Relation between Plasma Aldosterone Concentration and Renal Handling of Sodium and Potassium in Alcoholics during the Withdrawal Phase

Dr. Sergio De Marchi, Department of Medicine, Stabilimento Ospedaliero di Codroipo, Viale Duodo, 52, I-33033 Codroipo, Udine (Italy) Dear Sir, We were very interested in the article by Hené et al. [1] about the relation between plasma aldosterone concentration (PAC) and renal handling of sodium and potassium. These authors suggested that the determination of the ratio between excreted potassium (Uκ) and the distal sodium delivery (UNa+κ) and its relations to PAC, plasma renin activity (PRA) and serum potassium level is very useful for the analysis of disorders of potassium metabolism. It is clear that sodium intake, by its effects on PRA and urinary sodium excretion, is a major determinant of relations between any of these terms and PAC. On the other hand, potassium intake affects aldosterone secretion independently of sodium intake. It follows that PAC is commonly studied in relation to both urinary sodium and potassium excretion expressed as UNa/Uκ ratio. The use of the ratio Uκ/UNa+κ has the theoretical advantage of taking into account the fact that sodium delivery itself has a strong influence on potassium excretion. Potassium excretion is thought to be secondary to sodium reabsorp-tion and therefore highly dependent on the amount of sodium delivered to the excretion site, the ratio Uκ/ UNa+κ probably reflects the contribution of aldosterone to potassium excretion. Hené et al. [1] investigated the relationship between Uκ/UNa+κ and PRA or PAC in normal volunteers and in various groups of patients with primary and secondary hyperaldosteronism, renal insufficiency and essential hypertension treated with chlortal-idone or spironolactone. We report here our experience in alcoholism, another condition affecting potassium homeostasis in which we analyzed the relationship between sodiumpotassium exchange, PAC, PRA and serum potassium level. We studied 40 hospitalized withdrawing patients with a history of alcohol abuse from 10 years or more with a daily alcohol intake exceeding 160 g of ethanol/day during the last 6 months. Only patients without evidence of chronic liver disease and with creatinine clearance within the normal limits were included in the study. None of them was suffering of diarrhea or vomiting, nobody had respiratory or metabolic alkalosis. PAC, PRA, serum concentration and 24-hour urinary excretion of sodium (UNa) and potassium (Uκ) were measured during the first days of hospitalization in the phase of alcohol withdrawal. 19 patients (48%) showed a slight or moderate hypokalemia (mean 3.7 mEq/1; SD 0.3). PAC correlated with Uκ/UNa+κ (r = 0.515, p = 0.0011), UNa (r = 0.435, p = 0.0075) and UNa/Uκ ratio (r =-0.495, p = 0.0016). Slightly weaker correlations were found between PRA and Uκ/UNa+κ (r = 0.423, p = 0.007), UNa (r = -0.335, p = 0.034) and UNa/Uκ (r = -0.349, p =