Dialysance of Amino Acids and Related Substances

Abstract

The losses of amino acids and related compounds have been studied during hemodialysis of patients with the Kiil dialyzer and the Dow Hollow Fiber Artificial Kidney (HFAK). There was a linear relationship with close correlation for both direct dialysance (D_d) and indirect dialysance (D_p) between the two dialyzers, the HFAK being 31–46% more efficient than the Kiil dialyzer in removing these solutes. The volume from which the amino acids were extracted was found to be the plasma alone, since the ratio D_p/D_d was close to 1.00 for both dialyzers. A good correlation was found for both dialyzers between molecular weight and dialysance (r = 0.53,0.57) but the correlation was even closer between the diffusion coefficient in water and the dialysance of the solutes (r = 0.86, 0.89). The absolute losses of the amino acids during dialysis for short periods in the fasting state were extrapolated to 8 h, the usual duration of a dialysis. For the Kiil dialyzer extrapolated losses were sizeable (as percentage of minimal daily requirements) for only three essential amino acids: valine (36%), lysine (44%) and threonine (48%). With the HFAK the losses of all essential amino acids except phenylalanine and methionine were sizeable, the highest being for valine (59%), lysine (59%) and threonine (108%). The possible significance of these losses to patients on chronic dialysis are discussed.