Biomarkers of acute kidney injury in anesthesia, intensive care and major surgery: from the bench to clinical research to clinical practice.

Acute kidney injury (AKI) is common after major surgery and reportedly occurs in approximately 36% of ICU patients (RIFLE Risk/Injury/ Failure categories). It is associated with increased mortality, greater cost, and prolonged Intensive Care Unit (ICU) and hospital stay, despite attempts to develop therapies to prevent or attenuate AKI, which have had limited success. One major reason for this lack of success may be the result of delayed implementation due to the inability to detect AKI early. Traditional biomarkers of AKI (creatinine and urea) do not detect injury early enough. Thus, it is a priority to find reliable, early biomarkers that predict subsequent AKI. Innovative technologies such as functional genomics and proteomics have facilitated detection of several promising early biomarkers of AKI, such as neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (CyC), liver-type fatty acid binding protein (L-FABP), interleukin-18 (IL-18), and kidney injury molecule-1 (KIM-1). These biomarkers have many potential applications during anesthesia and in the ICU. They can be used to evaluate the effect of new techniques and therapies on kidney function, as safety markers to monitor toxicity and as measures of treatment effect. For example, NGAL and cystatin C have been used in a safety monitoring trial of hydroxyethylstarch therapy and to detect AKI early, during or immediately after cardiac surgery. Clinical use beyond research settings is rapidly expanding.