CRRT Settings and Protocols

Introduction to CRRT

The American Journal of Kidney Diseases recommends a typical CRRT effluent dose of 20-25 mL/kg/h for patients with acute kidney injury, with a prescription of 25-30 mL/kg/h to account for treatment interruptions and filter efficiency decline over time 1
CRRT is defined as any extracorporeal blood purification therapy intended to substitute for impaired renal function over an extended period of time and applied for 24 hours per day 2

Common CRRT modalities include CVVH (Continuous Venovenous Hemofiltration), CVVHD (Continuous Venovenous Hemodialysis), CVVHDF (Continuous Venovenous Hemodiafiltration), and SCUF (Slow Continuous Ultrafiltration) 2, 3
CVVH uses convection as primary mechanism with an external pump in a venovenous circuit 3
CVVHD uses diffusion with an external pump in a venovenous circuit 3
CVVHDF combines both diffusive and convective solute removal 3
SCUF is a form of CVVH without fluid replacement, primarily for fluid removal 3

The Kidney International society recommends avoiding subclavian veins for access due to risk of thrombosis and late stenosis 5
Always use ultrasound guidance for dialysis catheter insertion 4
Obtain chest radiograph promptly after placement of internal jugular or subclavian catheters 4
Regional citrate anticoagulation is recommended as first choice for patients without increased bleeding risk 4
Unfractionated or low-molecular-weight heparin can be used if citrate is contraindicated 4
CRRT can be carried out without anticoagulation in patients who are auto-anticoagulated or at high risk of bleeding 5

Bicarbonate rather than lactate should be used as buffer in dialysate and replacement fluid 1, 4
Dialysate or substitution fluid should contain physiologic concentrations of electrolytes 5
Avoid fluids with supra-physiologic glucose concentrations to prevent hyperglycemia 4, 5
Prescribed effluent dose should be 25-30 mL/kg/h to account for treatment interruptions and filter efficiency decline 1
Delivered effluent dose should target 20-25 mL/kg/h 1
Typical dialysate flow rates for CVVHD are 1-2 L/hour 2, 3
Blood flow rate is typically 100-150 mL/min for CVVHDF 6

Frequently assess actual delivered dose to adjust prescription as needed 4
Monitor filter performance and adjust prescription to achieve goals of electrolyte balance, acid-base balance, solute clearance, and fluid balance 4
During heparin anticoagulation, measure activated clotting times (ACT) or systemic partial thromboplastin time (PTT) 5
During citrate anticoagulation, frequently measure post-filter and serum-ionized calcium to titrate citrate and calcium replacement solutions 5

Use integrated fluid balancing systems rather than intravenous infusion pumps adapted for CRRT 4
Adaptive use of intravenous infusion pumps for CRRT has been shown to risk significant errors in fluid balance 2
Use dialyzers with a biocompatible membrane 4