Must metabolic acidosis be associated with malnutrition in haemodialysed patients?

Background: Metabolic acidosis was evaluated in the past as an independent variable of catabolism in haemodialysis (HD) patients. Nevertheless, it could in theory reflect a higher acid production from protein oxidation. The aim of this study was to evaluate the incidence and basis of metabolic acidosis in conjunction with a nutritional assessment in a HD population (n=120).

Methods: Three groups were identified based on three consecutive monthly predialysis plasma bicarbonate concentrations (P(HCO3)) and pH values. The effect of correction of metabolic acidosis on nutritional parameters was also studied in acidotic patients.

Results: The mean P(HCO3) ranged from 19.2+/- 0.4 mmol/l in group A (n=21) to 24.4+/-0.3 mmol/l in group B (n=80) and 27.5+/-0.4 mmol/l in group C (n=19). The adequency of dialysis (Kt/V) and ultrafiltration rates was comparable in the three groups. When compared with group B, group A had significantly higher body mass index (BMI), triceps skin fold thickness (TSF), dietary protein intake (DPI), normalized protein catabolic rate (nPCR) as well as serum creatinine, K(+) and intact parathyroid hormone (I-PTH). In contrast, when compared with group B, group C had a significantly lower DPI, nPCR, plasma creatinine and albumin. There was no significant difference in plasma inflammatory markers such as C-reactive protein (CRP) and interleukin 6 (IL-6) among all three groups. There was a significant negative correlation between P(HCO3) and nPCR (P<0.001), DPI (P<0.001), creatinine (P<0.001). Over a period of 6 months, the correction of metabolic acidosis in the HD patients did not affect nutritional parameters.

Conclusion: These findings suggest that metabolic acidosis as a result of a higher protein intake does not detrimentally affect nutritional status.