What is Continuous Renal Replacement Therapy (CRRT)?

From the Guidelines

Continuous Renal Replacement Therapy (CRRT) is a slow, continuous dialysis treatment used for critically ill patients with acute kidney injury or fluid overload who cannot tolerate conventional hemodialysis. The primary modes include CVVH (hemofiltration), CVVHD (hemodialysis), and CVVHDF (hemodiafiltration), with CVVHDF often preferred as it combines diffusion and convection for optimal solute clearance. Typical settings include a blood flow rate of 150-200 mL/min, dialysate rate of 20-35 mL/kg/hr, and replacement fluid rate of 20-35 mL/kg/hr when used. Anticoagulation is essential to prevent circuit clotting, with regional citrate (starting at 3-4 mmol/L) being preferred over systemic heparin (starting at 5-10 units/kg/hr) due to lower bleeding risk, as suggested by the KDIGO guideline 1. Electrolyte monitoring should occur every 6 hours initially, then every 12 hours once stable, with particular attention to calcium levels when using citrate. CRRT is effective because it allows for gentle, continuous removal of fluid and toxins, maintaining hemodynamic stability in unstable patients while providing time for kidney recovery. Some key considerations for CRRT include:

• The use of bicarbonate as a buffer in dialysate and replacement fluid, as recommended by the KDIGO guideline 1
• The importance of frequent assessment of the actual delivered dose of RRT, as noted by the Canadian Society of Nephrology commentary 1
• The need for individualization of the intensity of CRRT or IHD to meet a patient's requirements for maintenance of electrolyte and fluid balance, as suggested by the KDIGO guideline 1
• The potential benefits of using CRRT, rather than standard intermittent RRT, for hemodynamically unstable patients, as recommended by the KDIGO guideline 1. Overall, CRRT is a valuable treatment option for critically ill patients with acute kidney injury or fluid overload, and its use should be guided by the latest clinical evidence and guidelines, such as those provided by the KDIGO guideline 1 and the Canadian Society of Nephrology commentary 1.

From the Research

Definition and Purpose of Continuous Renal Replacement Therapy (CRRT)

• CRRT is a method of blood purification used in the treatment of critically ill patients with acute kidney injury (AKI) [ 2, 3,4,5,6 ].
• The main goal of CRRT is to optimize solute control, acid-base, and volume status in critically ill patients 3, 4.
• CRRT is typically used in intensive care unit settings, particularly in patients with severe AKI, fluid overload, and hemodynamic instability 3, 4.

Key Aspects of CRRT

• The dose of CRRT is reported as effluent flow in ml/kg body weight per hour (ml/kg/h) 4.
• Solid evidence supports that the delivered CRRT effluent dose for critically ill patients with AKI should be 20-25 ml/kg/h on average 4.
• To account for treatment interruptions and the natural decline in filter efficiency over time, it is recommended to prescribe 25-30 ml/kg/h of effluent dose 4.
• Preventing clotting in the CRRT circuit is a key goal to effective patient management, and regional anticoagulation with citrate is increasing in popularity 2, 5.

Recent Advances and Future Directions

• There have been major improvements in CRRT technology and utilization over the past 50 years 6.
• The last decade has seen a growing interest and demand for CRRT in worldwide ICUs, particularly since the COVID-19 pandemic 6.
• Further research is needed to identify interventions that can prolong the life of CRRT filters in critically ill patients 5.
• Digital health technologies may play a key role in building clinical decision support for CRRT and improving personalized bedside decisions 6.