Cardioprotective effects and the mechanisms of terminal warm blood cardioplegia in pediatric cardiac surgery

Abstract

Objectives Terminal warm blood cardioplegia has been shown to enhance myocardial protection in adult patients. However, the cardioprotective effects and the mechanisms of terminal warm blood cardioplegia in pediatric heart surgery were still unknown. Methods One hundred three consecutive patients were prospectively randomized to one of two groups. In the control group (n = 52), myocardial protection was achieved with intermittent hyperkalemic cold blood cardioplegia and topical cardiac cooling. In the terminal warm blood cardioplegia group (n = 51), this was supplemented with terminal warm blood cardioplegia before the aorta was declamped. Arterial and coronary sinus blood samples were analyzed to determine myocardial energy metabolism and tissue injury. Results There were no significant differences between the two groups in age (5.5 ± 0.6 years in the control group vs 5.6 ± 0.5 years in the terminal warm blood cardioplegia group), body weight (17.2 ± 1.4 kg in the control group vs 19.8 ± 1.7 kg in the terminal warm blood cardioplegia group), percentage of cyanotic heart diseases (50% in the control group vs 51% in the terminal warm blood cardioplegia group), number of patients who required right ventriculotomy (33% in the control group vs 39% in the terminal warm blood cardioplegia group), cardiopulmonary bypass time (194 ± 12.1 minutes in the control group vs 177 ± 8.6 minutes in the terminal warm blood cardioplegia group), aortic crossclamp time (83.3 ± 5.9 minutes in the control group vs 82.3 ± 5 minutes in the terminal warm blood cardioplegia group), lowest rectal temperature (27.4 ± 0.3°C in the control group vs 28.1 ± 0.3°C in the terminal warm blood cardioplegia group), and myocardial temperature (9.6 ± 0.6°C in the control group vs 9.6 ± 0.7°C in the terminal warm blood cardioplegia group). Spontaneous defibrillation occurred after reperfusion in 80% in the terminal warm blood cardioplegia group, which was significantly ( P < .05) higher than the control group (62%). The lactate extraction rate at 60 minutes of reperfusion was significantly ( P < .05) higher in the terminal warm blood cardioplegia group (9.0 ± 2.8%) than the control group (−3.3 ± 2.4%). The postreperfusion values of cardiac troponin T (7.4 ± 0.6 ng/mL vs 11.2 ± 1.0 ng/mL at 6 hours; 4.6 ± 0.6 ng/mL vs 9.3 ± 1.6 ng/mL at 18 hours) and heart-type fatty acid binding protein (137 ± 28 ng/mL vs 240 ± 30 ng/mL at 2 hours; 88 ± 19 ng/mL vs 162 ± 26 ng/mL at 3 hours) were significantly ( P < .05 vs the control group) lower in the terminal warm blood cardioplegia group. Conclusion Terminal warm blood cardioplegia enhances myocardial protection in pediatric cardiac surgery by an improvement in aerobic energy metabolism and a reduction of myocardial injury or necrosis.