1. Health Management Center, Linyi Central Hospital, Linyi, Shandong 276400, P.R. China
2. Intensive Care Unit (ICU), Dongying People's Hospital, Dongying, Shandong 257091, P.R. China
3. Department of Gastrointestinal Surgery, Shandong Provincial Qianfoshan Hospital, Jinan, Shandong 250014, P.R. China