1. Department of Anaesthetics, Royal Prince Alfred Hospital, Camperdown, Australia
2. Liverpool Hospital, Liverpool, Australia
3. University of Sydney, Sydney, Australia
4. Leiden University Medical Center, Leiden, The Netherlands
5. Surgical Outcomes Research Centre, Sydney Local Health District, Royal Prince Alfred Hospital, Camperdown, Australia
6. Department of Orthopaedic Surgery, Royal Prince Alfred Hospital, Camperdown, Australia