What is the difference between Continuous Renal Replacement Therapy (CRRT) and dialysis in patients with Impaired renal function?

From the Guidelines

Continuous Renal Replacement Therapy (CRRT) is preferred over dialysis in patients with impaired renal function who are hemodynamically unstable, as it provides a more gradual and continuous removal of waste products and excess fluid, helping to maintain hemodynamic stability. The main difference between CRRT and dialysis is their approach and application, with CRRT being a slow, continuous form of dialysis typically used in critically ill patients in intensive care units, running 24 hours a day, removing waste products and excess fluid gradually at 20-30 mL/minute 1. In contrast, conventional dialysis includes intermittent hemodialysis (IHD), which runs for 3-4 hours three times weekly, removing waste at 300-500 mL/minute, and peritoneal dialysis, which uses the peritoneal membrane as a filter.

Key Considerations

• CRRT is preferred for patients who cannot tolerate rapid fluid shifts due to hypotension, cerebral edema, or multiorgan failure, as it helps maintain hemodynamic stability 1.
• The choice between CRRT and conventional dialysis depends on the patient's hemodynamic stability, severity of illness, and specific clinical circumstances, with many patients transitioning from CRRT to intermittent dialysis as their condition stabilizes 1.
• CRRT requires continuous anticoagulation (typically with citrate or heparin), specialized nursing care, and is more expensive than intermittent dialysis 1.

Clinical Application

• The selection of modalities should be considered in the context of available resources and expertise of personnel, with the goal of delivering RRT that reaches the goals of electrolyte, acid–base, solute, and fluid balance for each specific patient 1.
• An effluent volume of 20–25 ml/kg per h should be delivered when continuous RRT is used, which may require a higher prescription of effluent volume 1.
• Modality transition from continuous RRT to intermittent hemodialysis in intensive care unit patients should be considered when vasopressor support has been stopped, intracranial hypertension has resolved, and positive fluid balance can be controlled by intermittent hemodialysis 1.

From the Research

Overview of Continuous Renal Replacement Therapy (CRRT) and Dialysis

• CRRT and dialysis are two different modalities of renal replacement therapy (RRT) used to support patients with impaired renal function, particularly those with acute kidney injury (AKI) [ 2 ].
• CRRT is a continuous process that provides solute management, acid-base stability, and volume control, and is often preferred for critically ill patients due to its ability to provide greater hemodynamic stability and better fluid management [ 3 ].

Key Differences between CRRT and Dialysis

• CRRT offers a more continuous and physiologic approach to kidney support, with greater solute control and lower bleeding risk compared to conventional hemodialysis [ 3 ].
• Dialysis, on the other hand, is an intermittent process that can be performed in various modes, including intermittent hemodialysis (IHD) and extended hemodialysis [ 2 ].
• The choice between CRRT and dialysis depends on various factors, including the patient's hemodynamic status, coexisting medical conditions, and renal outcome expectations [ 2 ].

Clinical Evidence and Recommendations

• Studies have shown that there is no significant difference in patient survival, length of intensive care unit/hospital stay, or renal outcomes between CRRT and IHD in critically ill patients with AKI [ 2, 4 ].
• However, CRRT may be beneficial in specific clinical scenarios, such as in hemodynamically unstable postoperative patients [ 2 ].
• The delivered CRRT effluent dose for critically ill patients with AKI should be 20-25 ml/kg/h on average, with consideration for higher doses in specific clinical scenarios [ 5 ].