1. Department of Emergency Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
2. Emergency Department, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China
3. Institute of Anesthesia, Guizhou Medical University, Guiyang, Guizhou 550002, P.R. China