[1] Harvard Med Sch, Boston, MA USA
[2] Massachusetts Gen Hosp, Dept Anesthesia Crit Care & Pain Med, Boston, MA USA
[3] Brigham & Womens Hosp, Dept Anesthesiol Perioperat & Pain Med, Boston, MA USA
[4] VA Boston Healthcare Syst, Anesthesiol Crit Care & Pain Med Serv, Boston, MA USA
[5] VA Bedford Healthcare Syst, Bedford, MA USA
[6] Johns Hopkins Med Inst, Dept Anesthesiol & Crit Care Med, Baltimore, MD USA
[7] Johns Hopkins Med Inst, Dept Neurol, Baltimore, MD USA
[8] Johns Hopkins Med Inst, Dept Phys Med & Rehabil, Baltimore, MD USA
[9] Johns Hopkins Med Inst, Dept Psychiat & Behav Sci, Baltimore, MD USA
[10] Walter Reed Natl Mil Med Ctr, Dept Phys Med & Rehabil, Bethesda, MD USA
[11] Walter Reed Natl Mil Med Ctr, Dept Anesthesiol, Bethesda, MD USA
[12] Massachusetts Gen Hosp, Dept Anesthesia Crit Care & Pain Med, 55 Fruit St, Boston, MA 02114 USA