EVIDENCE FOR AN INDEPENDENT ROLE OF METABOLIC-ACIDOSIS ON NUTRITIONAL-STATUS IN HEMODIALYSIS-PATIENTS

Background. Malnutrition in haemodialysis (HD) patients has been refer red to underdialysis with low protein intake, and to acidosis. However , the separate effects of underdialysis and acidosis on nutrition have not been clearly demonstrated. To evaluate the role of the dialysis d ose and of metabolic acidosis on nutrition, we measured the predialysi s serum HCO3, pH, serum albumin, PCRn, Kt/V, and BMI in 81 uraemic pat ients on maintenance bicarbonate HD for 93 +/- 80 months. Patients wit h chronic liver diseases, malignancies, and cachexia were excluded. Re sults. Mean age was 59 +/- 17 years, Kt/V was 1.29 +/- 0.21, PCRn 1.06 +/- 0.22 g/kg/day, serum albumin 4.07 +/- 0.28 g/dl, BMI 23 +/- 4 kg/ m(2), HCO3 21.1 +/- 1.9 mmol/l, pH 7.36 +/- 0.04. Serum albumin showed a significant direct correlation with: PCRn (P = 0.001), HCO3 (P = 0. 001), pH (P = 0.002), but no correlation with Kt/V and BMI. Serum HCO3 correlated inversely with PCRn (P = 0.027). Multiple regression analy sis cofirmed the significant role of serum bicarbonate and age, but no t of Kt/V, on serum albumin concentrations. The role of PCRn appeared to be marginal compared to serum bicarbonate in determining serum albu min levels. Dividing patients into two groups, serum albumin was 3.96 +/- 0.22 g/dl with HCO3 less than or equal to 20 mmol/l and 4.18 +/- 0 .31 g/dl in those with serum HCO3 greater than or equal to 23 mmol/l ( P = 0.002). PCRn in the same groups was respectively 1.14 +/- 0.24 g/k g/day and 1.01 +/- 0.23 g/kg/day (P = 0.03). Most importantly, serum a lbumin levels did not appear to be affected by the dialysis dose, with Kt/V ranging from 0.90 to 1.88. Conclusions. In HD patients with adeq uate Kt/V, metabolic acidosis exerts a detrimental effect on serum alb umin concentrations partially independently of the protein intake, as evaluated by PCRn. In the presence of moderate to severe metabolic aci dosis, PCRn does not reflect the real dietary protein intake of the pa tients, probably as a result of increased catabolism of endogenous pro teins. For this reason PCRn should be considered with caution as an es timate of the dietary protein intake in HD patients in the presence of metabolic acidosis.