Daily variability of acid-base status and determinants of serum bicarbonate in hemodialysis patients

Aim: We aimed to evaluate daily variability of bicarbonate in hemodialysis (HD) patients and identify the factors which affect that issue. Materials and methods: Blood samples of 41 patients for bicarbonate (total carbon dioxide (CO2)) and blood gas analysis (pH, bicarbonate (HCO3-)) were obtained, pre-dialysis and post-dialysis, on the first, second, and third session of the week. Those with pre-dialysis HCO3- < 22 mmol/L in all sessions were classified as acidotic. Demographic and laboratory data of acidotic and non-acidotic groups were compared, and the factors related to HCO3- level were identified. Results: pH, tCO(2), HCO3- of the first HD session were significantly lower than those of short inter-dialytic intervals (p < 0.001, respectively). Using Blant Altman analysis, pre- and post-dialysis tCO(2) did not show good agreement with HCO3-. Acidotic patients had higher levels of serum albumin and phosphorus (p < 0.01 and p = 0.02, respectively) and were more likely to use sevelamer (p = 0.04). Also, the value of HCO3- was inversely correlated with dialysis vintage (r = -0.432, p = 0.005) and serum albumin (r = -0.427, p = 0.005). Conclusion: Since tCO(2) did not show good agreement with HCO3-, relying solely on the pre-dialysis tCO(2) values to define metabolic acidosis may increase misclassification rate. More work is needed for optimal assessment of acid base status. Also, understanding the determinants of HCO3- may guide physicians for individualized HCO3- prescription.

Automated summary

This study aimed to evaluate the daily variability of bicarbonate in hemodialysis patients and identify the factors that affect this issue. The results showed that relying solely on pre-dialysis tCO2 values to define metabolic acidosis may lead to misclassification, as the agreement between pre- and post-dialysis tCO2 and HCO3- was not good.