Diffusive and convective solute clearances during continuous renal replacement therapy at various dialysate and ultrafiltration flow rates

Citation
S. Brunet et al., Diffusive and convective solute clearances during continuous renal replacement therapy at various dialysate and ultrafiltration flow rates, AM J KIDNEY, 34(3), 1999, pp. 486-492
Citations number
15
Categorie Soggetti
Urology & Nephrology
Journal title
AMERICAN JOURNAL OF KIDNEY DISEASES
ISSN journal
02726386 → ACNP
Volume
34
Issue
3
Year of publication
1999
Pages
486 - 492
Database
ISI
SICI code
0272-6386(199909)34:3<486:DACSCD>2.0.ZU;2-Y
Abstract
Clearances of several solutes (urea, creatinine, phosphate, urates, beta(2) -microglobulin [beta(2)-M]) were measured during venovenous continuous rena l replacement therapy (CRRT) at Various ultrafiltration (Q(UF); 0 to 2 L/h) and dialysate flow rates (Q(D); 0 to 2.5 L/h). Preset Multiflow-60 and Mul tiflow-100 hollow-fiber dialysers (M-60 and M-100; Hospal-Gambro, St-Leonar d, Canada) were compared (five patients for each type). First, we evaluated the impact of predilution on convective clearances: a progressive decrease in patient clearances, similar for both filters, was observed, reaching a maximum of 15%, 18%, and 19% for urea, urates, and creatinine, respectively , with predilution at a Q(UF) of 2 L/h. Second, we compared convective and diffusive clearances. Because effluent to plasma ratio (E/P) remained at 1 for small solutes (urea, creatinine, phosphate, urates) during convection, clearances were equal to the effluent rate for both dialyzers. However, we observed greater diffusive clearances for small molecules with M-100 than w ith M-60 at a Q(D) of 1.5 to 2.5 L/h, the difference being more significant as molecular weight increased. For beta(2)-M, diffusive clearance was very low and rapidly reached a plateau of 8 and 12 mL/min for M-60 and M-100, r espectively at a Q(D) greater than 1.5 L/h. Convective clearances for beta( 2)-M increased nonlinearly up to 20 +/- 2 mL/min at a progressively greater Q(UP) (from 0.5 to 2 L/h) for both M-60 and M-100. This nonlinear increase was attributed to an increase of almost 40% in UP for beta(2)-M from a Q(U F) of 0.5 to 2 L/h. Third, the interaction between convection and diffusion was assessed by measuring solute clearances at a fixed Q(UF) (1 and 2 L/h) and variable Q(D) (0.5 to 2.5 L/h). For small molecules, no significant in teraction between convection and diffusion was noticed with M-100, whereas only a small interaction was noticed with M-60. However, for beta(2)-M, the addition of diffusion (Q(D), 0.5 to 2.5 L/h) did not result in any signifi cant increase in total clearances over convective clearances for M-60 and M -100. This observation suggests that the diffusive clearances for Sp-M obse rved with M-60 and M-100 at a Q(UF) of 0 L/h and at various Q(D) probably o ccurs by convective fluxes across the membrane. These results demonstrate t hat convection is more efficient than diffusion in removing mixed-molecular -weight solutes during CRRT. (C) 1999 by the National Kidney Foundation, In c.