Novel biomarkers of acute kidney injury and failure: clinical applicability.

Acute kidney injury (AKI) has a number of triggers, including ischaemia, nephrotoxins, radiocontrast, and bacterial endotoxins. It occurs in around one-third of patients treated in intensive care unit (ICU) and is even more prevalent in cardiac surgery patients. There is a higher mortality in patients with AKI compared with non-AKI counterparts, and in severe AKI requiring renal support, the 6 month mortality is >50%. Unlike the progressive development of biomarkers in cardiology, there have been few changes in kidney diagnostic markers. Creatinine is still used as an indicator of kidney function but not of the parenchymal kidney injury. Serum creatinine (sCr) concentration does not change until around 50% of kidney function is lost, and varies with muscle mass, age, sex, medications, and hydration status. The lag time between injury and loss of function, risks missing a therapeutic opportunity, and may explain the high associated mortality. Novel biomarkers of AKI- and failure include neutrophil gelatinase-associated lipocalin, N-acetyl-β-d-glucosaminidase, kidney injury molecule-1, interleukin-18, and cystatin C. The pathophysiology associated with accumulation of these markers in plasma and urine is not clear, but a common denominator is inflammation. Some of these new AKI biomarkers may have clinical applicability in anaesthesia and intensive care in the future. It is possible that a 'kidney biomarker panel' will become standard before and after major surgery. If elevated or positive, the anaesthetist must take special care to optimize the patients after operation on the surgical wards or ICU to avoid further nephrotoxic insults and initiate supplementary care.