Dose of continuous renal replacement therapy for acute kidney injury in critically ill patients

Continuous renal replacement therapy (CRRT) is commonly used for critically ill patients with acute kidney injury (AKI). Despite two decades of clinical research, the optimal CRRT dose remains uncertain. Early studies suggested benefits of high-intensity therapy; however, subsequent multicentre randomised clinical trials (RCTs) have demonstrated no survival advantage of effluent rates above 25 mL/kg/h, thereby establishing the current “standard dose” of 20–25 mL/kg/h recommended by guidelines. This narrative review synthesises current knowledge on the concept of CRRT dose, including physiologic principles of solute control, historical evolution of dosing strategies, distinctions between prescribed and delivered dose, and the potential adverse consequences of excessive clearance. Although standard dosing is based on achieving small-solute clearance, clinical practice varies widely, with some intensive care units (ICUs) delivering substantially lower doses, i.e., 13–16 mL/kg/h, without apparent harm. Excessive clearance increases the risk of hypophosphatemia, nutrient loss, altered drug exposure, and potentially delayed renal recovery, which are collectively described as dialytrauma. Experimental and clinical observations have renewed interest in permissive azotaemia, proposing that moderate urea levels may facilitate renal repair. In parallel, real-world data have revealed significant global heterogeneity and have suggested that the minimum effective dose may be lower than traditionally assumed. Three ongoing RCTs are evaluating whether lower-intensity regimens are feasible, safe, and beneficial. Accordingly, the debate has shifted from “high vs. standard” to “standard vs. low”. The results of the ongoing clinical trials will likely redefine optimal CRRT dosing and inform future international guidelines and clinical practice.

Acute kidney injury; Renal replacement therapy; Dialysis dose; Dialytrauma; Kidney recovery; Permissive azotaemia

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