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Abstract: FR-PO468

Study of Dilution Modes Under Different Operational Conditions in Continuous Venovenous Hemofiltration

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Huang, Zhongping, West Chester University, Glenmoore, Pennsylvania, United States
  • Attaluri, Anilchandra, Pennsylvania State University - Harrisburg, Middletown, Pennsylvania, United States
  • Letteri, Jeffrey J., Baxter, Nantucket, Massachusetts, United States

The landmark CRRT dose trial (Ronco et al, Lancet 2000) was performed in the post-dilution CVVH mode. The clinical benefits provided by different CRRT modes may influence MM clearance. The purpose of this experimental CVVH study was to measure the clearance of small solutes (urea, creatinine) and MM surrogates (vancomycin, inulin) in different dilution modes, degree of pre-dilution, and flow conditions along with MM sieving coefficient (SC) values over extended periods.


The Prismaflex (Baxter) machine was used to deliver replacement fluid at different dilution points [pre-blood pump dilution (PBP), pre-dilution (PRE) and post-dilution (POST)]. Simulated treatment involved 6 liters of bovine blood (Hct ~ 35%) processed at zero net ultrafiltration for a duration of 240 minutes. A 1.4 m2 hemofilter (HF 1400) was used. The three experimental conditions were: 1) blood flow rate (QB): 190 mL/min; replacement flow rate (QR): 2 L/hr, 2) QB: 290 mL/min; QR: ~3 L/hr, 3) QB: 380 mL/min; QR: ~4 L/hr. These conditions were chosen to maintain filtration less than 25% in POST. Solute clearance at various times were calculated based on mass balance.


There were significant differences (p < 0.001) in urea & creatinine clearance for the different experimental conditions. There was a significant decrease (p < 0.01) in urea and vancomycin clearance from POST to PRE and from POST to PBP, although there were no significant differences between PRE and PBP for any of the solutes. Neither urea nor creatinine clearance changed significantly over time for any of the operational conditions and dilution modes. There were significant differences (p < 0.001) in inulin and vancomycin clearance in these 3 experimental conditions. No significant differences (p > 0.05) in inulin clearance between post-dilution and pre-dilution mode, post-dilution and pre-pump-dilution mode, and pre-dilution and pre-pump-dilution mode were observed. A significant decrease in inulin and vancomycin SC occurred over time under all conditions was most evident in POST.


1) Small MW solute clearance increased as the extent of pre-dilution decreased 2) MM SC decreased substantially (especially in POST) with time, most likely due to secondary membrane effects. 3) The data obtained by varying pre- and post-dilution percentages are predictable for small solutes but are not entirely consistent for MMs.