1. Department of Anaesthesia and Perfusion Services, The Prince Charles Hospital, Brisbane, Queensland, Australia
2. Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
3. Department of Urology, The Prince Charles Hospital, Brisbane, Queensland, Australia
4. Statistics Unit, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
5. Department of Anaesthesia, Caboolture Hospital, Caboolture, Queensland, Australia.