Sympathetic nervous system activity during sodium restriction in essential hypertension.

Sympathetic nervous system activity was studied in 38 patients with essential hypertension during high- and low-sodium diets. Salt restriction was associated with a modest (6 mmHg) decline in mean arterial pressure, while the urinary excretion of catecholamines, metanephrines, and vanillylmandelic acid increased significantly. Plasma renin activity also increased. It is concluded that short-term low-sodium diet therapy for essential hypertension results in only small decrements in mean arterial pressure and may be limited in hypotensive effect by activation of the sympathetic nervous system. Support is offered for the rationale of sympatholytic drug therapy as an initial step in the management of hypertensive patients requiring arterial pressure reductions greater than those afforded by diet alone.