Acute kidney injury in critically ill patients admitted to the ICU is a common complication associated with high mortality or long-term chronic kidney damage. Some of these patients require continuous renal replacement therapy (low-intensity hemodialysis for 24 hours) until renal function recovery is achieved.

Continuous Renal Replacement Therapy (CRRT) is a crucial treatment for ICU patients with acute renal failure. It offers continuous toxin removal and prevents fluid accumulation in the patient's body. The therapy not only eliminates toxins but also physiological substances, including micronutrients and essential elements for cellular metabolism and organ function.

Currently, there is limited information available to adjust the renal therapy dose and avoid or balance the loss of these substances without causing toxin accumulation. Some studies suggest that high doses of therapy do not provide benefits and increase complications.

The objective of this study is to evaluate two doses of continuous renal therapy in terms of internal environment control (sodium, potassium, and acids and bases), micronutrient loss, and toxin elimination. After 48 hours of therapy, patients will be assigned to continue with a dose equal to the initial dose or a decrease in the initial dose. These two options are part of the current standard practice in our center.

Patients participating in the study will be randomly assigned one of the continuous renal therapy doses. The study is open, so treating physicians will always know the therapy the patient is receiving and can freely adjust it if deemed necessary.

The intervention duration is 96 hours, after which the dose will be at the discretion of the treating medical team. A follow-up will be conducted through medical records or phone calls approximately 90 days after starting therapy.

The risks for the patient are minimal, as toxin elimination monitoring will be even more intensive than usual. The study plans to include approximately 100 patients.

Inclusion Criteria:

• Patients 18 years of age or older
• Acute renal failure (AKIN 3) requiring Continuous Renal Replacement Therapy
• Requirement of vasoactive drugs (norepinephrine > 0.1 mcg/kg/min)
• Written informed consent (patient or family)

Exclusion Criteria:

• Lack of informed consent.
• Possibility of using plasma exchange or MARS therapy at the at the time of inclusion.
• Baseline renal function with an estimated glomerular filtration rate (CKD-EPI) less than 30 ml/min.

The sharing of participants' individual data with third parties must be evaluated by the center's Research Ethics Committee. Collection of individual data may only be carried out within the parameters permitted by European data protection legislation.

Statistical analysis