[1] Duke Univ, Med Ctr, Dept Anesthesiol, Durham, NC 27710 USA
[2] Singapore Gen Hosp, Dept Anesthesiol, Singapore, Singapore
[3] Duke Univ, Med Ctr, Dept Surg Neurosurg, Durham, NC 27710 USA
[4] Duke Univ, Med Ctr, Dept Radiol, Durham, NC 27710 USA
[5] Duke Univ, Sch Med, Durham, NC 27710 USA
[6] Duke Univ, Med Ctr, Dept Neurol, Div Neurocrit Care, Durham, NC 27710 USA