CAT and delirium: Specifically, anesthesia/surgery result in excessive reactive oxygen species (ROS) production (Peng et al., 2016) and reduce the activities of some antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) (Zhang et al., 2018), as well as inducing delirium-like behavior in mice, indicating that oxidative stress is of great importance to the development of POD.