1. Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
2. Department of Anesthesiology, Traditional Chinese Medicine Hospital Affiliated to Southwest Medical University, Luzhou, Sichuan 640000, P.R. China
3. Department of Anesthesiology, The First Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China