1. Department of Anesthesiology, Affiliated Nanhua Hospital, University of South China, Hengyang, Hunan 421001, P.R. China
2. Department of Neurology, The First Affiliated Hospital, University of South China, Hengyang, Hunan 421001, P.R. China
3. Department of Anesthesiology, The First Affiliated Hospital, University of South China, Hengyang, Hunan 421001, P.R. China