Hemodynamic effects of alterations in potassium.

Potassium is the major intracellular cation. Despite this fact, the systemic and renal hemodynamic effects of alterations in either serum K or in total body K are only partially understood. In isolated preparations acute K excess causes vasodilation while acute K deficiency results in vasoconstriction. Although chronic K excess may decrease arterial pressure in experimental models of hypertension, no definitive conclusions can be stated on the effect of K excess in hypertensive patients. In normotensive animals, chronic K depletion is associated with decreased systemic vascular resistance and increased renal vascular resistance. Although a number of studies have shown that K depletion ameliorates experimental hypertension, no definitive conclusions can be stated on the effect of K depletion in hypertensive patients. The vasodilatory effect of K depletion appears to be a direct effect on vascular smooth muscle since it is associated with an increase in total body Na as well as an increase in cardiac output and in renin ane arginine vasopressin levels. Although renin levels are increased in K deficient rats to a value comparable to na-depleted rats, angiotensin antagonism results in a substantially smaller decrease in arterial pressure than in Na-depleted rats (11 +/- 1.6 vs 24 +/- 3.4 mm Hg, p less than 0.01). This relative resistance to the pressor effect of angiotensin also results in a blunted pressor sensitivity to exogenous angiotensin II. Since changes in K balance appear to have a major effect on the control of hemodynamics, further studies are warranted to determine whether alterations in K balance would be useful in the treatment of hypertension.