OBJECTIVETo study the effects of cold autoblood cardioplegia on oxygen free radicals in the myocardium in infants who underwent cardiopulmonary bypass and to explore the possible mechanism of myocardial protection of autoblood cardioplegia.

METHODSThirty infants with acyanotic congenital heat disease (CHD) (weight< or =8 kg) were randomized to receive cold crystalloid, cold blood or cold autoblood cardioplegia (n=10 each group) during cardiopulmonary bypass. The biopsy samples were taken from the right atrium just before heart arrest and after heart self-recovery for the measurement of malonaldehyde (MDA) and superoxide dismutase (SOD) contents. The time and the rate of the heart self-recovery to sinus rhythm, and the incidence of ventricular fibrillation were recorded during operation. The cardiac index (CI) and the dependence of positive inotropic drugs were monitored after operation.

RESULTSBefore the operation, there were no significant differences in myocardial MDA (0.87+/-0.14, 0.88+/-0.11 and 0.86+/-0.15 nmol/mg prot, respectively) and SOD contents (61.3+/-3.4, 69.2+/-3.1 and 64.4+/-4.2 U/g, respectively) among the crystalloid, the blood and the autoblood cardioplegia groups. After operation, the myocardial MDA content increased (3.12+/-0.21, 2.93+/-0.27 and 1.67+/-0.15 nmol/mg prot, respectively) and SOD content (42.6+/-2.3, 44.6+/-3.1 and 57.7+/-2.1 U/g, respectively) decreased significantly in the three groups (P<0.05 or 0.01). The autoblood cardioplegia group had lower myocardial MDA content and higher SOD content than the crystalloid and the blood cardioplegia groups (P<0.05). The time of heart self-recovery was shortened and the dependence of positive inotropic drugs were reduced in the autoblood cardioplegia group compared with the crystalloid and the blood cardioplegia groups (P<0.05). Post-operational CI in the autoblood cardioplegia group was significantly higher than that in the blood and the crystalloid cardioplegia groups. There were significant differences in the time of heart self-recovery, the dependence of positive inotropic drugs and the CI between the blood and the crystalloid cardioplegia groups (P<0.05 or 0.01).

CONCLUSIONSCold autoblood cardioplegia reduces oxygen free radicals in the myocardium, thus providing myocardial protections in infants undergoing cardiopulmonary bypass.