Pediatric patients aged under 8 years old are enrolled in this study. VOT is performed in 3 times : after induction of anesthesia, during cardiopulmonary bypass (CPB) for main surgical procedure and after weaning from CPB. The relationship between postoperative outcome variables and the dynamic parameters from VOT, such as desaturation and reoxygenation rate, and reactive hyperemic area, will be evaluated.

Pediatric SomaSensor for INVOS 5100C is attached at calf muscle and non-invasive blood pressure cuff is applied to ipsilateral thigh. VOT is performed as: after baseline oxygen saturation value is recorded, cuff pressure is rapidly increased to 30 mmHg over than systolic blood pressure. After 3 minutes of ischemic time, cuff pressure is rapidly decreased. It is performed at 3 time periods : before start of operation, during cardiopulmonary bypass, and after weaning from cardiopulmonary bypass.

Major adverse event is defined as cardiac compression, re-sternotomy because of hemodynamic instability, ECMO support, Cr> 2mg/dL, cerebral hemorrhage or infarct and mortality.

Use of inotropic and vasoactive drugs is evaluated using vasoactive-Inotropic scores (VIS). VIS is calculated as: dopamine dose (㎍/kg/min) + dobutamine dose (㎍/kg/min) + 100 x epinephrine dose (㎍/kg/min) + 10 x milrinone dose (㎍/kg/min) + 10,000 x vasopressin dose (U/kg/min) + 100 x norepinephrine dose (㎍/kg/min).(7) VIS at 0, 24, 48, and 72 hours after surgery ended are collected in all patients.