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To develop models to estimate nitrogen (N) losses of children on chronic peritoneal dialysis (CPD) from easily measurable indexes and laboratory tests, we measured the N content and all nitrogenous compounds in dialysate (D), urine (U), and feces over 3 days in 19 pediatric patients on CPD. Total measured N losses (TNm) were 5.56+/-2.26 g/day (69.9+/-11.1% in dialysate, 16.3+/-10.6% in urine, and 13.6+/-4.6% in feces). Correlation coefficients between measured dialysate and urinary N losses and the single nitrogenous compounds indicated values of over 0.9 only for urea in dialysate and urine; fecal N losses correlated well with body surface area (BSA). Taking into account these correlations, we developed a univariate additive model and three multivariate models to predict total estimated N losses (TNe). The best prediction of TNm was obtained with model 3, which considered not only urea output in dialysate and urine but also dialysate protein loss and BSA: TNe (g/day)=0.03+/-1.138 UN urea+0.99 DN urea+1.18 BSA+0.965 DN protein. A confirmatory analysis performed on a second group of 23 pediatric patients on CPD, using all four models, showed a higher percentage of studies with a relative difference between TNm and TNe less than 10% for model 3 than for the other models. Thus, N losses of pediatric patients on CPD can be estimated from measured urea and protein losses in dialysate and urea loss in urine, together with BSA.

Protein and energy requirements of children on automated peritoneal dialysis (APD) have still not been sufficiently well defined, although their adequacy is important to maintain a positive nitrogen (N) balance and prevent malnutrition. We carried out 42 studies to estimate N balance in 31 children over 3 years on APD for 19.8+/-15.7 months. Twenty metabolic studies were performed in patients dialysed for less than 1 year (7.2+/-3.3 months) and 22 in patients treated for more than 1 year (31.3+/-13.6 months). The mean estimated N balance of all metabolic studies was 57.5+/-62.8 mg/kg per day. In only 21 of 42 studies was N balance estimated to be over 50 mg/kg per day, which is considered adequate to meet N requirements for all metabolic needs and growth of uremic children. Estimated N balance correlated significantly with dietary protein intake (r=0.671, P=0.0001) and total energy intake (r=0.489, P=0.001). Using the equations of correlation, the values of dietary protein intake [=144% recommended dietary allowance (RDA)] and total energy intake (89% RDA) required to obtain an estimated N balance >50 mg/kg per day were calculated. Significantly lower estimated N balance values were obtained in the studies performed on patients on APD for over 1 year (36.09+/-54.02 mg/kg per day) than in patients treated for less than 1 year (81.11+/-64.70 mg/kg per day). In conclusion, based on the values of estimated N balance, we were able to establish adequate dietary protein and energy requirements for children on APD.

To achieve more adequate dialysis in a shorter treatment time, seven children, characterized as high/high average (H/HA, 5 patients) and low/low average (L/LA, 2 patients) transporters according to the peritoneal equilibration test, were treated with tidal peritoneal dialysis (TPD) for 13.7 +/- 5.7 months, after being treated with nightly intermittent peritoneal dialysis (NIPD) for a similar period. We determined the TPD prescription necessary to provide improved clearances compared with NIPD within the same or less treatment time. Dialysis flow rate was significantly higher in TPD than NIPD, due to a reduction of dwell time and an increase in the number of exchanges. Peritoneal and total clearances of urea and creatinine were higher, whereas serum creatinine and urea nitrogen levels were lower and treatment duration shorter during TPD than NIPD, notwithstanding a decrease of residual renal function. Moreover, a mean time-averaged blood urea nitrogen level as low as 48.5 +/- 11.6 mg/dl was achieved during TPD. The improvement was more significant in H/HA than in L/LA patients.