Reducing postischemic reperfusion damage in neonates using a terminal warmsubstrate-enriched blood cardioplegic reperfusate

Background. In adult cardiac operations, a warm cardioplegic reperfusate (" hot shot") before removing the aortic cross-clamp improves postbypass myoca rdial function and metabolic recovery. This modality, however, is rarely us ed in infants, despite the fact that postbypass cardiac dysfunction remains problematic, especially in cyanotic ("stressed") patients. Methods. To produce stress, 15 neonatal piglets underwent 60 minutes of ven tilator hypoxia (fraction of inspired oxygen, 8% to 10%). All piglets then received similar protection with multidose cold blood cardioplegic solution during 70 minutes of arrest and were separated into three groups to examin e the role of a warm reperfusate as well as possible augmentation by aspart ate and glutamate enrichment. In 5 piglets (group 1), the cross-clamp was s imply removed; in 5 (group 2), an unsupplemented warm blood cardioplegic re perfusate was given; and in 5 (group 3), the warm reperfusate was enriched with aspartate and glutamate. Myocardial function was assessed using pressu re-volume loops and expressed as a percentage of control. Results. Compared with hearts receiving reperfusion with unmodified blood ( group 1), a warm unsupplemented cardioplegic reperfusate (group 2) slightly im-proved systolic contractility (end-systolic elastance, 41% versus 50%; p < 0.05 versus group 1) and preload recruitable stroke work (41% versus 52 %; p < 0.05 versus group 1), reduced diastolic stiffness (263% versus 245%; p < 0.05 versus group 1), and increased adenosine triphosphate (10.7 versu s 11.9 mu g/g tissue, p < 0.05 versus group 1). However, if aspartate and g lutamate was included in the warm reperfusate (group 3), there was complete recovery of systolic function (end-systolic elastance, 105% +/- 3%; p < 0. 001 versus all groups) and preload recruitable stroke work (103% +/- 2%; p < 0.001 versus all groups), a minimal rise in diastolic stiffness (154% +/- 7%; p < 0.001 versus all groups), and preservation of adenosine triphospha te (15.5 +/- 0.5 mu g/g; p < 0.001 versus all groups). Conclusions. A warm cardioplegic reperfusate helps reduce the reperfusion i njury, resulting in improved myocardial function and metabolic recovery in hypoxic (stressed) neonatal hearts, and this effect is maximized if the rep erfusate is enriched with aspartate and glutamate, which completely preserv es myocardial function. (Ann Thorac Surg 2000;70:765-70) (C) 2000 by The So ciety of Thoracic Surgeons.