1 Department of Anaesthesia, National University Hospital, Singapore; Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. Electronic address: andrea_yap@nuhs.edu.sg.
2 Department of Anaesthesia, National University Hospital, Singapore.
3 Department of Anaesthesia, National University Hospital, Singapore; Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.