1. Anaesthesia and Critical Care Section; Division of Clinical Neuroscience; Queen's Medical Centre; University of Nottingham; Nottingham UK
2. Department of Anaesthesia; Nottingham University Hospitals NHS Trust; Nottingham UK
3. Brighton and Sussex University Hospitals NHS Trust; Brighton UK
4. Peterborough and Stamford Hospitals NHS Trust; Peterborough UK
5. UCLH Surgical Outcomes Research Centre; University College London Hospitals; NIAA Health Services Research Centre; Royal College of Anaesthetists; London UK