ABSTRACT
Perioperative causes The etiology of neurological impairment after cardiac surgery is multifactorial. The durations of cardiopulmonary bypass and deep hypothermic circulatory arrest (as well as related reperfusion injury and embolic phenomena) are frequently implicated as significant causes of neurologic impairment in the population of children undergoing neonatal cardiac surgery. The precise impact that these necessary surgical support techniques have on the neonatal brain remains poorly understood, but durations of hypothermic circulatory arrest longer than 40 minutes have been associated with a greater incidence of neurologic impairment. 5,8,17-20 Modifications of intraoperative support techniques, such as temperature management, hemodilution, and the specific acid – base strategy have also been implicated as risk factors for neurologic complications. 21,22 Other uncontrollable factors include lower parental intelligence quotient (IQ) and socioeconomic status, which have been associated with worse performance on subsequent childhood neurodevelopmental testing. 8,23
An association between acute postoperative events, such as seizures and tone abnormalities, and later neurodevelopmental impairment exists. 3,24-26 Hospital length of stay has also been shown to be a predictor for poor neurodevelopmental outcome. 25,27 In addition, periventricular leukomalacia, a finding noted on brain imaging, has been reported in up to 54 % of neonates after cardiac surgery. 28,29 Periventricular leukomalacia is characterized by lesions in the cerebral white matter, and is typically associated with cerebral ischemia and hypoxia ( Figure 50.1 ). The presence of this central nervous system abnormality in infants has been linked to developmental delay, motor delay, and attention deficit hyperactivity disorder in children without congenital heart disease. 30,31
Preoperative causes While there are a number of perioperative events which can potentially affect the clinical status of children with congenital heart disease, the prenatal condition of the fetus is likely a significant contributor to eventual outcome. Preoperative neurological findings are abnormal in up to 50 % of some neonates with congenital heart disease, including seizures, tone abnormalities, motor function deficits, and poor orienting responses. 6,32 There are numerous prenatal factors to consider which can contribute to the neurological impairment appreciated in older children with congenital heart disease.
