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Abstract: TH-PO362

Pre-Filter CVVH Results in Longer Filter Life Than CVVHD

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Griffin, Benjamin, University of Colorado, Aurora, Colorado, United States
  • Arruda, Nigel, University of Colorado, Aurora, Colorado, United States
  • Teitelbaum, Isaac, University of Colorado Health Science Center, Aurora, Colorado, United States
  • Ambruso, Sophia L., University of Colorado, Aurora, Colorado, United States
  • Teixeira, Joao Pedro, University of Colorado, Aurora, Colorado, United States
  • Gist, Katja M., University of Colorado, Children''s Hospital Colorado, Aurora, Colorado, United States
  • Jovanovich, Anna Jeanette, Denver VA / University of Colorado, Denver, Colorado, United States
  • Faubel, Sarah, University of Colorado Denver , Denver, Colorado, United States

Continuous renal replacement therapy (CRRT) is used to treat severe acute kidney injury (AKI) in hemodynamically unstable patients. The two main CRRT modalities are continuous venovenous hemofiltration (CVVH, convective clearance) and continuous venovenous hemodialysis (CVVHD, diffusive clearance). Filtration fraction, an estimate of hemoconcentration through a filter, is thought to be a major determinant of filter clotting risk in CRRT. In theory, CVVHD produces less hemoconcentration, and therefore less potential for filter clotting, than either pre-filter or post-filter CVVH. However, data to support this claim remain limited. The purpose of this study was to examine filter life in patients treated with either pre-filter CVVH or CVVHD.


We conducted a retrospective analysis of adult patients initiated on CRRT at the University of Colorado Hospital (UCH) between 2014 and 2016. Filter life was recorded for all filters, which were changed if clinically warranted or after a maximum of 72 hours. Cox regression was used to evaluate time to filter loss in CVVH versus CVVHD, and the model was adjusted for blood flow rate, anticoagulation type, replacement or dialysis fluid flow rate, ultrafiltration rate, and patient weight.


A total of 415 filters from 160 patients were included in the analysis, of which 275 were used in a CVVH circuit and 140 in a CVVHD circuit. The average filter life in those undergoing pre-filter CVVH was 42 hours (SD 25.2) compared to 35 hours (SD 24.3) in CVVHD (p = 0.01). Cox regression showed a hazard ratio of 1.3 (CI 1.03 – 1.65, p=0.028) for filter loss with CVVHD.


Contrary to out hypothesis, pre-filter CVVH had a longer average filter life than CVVHD, and this pattern remained significant in a Cox regression model. CVVHD results in less hemoconcentration than CVVH, but is not associated with increased filter life. Pre-filter CRRT may be associated with longer filter life through dilution of clotting factors, but further investigation into the mechanism of filter clotting in these CRRT modalities is needed.


  • Other NIH Support