1. Faculty of Medicine, Siriraj Hospital, Mahidol University; Department of Anaesthesiology; 2 Prannok Road Siriraj, Bangkok-noi Bangkok Thailand 10700
2. Khon Kaen University; Department of Anaesthesiology; Faculty of Medicine Khon Kaen Thailand 40002
3. Khon Kaen University; Department of Biostatistics and Demography, Faculty of Public Health; Mitraparp Road Mueng District Khon Kaen Khon Kaen Thailand 40002
4. Khon Kaen University; Department of Obstetrics and Gynaecology, Faculty of Medicine; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002