[1] Univ Calif Los Angeles, Dept Surg, Los Angeles, CA 90095 USA
[2] VA Greater Los Angeles Healthcare Syst, Los Angeles, CA 90095 USA
[3] Amer Coll Surg, Div Res & Optimal Patient Care, Chicago, IL 60611 USA
[4] Northwestern Univ, Feinberg Sch Med, Dept Surg & Surg Outcomes, Chicago, IL 60611 USA
[5] Northwestern Univ, Feinberg Sch Med, Qual Improvement Ctr, Chicago, IL 60611 USA
[6] Univ Colorado, Sch Med, Dept Surg, Aurora, CO USA