The pattern of electrolyte excretion in normal and hypertensive subjects before and after saline infusions. A simple electrolyte formula for the diagnosis of primary aldosteronism

Electrolyte excretion and serum electrolytes were studied in 99 subjects-19 normal subjects, 62 patients with essential hypertension, 10 with hypertension and renal disease, and 8 patients with primary aldosteronism-during administration of a low sodium diet and during 2 days of intravenous sodium loading. With saline infusions patients with primary aldosteronism gained significantly less weight, excreted significantly more potassium on each day of infusion, and excreted significantly more sodium on the first day of infusion only, than the other groups studied. Mean serum potassium levels fell significantly with saline infusions in patients with primary aldosteronism but remained unchanged in the other groups. From these observations a diagnostic formula based on potassium clearance corrected for sodium excretion was derived by which patients with primary aldosteronism could be separated completely from the other groups, with the exception of 1 patient with renal disease. Although patients with primary aldosteronism tended to have lower salivary sodium/potassium ratios than patients with essential hypertension, the difference was not significant.