Acute Kidney Injury and Intermittent Dialysis Dose

Intermittent hemodialysis (IHD) is the first-line kidney replacement modality in 50% of severe acute kidney injury (AKI) cases in French intensive care units (ICUs). It clears uremic toxins and restores acid-base and fluid-sodium balance, but the osmotic imbalance it induces can cause or worsen hemodynamic and neurological failure. Dialysis dose is a major prognostic issue, yet the optimal target and the best tools to quantify it in AKI remain debated. Kt/Vd, validated in chronic kidney disease, is largely biased in AKI because the urea distribution volume is altered by fluid overload, capillary hyperpermeability and impaired tissue perfusion. Alternatives include the urea reduction ratio (URR) and the solute removal index (SRI), simple measures that each require only one additional sample, but their relevance for guiding IHD strategy remains to be demonstrated. Kt alone is considered reliable in AKI, as urea clearance measured by ionic dialysance has been validated in the ICU, but neither Kt nor Kt indexed to body weight or body surface area has been evaluated in clinical practice. Current recommendations set a minimum dose of three 4-hour sessions per week, with a blood flow \> 200 mL/min and a dialysate flow \> 500 mL/min. This target standardizes care and simplifies planning, but the lack of personalization and of session quality measurement may lead to an inadequate dose in some patients. AIKIDDO is an observational study of 200 adult ICU patients with KDIGO stage 3 AKI treated with IHD. It aims to assess the agreement between dialysis dose measures (Kt/Vd, double-pool Kt/Vd, Kt, URR, SRI) obtained at each dialysis session. Patients are followed until Day 29 for death, dialysis dependence, renal recovery, neurological status, hemodynamic instability during sessions and duration of invasive mechanical ventilation.

Inclusion Criteria: * Adult patient (age \> 18 years) admitted to the ICU * Affiliated with a social security scheme * KDIGO stage 3 acute kidney injury during the ICU stay * Treated with IHD, either first-line or following continuous kidney replacement therapy * Consent signed by the patient or a relative at inclusion Exclusion Criteria: * Patient receiving chronic dialysis (hemodialysis, peritoneal dialysis) * Patient who has received two or more IHD sessions during the ICU stay * Kidney transplant recipient with a functioning graft * Ongoing veno-venous or veno-arterial ECMO (extracorporeal membrane oxygenation) * Kidney replacement therapy initiated for an indication other than KDIGO stage 3 acute kidney injury (e.g., drug poisoning) * Pregnant or breastfeeding patient * Moribund patient with an estimated life expectancy of less than 24 hours * Patient under guardianship, curatorship or other legal protection * Patient covered by French State Medical Aid (AME) * Patient previously included in the study