1. Sunnybrook Research Institute, Sunnybrook Health Sciences Center, Toronto, Ontario, Canada
2. Clinical Epidemiology Program, Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
3. Division of General Surgery, University of Toronto, Toronto, Ontario, Canada
4. National Emergency Medical Service Information System Technical Assistance Center, Salt Lake City, Utah
5. Department of Pediatrics, University of Utah School of Medicine, Salt Lake City
6. Department of Surgery, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada
7. Department of Surgery, St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada
8. Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada