A QUANTITATIVE-ANALYSIS OF SODIUM-TRANSPORT AND REMOVAL DURING PERITONEAL-DIALYSIS

To quantitatively evaluate peritoneal sodium transport, the diffusive mass transport coefficient (K-BD) and sieving coefficient (S), as well as the mass of sodium transported by diffusion (DM), by convection (C M) and by fluid absorption (AM) and the total sodium mass removed (RM) were calculated during a series of single dwell studies in CAPD patie nts. A six-hour dwell study was performed in 68 patients using 2 liter of 1.36% (N = 13), 2.27% (N = 9) or 3.86% (N = 46) glucose dialysis f luid with I-131-albumin as the intraperitoneal volume marker. The pati ents in whom the 3.86% glucose dialysis fluid was applied were further divided into four transport groups according to a modified peritoneal equilibration test: high (H), high-average (H-A), low-average (L-A), and low (L) transport. There was no significant difference in K-BD nor in S for sodium among different solutions. However, the removed sodiu m mass (RM) was significantly higher in the 3.86% (70.5 +/- 31.5 mmol) and 2.27% (36.0 +/- 21.0 mmol) solutions as compared to that of the 1 .36% (-1.8 +/- 26 mmol) solution mainly due to increased both CM and D M. In general, CM was twice as high as DM. AM substantially decreased sodium removal. Among the different transport groups, the K-BD and S v alues for sodium were significantly higher in the H group as compared to the other transport groups (both P < 0.05). However, RM was signifi cantly lower in the H group mainly due to higher AM. Using a 3.86% glu cose solution, the D/P for sodium was found to be significantly differ ent (but only after 120 min of the dwell) between all the different tr ansport groups. In conclusion, sodium removal in CAPD is strongly rela ted to the fluid removal. The ultrafiltration induced convective trans port (CM) and peritoneal absorption of sodium (AM) were of similar mag nitude and were twice as high as the diffusive transport (DM) and both play an important role in the peritoneal sodium balance. A D/P for so dium using the 3.86% glucose solution, especially at the end of the dw ell, can be used to discriminate between different transport categorie s of patients. High transport patients have a poor fluid and sodium re moval that are likely to affect their clinical outcome.