From May 1992 to May 1993,34 children with severe congenital heart diseases underwent open heart operation.We used cold blood cardioplegia(BCP) for 16 patients,cold crystalloid cardioplegia(CCP) for 18 patients.The results indicated that:the postoperative cardiac isoenzyme of creatine kinase,lactate dehydrogenase and aspartate aminotransferase levels in the CCP group were higher than those in the BCP group.In the BCP group 93% of the patients resumed heart beat spontaneously,with less inotropic drug support,and no patient weaned difficultly from cardiopulmonary bypass. No low cardiac output syndrome or death was recorded.