Similarities and Differences between the Effects of Amino Acids and Nitroprusside on Peritoneal Permeability during CAPD

Abstract

Objective: Intraperitoneal administration of amino acid based dialysis solutions affects the surface area available for diffusion, with almost no effect on the intrinsic permeability to macromolecules. Intraperitoneally administered nitroprusside affects the vascular surface area and the intrinsic permeability without effect on the peritoneal blood flow. In the present study, these differences were translated into different effects on the radii of the pores in the peritoneal membrane. Methods: Effects of amino acid based dialysate and nitroprusside on peritoneal permeability characteristics were evaluated in standard peritoneal permeability analyses with L-arginine-containing amino acid dialysate (10 patients) or with 1.36% glucose dialysate with nitroprusside (10 patients). In each patient a control experiment with 1.36% glucose was performed. Kinetic modeling was done to analyze the effects in terms of the pore theory. Results: Both interventions increased the mass transfer area coefficients of low molecular weight solutes. This is in accordance with an increase in the unrestricted area over diffusion distance found with modeling. With amino acids almost no effect was found on the protein clearances; the increase in the large-pore radius was only small. Nitroprusside induced a marked increase in protein clearances. This was in accordance with an evident increase in the average large-pore radius. Conclusions: Amino acids affect the radii of the small pores and the large pores to the same extent. Nitroprusside influences especially the large pores. Both amino acids and nitroprusside are vasoactive, although the effects on the peritoneal microcirculation are different.

Peritoneal Transport Characteristics with Glycerol-Based Dialysate in Peritoneal Dialysis

“…Kinetic modeling using the pore model, suggested by Rippe and Stelin, showed similar values for the small-and large-pore radii, and for the unrestricted pore areas over unit diffusion distance, irrespective of whether they were calculated on the glucose experiments or on the glycerol experiments. These parameters were also similar to previously published values for 1.36% glucose (32). However, the reflection coefficient for glycerol was significantly lower than that for glucose, with a mean difference of 0.01 between the two osmotic agents.…”