[1] Oxford Univ Hosp NHS Fdn Trust, John Radcliffe Hosp, Neurosci Intens Care Unit, Level 1 West Wing,Headley Way, Oxford OX3 9DU, England
[2] Univ Oxford, John Radcliffe Hosp, Nuffield Dept Clin Neurosci, Level 6 West Wing,Headley Way, Oxford OX3 9DU, England
[3] Wake Forest Baptist Med Ctr, Neurocrit Care Unit, Med Ctr Blvd, Winston Salem, NC 27157 USA
[4] Oxford Univ Hosp NHS Fdn Trust, John Radcliffe Hosp, Neurosci Dept, Level 2 West Wing,Headley Way, Oxford OX3 9DU, England
[5] McGill Univ, Dept Anesthesia, Crit Care Program, 845 Sherbrooke St W, Montreal, PQ H3A 0G4, Canada
[6] Imperial Coll NHS Trust, Charing Cross Hosp, Dept Anesthesiol & Intens Care Med, Hlth Ctr,Intens Care Unit, Fulham Palace Rd, London W6 8RF, England