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, tCO2, 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 tCO2 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 tCO2 did not show good agreement with HCO3-, relying solely on the pre-dialysis tCO2 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.