The purpose of the study is to evaluate the potential role of plasmatic Fibroblast Growth Factor 23 (FGF-23) as a prognosis predictor of clinical outcomes in Critical Care patients.

Observational study of patients admitted in the Critical Care Unit (CCU) of University of Chile Clinical Hospital, admitted with diagnosis of severe sepsis/septic shock.

Exclusion criteria: Pregnancy, organ transplantation. Informed consent is solicited to patients before admission in study. If the patient cannot give it because of his/her clinical condition, it will be solicited to a patient representative.

After admission in CCU and achievement of informed consent, a venous blood sample will be obtained, to determinate plasmatic levels of Fibroblast Growth Factor 23 (FGF-23). New samples will be obtained at 24 and 48 hours after admission. Determination of FGF-23 will be performed by ELISA technique in Integrated Physiology laboratory.

Demographics, clinical and biochemical data will also be obtained. The data will be collected by the Principal Investigator. Confidentially of all data will be preserved during and after the completion of the study.

The study is divided in 2 parts:

1. - Evaluation of a sample of 14 patients to determinate the impact of FGF-23 to predict presence and severity of Acute Kidney Injury (AKI), and to estimate sample size to predict primary outcomes.
2. - Evaluation of a larger sample, to determinate the impact of FGF-23 to predict primary outcomes.

Primary outcomes:

1. - Development of acute kidney injury
2. - Severity of AKI, determinate by AKIN classification
3. - In-hospital mortality

Secondary outcomes:

1. - Requirements of renal replacement therapy
2. - Requirements of mechanical ventilation
3. - Requirements of vasoactive drugs
4. - Duration of ICU stay and hospital stay

As a post-hoc analysis, we performed a measurement of a combined biomarker, including FGF-23 and other 2 biomarkers, Klotho and Erythropoietin, measured in blood samples, to determinate its predictive capacity for AKI diagnosis and mortality.

The protocol was approved by the Ethical Committee of University of Chile Clinical Hospital. The study is monitored by the Clinical Investigation Support Office (OAIC) of the hospital.

Inclusion Criteria:

• Admission in Critical Care Unit
• Sepsis

Exclusion Criteria:

• Pregnancy
• Organ transplantation

Patients admitted in Critical Care Unit with diagnosis of severe sepsis/septic shock.

Pregnant women and transplanted patients are excluded.