Behaviour of phosphate removal with different dialysis schedules

Abstract

peritoneal fluid makes a reduction of phosphate dietary Phosphate metabolism in chronic renal failure intake impractical, the protein content of the diet being strictly linked to that of phosphate. Even though hypophosphataemia has been reportedWeekly phosphate removal in CAPD has been occasionally in chronic renal failure patients on dialysis reported to be ~70 mmol, with 4×2 l exchanges per treatment [1,2], phosphate (Pi) retention, often associday [12]. This value is quite similar to that found in ated with increased serum Pi, is the most common 35 of our CAPD patients (65.5±40.6 mmol/week), finding in this clinical setting. Pi retention is secondary and is ~20 mmol per week less than in haemodialysis to reduced or null renal excretion, and dialysis removal (HD) (84.3±19.1 mmol/week). However, in our is often, but not always, insufficient as compared with CAPD patients, urinary excretion (48.8±21.4) suba variably reduced intestinal absorption of Pi [3][4][5].stantially contributes to Pi balance, representing ~40% The main metabolic consequences of phosphate of the total Pi removed, while in most HD patients retention have been related to: (i) a possible direct [6 ] this route of Pi excretion is negligible. We found that and indirect (mediated by calcium and calcitriol reducurinary Pi excretion was linearly related to glomerular tion) [7,8] stimulation of parathyroid hormone; (ii) a filtration rate (GFR) values, evaluated as the mean direct involvement in extraosseous calcifications [9]; of creatinine and urea clearances in our CAPD and (iii) a detrimental effect on renal function [10], that can still be maintained at a significant level in patients (uPi mmol/day=−1.11+1.39×GFR; r=0.91, continuous ambulatory peritoneal dialysis (CAPD) P<0.001), stressing the importance of the preservation patients.of residual renal function in maintaining a good Before addressing the problem of Pi removal by metabolic balance in CAPD. dialysis treatment, it might be useful to recall some When we considered the factors affecting the dialytic points on Pi body distribution. Of the more than 650 g removal of phosphate in our CAPD patients by means of Pi contained in a medium-sized man, ~85% is of a multiple regression analysis ( Table 1), we found contained in bone, 14% in the cells and only 1% or that plasma Pi concentration plays the main role. less is in the plasma. It is also important to bear in Another important factor is represented by the glucose mind that the bulk of intracellular Pi is represented by concentration in the dialysate, and its influence on organic phosphate (nucleoside phosphate compounds, Pi removal was independent of ultrafiltration rate. phosphorylated enzymes, 2,3-diphosphoglycerate, pho-Finally, Pi removal by peritoneal dialysis was greatly sphocreatine, etc.) at 10-100 times the concentration affected by dialysate volume, with a calculated removal of inorganic phosphate with which it is in equilibrium. of ~95 mmol/week at a dialysate volume of 12 l per The inorganic intracellular phosphate is in turn...

Inorganic Phosphorus Homeostasis during the First Hour of Dialysis

“…14 The results of our study showed a progressive fall in sP concentration during the first hour of the HD session. 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.…”

“…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.…”

“…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.…”

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

“…Thereafter phosphatemia stabilizes until the end of both dialysis procedures. The second flat phase implies attainment of equilibrium between removal of phosphate through the dialyzer and matched release from intracellular pools, just sufficient to replenish blood losses [19]. The finding of sustained and similar phosphate blood levels with two dialysis prescriptions resulting in different hourly phosphate mass removal supports this hypothesis.…”

Impact of increasing haemodialysis frequency versus haemodialysis duration on removal of urea and guanidino compounds: a kinetic analysis

“…Other studies have concentrated on phosphate, which is known to be distributed in at least two to four different compartments [27]. Not surprisingly, a positive impact of longer dialysis was observed for the removal of solutes like β2-microglobulin [2,3,7] and phosphate [1,[8][9][10][11]28]. The different removal when enhancing dialysis Table 2.…”