Acute kidney injury (AKI), a frequent complication in hospitalized patients, is a complex syndrome occurring in many clinical situations, which can be manifested from mild increases serum creatinine (SCr) to anuric kidney failure. In intensive care units (ICU) patients its frequency can reach up to 50%. It has been difficult to do comparisons among different studies and to generalize its results due to the large number of different definitions that have been used for AKI diagnosis. Therefore, new diagnosis criteria were proposed aiming to standardize AKI diagnosis. Thus, two new definitions were developed: RIFLE (Risk, Injury, Failure, Loss and End-Stage Kidney Disease) and AKIN (Acute Kidney Injury Network). Both definitions use small and abrupt increase in SCr and urinary output decrease for AKI diagnosis. The recently launched AKI Kidney Disease: Improving Global Outcomes (KDIGO) Guidelines proposed a new criterion, looking to harmonize these two previous definitions. According to KDIGO, AKI is defined as an increase of SCr e 0.3 mg/dl within 48 hours, or a SCr increase e 50% from baseline, which is known or presumed to have occurred within the prior 7 days, or urine volume < 0.5 ml/kg/h for 6 hours. However, when the SCr increases the drop in the glomerular filtration rate (GFR) has already occurred. In consequence, new biomarkers able to perform an early kidney injury diagnosis, before GFR decrease, have been researched in order to allow maneuvers to avoid or at least attenuate AKI. Two tubular cell injury biomarkers with potential to attend these expectations are the neutrophil gelatinase-associated lipocalin (NGAL) and the kidney injury molecule 1 (KIM-1). We propose an exploratory study aiming to assess if an early increase in NGAL and/or KIM-1, associated or not to subsequent AKI development (defined by RIFLE, AKIN or KDIGO criteria) will be associated to the morbidity and mortality in patients who will be submitted to major, elective, abdominal, non-vascular surgeries. It will be a prospective, exploratory, quantitative field research study, to be performed in 1,000 patients e 18 years old, who were submitted to major, elective, abdominal, non-vascular surgeries, and who had their pos-op in two surgical ICUs for adults at the Hospital das Clínicas da Faculdade de Medicina da USP. These patients will be studied throughout the first seven days of ICU hospitalization (or until discharge, if it happens before seven days). The tubular injury biomarkers will be assessed in four steps: at the pre-op time, at ICU admission, at 12 hours and at 24 hours after ICU admission. SCr will be assessed at the pre-op time, at ICU admission, and daily for seven days after ICU admission, or up to discharge (if occurs before seven days). Patients with previous diagnosis of chronic kidney disease stages IV or V, patients who had used nephrotoxic drugs before the surgery, patients with ICU stay less than 48 hours with diagnosis of sepsis during ICU stay will be excluded. The project will start only after the approval of the Ethical Committee of the Hospital das Clínicas da Faculdade de Medicina da USP. Patients have to sign Free Informed Consent before entering the study. Key words: Acute kidney injury (AKI), biomarkers, major surgery, intensive care unit (ICU), RIFLE, AKIN, KDIGO.
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