"Outpatient hyperkalemia" syndrome in renal and hypertensive patients with suppressed aldosterone production.

"Outpatient hyperkalemia" is a new clinical syndrome in which high serum potassium levels (SK) are found in the outpatient condition returning toward normal without any specific treatment after admission to the hospital. We report here of six patients with high blood pressure of various origin (chronic glomerulonephritis, interstitial nephritis, diabetic nephropathy, Gordon syndrome) in whom dietary and postural factors were found to be responsible for the outpatient hyperkalemia. The Na content of the "ad libitum" outpatient diet was definitely higher than that of the regular hospital diet. Increasing the Na intake from 120 mEq to 300 mEq induced a marked elevation of SK (from 5.21 +/- 0.16 to 6.34 +/- 0.40 mEq/l; p less than 0.001) in two hospitalized, recombent patients. On the other hand, Na restriction induced a dramatic improvement in hyperkalemia (from 5.89 +/- 0.11 mEq/l to 4.79 +/- 0.08 mEq/l:; p less than 0.001) in 4 patients in whom the effect was studied in the outpatient state. Although the mean plasma aldosterone (PA) was significantly lower in the patient group than in the healthy group, during normal Na intake there was a considerable overlap. A clearer distintion was made by using the new index of PA per SK ratio expressing the diminution in the apparently normal PA when related to the abnormally high SK. During high Na intake, PA was definitely suppressed and during Na restriction there was a dramatic relief from suppression. The present studies confirmed the previously described phenomenon of "upright hyperkalemia" which may have played an additional role in the development of outpatient elevation of SK. The knowledge of the clinical syndrome of "outpatient hyperkalemia" may be important to single out certain cases of easily correctable insufficient (suppressed) aldosterone production.