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