Protein losses in continuous renal replacement therapies

Introduction

Continuous renal replacement therapies (CRRT) readily allow for the nutritional support of these high catabolic states, but also contribute to the nitrogen loss through filtration of free amino acids and small peptides across the hemofilters. Amino acid clearances and calculated losses in adults on continuous venovenous hemofiltration (CVVHD) have been reported in the range of 2–11% of dietary intake.

Objective

To analyse protein losses from CRRT treatments in critically ill patients.

Materials and methods

Paired samples from serum, venous and dialysate/ultrafiltrate were obtained during CRRT procedures from 41 patients in a 27-bed ICU from July 2002 to May 2003. Paired samples were collected from 1, 6, 12, 24, 36 and 48 hours of continuous hemodialysis, a total of six samples of serum, venous and dialysate. PAN 650 filters were used in all patients. Blood flow was 150 ml/min in all patients and the dialysate flow during CVVHD was 16.6 ml/min. Five patients received no diet. Four patients received an oligomeric diet, one patient hyperalimentation intravenously, and the others received polymeric diets. The protein given was 1.3–1.7 g/kg. Total calorie intake was 22–25 kcal/kg. The amino acid assays, using high-pressure liquid chromatography serum, venous and dialysate, were performed by laboratory CTN and Pardini.

Results

The average patient age was 73.08 years (43–88 years) and the APACHE II score was 18.37 (11–28). Serum, venous and dialysate amino acids were obtained in 41 patients and analysed 23 amino acids. Analyses were performed on the average of amino acids. Statistical calculations were by analysis of variance, linear, nonlinear and logarithmic regression.

Conclusion

The losses of amino acids are more evident with amino acids that are more elevated in the plasma such as glutamine, alanine, glycine, glutamic acid. It seems that dialysis does not modify the behaviour of plasma amino acids.