ExtractIn a program concerned with regulatory mechanisms influencing the renal contribution to acid-base balance in pediatric-aged subjects, two patients with hypokalemic alkalosis were studied. The relation of scrum potassium level to proximal tubular bicarbonate reabsorption was assessed at different potassium levels during states of equal plasma volumes or equal extracellular fluid (ECF) volumes. Renal bicarbonate threshold was cither determined by means of bicarbonate titration studies or estimated from urinary pH and simultaneous plasma bicarbonate concentration. Estimation of threshold was judged to be acceptable if pH values in urine were close to 6.2, thereby indicating little or no spilling of bicarbonate into the urine. Simultaneous plasma bicarbonate concentrations indicated renal bicarbonate threshold.Patient NAI exhibited a renal bicarbonate threshold of 25 mmoles/liter at a serum potassium level of 1.7 mval/liter and 20.5 mmoles/liter at a potassium level of 2.7 mval/liter. Plasma volume was 54.7 and 52.9 ml/kg body weight, respectively.Patient BE showed a renal bicarbonate threshold of 24.3 mmoles/liter with an ECF volume of 474 ml/kg body weight and a serum potassium level of 1.7 mval/ liter; however, this patient exhibited a renal bicarbonate threshold of less than 21 mmoles/liter with an ECF volume of 454 ml/kg body weight and a potassium level of 3.2 mval/liter.In both patients, renal bicarbonate threshold decreased when serum potassium levels increased. Moreover, plasma volume in one patient and ECF volume in the other either had decreased slightly or had remained essentially unchanged. Hence, an indirect relation was found between serum potassium level and renal bicarbonate threshold. Plasma volume, known to influence renal bicarbonate threshold, was without effect on this relation.
SpeculationIn hypokalemic alkalosis the level of serum potassium itself or the levels of serum potassium as indicators of whole body potassium might be among the factors influencing renal bicarbonate reabsorption.
618Hypokalemia and renal bicarbonate reabsorption 619