[1] Univ Penn, Perelman Sch Med, Dept Surg, Philadelphia, PA 19104 USA
[2] Univ Penn, Perelman Sch Med, Div Traumatol Emergency Surg & Surg Crit Care, 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 Emergency Care Policy & Res, Dept Emergency Med, Philadelphia, PA 19104 USA