Kinetic behavior of urea is different from that of other water-soluble compounds: The case of the guanidino compounds

Abstract

The kinetics of the guanidino compounds under study are different from that of urea; hence, urea kinetics are not representative for the removal of other uremic solutes, even if they are small and water-soluble like urea.

HEMO Revisited: Why Kt/Vurea Only Tells Part of the Story

“…10 The assumption by Meyer et al that using a two-compartment model probably would not have affected the conclusions dramatically may be correct, but it would be worthwhile to check this thesis, now that detailed data for several protein-bound compounds have become available. 11,12 Of note, whereas intercompartmental clearances of BUN and methylguanidine are similar, 10 those of protein-bound solutes are often lower by a factor of 4 or more.…”

“…10 The assumption by Meyer et al that using a two-compartment model probably would not have affected the conclusions dramatically may be correct, but it would be worthwhile to check this thesis, now that detailed data for several protein-bound compounds have become available. 11,12 Of note, whereas intercompartmental clearances of BUN and methylguanidine are similar, 10 those of protein-bound solutes are often lower by a factor of 4 or more. 11 Altogether, the data from the study by Meyer et al strengthen the thesis that the uremic environment is not only determined by dialytic clearance but is equally dependent on the production, adsorption, and/or endogenous metabolism of individual uremic solutes.…”

The Patient as a Limit to Dialysis Technology

“…This certainly ameliorates the quality of sleep and thus quality of life. Furthermore, as the need for water will increase in the years to come, also an ecological dimension might be added to the economical considerations.Besides these positive findings, it should be remarked that Ward et al were only focusing on urea, which is biologically relatively inert (16) and not very representative for other compounds with different kinetic behavior (17,18). Neither the HEMO in hemodialysis (19) nor the ADEMEX study in peritoneal…”

“…Besides these positive findings, it should be remarked that Ward et al were only focusing on urea, which is biologically relatively inert (16) and not very representative for other compounds with different kinetic behavior (17,18). Neither the HEMO in hemodialysis (19) nor the ADEMEX study in peritoneal…”

“…In this context, urea as a marker offers a best-case scenario. Although middle molecules like ␤2-microglobulin distribute over at least two compartments (22,23) and the shift from the extravascular to the intravascular compartment is hampered, even several guanidino compounds, molecules of a similar metabolic origin as urea and with similar molecular weights and absent protein binding, are distributed over distribution volumes that are up to three times as large as that of urea (17,18).…”