Relationship between parameters of the urea kinetic model and serum amino acid levels in patients on hemodialysis

Background. The parameters of the urea kinetic model (UKM) [product of dialyzer urea clearance and treatment time divided by body urea volume (Kt/V), protein catabolic rate (PCR), percent creatinine generation rate (%CGR)] are predictors of prognosis in patients on hemodialysis. In addition, adequate nutritional status has been recently recognized to be important for patient survival. We examined the relationship between serum amino acid levels and the parameters of the UKM, and investigated whether they could be predictors of patients' prognosis. Method. We studied 56 non-diabetic patients undergoing hemodialysis, and compared them with 101 normal controls. Serum amino acid levels were measured by high-performance liquid chromatography. Kt/V, PCR, and %CGR were calculated by Shinzato's method. Results. The serum amino acid patterns of patients on hemodialysis were characterized by low essential amino acid levels and high non-essential amino acid levels. Kt/V did not correlate with any amino acid levels. PCR correlated positively with urea and 3-methylhistidine, and negatively with aspartic acid and glutamic acid. %CGR correlated positively with serine, and negatively with glutamic acid. There were no correlations between valine/glycine and PCR, both of which are indicators of protein intake. Conclusions. We considered that serum amino acid levels are poor predictors of patients' prognosis. Of the various causes of alterations in serum amino acid levels, renal metabolic dysfunction and protein-calorie malnutrition appear to be important.