Abstract: FR-PO824

Urea Clearance Modelling Using 300 ml/min of Dialysate Flow

Session Information

Category: Dialysis

  • 601 Standard Hemodialysis for ESRD


  • Leypoldt, J. Ken, None, Menlo Park, California, United States
  • Prichard, Sarah S., Outset Medical, San Jose, California, United States
  • Chertow, Glenn Matthew, Stanford University School of Medicine, Palo Alto, California, United States
  • Alvarez, Luis, None, Menlo Park, California, United States

High dialysate flow rates (QD) of 500-700 mL/min are generally used in the outpatient setting to maximize urea removal in a time efficient manner. Lower dialysate flows of 100-200 mL/min are often employed in critically ill patients and in patients at high risk of dialysis disequilibrium. There are few data describing the use of a mid-rate QD (300mL/min) in a modern outpatient dialysis setting. We present urea kinetic modeling of 300 mL/min dialysate flow rates and investigate differential urea clearances between 300 and 500 mL/min QD.


Urea kinetic models were used to predict urea clearances at 300 mL/min dialysate flows. Using the FHN trial group urea model assumptions in combination with published dialyzer characteristics (KoA), a weekly urea concentration profile was obtained. The model was then applied to patients of different weights and volumes of distribution (VOD) at blood flows (QB) of 400 mL/min. Finally, a clearance relationship for spKt/V of 300 vs. 500 mL/min QD was obtained.


Table 1 shows modelled spKt/V when QD is 300mL/min or 500 mL/min at the same QB of 400 mL/min. Across VOD, the model demonstrates a QD of 300 mL/min results in a predicted spKt/V that meets urea clearance targets. There was a small difference in spKt/V between a QD of 300 mL/min and 500 mL/min QD. Use of a larger KoA (LKoA) dialyzer and 15 minutes of additional time narrows the spKt/V difference.


A QD of 300mL/min can be expected to achieve urea clearance targets. Decreasing dialysate flow rate to 300 mL/min results in a modest, but clinically insignificant, spKt/V difference. For patients with clearance challenges at 500mL/min QD, the use of a 300 mL/min QD with a larger KoA dialyzer and incremental time can be considered, which may itself allow for lower rates of ultrafiltration and better-tolerated hemodialysis therapy.

Table 1: Calculated spKt/V
Dialysate Flow (mL/Min)500300300
Dialyzer +
15 min
VOD=25L, Treatment Time=180 minutes1.68*1.461.60
VOD=30L, Treatment Time=210 minutes1.641.421.56
VOD=30L, Treatment Time=240 minutes1.841.591.72
VOD=35L, Treatment Time=240 minutes1.611.391.51



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