1. Faculty of Medicine, Siriraj Hospital, Mahidol University; Department of Anesthesiology; 2 Wanglang Road, Siriraj, Bangkok-noi Bangkok Thailand 10700
2. Khon Kaen University; Department of Biostatistics and Demography, Faculty of Public Health; Mitraparp Road Mueng District Khon Kaen Khon Kaen Thailand 40002