End-Stage Renal Disease Patients Lose a Substantial Amount of Amino Acids during Hemodialysis

BACKGROUND: Poor nutritional status is frequently observed in end-stage renal disease patients and associated with adverse clinical outcomes and increased mortality. Loss of amino acids (AAs) during hemodialysis (HD) may contribute to protein malnutrition in these patients. OBJECTIVE: We aimed to assess the extent of AA loss during HD in end-stage renal disease patients consuming their habitual diet. METHODS: Ten anuric chronic HD patients (mean +/- SD age: 67.9 +/- 19.3 y, BMI: 23.2 +/- 3.5 kg/m2), undergoing HD 3 times per week, were selected to participate in this study. Spent dialysate was collected continuously and plasma samples were obtained directly before and after a single HD session in each participant. AA profiles in spent dialysate and in pre-HD and post-HD plasma were measured through ultra-performance liquid chromatography to determine AA concentrations and, as such, net loss of AAs. In addition, dietary intake before and throughout HD was assessed using a 24-h food recall questionnaire during HD. Paired-sample t tests were conducted to compare pre-HD and post-HD plasma AA concentrations. RESULTS: During an HD session, 11.95 +/- 0.69 g AAs were lost via the dialysate, of which 8.26 +/- 0.46 g were nonessential AAs, 3.69 +/- 0.31 g were essential AAs, and 1.64 +/- 0.17 g were branched-chain AAs. As a consequence, plasma total and essential AA concentrations declined significantly from 2.88 +/- 0.15 and 0.80 +/- 0.05 mmol/L to 2.27 +/- 0.11 and 0.66 +/- 0.05 mmol/L, respectively (P < 0.05). AA profiles of pre-HD plasma and spent dialysate were similar. Moreover, AA concentrations in pre-HD plasma and spent dialysate were strongly correlated (Spearman's rho = 0.92, P < 0.001). CONCLUSIONS: During a single HD session, approximately 12 g AAs are lost into the dialysate, causing a significant decline in plasma AA concentrations. AA loss during HD can contribute substantially to protein malnutrition in end-stage renal disease patients. This study was registered at the Netherlands Trial Registry (NTR7101).