1. Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
2. Department of Emergency Medicine, HCA, Aventura, FL 33180, USA
3. Surgical Outcomes Research Institute, John D. Dingell Veterans Affairs Medical Center, Detroit, MI 48906, USA
4. Department of Surgery, Western Michigan University, Kalamazoo, MI 48109, USA
5. Department of Surgery, Yale New Haven Hospital, New Haven, CT 06510, USA
6. Department of Surgery, Medical City, Plano, TX 75075, USA
7. College of Osteopathic Medicine, Michigan State University, Detroit, MI 48824, USA