Nitrogen Balance in Hemodialysis Patients

Abstract

Nitrogen (N) balance studies were performed on four anephric patients undergoing hemodialysis twice weekly. Dietary protein ranged from 0.40 g/kg to 1.48 g/kg high quality protein (HQPr) or from 0.14 g/kg to 0.95 g/kg low quality protein (LQPr) per day. Caloric intake was maintained constant with each patient (50-55 kcal/kg per day). From 2.0 to 3.5 g α-amino N were recovered from the dialysate. Plasma α-amino N decreased below normal when HQPr was less than 0.75 g/kg per day. Negative N balance and serum albumin decrements also resulted if HQPr was less than 0.75 g/kg per day. Nitrogen balance was neutral or slightly positive when HQPr was 0.75 g/kg per day. Greater than 0.75 g/kg per day of HQPr resulted in blood urea nitrogen (BUN) increments, without further augmenting nitrogen balance. Negative N balance and profound increments in BUN were produced on 0.95 g/kg per day of LQPr. These results suggest that approximately 0.75 g/kg per day of high biological value protein is necessary to maintain neutral nitrogen balance in anephric patients who are dialyzed twice weekly. Additional protein, whether of high or low quality, produced increments in blood urea nitrogen without augmenting nitrogen balance.