Yongxing Xu1, Pengei Liu2, Jianwen Gu3. 1. Department of Nephrology, People's Liberation Army Strategic Support Force Characteristic Medical Center, Beijing, China. 2. Department of Anesthesiology, Beijing Shijitan Hospital, Capital Medical University, Beijing, China. 3. The Leading Group on COVID-19 Prevention and Control, People's Liberation Army Strategic Support Force Characteristic Medical Center, Beijing 100101, China. Electronic address: gujianwen5000@sina.com.