No difference in nitrogen balance between standard prescriptions of hemodialysis and peritoneal dialysis

It has been thought that peritoneal dialysis (PD) may not achieve adequate solute removal after the loss of residual renal function when compared to hemodialysis (HD). However, it should be noted that adequate solute removal depends not only on dialysis dose but also on dietary intake. Therefore, in the present study, we compared, both theoretically and clinically, the dietary protein intake and nitrogen removal between standard HD and PD as currently practiced in China.

The nitrogen removal for both HD and PD was calculated theoretically with defined membrane permeability. For HD, the urea removal was based on a 2-compartment model. We compared the dietary protein intake and the amount of nitrogen removed at dialysis in 38 anuric well-nourished hemodialysis patients and 44 peritoneal dialysis patients.

With the theoretical calculation, setting the blood urea level at 21 or 26 mmol/l for both dialysis modalities, with the current practice pattern (4 exchanges of 2 liters of dialysis solution a day for PD and 4 h x 3 per week for HD), HD and PD removed almost identical amounts of nitrogen, and the allowable dietary protein intakes to achieve nitrogen balance for each modality were about 0.9 and 1.0 g/kg/day, respectively. In the 38 HD patients, the peak blood urea concentration was 26.44 +/- 3.96 mmol/l, significantly higher than that of PD patients (20.85 +/- 4.08 mmol/l). There was no significant difference in the dietary protein intake between the 2 modalities: 1.01 +/- 0.29 and 0.91 +/- 0.28 g/kg/day for HD patients and PD patients, respectively.

Our study suggests that to achieve the same level of blood urea level, the protein intake and nitrogen removal is almost identical between HD and PD with the current practice pattern, indicating PD could provide similar dialysis adequacy to that of HD when patients lose their residual renal function.