1. Chiang Mai University; Department of Anesthesiology, Faculty of Medicine; Chiang Mai Thailand 50200
2. Faculty of Medicine, Khon Kaen University; Department of Anesthesiology; 19-32 Chuabchuen Road Khon Kaen Thailand
3. Khon Kaen University; Department of Epidemiology and Biostatistics, Faculty of Public Health; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002
4. Faculty of Medicine, Chiang Mai University; Department of Anesthesiology; Chiang Mai Thailand 50200