Phosphate Dialytic Removal: Enhancement of Phosphate Cellular Clearance by Biofiltration (with Acetate-Free Buffer Dialysate)

Abstract

Phosphate dialytic removal (PDR) depends in part on the type (acetate or bicarbonate) and the concentration of the buffer dialysate. Plasma phosphate reduction or PDR during a dialysis treatment is the algebraic sum, of phosphate cellular flux (removal or captation) and of phosphate tissular precipitation. High bicarbonate levels induce an intracellular shift of phosphate, thus not available for dialytic removal. On the contrary, acidosis prevents P shifting into the intracellular space, thus more P is available for dialytic removal. In order to evaluate cellular phosphate sequestration (CPS) we tested PDR in a crossover study. Three children were dialyzed (18 sessions) successively using either biofiltration with free buffer dialysate and a constant bicarbonate fluid infusion rate (BF) or using sequential biofiltration (SBF) with an initial controlled acidosis period realized by bicarbonate reinjection fluid rate modelling. PDR was higher in SBF (32 ± 4 mmol/session) than in BF (24 ± 6 mmol/session). SBF seemed to be efficient against CPS; it clearly demonstrates that bicarbonate modelling is a promising dialytic approach to enhance PDR. The real clinical relevance of these biological results needs clinical long-term evaluation.

Phosphate Mass Removal during Hemodialysis: A Comparison between eKT/V-Matched Conventional and Extended Dialysis

“…The rapid early fall is probably the consequence of phosphate high diffusibility through the hemodialysis membrane coupled with sluggish or even negative mobilization from intracellular stores [17,18]. Thereafter phosphatemia stabilizes until the end of both dialysis procedures.…”

Diffusion Kinetics in Blood during Haemodialysis and in vivo Clearance of Inorganic Phosphate

“…Bazzato et al [11] report that acetate -but not bicarbonate -dialysis even causes an increase in the RBC content of iPh related to a shift into the intracellular compartment. However, Fischbach et al [23] reported the same phenomenon during acetate-free biofiltration, but not during sequential biofiltration with an initially controlled acidosis.…”

Inorganic Phosphorus Homeostasis during the First Hour of Dialysis

“…Moreover, we found a negative contribution of IPR to TPR in the first 10 min of the HD session which is in accordance with the results of two previous studies. 7,14 Messa et al 14 showed that during the first 45 min the extracellular phosphate removal was greater than total, which could be explained either by an influx of phosphate into the intracellular space or alternatively by a possible overestimation of the effective distribution volume of phosphate, which during the first 45 min might be lower than that estimated. We chose to investigate alterations in extra-(serum) and intracellular (RBC) inorganic phosphorus concentrations during the first hour of the HD session as detailed data are lacking for this early period of time and it has been shown that this first quadrant of an HD session is critical as more than 30% of the total phosphorus mass removal occurs during it.…”

“…4,5 A number of previous studies have investigated phosphorus removal during HD. [5][6][7][8] Phosphorus kinetics is characterized by (1) a rapid decline in serum phosphorus concentration during the first half of the HD session, (2) an almost stabilized concentration during the rest of the HD time in which phosphorus removal continues, and (3) a rebound phenomenon which starts before HD session ends. [9][10][11][12][13] These observations suggest that inorganic phosphorus is transferred from intracellular compartment or other phosphorus pools to intravascular compartment at different mass rates.…”

“…However, data are limited regarding the contribution of intracellular compartment to total inorganic phosphorus mass removal during the early period of an HD session, while the existing data suggest that this contribution is negligible or negative. 7,14 The aim of this study was to investigate in depth the inorganic phosphorus homeostasis (intra-and extracellular) during the early period of an HD session through multiple and consecutive measurements of phosphorus indexes.…”