Department of Emergency Medicine, UC Davis School of Medicine, 4150 V. Street, PSSB 2100, Sacramento, CA, 95817, USA. Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA. Department of Pediatrics, Division of Pediatric Emergency Medicine, Ohio State University School of Medicine, Nationwide Children's Hospital, 700 Children's Dr, Columbus, OH, 43205, USA. Department of Pediatrics, Division of Pediatric Emergency Medicine, University of Utah School of Medicine, Primary Children's Hospital, 100 N. Mario Capecchi Dr, Salt Lake City, UT, 84113, USA. Department of Pediatrics, Division of Pediatric Emergency Medicine, Perelman School of Medicine, University of Pennsylvania, Children's Hospital of Philadelphia, 3401 Civic Center Blvd. Philadelphia, PA, USA, 19104. Department of Radiology, UC Davis School of Medicine, Stockton Blvd. Sacramento, CA, 95817, USA. Department of Pathology and Laboratory Medicine, University of California, Davis, 4400 V. Street, CA, 95816, USA. Department of Psychology, University of California, Davis, 102K Young Hall, 1 Shields Ave. Davis, CA, 95616, USA. Department of Pediatric Neurosciences, Neurological Institute at Phoenix Children's Hospital, 1919 E. Thomas Rd, Phoenix, AZ, 85016, USA. Clinical Trials Unit, School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK. Department of Orthopedics and Rehabilitation, University of Wisconsin, 317 Knutson Drive, Madison, WI, 53704, USA. Departments of Emergency Medicine and Pediatrics, UC Davis School of Medicine, 4150 V. Street, PSSB 2100, Sacramento, CA, 95817, USA.