[1] Univ Melbourne, Anaesthesia & Pain Management Unit, Dept Pharmacol, Carlton, Vic 3053, Australia
[2] Royal Melbourne Hosp, Dept Anaesthesia & Pain Management, Carlton, Vic, Australia
[3] UCL, Behav Med Unit, London WC1E 6BT, England
[4] City Univ London, Fac Hlth Sci, London EC1V 0HB, England
[5] Univ Melbourne, Dept Surg, Melbourne, Vic 3010, Australia
[6] Royal Melbourne Hosp, Dept Cardiac Surg, Melbourne, Vic, Australia