Nephrol Dial Transplant (1993) 8: 735-739
© 1993 European Renal Association-European Dialysis and Transplant Association
research-article
Effect of age on protein catabolic rate, morbidity, and mortality in uraemic patients with adequate dialysis
Division of Nephrology, School of Medicine, Spedali Civili and University of Brescia Italy
Correspondence and offprint requests to: Correspondence and offprint requests to: Dr E Movilli, Division of Nephrology Spedali Civili, P le Ospedale Civile I, 25125 Brescia, Italy.
To test the validity of the assumption that the protein catabolic rate (PCRn g/kg/day) is dependent on the normalized dose of dialysis (Kt/V urea), and to try to define the charactenstics of the patients in the undefined domain A of the mechanistic map of the National Cooperative Dialysis Study (NCDS), which should include patients with adequate amount of dialysis but inadequate PCRn, urea kinetic model ling was performed over 12 months on 85 patients undergoing haemodialysis All the patients were man aged to maintain a Kt/V urea 
0.9. During the entire period of study the total number of hospitalizations and the number of days of hospitalization were recorded. Total serum proteins and serum albumin concentrations were measured at the start and at the end of the study. The results of the study show that there was no correlation between Kt/V and PCRn nor between Kt/V and patient's age, but there was a strong inverse correlation between age and PCRn (r=0.578; P <0.0001). Further division of the patients into four groups according to age showed that the lowest values of PCRn were for the group of patients 75 years old. Twelve patients with PCRn
0.8 and Kt/V0.9 were included in domain A of the mechanistic map. Eleven (92%) of these 12 patients were years old. No correlations were found between the total number of hospitalizations, the total days of hospitalization, Kt/V, time on HD, body weight and PCRn by multiple regression analysis, while the inverse correlation between PCRn and age was confirmed. Body weight, total serum proteins and serum albumin concentration remained stable throughout the study. However, the basal serum albumin was less in the group of patients 75 years old. We conclude that if an adequate amount of dialysis is delivered, the protein intake becomes independent of the quantity of dialysis and dependent on other factors not yet known. In this situation, the age of the patients exerts a great negative influence on PCRn, particularly in patients 75 years old. In the 12 patients from the whole group with Kt/V 0.9 and PCRn 0.8g/kg/day (domain A of the mechanistic map), we could find no differences in death, hospitalization rate, or duration of hospitaliza flon compared to the others. The reduced PCRn in the oldest patients does not affect body weight, total serum protein, and serum albumin concentrations over time. This suggests that these patients might do well even with less protein intake.
Keywords: dialysis; protein catabolic rate; Kt/V; uraemia; nutrition