Neurologic complications remain a primary cause of morbidity and mortality after cardiac operations.Perioperative stroke,defined as neurologic deficit that occurs within 30 days of operation and persists longer than 1 week,occurs in 1.5% to 6.1% of patients.The mortality rate of patients who experience a stroke after cardiac operations has been reported at 20% to 38%.The most important cause of neurologic dysfunction after CPB is believed to be cerebral emboli.