Amelioration of metabolic acidosis by dietary potassium restriction in hyperkalemic patients with chronic renal insufficiency.
Hyperkalemia has been implicated in the pathogenesis of metabolic acidosis in chronic renal insufficiency because acidosis is ameliorated after administration of medications that correct hyperkalemia: mineralocorticoids, diuretics, intestinal K+-binding agents. However, the acidosis-ameliorating effect of these medications may be a consequence not of their ability to correct hyperkalemia, but of their ability to directly stimulate renal or intestinal excretion of acid. To investigate the specific effect of correcting hyperkalemia, balance studies were performed wherein hyperkalemia was corrected solely by restriction of dietary K+ in three patients with moderate chronic renal insufficiency (Ccreat 36, 44, and 58 ml/min/1.73 m2, respectively). Reduction of K+ intake was effected by substitution of Na+ for K+ in the electrolyte supplement to a whole-food diet of low K+ content. This maneuver resulted in correction of hyperkalemia and sustained amelioration of metabolic acidosis in each patient. Net acid excretion increased only transiently, and not enough to fully account for the magnitude of the increment in plasma [HCO3-], suggesting that an extrarenal mechanism of HCO3- input to the systemic circulation was the major factor that ameliorated the systemic acidosis. Evidence of an extrarenal mechanism was obtained only during the phase of decreasing plasma [K+]. Subsequently, during sustained normokalemia, the increased plasma [HCO3-] was maintained as a consequence of a sustained increase in total renal H+ secretion, evidenced by complete reabsorption of the increased filtered load of HCO3- and no reduction in net acid excretion from control values. These results indicate that in some patients with moderate chronic renal insufficiency, metabolic acidosis is ameliorated when hyperkalemia is corrected by restriction of dietary K+ (Na+ substitution) without otherwise changing diet composition and without administration of medication. Amelioration of the acidosis is predominantly effected by extrarenal mechanisms, and is sustained by an increase in the set point at which plasma [HCO3-] is regulated by the kidney.
D000141:Acidosis, Renal Tubular / Q000178:diet therapy*; D000368:Aged; D000450:Aldosterone / Q000652:urine; D000641:Ammonia / Q000652:urine; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006947:Hyperkalemia / Q000097:blood / Q000150:complications* / Q000178:diet therapy; D007676:Kidney Failure, Chronic / Q000150:complications*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood / Q000378:metabolism; D012083:Renin / Q000097:blood
D000450:Aldosterone; D000641:Ammonia; D012083:Renin; D011188:Potassium