[1] Univ Edinburgh, Dept Anaesthesia, Crit Care & Pain Management, Edinburgh EH8 9YL, Midlothian, Scotland
[2] Crit Care Med, Pittsburgh, PA 15261 USA
[3] Nuovo Osped S Gerardo, Dipartimento Anestesia & Rianimaz, I-20052 Monza, MI, Italy
[4] Univ Turin, Osped S Giovanni Battista, Dipartimento Anestesiol & Rianimaz, Turin, Italy
[5] Univ Edinburgh, Sch Med, Publ Hlth Sci Sect, Div Community Hlth Sci, Edinburgh EH8 9AG, Midlothian, Scotland
[6] Osped Maggiore, Policlin IRCCS, Terapia Intens Neurosci, I-3520122 Milan, Italy
[7] Univ Cambridge, Dept Anaesthesia, Div Anaesthesia, Cambridge CB2 1TN, England
[8] London Sch Hyg & Trop Med, Clin Trials Unit, London WC1E 7HT, England
[9] Free Univ Brussels, Erasme Univ Hosp, B-1070 Brussels, Belgium