Acute kidney failure remains one of the most challenging entities to diagnose in clinical medicine, especially in the field of intensive care. The diagnosis of acute kidney injury is based solely on urine output and serum creatinine, both of which could also be influenced by other factors. A more sensitive and faster diagnostic option would not only be desirable but of utmost clinical importance. Therefore, the investigators aim to identify Neuronal Guidance Proteins (NGPs) as potential biomarkers for the identification and early detection of AKI with this investigation. This investigation aims to identify the possibility of diagnosing acute kidney injury, the subsequent validation of a potential biomarker will then have to take place in a multicenter study approach: Data in preclinical mouse models suggest that SEMA7A as one of the NGPs could be valuable as a biomarker, the study now aims to attempt a preliminary survey in humans and measure various NGPs.

Inclusion Criteria:

• Patients undergoing cardiac surgery
• written consent

Exclusion Criteria:

• no written consent possible
• Polytrauma, severe burns
• Immunosuppression
• Pregnancy
• Diagnosis of Hepatitis B, Hepatitis C, and/or HIV
• Sepsis
• Pre-existing kidney damage

Patients undergoing elective cardiac surgery followed by postoperative surveillance in the intensive care unit