1. Beijing Obstetrics and Gynecology Hospital, Capital Medical University; Department of Anesthesiology; Beijing China
2. Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College; Department of Anesthesiology; Beijing China 100730
3. Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College; Emergency Department; No.1, Shuaifuyuan, Dongcheng District Beijing China 100730
4. University of North Dakota School of Medicine and Health Sciences; 1919 Elm Street N Fargo North Dakota USA 58103
5. West China Hospital, Sichuan University; Chinese Clinical Trial Registry, Chinese Ethics Committee of Registering Clinical Trials; No. 37, Guo Xue Xiang Chengdu Sichuan China 610041