Amino acid adherence in continuous renal replacement therapies
© BioMed Central Ltd 2005
Published: 9 June 2005
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, and possible adherence of amino acids.
To evaluate amino acid adherence in CRRT.
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. The blood flow was 150 ml/min in all patients and the dialysate flow during CVVHD was 16.6 ml/min.
Amino acid assays, using high-pressure liquid chromatography serum, venous and dialysate, were performed by laboratory CTN and Pardini. Adherence was calculated as: clearance hemodialysis (CH) / serum clearance (SC); CH = (16.6 × dialysis) / serum amino acids; SC = 150 × (serum amino acids - venous amino acids) / dialysis amino acids.
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 23 amino acids were analysed (μmol/l): aspartic acid, glutamic acid, alanine, arginine, asparagine, cystine, phenylalanine, glycine, glutamine, hydroxyproline, histidine, isoleucine, leucine, lysine, methionine, ornithine, proline, serine, taurine, tyrosine, threonine, tryptophan, valine. Analyses were performed on the average of the amino acids. Adherence was not statistically significant, and did not correlate with time of hemodialysis or with serum amino acids. Statistical calculations were made by analysis of variance, linear, nonlinear and logarithmic regression: glutamine (R2 = 0.978691062), alanine (R2 = 0.575243703), taurine (R2 = 0.612666425), valine (R2 = 0.743575525).
We should not estimate the protein necessity in a septic or trauma patient on CHVVD based exclusively on the amino acid loss. Other factors, such as the adsorption of amino acids, may contribute to the continuous catabolism seen in these critically ill patients.