A 6-day-old term male infant with long segment coarctation of the aorta undergoes an extensive arch repair. On postoperative day two, he is awake, receiving nasal cannula oxygen, and hemodynamically stable. His nurse reports that he is making jerky movements of his shoulders and feet and rhythmic movements with his fingers that do not continue during sleep. Labs are normal. Which of the following is the MOST likely explanation for his presentation?