The investigators previously investigated the cardioprotective effect of an adenosine-lidocaine cardioplegia with moderate-potassium (K+, 10.0 mmol/L) in pediatric cardiac surgery, which was associated with better myocardial protective effects when compared with conventional high-potassium cardioplegia. However, this cardioplegia could not be sucked back into the cardiopulmonary bypass (CPB) circuit because of excessive hemodilution and severe systemic hypotension induced by adenosine. Therefore, the investigators supposed that a moderate-potassium (K+, 10.0 mmol/L) blood cardioplegia without adenosine could also arrest the heart and have better myocardial protective effects compared with conventional hyperkalamic cold blood cardioplegia during cardiac operations without excessive hemodilution and systemic hypotension.

Inclusion Criteria:

• pediatric patients (body weight<10 kg)
• congenital heart diseases and scheduled for a repair operation with CPB in the Department of Cardiovascular Surgery, Xijing Hospital.

Exclusion Criteria:

• other systemic diseases