The state of hyperhydration in critically ill patients with acute kidney injury (AKI) is associated with increased mortality. Bioelectrical impedance vector analysis (BIVA) appears to be a viable method to access the fluid status of critical patients but has never been evaluated in critical patients with AKI. The objective of this study is to evaluate the hydration status using BIVA in critical patients under intensive care at the time of AKI diagnosis and to correlate this measurement with mortality. A sample of 224 patients with AKI will be evaluated by BIVA and followed until they are discharged or death in intensive care unit and the BIVA vectors will be analysed to define differences in hydration characteristics from each group.

Patients admitted to Intensive Care Unit (ICU) will be assessed by BIVA at the moment of the AKI diagnosis. They will be followed up to 12 weeks, until hospital discharge or death. The association between survival and hydration status, as assessed by BIVA in the first AKI day, will be tested.

Inclusion Criteria:

• Patients older than 18 years who developed acute kidney injury after admission in Intensive Care Unit

Exclusion Criteria:

• Chronic kidney injury, dialysis-dependent chronic kidney injury, acute kidney injury before ICU admission, kidney transplant, morbidity obesity and limb amputation.

Intensive care patients who developed acute kidney injury after ICU admission