Serum-creatinine level (s-Cr) is an important factor for predicting perioperative patient's outcome regarding acute kidney injury. Although cardiopulmonary bypass (CPB), an essential procedure for cardiac surgery, dilutes patient's blood components, possible impact of applying acute normovolemic hemodilution (ANH) and CPB on s-Cr has not been well investigated.

In patients undergoing cardiac surgery employing moderate hypothermic CPB (age 20-71 years, n=32), ANH will be randomly applied to 15 patients (Group-ANH) but not in 17 patients (Group-C) before initiating CPB. For ANH procedure consisting of 5 ml/kg of blood salvage and administering 5 ml/kg of balanced hydroxyethyl starch (HES) 130/0.4 for 15 min will be started at 30 min after anesthesia induction and before CPB application for surgery. In both groups, moderate hypothermic CPB will be initiated by using 1600-1800 ml of bloodless priming solution. The changes of hematocrit (Hct), Na+, K+, HCO3-, Ca2+, osmolarity, s-Cr will be determined before ANH (T1), after the first ANH of 2.5 ml/kg (T2), and after the second ANH of 2.5 ml/kg (T3), 30 sec and 60 sec after the initiation of CPB (T4, T5), immediately and 1 hour after the weaning from CPB (T6, T7) and at the end of surgery (T8). S-Cr will be determined by using a point-of-care test device (StatSensor™ Creatinine, Nova Biomedical, USA).

Inclusion Criteria:

• patients undergoing cardiac surgery with cardiopulmonary bypass who signed written informed consent

Exclusion Criteria:

• preoperative renal failure requiring reran replacement therapy
• preoperative liver disease
• preoperative low cardiac output (EF < 50%)
• Preoperative IABP application, Atrial fibrillation, Pacemaker,
• contraindication for applying TEE
• intraoperative withdrawal

Patients undergoing elective cardiac surgery due to valvular heart disease