Oxidative Stress and Circulating Nuclear DNA (cfDNA) in Acute Kidney Injury and Continuous Renal Replacement Therapies.

Inclusion Criteria: * Adult intensive care patients (age \> 18) admitted to the ICU with AKI requiring treatment with continuous renal replacement technique. * Patients able to accept being included in the study by signing the Informed Consent (IC). If the patient can not give consent, family consent is requested and, by default, the opinion of the person of trust or designated decision, if present. If there is no family present, trusted person or legal representative designated, the possibility of deferred consent is not contemplated. In this case the patient will not be included in the study. Exclusion Criteria: * Age under 18 years old. * Pregnancy and/or lactation. * Terminal diseases or life expectancy lower than 48 hours. * Increased risk of bleeding (defined as platelet count less than 40x109 / L, partial thromboplastin time (TTPA) over 60 seconds, prothrombin time (PT)international normalized ratio (INR) greater than 2.0 or recent major bleeding). * Need of systemic anticoagulation therapy. * Contraindication for heparin. * Heparin-induced Thrombocytopenia (HIT). * Dialysis in the 24 hours prior to inclusion. * Hypercalcemia (\> 3 mmol / L). * Severe Hepatitis: glutamic oxaloacetic transaminase (GOT) or glutamic pyruvic transaminase (GPT) \> 1000 IU / L. * Cirrhosis. * Inclusion in another research protocol.