[1] Pain Management Ctr Amer, 2831 Lone Oak Rd, Paducah, KY 42001 USA
[2] Univ Louisville, Anesthesiol & Perioperat Med, Ambulatory Surg Ctr & Pain Care Surg Ctr, Louisville, KY 40292 USA
[3] LSU Hlth Sci Ctr, Sch Med, Dept Anesthesiol, Shreveport, LA 71118 USA
[4] Massachusetts Gen Hosp, Intervent Care, Boston, MA 02114 USA
[5] Harvard Med Sch, Boston, MA 02115 USA
[6] Neiman Hlth Care Policy Inst, Reston, VA USA