In cases of cardiac surgery or sepsis which cause inflammation, oxidative stress, endothelial injury and vasoplegia, serum vitamin C concentration is sharply decreased. The anti-inflammatory and anti-oxidant effects of vitamin C and the effects of reducing vasoconstrictor use have been demonstrated in patients with sepsis and septic shock, however, the foregoing effects have not been validated in patients undergoing cardiac surgery.

In this study, investigators investigate the effect of intravenous vitamin C on the incidence of acute renal injury after valvular heart surgery.

Inclusion Criteria:

• Patients older than 20 years and undergoing elective valvular heart surgery whose preoperative acute renal failure score is ≥3 (moderate to severe risk).

Exclusion Criteria:

• Emergency operation
• Cardiogenic shock or ventricular-assist device (eg. ECMO, IABP)
• Severe chronic kidney disease (GFR(CKD-EPI) <30ml/min/1.73m2)
• Patients with past history of gout or renal stone or hyperoxaluria or cystinuria
• Hemolytic anemia due to pyruvate kinase deficiency or glucose-6-phosphate dehydrogenase deficiency
• Sicklemia or thalassemia
• Hemochromatosis
• Allergy to disodium ethylenediamine-tetraacetate or ascorbic acid
• Patients taking aspirin up to 3 days before surgery
• Patients taking antiepileptic drug or fluphenazine or steroid
• Patients taking vitamin C within a month of surgery
• Pregnant or lactating women
• Patients who cannot understand the informed consent (eg. Foreigner)

Neither participants, all care providers, investigators nor outcomes assessors know the treatment allocations.