Developmental and neurologic outcomes late after neonatal corrective surgery

See related article on page 448. W ith the many advances in treatment of congenital heart defects, including prenatal detection, improved perioperative management, and surgical technique, operative results for most complex congenital heart lesions requiring neonatal intervention have steadily improved. Now that operative mortality is low for many lesions, the focus has shifted from assessment of short-term results to measures of late functional outcome, including assessment of hemodynamic and neurodevelopmental statuses. Investigators in this field have recognized, however, that the wide range of anatomic defects treated may have direct and indirect effects on late outcomes, making the design of experiments aimed at evaluating specific management techniques difficult, and these studies often require a large cohort to establish statistical power. The group of infants born with the D-transposition of the great arteries represents a unique study cohort in that the anatomic defect results in a predictable clinical presentation and the preoperative and surgical management have now become standardized in most institutions. At best, the uniformity of age, low incidence of associated important hemodynamic defects, standardized surgical technique, and very low rate of associated noncardiac genetic defects makes this an ideal group for both retrospective and prospective randomized trials. Thus many clinical trials studying the effects of specific surgical techniques, such as the use of deep hypothermic circulatory arrest,1 pH management on bypass,2 and degree of hemodilution, have been done in this particular patient population. Despite the apparent homogeneity of this group however, it is important to recognize that there are a number of uncontrolled clinical variables that may significantly affect the end points being measured. In particular, neurologic and developmental measures determined late after surgery are likely to be greatly affected by such factors as severe cyanosis, metabolic acidosis, and hemodynamic instability, which may be present to varying degrees in the immediate neonatal period before surgery. The deleterious effects of cardiopulmonary bypass and circulatory arrest may further compound the injury imposed by these stresses.3 It is also important to recognize that with this particular anatomic defect surgical technique and experience of the surgeon may have an impact on hemodynamic stability in the early postoperative period, which may add to the neurologic injury. Therefore, although the operative technique has been standardized, the surgeon’s “learning curve” may also adversely affect late neurodevelopmental outcomes among these patients.4 Several methods have been developed to assess the effects of cardiac surgery on brain function and integrity in neonates and infants. Intraoperative indices of neurologic function have been used in pediatric and adult patients. These tests include metabolic studies (such as measurements of cerebral oxygen consumption or cerebral venous oxygen content), return of electroencephalographic activity after From the Department of Cardiac Surgery, Children’s Hospital, Harvard Medical School, Boston, Mass.