Dietary protein requirements and dialysate protein losses in chronic peritoneal dialysis patients

BACKGROUND: Recommended dietary protein allowances for chronic peritoneal dialysis (PD) patients are approximately 60% higher than the dietary protein allowances for healthy adults. The relative contribution of dialysate protein and amino acid losses to these high protein requirements or total nitrogen losses is uncertain. METHODS: Following a peritoneal equilibration test, two 24-hour dialysate collections (24-1 and 24-2) were performed in 9 stable patients undergoing automated PD [4 males, 3 diabetics, age 43 +/- 5 years (mean +/- SEM), dialysis vintage 42 +/- 6 months, dialysate-to-plasma ratio of creatinine 0.61 +/- 0.04]. Dialysate effluent from nighttime cycling was collected separately from the daytime dwells. RESULTS: The measured 24-hour protein losses were 9.4 +/- 0.6 (24-1) and 10.8 +/- 0.8 (24-2) g/day. Even though day dwells accounted for 27% of daily dialysate volume, they accounted for 40% of daily protein and amino acid losses. The frequency of nighttime cycling and duration of dwell were significant predictors of peritoneal protein losses. Dialysate protein and amino acid losses constituted 24% +/- 2% and 3.1% +/- 0.3% of dialysate nitrogen and 14% +/- 1% and 1.7% +/- 0.1% of dietary nitrogen intake respectively. CONCLUSIONS: Treatment with automated PD is associated with somewhat higher 24-hour dialysate protein losses compared to previous reports among continuous ambulatory PD patients. Dialysate protein and amino acid losses constitute a small, albeit significant, proportion of total nitrogen appearance and thus may contribute to the increased dietary protein requirements of chronic PD patients