[1] Univ Warwick, Warwick Med Sch, Coventry CV4 7AL, W Midlands, England
[2] Univ Hosp Birmingham, Crit Care Unit, Birmingham, W Midlands, England
[3] Univ Pittsburgh, Sch Med, Pittsburgh, PA USA
[4] Univ Michigan, Dept Emergency Med, Michigan Ctr Integrat Res Crit Care, Ann Arbor, MI 48109 USA
[5] Lund Univ, Skane Univ Hosp, Dept Clin Sci Lund, Neurol, Lund, Sweden
[6] Univ Oxford, Nuffield Dept Clin Neurosci, Kadoorie Ctr Crit Care Res, Oxford, England
[7] Univ Helsinki, Dept Emergency Care & Serv, Helsinki, Finland
[8] Helsinki Univ Hosp, Helsinki, Finland
[9] Royal United Hosp, Anaesthesia & Intens Care Med, Bath, Avon, England