Inclusion Criteria:  1) Patients undergoing aortic surgery with moderate hypothermic circulatory arrest.  Exclusion Criteria:  patients with chronic kidney disease or with dialysis, eGFR < 15ml/min/1.73m2 allergy to acetaminophen or propacetamol HCl history of liver cirrhosis or total bilirubin > 2.0mg/dL  3) patients taking acetaminophen or diclofenac 4) patients who cannot understand informed consent