Division of Emergency Medicine, Department of Pediatrics, Nemours/A.I. DuPont Hospital for Children, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA. Department of Emergency Medicine, University of California Davis Health, University of California Davis, School of Medicine, Sacramento, CA; Department of Pediatrics, University of California Davis Health, University of California Davis, School of Medicine, Sacramento, CA. Division of Emergency Medicine, Department of Pediatrics, Children's National Medical Center, The George Washington School of Medicine and Health Sciences, Washington, DC. Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT. Division of Emergency Medicine, Department of Pediatrics, Texas Children's Hospital, Baylor College of Medicine, Houston, TX. Division of Emergency Medicine, Department of Pediatrics, The Colorado Children's Hospital, University of Colorado-Denver School of Medicine, Denver, CO. Division of Emergency Medicine, Department of Pediatrics, Nationwide Children's Hospital, The Ohio State University School of Medicine, Columbus, OH. Department of Emergency Medicine, University of California Davis Health, University of California Davis, School of Medicine, Sacramento, CA. Departments of Emergency Medicine and Pediatrics, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI. Division of Emergency Medicine, Department of Pediatrics, Children's Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA. Division of Emergency Medicine, Department of Pediatrics, St. Louis Children's Hospital, Washington University School of Medicine in St. Louis, St. Louis, MO. Division of Emergency Medicine, Department of Pediatrics, Ann and Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, IL. Division of Emergency Medicine, Department of Pediatrics, New York Presbyterian Morgan Stanley Children's Hospital, Columbia University College of Physicians and Surgeons, New York, NY. Division of Emergency Medicine, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA. Department of Psychology, University of California Davis, Sacramento, CA. Department of Pediatrics, University of California Davis Health, University of California Davis, School of Medicine, Sacramento, CA. Electronic address: nsglaser@ucdavis.edu.