Changes in plasma concentrations of hypoxanthine and uric acid before and after hemodialysis.

INTRODUCTION Purine metabolites constitute a major class of uremic toxins, and reliable characterization of which helps nephrologists to choose the most appropriate treatment for the patients individually. In the present study, we assessed plasma concentrations of hypoxanthine and uric acid as purine metabolites in patients on maintenance hemodialysis, before and after a dialysis session. MATERIALS AND METHODS A total of 20 patients on maintenance hemodialysis were enrolled in this study. All of the patients underwent a routine 4-hour dialysis, as scheduled 3 times per week. Polysulfone membranes and bicarbonate dialysis solution were used in all dialysis sessions. Blood specimens were taken from the arteriovenous fistula immediately before and after one hemodialysis session, in order to measure plasma concentrations of hypoxanthine and uric acid by high-performance liquid chromatography, and to compare the predialysis and postdialysis values. RESULTS Before hemodialysis, the mean plasma hypoxanthine and uric acid concentrations were 18.93 +/- 8.28 micromol/L and 44.16 +/- 22.88 micromol/L, respectively. After hemodialysis, these concentrations reduced to 13.68 +/- 4.42 micromol/L and 15.61 +/- 11.12 micromol/L, respectively. Hypoxanthine concentration had a 27.7% decrease after hemodialysis (mean difference, 5.25 +/- 6.24 micromol/L; 95% confidence interval, 2.32 to 8.10; P < .001). Also, uric acid concentration decreased by 64.6% (mean difference, 28.55 +/- 14.39 micromol/L; 95% confidence interval, 21.81 to 32.28; P < .001). CONCLUSIONS Plasma concentrations of hypoxanthine and uric acid are higher than normal before hemodialysis, and they decrease significantly after hemodialysis; however, both of them may be still higher than normal values.