This study evaluates the impact of a biomarked guided intervention on the development of acute kidney injury in high risk surgical patients. Eligible patients are screened for marker of tubular stress in the urine; if patient specific results are above a pre-defined cutoff they are randomized into a standard care group or an interventional group in which patients receive intensified volume therapy.

This study evaluates the impact of a biomarked guided intervention on the development of acute kidney injury in high risk surgical patients.Used markers have been identified as markers of tubular stress and have been validated in previous studies with more than 1500 patients. The advantage of a biomarker guided approach is the saving of time for the diagnosis a developing acute kidney injury (AKI) in high risk surgical patients, since clinical signs of AKI (rise in creatinine/decline of estimated Glomerular Filtration Rate (eGFR), decline of diuresis). If used biomarkers are above a predefined cutoff within < 4 hours after surgery, patients are randomized in to a standard care population receiving treatment in accordance with Kidney Disease Improving Global Outcomes (KDIGO) guidelines. In the intervention population patients receive individual volume therapy (= balanced electrolyte solution (Ionosteril)) (1,25 ml/kg bw up to 5 ml/kg bw for 6 hours). Degree of volume therapy is estimated by several predifined parameters, e.g. central venous pressure (CVP).

"Inclusion Criteria":

• major surgery with a duration > 4 hours plus one of the following criteria:
• age > 75 years, or
• sepsis, or
• shock, or
• polytrauma, or
• need for invasive ventilation or catecholamines, or
• intra-operative application of contrast-medium, or
• preexisting chronic kidney disease (CKD1-4),
• informed consent

Exclusion Criteria:

• age < 18 years,
• end stage renal disease (ESRD),
• preexisting dialysis,
• withdrawal of consent,
• pregnancy,
• breastfeeding