Pro: Deep hypothermic circulatory arrest is preferable to low-flow bypass

Abstract

ORTALITY RATES in infants undergoing cardiopulmonary bypass (CPB) for repair of complex congenital heart disease were unacceptably high until deep hypothermic circulatory arrest (DHCA) techniques began to be used extensively in the 1970s. During this time, there was a great deal of morbidity related to CPB in infants and an appreciable mortality. In several studies, mortality and morbidity in infants having cardiac operations using CPB were inversely related to the age and size of the child; younger and smaller children had more problems, especially in the infant age group.’ Although this may have been related in part to the severity of disease observed in young infants, activation of complement was greater in small infants; longer CPB times were directly related to the morbidity of CPB.’ Use of DHCA eliminated much CPB time, minimizing morbidity and dramatically improving mortality in small children undergoing cardiac surgical procedures. The mechanisms of CPB-related damage and morbidity are not yet well understood, particularly in the infant. However, cardiac morbidity related to inadequate myocardial protection during ischemia is decreased by using deep, whole-body hypothermia and circulatory arrest. With deep hypothermia there is less conductive heat transfer to the heart from the warmer surrounding tissues, and with circulatory arrest, washout of cardioplegia and cardiac rewarming by noncoronary collateral circulation does not occur. Given the dubious value of many cardioplegic solutions in the immature heart, improved myocardial protection with DHCA is an important consideration, particularly in defects such as hypoplastic left heart syndrome (HLHS), in which the use of conventional aortic root cardioplegia is technically impractical. Improvements in the technology of CPB and general care of infants with congenital heart disease have considerably lessened CPB-related morbidity and mortality in young cardiac patients. Although these developments make the rationale for use of DHCA less convincing, CPB-related morbidity remains a considerable problem in infants undergoing cardiac sur