No Difference in Nitrogen Balance between Standard Prescriptions of Hemodialysis and Peritoneal Dialysis

Abstract

Background: 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. Methods: 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. Results: 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 × 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. Conclusions: 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.

British Dietetic Association evidence‐based guidelines for the protein requirements of adults undergoing maintenance haemodialysis or peritoneal dialysis

“…). Of the twelve included studies (Table ), six were cohort studies (Beddhu et al ., ; Araujo et al ., ; Shinaberger et al ., ; Rambod et al ., ; De Mutsert et al ., ; Segall et al ., ), five were cross‐sectional studies (Bossola et al ., ; Ichikawa et al ., ; Thijssen et al ., ; Lu et al ., ; Sahin et al ., ) and one was an uncontrolled before and after study (Stojanovic et al ., ). All the included studies were based on stable adults undergoing HD for longer than 90 days.…”

“… For adults undergoing HD, there is moderate weak evidence to indicate that a protein intake equal to or >1.16 g kg −1 IBW per day is associated with pre‐albumin equal to or >40 g L −1 (Rambod et al ., ) and well nourished status with SGA (Stojanovic et al ., ); and that an intake equal to or >1.2 g kg −1 IBW per day is associated with decreased mortality (Segall et al ., ), higher albumin and higher body mass index (BMI) (Bossola et al ., ). SIGN 3, 2+, 3, 2− There is moderate weak evidence to suggest that a protein intake of >1.0 g kg −1 IBW per day is associated with higher serum albumin (Thijssen et al ., ), good nutritional status with SGA (Lu et al ., ) and reduced mortality (Araujo et al ., ). SIGN 2+, 3, 3 There is limited weak evidence to suggest that a protein intake equal to or >1.1 g kg −1 IBW per day but not exceeding 1.4 g kg −1 IBW per day, may be associated with a reduced risk of death (Shinaberger et al ., ).…”

“…All included studies were based on adults who had been undergoing PD for a minimum of 1 month. The total duration with respect to undergoing PD varied from 1 month to a mean of 38 months (Lu et al ., ). The principal outcome measures were SGA, albumin, anthropometric measurements and mortality.…”

“… There is moderate good quality evidence to indicate that a protein intake of 0.9–1.0 g kg −1 per day may be sufficient to maintain nutritional status in stable PD patients if matched by an adequate total calorie intake of 126–146 kJ kg −1 (30–35 kcal kg −1 ) per day (Jiang et al ., a,b; Lu et al ., ; Sutton et al ., ). SIGN 1+, 1−, 3, 1+ There is moderate weak evidence to suggest that a protein intake below 1.0 g kg −1 per day and/or total calorie intake <126 kJ kg −1 (<30 kcal kg −1 ) per day increases the risk of malnutrition in stable PD patients (Flanigan et al ., ; Wang et al ., ; Martin‐del‐Campo & Gonzalez‐Espinoza, ; Prasad et al ., ).…”

“…). The remaining twelve studies included four randomised controlled trials (RCTs) (Chen et al ., ; Gonzalez‐Espinoza et al ., ; Jiang et al ., b; Sutton et al ., ), one quasi‐experimental study (Martin‐del‐Campo & Gonzalez‐Espinoza, ), one nonrandomised trial (Jiang et al ., ); one prospective cohort study (Chung et al ., ), two cross‐sectional studies (Wang et al ., ; Lu et al ., ) and three case series (Flanigan et al ., ; Chow et al ., ; Prasad et al ., ) (Table ). Most studies used nPNA and nPCR as markers of protein intake, with a very small number of studies using more detailed nutritional assessments such as food frequency questionnaires and diet records.…”