The pK'1 of the carbonic acid-bicarbonate buffer system in hemodialyzed patients

Blood gas analysis is crucial for the proper evaluation of systemic acid-base disorders, but several reports have been critical of the current approach which relies on the Henderson-Hasselbalch equation and other possibly erroneous assumptions about the bicarbonate-carbonic acid buffer system of blood. This report studied renal failure patients receiving dialysis and nondialyzed medical patients with respect to variations of the pK'1 of carbonic acid dissociation and discrepancies between measured and calculated bicarbonate. Among dialyzed patients, the mean pK'1 differed significantly from 6.10, and a significant difference was found between calculated and measured total CO2 even though all assays were performed on the same arterial blood. Significant correlations were observed between pK'1 and calculated-measured total CO2 as well as serum phosphate converted to mEq/l in the dialyzed group. These data suggest that there is a need to reevaluate current acid-base analysis, especially as it is applied to very seriously ill individuals.