PHOSPHATE REMOVAL DURING NOCTURNAL HEMODIALYSIS: A STUDY WITH TOTAL DIALYSATE COLLECTION

Aim: To quantify phosphate removal during nocturnal HD (NHD) by measuring concentrations in serum, hourly and total dialysate collection. Methods: 8 patients (3 women) receiving NHD were studied for one session on the longest break between NHD. Serum and total dialysate phosphate concentration was measured every hour. Duration of the NHD was 8 hours in 3 patients and 7 in 5. Results: Phosphate removal assessed in serum was more important during the first 2 hours, then a plateau was reached. Average serum concentration before NHD was 1,43 mmol/l and 0,78 mmol/l and 0,81 mmol/l after 7 and 8 hours, respectively. The reduction was statistically significant (p = 0,005 in p = 0,02, respectively). The highest average concentrations in total dialysate was in the 1 super(st) hour (0,31 mmol/), then concentrations remained stable (0,23; 0,24; 0,24, 0,25, 0,21, 0,21 and 0,18 mmol/l for every next hour, respectively). Average total reduced mass of phosphate quantified from hourly and total dialysate was 5195,7 mg and 5466, 2 mg. Reduction ratio for 7 and 8 hours NHD was 45,3% and 43,1%. Conclusions: Phosphate has been removed in a consistent manner during whole duration of nocturnal hemodialysis (despite the plateau in serum concentration), indicating phosphate transfer from intracellular space. Total reduced mass quantified from hourly and total dialysate in our study was more than four times higher than previously reported.