One known risk of pediatric heart surgery is the possibility for brain damage. This problem results from a lack of oxygen rich blood flow to the brain during surgery. In order to provide the patient's brain with blood during this operation, selective cerebral perfusion is sometimes used. This technique allows for adequate blood flow to the brain, and is monitored using special sticker sensors. The sensors are applied to the patient's forehead, and a corresponding monitor indicates oxygen levels in the front part of the brain. The goal of this study is to find out if these same stickers can be applied to the base of the skull to measure cerebral oxygenation at the back of the brain, and to determine if the back of the brain is adequately oxygenated during selective cerebral perfusion in patients undergoing complex aortic arch reconstruction.