No abstract

The present controlled study using a crossover design indicates that small and middle molecules are removed more adequately from the deeper compartments when performing a prolonged HD, even if blood and dialysate volumes are kept constant. Hence, factor time t is very important for these retention solutes. The kinetic behaviour of protein-bound solutes is completely different from that of small and middle molecules, mainly because of the strength of their protein binding.

Our data show incontrovertibly that, when dialyzing with a dialysate Ca concentration of 1.50 mmol/L, 4h standard bicarbonate HD and 8h slow-flow bicarbonate HD always achieve a quite similar positive Ca++MB for the patients.

These highly controlled experiments showed that hemodynamic stability does not appear to be statistically significantly influenced by any specific dialysate tCa concentration in this peculiar subset of patients.

Bioelectrical impedance analysis (BIA) is composed of resistance (R) and reactance (Xc). The aim of this study was to investigate whether BIA may be influenced by the duration of hemodialysis (HD) sessions. Eleven uremic patients underwent one 4-hour and one 8-hour bicarbonate HD session. Volume of blood and dialysate processed, volume of ultrafiltration (V(UF)), and dialysate electrolyte concentrations were prescribed to be the same. R and Xc were determined at the start and the end of each session, injecting 800 μA at 50 kHz alternating sinusoidal current (BIA 101; Akern, Italy). Mean pre- and postdialysis body weights and V(UF) were not significantly different in the 4-hour and 8-hour treatments. Postdialysis R, ΔR (the difference between post- and predialysis R values), and percent increase of R values were significantly higher in the 8-hour sessions, when compared with the corresponding values of the 4-hour sessions (p < 0.0001, 0.02, and 0.02, respectively). In conclusion, this study shows that 8-hour HD sessions were associated with postdialysis R, ΔR, and percent increase of R values significantly higher than the corresponding ones of 4-hour sessions. If higher R values may represent a proxy of a correct dry body weight, it remains a matter of future research.