[1] Univ Calif Davis, Sch Med, Dept Anesthesiol & Pain Med, Div Pain Med, Sacramento, CA 95817 USA
[2] Philadelphia VA Med Ctr, Dept Anesthesia, Pain Med Serv, Philadelphia, PA USA
[3] Univ Penn, Dept Psychiat, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Anesthesiol, Philadelphia, PA 19104 USA
[5] Tufts Univ, Sch Med, Dept Anesthesiol, Boston, MA 02111 USA
[6] Tufts Univ, Sch Med, Dept Internal Med, Boston, MA 02111 USA
[7] Morehouse Coll Sch Med, Off President Emeritus, Atlanta, GA USA