Solute kinetics in hypertonic hemodiafiltration and standard hemodialysis

Hemodiafiltration (HDF) is a new dialysis treatment that combines convective and diffusive forces. In order to assess the efficiency of a peculiar model of hypertonic HDF (H HDF), we studied eight uremic patients when they were undergoing five sessions of H HDF of 180 minutes duration and two sessions of standard hemodialysis (HD) of 270 minutes duration with a comparable blood (approximately 400 mL/min) and dialysate flow rate (approximately 520 mL/min). The plasma water clearances (Kw) of small [urea (U), creatinine (C), uric acid (UA), and phosphorus (P)] and middle molecules [netilmicin (N) and inulin (I)] were exceedingly higher in H HDF than in HD; however, because of the different treatment times, U and C removal (R) in HD overcame and UA and P R in HD equalized that in H HDF. The factor time was not sufficient to HD to compensate for the large difference in Kw in the case of I. Additional studies were performed in seven out of the eight patients after two sessions of H HDF and one session of HD. Two significantly higher rebounds were observed when comparing both treatments: for U after HD and for parathyroid hormone (PTH) after H HDF; however, PTH Cx/Cs ratios (ratios of the plasma water concentration of PTH at any postdialysis time to the plasma water concentration of PTH at the start of the run) were not different in both treatments, meaning that there was an increased PTH secretion in the early post H HDF hours in order to compensate for the larger PTH R with H HDF.(ABSTRACT TRUNCATED AT 250 WORDS)