Due to recent studies that found a potentially important mechanistic role of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in delirium of critically ill patients on non-surgical ICU or in non-cardiac surgery patients, the main focus of this paper was to examine AChE and BChE in patients after cardiac surgery and their association with postoperative delirium [12, 14, 16, 19]. The gene discussed is BCHE; the disease is delirium.