. However, in these there was no compensatory vasodilatation in response to the high cardiac output: forearm blood flow was normal and venous distensibility below that of the control subjects. Blood volume was normal. PRA was the same as in the normotensive renal patients. A re-examination of these patients 2-8 yr after they were first studied revealed that 11 of the 12 originally hyperkinetic normotensive renal patients were now hypertensive compared with only 1/2 of the originally normokinetic normotensive renal subjects. Apparently, an inability of the diseased kidney to control volume homeostasis leads to hypervolemia, which raises cardiac output in the renal patients while still normotensive. As long as the arterioles adjust to the high output and the capacitance system to the high volume, blood pressure remains normal. When this adaptation of the periphery ceases, blood pressure rises, normalizing (possibly through a pressure diuresis) blood volume. PRA does not correlate with any of these changes and only in advanced renal hypertension may its rise partly contribute to the maintenance of high blood pressure without being its cause.