Use of ascorbate-rich dialysate to attenuate oxidative stress in maintenance hemodialysis patients.

BACKGROUND: Oxidative stress exists in uremic milieu, particularly in maintenance hemodialysis (MHD) patients, and accounts for certain long-term complications. Yet little is known about whether supplementation of ascorbic acid (vitamin C, or vitC) via extracorporeal circuit has substantial effects on minifying oxidative impairment. SUBJECTS AND METHODS: The entire experiment consisted of three sections: 1) Practicing ascorbate dialysate among 8 MHD patients in a single dialysis session, compared with a conventional hemodialysis session and another one with intravenous injection of vitC. In each session, oxidative stress markers--namely, plasma total ascorbic acid (TAA), ratio of dehydroascorbic acid (DHAA) to TAA (DHAA/TAA), vitamin E (vitE), and malondialdehyde (MDA)--in both plasma and erythrocytes were measured. 2) A relatively long-term application of ascorbate dialysate in 12 of 23 MHD patients, who were randomly allocated to experimental group (n = 12), and control group (n = 11). Oxidative stress markers and main hematological and biochemical indices were determined at the beginning and end of the period. 3) Application of ascorbate dialysate in 10 MHD patients with intravenous iron treatment, performed in similar procedures as section 1. In addition to determining the aforementioned oxidative stress markers, area under the curve (AUC0-180 min) of ratio of plasma MDA to cholesterol (MDA:Cho) was calculated to evaluate the extent of lipoperoxidation. RESULTS: 1) Plasma TAA gradually decreased during dialysis, whereas a mild increase appeared in MDA. A protruding TAA concentration peak, as well as an extreme DHAA/TAA reduction, followed the injection of vitC, but soon a precipitous fall in DHAA/TAA ensued. Stable plasma TAA and slightly raised vitE were observed when applying ascorbate dialysate. 2) Plasma TAA augmented (27.4 +/- 13.3 vs. 16.8 +/- 9.5 mg/dL, P < .05) and plasma low-density lipoprotein (oxLDL) became two-thirds of baseline data (32.6 +/- 25.2 vs. 83.8 +/- 56.5 micromol/L, P < .05) in the experimental group, whereas oxLDL in the control group reduced quantitatively but not significantly in statistics. (3) As iron sucrose was infused, the decline of TAA and ascending of MDA would be abated not only by intravenous drop of vitC, but also by ascorbate dialysate; however, TAA or MDA curve manifested totally distinguished in the two modalities. AUC0-180 min in ascorbate dialysate group was significantly less than that in control group (400.25 +/- 28.54 vs. 487.25 +/- 109.82). CONCLUSION: Plasma ascorbic acid diminished a great deal during hemodialysis, and at the same time oxidative stress formed and intensified, which will be exacerbated by a remedy of frequent intravenous iron. Ascorbate supplementation, by means of either infusion or extracorporeal circuit, can lessen the loss and therefore attenuate oxidative stress. The latter pattern takes the advantage of retaining the approximate internal balance instead of exquisite change in vivo due to administration of intravenous vitC.

Determination of vitamin C in plasma and dialysate from uremia patients by high performance liquid chromatography with electrochemical detection.

A convenient and valid method for the determination of ascorbic acid(AA) and dehydroascorbic acid(DHAA) in plasma and dialysate from patients with uremia by high performance liquid chromatography with electrochemical detection is described. A mixture of 0.8 g/L metaphosphoric acid and 18% (volume fraction) perchloric acid was used as a protein precipitant and the extractant for AA from biosamples. It was also a good stabilizer for AA in samples. The proposed method is satisfied for routine screening of vitamin C in clinical applications with a correlation coefficient of more than 0.99 in the range of 2 mumol/L-40 mumol/L AA. The within-day precision was less than 8.9% and 10.55% for AA and DHAA, respectively. The recoveries of AA in plasma and dialysate were over 95% and 78%, respectively.