Yi Liu1, Fu-Shan Xue2, Ya-Yang Liu3, Gui-Zhen Yang3. 1. Department of Anesthesiology, Shanxi Province Tumor Hospital, Taiyuan, China. 2. Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. Electronic address: xuefushan@aliyun.com. 3. Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.