**5.4 Blood volume biofeedback and sodium overload**

One of the potential risks of automated BV regulation using sodium (Na) or conductivity modulation is alteration in sodium removal, with consequent Na overload and increased thirst, which can theoretically lead to increased interdialytic weight gain and worsening hypertension. Most of the studies described above did not find a significant change in pre and post HD sodium concentration (Santoro et al., 2002; Wolkotte et al., 2002; Dasselaar et al., 2007b, etc.), although plasma Na is a poor surrogate of real sodium balance.

Moret et al. (2006) assessed the effect of such devices on sodium transfer during hemodialysis. In a cross-over randomized trial of 10 patients with frequent hypotension, plasma conductivity (PC) and ionic mass balance (IMB) were compared in four different HD modalities: standard HD with fixed Na concentration (140 mmol/L), linear Na profiling (150 to 140 mmol/L), BV-controlled feedback with Hemocontrol® (mean dialysate conductivity (DC) 14,0 mS/cm) and plasma-conductivity (PC)-controlled feedback with Diacontrol® (see below) (post-dialytic PC target of 14,0 mS/cm). Mean pre- and post-dialytic PC were statistically higher during Na-profiled HD, and post-dialytic PC was lower in PC-controlled feedback, compared to the other three modalities. The effects of BV-regulated HD on PC and IMB did not differ from those of standard HD, and thus it seems that BV-regulated HD can be prescribed without any safety concern regarding sodium loading.
