Evaluation of pre- and postdilutional on-line hemodiafiltration adequacy by partial dialysate quantification and on-line urea monitor

On-line highflux hemodiafiltration (HDF) is a clinically interesting and ef fective mode of renal replacement therapy, which offers the possibility to obtain an increased removal of both small and large solutes. The fundamenta l role of urea kinetic monitoring to assess dialysis adequacy in convention al hemodialysis has been widely studied. Both direct measurement of the ure a removed by the modified direct dialysate quantitation (mDDQ) based on par tial dialysate collection (PDC) and dialysate-based urea kinetic modeling ( DUKM) using urea monitor have been advocated. The validity of this assessme nt tool in the patients with on-line HDF remained unclear. The aims of this investigation were (1) to compare the delivered Kt/V, urea mass removal (U MR), solute removal index (SRI) and normalized protein catabolic rate (nPCR ) between pre- and postdilutional high-flux HDF; (2) to verify and compare the efficiency of pre- and post-dilutional HDF using DUKM with on-line dial ysate urea sensor, and mDDQ with partial dialysate collection. During both mode of HDF, the paired analysis urea removed and Kt/V showed no significan t difference. Using mDDQ, mean values for predilutional mode were as follow s: Kt/V 1.53 +/- 0.01 UMR, 16.8 +/- 0.3 g/session; urea clearance 170 +/- 1 8 ml/min; SRI 75.5 +/- 7.7%; urea distribution volume (V) 28.3 +/- 1.2 lite rs; nPCR 1.34 +/- 0.18 g/kg/day; on the other hand, mean values for postdil utional mode were Kt/V 1.58 +/- 0.01; UMR 17.10 +/- 0.28 g/session; urea cl earance 184 +/- 21 ml/min; SRI 77.2 +/- 3.5%; urea distribution volume, 27. 8 +/- 1.5 liters; nPCR 1.34 +/- 0.19 g/kg/day. The mean value of urea gener ation rate was 5.82 +/- 1.12 mg/min during HDF. Our results showed that dia lysis adequacy was achieved with both high-volume predilutional HDF and pos tdilutional HDF. These two modes of HDF provided similar and adequate small solute clearance. In addition, we found that on-line analysis of urea kine tics is a reliable tool for quantifying and assuring delivery of adequate d ialysis.