1. Department of Anesthesiology, The Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, Shandong 264000, P.R. China
2. Yantai Center of Disease Control and Prevention, Yantai, Shandong 264003, P.R. China
3. Department of Anesthesiology and Pain Medicine, University of California Davis Health, Sacramento, CA 95817, USA