Department of Anesthesiology and Center for Brain Science, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China. Department of Anesthesiology, Weinan Central Hospital, Weinan, China. Department of Anesthesiology, Xi'an Central Hospital, Xi'an, China. Department of Anesthesiology, Shaanxi Provincial People's Hospital, Xi'an, China. Department of Anesthesiology, Affiliated Hospital of Shaanxi University of Chinese Medicine, China. Department of Anesthesiology, Xi'an Hospital of Traditional Chinese Medicine, Xi'an, China. Department of Anesthesiology, Affiliated Hospital of Yan'an University, Yan'an, China. Department of Anesthesiology, Ankang Hospital of Traditional Chinese Medicine, Ankang, China. Department of Anesthesiology, Ankang Central Hospital, Ankang, China. Department of Anesthesiology, Central Railway Group of Xi'an Central Hospital, Xi'an, Shaanxi, China. Clinical Research Center, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China. Division of Anaesthetics, Pain Medicine, and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, London, UK. Electronic address: d.ma@imperial.ac.uk. Department of Anesthesiology and Center for Brain Science, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China. Electronic address: dr.wangqiang@mail.xjtu.edu.cn.