The aim of this study is to evaluate whether the application of glutamine versus control in patients with high risk for AKI identified by biomarkers can reduce kidney damage after cardiac surgery.

Cardiac surgery is characterized by an increased production of free radicals as a consequence of surgical trauma, ischemia-reperfusion injury, inflammatory response syndrome in response to the use of the extracorporeal circulation. This results in an increased production and release of free radicals which may lead to an exhaustion of antioxidants and organ failure since the lungs, kidneys, liver and gastrointestinal tract are particularly susceptible to reactive oxidant species. Glutamine is considered as a conditionally indispensable amino acid in catabolic states of critically ill patients. It belongs, together with other mediators, to the host defense as major intracellular direct free radical scavengers. Its depletion has been demonstrated to be an independent predictor of mortality in a group of ICU (intensive care unit) patients. Clinical studies showed a positive outcome effect. In animal models, glutamine reduces the occurrence of AKI after ischemia-reperfusion injury. This could be demonstrated through reduced functional markers as well as reduced renal biomarker levels. Preliminary data suggest that glutamine has pleiotropic effects since it has effects on the immune system (reduced expression of cytokines) as well as on tubular epithelial cells (unpublished animal data from our laboratory).

Thus, a randomized-controlled trial to analyze the effects of glutamine supplementation in high risk patients identified by renal biomarkers undergoing cardiac surgery with cardiopulmonary bypass (CPB) on the effects of kidney damage is urgently needed.

Inclusion Criteria:

• Adult patients undergoing cardiac surgery with CPB
• Urinary [TIMP-2]*[IGFBP7] >= 0.3 4h after CPB
• Written informed consent

Exclusion Criteria:

• Preexisting AKI (stage 1 and higher)
• Patients with cardiac assist devices
• Pregnant women, nursing women and women of childbearing potential
• Known (Glomerulo-) Nephritis, interstitial nephritis or vasculitis
• Chronic kidney disease (CKD) with estimated glomerular filtration rate (eGFR) < 30 ml/min
• Dialysis dependent CKD
• Prior kidney transplant within the last to 12 months
• Hypersensitivity to the active substance, or to any of the excipients of the study medication
• Hepatic insufficiency
• Severe metabolic acidosis (pH < 7.2)
• Participation in another intervention trial in the past 3 months
• Persons with any kind of dependency on the investigator or employed by the institution responsible or investigator
• Persons held in an institution by legal or official order