[1] Univ Penn, Perelman Sch Med, Dept Anesthesiol & Crit Care, 308 Blockley Hall,423 Guardian Dr, Philadelphia, PA 19106 USA
[2] Univ Penn, Perelman Sch Med, Ctr Perioperat Outcomes Res & Transformat, Philadelphia, PA 19104 USA
[3] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[5] Johns Hopkins Med Inst, Dept Anesthesiol & Crit Care Med, Baltimore, MD 21205 USA
[6] Cleveland Clin, Dept Outcomes Res, Cleveland, OH 44106 USA
[7] Univ Maryland, Sch Med, Dept Epidemiol & Publ Hlth, Baltimore, MD 21201 USA
[8] Thomas Jefferson Univ, Dept Anesthesiol, Sidney Kimmel Med Coll, Philadelphia, PA 19107 USA
[9] Univ Alberta Hosp, Dept Anesthesiol & Pain Med, Edmonton, AB, Canada
[10] Beth Israel Deaconess Med Ctr, Dept Med, Boston, MA 02215 USA
[11] Ctr Advocacy Rights & Interests Elderly, Philadelphia, PA USA
[12] Univ British Columbia, Dept Orthopaed, Vancouver, BC, Canada
[13] Ottawa Hosp, Div Orthopaed, Civ Campus, Ottawa, ON, Canada
[14] Univ Penn, Dept Orthopaed Surg, Perelman Sch Med, Philadelphia, PA 19104 USA
[15] NYU Langone, Med Ctr, Dept Anesthesiol, New York, NY USA
[16] Wake Forest Sch Med, Dept Anesthesiol, Winston Salem, NC 27101 USA
[17] Univ Pittsburgh, Med Ctr, Dept Anesthesiol, Pittsburgh, PA USA
[18] Lahey Hosp & Med Ctr, Dept Anesthesiol, Burlington, MA USA
[19] SUNY Stony Brook, Dept Anesthesiol, Stony Brook, NY 11794 USA
[20] Inova Fairfax Med Campus, Dept Orthoped Surg, Falls Church, VA USA
[21] Univ Toronto, Dept Anesthesiol & Pain Med, Toronto, ON, Canada
[22] Hartford Hosp, Dept Anesthesiol, Hartford, CT 06115 USA
[23] Oregon Hlth & Sci Univ, Portland, OR 97201 USA
[24] Univ Florida, Coll Med, Dept Anesthesiol, Gainesville, FL USA
[25] Temple Univ, Dept Anesthesiol, Lewis Katz Sch Med, Philadelphia, PA 19122 USA
[26] Univ Vermont, Dept Anesthesiol, Larner Coll Med, Burlington, VT USA
[27] Univ Penn, Dept Orthopaed Surg, Perelman Sch Med, Philadelphia, PA 19104 USA
[28] Rutgers Robert Wood Johnson Med Sch, Div Gen Internal Med, New Brunswick, NJ USA