1 Perioperative Medicine Fellow, Department of Anaesthesia, Westmoreland Street Hospital, University College London Hospitals NHS Foundation Trust, London NW1 2BU.
2 ST7 Anaesthetics, Department of Anaesthesia, King's College Hospital NHS Foundation Trust, London.
3 Professor of Perioperative Medicine, Department of Anaesthesia, Westmoreland Street Hospital, University College London Hospitals NHS Foundation Trust, London.