Variation of carbonic acid pK'1g in blood and urine during NaHCO3 infusion and NH4Cl loading: a study of two renal acidotic patients
van Stekelenburg, G.J.; Valk, C.; Donckerwolcke, R.A.
Clinical Chemistry 26(1): 60-65
1980
ISSN/ISBN: 0009-9147 PMID: 7356574 Document Number: 160677
In the Henderson-Hasselbalch equation, pH = pk1 + log(HCO3-/S .cntdot. PCO2), the millimolar partition coefficient, per mmHg pressure(s), and pK'1 are considered to be constants. Combining these 2 constants gives pH = pK'1g + log(HCO3-/PCO2). The results of a study designed to test the constancy of pK'1g are reported. This was done by varying the blood and urine pH in 2 patients by administration of NaHCO3 and NH4Cl. The PCO2 [partial pressure of CO2] pH and total CO2 were determined independently and the values obtained more substituted in the equation, solving for pK'1g. The pK'1g was variable in the blood and urine of both patients. In a 16 mo. old child, suffering from a transient type of renal acidosis, a linear relationship between pH and pK'1g was noted. In blood, the relationship was pK'1g = 10.25-0.352 pH and for urine, pK'1g = 9.46-0.248 pH. When this patient was restudied 6 mo. later, the results were confirmed. Similar observations were made in a 10 yr old patient suffering from distal tubular acidosis syndrome. A linear relationship between pK'1g and pH of blood and urine was observed in this case, but the equations were somewhat different: for blood, pK'1g = 8.55-0.129 pH and for urine, pK'1g = 7.78-0.028 pH. The correlation coefficient with the line of best fit in these studies ranged from 0.81-0.95, indicating that these observations are statistically significant.