[Evaluation of nitrogen balance in patients treated with continuous ambulatory peritoneal dialysis]

Abstract

The aim of the study was an estimation of nitrogen balance (NB) in patients treated with continuous ambulatory peritoneal dialysis (CAPD) and an evaluation of relationship between NB and CAPD adequacy parameters, dietary intake and nutritional status of CAPD patients. Examinations, preformed every 3 months through 2 years, included the group of 44 patients in the age of 45 +/- 12 years, treated with CAPD through 17 +/- 10 months. NB was calculated as a difference between nitrogen intake (value obtained using dietary protein intake taken from computer analysis of diet histories--Method I or using protein catabolic rate calculated according to Randerson et al.--Method II) and amount of nitrogen excreted with dialysate and urine, estimated with modified Kjeldahl method. Results of NB I and NB II were normalized using actual total, standard, ideal or lean body mass (TBM, SBM, IBM and LBM, respectively). LBM was estimated with 3 methods: from creatinine kinetics (LBMcr), anthropometric measurements (LBManthr) and as 1/0.73 of total body water (LBMTBW/0.73). Mean values of NB were positive during the entire period of CAPD treatment. Results of NB I exceeded that of NB II (6.31 +/- 3.26 v. 4.80 +/- 2.94 g/day with daily protein and energy intake of 1.0 g/kg IBM and 37 kcal/kg IBM, respectively). Mean values of NB I or NB II, normalized using total body mass, were the highest when IBM was used, and the lowest--when TBM was applied. When normalization of NB was done with LBM, the highest values were expressed in g/kg LBMcr, the lowest--in g/kg LBManthr. Significant positive correlation was shown between NB I and plasma concentration of total protein and albumin, clinical-laboratory scores (Missouri system), dietary intake of fat, fatty acids, carbohydrates, sodium, potassium, calcium, ferrum, leucin, alanin, glycin and energy (without and with energy of glucose absorbed from the peritoneal cavity). Negative correlation was shown between NB I and dialysis duration. The highest correlation coefficients occurred when NB I was expressed in g/day, the lowest--when NB I was normalized with LBMcr. Values of NB II showed positive correlation with plasma albumin concentration, negative one--with CAPD efficacy number and creatinine D/P ratio in the peritoneal equilibration test. The highest correlation coefficients were obtained for NB II in g/kg LBManthr/day, the lowest--when NB II was expressed in g/day. Values of NB and their relationships with other parameters dependent on methods of NB estimation: when in calculations diet histories were applied, an influence of NB on plasma protein concentration and clinical-laboratory scores as well as relationship between NB and dietary intake and dialysis duration were shown; the use of protein catabolic rate for NB calculation revealed correlation between NB and plasma albumin concentration, peritoneal membrane permeability and CAPD adequacy. Patients, in whom nightly exchange of standard dialysis solution was replaced with amino acid containing dialysis solution, showed significantly higher NB II as compared to that of patients treated exclusively with standard solutions.