Background: Postoperative renal failure is a common complication after open repair of an abdominal aneurysm. The amino-acid arginine is formed in the kidneys from its precursor citrulline, citrulline from glutamine in the intestines. Arginine enhances the function of the immune and cardiovascular system, which is important for recovery after and during surgery. We hypothesized that renal arginine production is diminished after ischemia-reperfusion injury by clamping of the aorta during open abdominal aortic surgery and that parenteral glutamine supplementation may compensate this impaired arginine synthesis. Methods: two groups of patients who underwent clamping of the aorta during open abdominal aortic surgery were randomized to this open label randomized clinical trial, to receive a perioperative supplement of intravenous alanyl-glutamine (0,5 g/kg/day) (group A, n=5) or no supplement (group B, n=5). Metabolism and conversion of glutamine, citrulline and arginine were analyzed using stable isotopes and tracer methodology. Results: Whole body metabolism of glutamine, citrulline and arginine was significantly higher in group A compared to B (p<0.01). Synthesis of citrulline from glutamine (p<0,01, 4,8±0,7 versus 1,6±0,3 μmol/kg/h) and citrulline from arginine (p<0,01, 2,3±0,3 versus 0,96±0,1 μmol/kg/h) and arginine from glutamine (p<0,001, 7,7±0,4 versus 2,8±0,2 μmol/kg/h) was significantly higher in group A compared to B. Conclusion: Production of citrulline and arginine is severely reduced after clamping during aortic surgery. This study shows that an intravenous supplement of glutamine increases the production of citrulline and arginine, and compensates for the inhibitory effect of ischemia-reperfusion injury.