Variation of trace element concentrations in patients undergoing hemodialysis in the north of Spain.

BACKGROUND: Trace elements are essential substances for the proper physiological and biochemical functioning of the organism. Hemodialysis patients are potentially at risk of deficiency or excess of these elements. The application of inductively coupled plasma mass spectrometry (ICP-MS) allows the simultaneous quantification of very small amounts of multiple trace elements. The aim was to measure the serum concentration of copper (Cu), zinc (Zn), selenium (Se), and nickel (Ni), and the whole blood concentration of arsenic (As), lead (Pb), and manganese (Mn), in patients undergoing hemodialysis as well as in controls. METHODS: The study was carried out in 57 hemodialysis patients compared with 57 controls with normal renal function. Serum and whole blood samples from the dialysis group were collected before and after hemodialysis sessions and Cu, Zn, Se, Ni, As, Pb and Mn levels were determined using ICP-MS. RESULTS: Hemodialysis patients showed significantly lower blood levels of Cu, Zn and Se than controls (p < 0.001) and higher concentrations of Ni, As and Pb (p < 0.0001). The levels of Mn were similar in both groups. After performing hemodialysis, Cu, Zn, Se and Ni concentrations were significantly higher than the pre-hemodialysis levels (p < 0.0001). However, the concentration of As decreased (p < 0.0001) and Pb and Mn levels were not significantly altered after the dialysis session. CONCLUSION: Hemodialysis patients are at increased risk of trace elements deficiency (especially for Zn and Se) or excess (Ni) in respect to healthy subjects. Monitoring of blood levels and supplementation of some trace elements may be indicated in patients undergoing hemodialysis.

Increase in and clearance of cell-free plasma DNA in hemodialysis quantified by real-time PCR.

BACKGROUND: Recently cell-free plasma DNA has been described as a marker of apoptosis during hemodialysis (HD), but little is known about how different dialysis membranes may contribute to this process or whether pre-HD levels are restored afterwards. Here we evaluate the influence of the dialysis membrane on cell-free plasma DNA levels and investigate the clearance of plasma circulating DNA after HD. METHODS: Cell-free plasma DNA was measured using a real-time quantitative PCR for the beta-globin gene. Reference values for plasma DNA were established in a group of 100 healthy voluntary blood donors. Pre- and post-HD levels were also measured in 30 patients with end-stage renal disease on regular HD (52 sessions; 104 samples). The sessions lasted for 2.5-5 h. Different dialysis membranes were compared: high-flux (n=37) vs. low-flux (n=15) and polysulfone (n=42) vs. modified cellulose (n=10). To determine the time at which pre-HD levels are restored, DNA was quantified in serial plasma samples obtained from 10 of these 30 patients, just before and immediately after HD, as well as at 30, 60 and 120 min after HD. RESULTS: Reference plasma DNA values for healthy blood donors ranged from 112 to 2452 gEq/mL (median 740 gEq/mL). Cell-free plasma DNA levels significantly increased during HD (Wilcoxon test for paired samples, p<0.0001), with increases of more than four-fold observed in 75% of the patients after HD. There was no significant linear association between the length of the HD session (between 2.5 and 5 h) and the increase in cell-free plasma DNA concentration (Pearson correlation). No significant differences were observed between different types of membranes (Mann-Whitney U-test). Plasma DNA returned to pre-HD levels by 30 min after HD, regardless of the starting concentration. CONCLUSIONS: Plasma DNA levels significantly increase after a conventional 2.5-5-h HD session. Therefore, HD patients require special consideration for correct interpretation of plasma DNA concentrations. This parameter can be considered a reliable diagnostic tool for certain pathologies when measured at least 30 min after a HD session without further complications. The different dialysis membranes used in this study had no influence on cell-free plasma DNA concentrations, so the level of circulating DNA is not an appropriate marker of dialysis membrane biocompatibility.