[1] Wellington Hosp, Dept Neurosurg, Wellington, New Zealand
[2] Monash Univ, Australian & New Zealand Intens Care Res Ctr, Melbourne, Vic, Australia
[3] Alfred Hosp, Intens Care Unit, Melbourne, Vic, Australia
[4] Australian & New Zealand Intens Care Soc ANZICS, Ctr Outcome & Resource Evaluat, Melbourne, Vic, Australia
[5] Med Res Inst New Zealand, Wellington, New Zealand
[6] Wellington Hosp, Intens Care Unit, Wellington, New Zealand