Increase of serum potassium in the upright posture in selective hypoaldosteronism.

The effect of a 4 hr upright posture on serum potassium (SK) levels was investigated in a certain group of hospitalized renal patients with selective hypoaldosteronism and in healthy subjects. Significant (p less than 0.001) postural increase in SK (0.4 MMol/L) was found only in the 3 young patients with chronic glomerulonephritis and hypoaldosteronism who presented with hyperkalemia (5.84 +/- 0.13 mMol/L) as outpatients, but showed a marked improvement toward normokalemia (4.95 +/- 0.13 mMol/L; p less than 0.001) within the hospital without any specific treatment. In healthy persons in the fastqng condition the influence of the upright position of short duration (45 min) was also studied on SK and a very small but significant increase (0.15 mMol/L) was found. It was concluded: 1. the postural SK INCREASE MAY OFFER AN--AT LEAST PARTIAL--EXPLANTATION FOR THE "OUTPATIENT HYPERKALEMIA", 2. The normal activity of renin-angiotensinaldosterone system may play a role in the counteraction of the trend for SK rise in the upright posture.