Metabolic acidosis components in advanced chronic kidney disease: association with serum albumin and parathyroid hormone.

OBJECTIVE

To investigate the associations between the 2 main components of metabolic acidosis (unmeasured anions [UA] and hyperchloremia) with serum albumin and intact parathormone (iPTH) in patients with advanced chronic kidney disease.

METHODS

Cross-sectional study with advanced chronic kidney disease patients (estimated glomerular filtration rate <30 mL/minute/1.73 m(2)) not receiving phosphate binders, alkali therapy, or vitamin D analogs. Arterial blood sample was collected for biochemical and blood gas analysis. UA and strong ion difference (SID) were calculated according to quantitative acid-base analysis. Reduced SID was used as a measure of hyperchloremia.

METHODS

Serum albumin and parathormone (iPTH).

RESULTS

A total of 383 patients were included with a mean age of 64.7 ± 16.3 year and a mean estimated glomerular filtration rate of 19.9 ± 12.1 mL/minute/1.73 m(2). Among patients with metabolic acidosis, 45.7% had metabolic acidosis exclusively because of UA and 53.7% had a hyperchloremic component (either mixed metabolic acidosis or pure hyperchloremic metabolic acidosis). Considering the main acid-base status determinants, only UA had a significant correlation with serum albumin (r = -0.278, P < .001). There was no correlation between serum albumin and SID (r = 0.083, P = .156). This is in opposition to serum iPTH, where there was no correlation with UA (r = 0.082, P = .114), but an inverse correlation between iPTH and SID was observed (r = -0.228, P < .001). Multiple linear regressions with all acid-base determinants confirmed these findings.

CONCLUSIONS

Our data brings further knowledge on the associations between metabolic acidosis with bone disorders and nutritional status, suggesting that the two main metabolic acidosis components (UA and hyperchloremia) have different effects on serum parathormone and serum albumin.