Recommended Flow Rates for Continuous Renal Replacement Therapy (CRRT)

Evidence-Based Dosing Recommendations

The KDIGO Clinical Practice Guidelines strongly recommend (Level 1A evidence) delivering an effluent volume of 20-25 mL/kg/h for CRRT in acute kidney injury 1, 2
This recommendation is based on rigorous evidence from large randomized controlled trials, including the RENAL and ATN studies 3
The prescribed dose should be higher than the target delivered dose, as the actual delivered dose often falls short of what is prescribed 4
Frequent assessment of the actual delivered dose is recommended to ensure adequate therapy 3, 5

The RENAL (Randomized Evaluation of Normal Versus Augmented Level) study randomly assigned 1,508 patients to CVVHDF at effluent flow rates of either 40 or 25 mL/kg/h 4, 3
The VA/NIH Acute Renal Failure Trial Network (ATN) study randomly assigned 1,124 patients to either more intensive (CVVHDF at 35 mL/kg/h) or less intensive (CVVHDF at 20 mL/kg/h) therapy 4, 3
Both studies demonstrated no survival benefit or improvement in kidney function recovery with higher intensity therapy 3, 5
These findings led to the current recommendation of 20-25 mL/kg/h as the optimal dose 1

For CVVH (Continuous Venovenous Hemofiltration), the effluent rate refers to the ultrafiltration rate 6, 7
For CVVHD (Continuous Venovenous Hemodialysis), the effluent rate refers to the dialysate flow rate 6, 7
For CVVHDF (Continuous Venovenous Hemodiafiltration), the effluent rate is the sum of dialysate and ultrafiltration rates 6, 7

Hemodynamically unstable patients and those with acute brain injury may particularly benefit from CRRT over intermittent hemodialysis 8, 7
Bicarbonate-based replacement fluids are preferred over lactate-based solutions, especially in patients with shock, liver failure, or lactic acidemia 3, 8
Anticoagulation strategy should be tailored to the patient's bleeding risk 8

The RENAL Study (1,508 critically ill patients) demonstrated that a higher intensity CRRT dose of 40 mL/kg/h did not improve survival compared with the standard 25 mL/kg/h dose (Level 1A evidence) 9.
The ATN Study (1,124 critically ill patients) showed no mortality benefit when an intensive CRRT dose of 35 mL/kg/h was compared with a less intensive dose of 20 mL/kg/h (Level 1A evidence) 9.

CRRT doses above 25 mL/kg/h provide no additional survival advantage or improvement in kidney‑function recovery; the optimal target remains 20–25 mL/kg/h (Level 1A) 9.
Early 2002 Kidney International investigations suggested that a dose of 35 mL/kg/h might improve outcomes versus 20 mL/kg/h, but these findings have been superseded by the larger RENAL and ATN trials (Level 2 evidence) 10, 11.

In a 70‑kg adult receiving CVVHDF, setting the dialysate flow to 1,500 mL/h and the ultrafiltration rate to 500 mL/h yields a total effluent rate of 2,000 mL/h, corresponding to a prescribed dose of ≈28.6 mL/kg/h (used to ensure delivery of the target 20–25 mL/kg/h) 10.

Routine measurement of the actual delivered CRRT dose is essential and should be used as a quality‑indicator metric; discrepancies between prescribed and delivered dose must be identified and corrected (Level 1A) 9.

Patients with acute brain injury or at risk for cerebral edema should preferentially receive CRRT rather than intermittent hemodialysis to minimize rapid fluid shifts and intracranial pressure changes (Level 2 evidence) 11.