[1] St Vincents Hosp, Fitzroy, Vic, Australia
[2] Univ Melbourne, Fitzroy, Vic, Australia
[3] Mayo Clin, Dept Neurol, Rochester, MN USA
[4] Univ Florida, McKnight Brain Inst, Dept Neurol, Gainesville, FL USA
[5] Univ Copenhagen, Dept Anaesthesia, Ctr Head & Orthopaed, Rigshosp, Copenhagen, Denmark
[6] Johns Hopkins Univ, Sch Med, Div Geriatr Med & Gerontol, Baltimore, MD USA
[7] Harvard Med Sch, Brigham & Womens Hosp, Boston, MA USA
[8] Duke Univ, Med Ctr, Dept Anesthesiol, Neurol Outcomes Res Grp, Durham, NC 27710 USA
[9] Univ Penn, Sch Med, Dept Anesthesiol & Crit Care, Philadelphia, PA 19104 USA