Protection Of The Immature Myocardium: A Experimental Study On The Isolated Perfused Rat Heart

Myocardial protection for operations in neonates and infants is of great importance in preventing perioperative morbidity and mortality, and may have a long-term impact on the preservation of postoperative myocardial function. Although there is laboratory evidence for greater tolerance to ischemia in the immature heart, clinical myocardial protection strategies and cardioplegic solutions that are effective in adult hearts have been less effective in the immature infant or neonatal heart than in adult hearts. To design a formulation of cardioplegic solution optimal for immature heart, a series of experiments including four partes were carried out in an isolated working rat heart model.Part Ⅰ . Myocardial Protection in The immarture and Mature heart: A Comparision of topical hypothermia and crystalloid and blood cardioplegic solutions.In this study, three methods of myocardial protection were tested in isolated working hearts of adult (10～12 weeks) and infant (18～21 days) rats. Com-parisions were made among five groups : Ⅰ . adult hearts protected with St. Thomas' Ⅱ cardioplegic soultion; Ⅱ . adult hearts with cold blood cardioplegia; Ⅲ . infant hearts with St. Thomas' Ⅱ cardioplegic solution; Ⅳ. infant hearts with cold blood cardioplegia; Ⅴ . infant hearts with topical hypothermia alone. Multidose cardioplegia was used during 2 hours of ischemia and myocardial temperature was maintained at 14 C. The percent recovery of aortic flow was significantly lower in Group Ⅲ. than in group Ⅰ (62. 7% ± 7. 1% versus 91. 7% ±5. 4%, P<0. 01) and in Group Ⅳ than in Group Ⅱ (75. 2% ± 5. 9% versus...