Abstract: AIM:In the present study, we compared the effect of two kinds of cardioplegia on myocardial protection in infants. METHODS: Thirty six patients with congenital heart disease were enrolled in this trial, and all patients had a body weight <15 kg. All patients were randomly divided into two groups: cold blood cardioplegia with 1∶1 ratio of crystal and blood was used as myocardial protective liquid in group A (n=18), whereas warm blood cardioplegia with 1∶4 ratio of crystal and blood was used in group B. Some inflammatory factors like TNF-α and IL-8 were detected before induction of anesthesia (T1), at 5 min after aortic clamping (T2), 5 min after opening (T3), 5 min after operation (T4), 1 h after operation (T5) or 24 h after operation (T6), respectively. Myocardial enzymes and myocardial injury markers were detected at T1, T5, T6 and 48 h after operation (T7). Time of ventilation, ICU stay time, mortality and postoperative complications of both two groups were all recorded. Results: There was no significant difference in the comparison of age, weight, priming solution composition, myocardial protective liquid dosage, cardiopulmonary bypass time, aortic clamping time and myocardial protective liquid filling times between groups. Plasma colloid osmotic pressure of myocardial protection fluid was significantly higher in group B than in group A ［(14.9±0.8) mmHg vs.(8.0±0.5) mmHg, P<0.01］. Group B had lower cardioplegia perfusion pressure compared with group A ［(51±5) mmHg vs.(107±8) mmHg, P<0.01］. After opening ascending aorta, group B had higher automatic rebeating rate (94% vs. 89%) and shorter rebeating time than group A ［(19.43±2.26) s vs.(64.86±2.72) s, P<0.01］. During cardiopulmonary bypass, patients in group B excreted more urine ［(43±6) ml vs.(29±11) ml, P<0.05］. There was no significant difference in regard to myocardial injury markers and TNF-α between groups during the perioperative period. At T3 time, concentration of inflammatory factor IL-8 plasma was significantly lower in group B than in group A (P<0.05, P<0.01). There was no significant difference in regard to postoperative mechanical ventilation time and ICU stay time between groups. Conclusion: The warm blood myocardial protection fluid may improve the effects of myocardial protection to a certain extent, but there is no significant difference in clinical outcome.