1 Adult Critical Care Unit, Barts and the London School of Medicine and Dentistry, Queen Mary's University of London, Royal London Hospital, London E1 1BB, UK. Electronic address: r.pearse@qmul.ac.uk.
2 Department of Anaesthesiology, University of Bonn, Bonn, Germany.
3 UCINC, Hospital de São José, Centro Hospitalar de Lisboa Central, EPE, Lisbon, Portugal.
4 IRCCS AOU San Martino-IST, Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy.