Division of Pediatric Emergency Medicine, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Sick Kids Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Section of Pediatric Emergency Medicine, Department of Pediatrics, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. Section of Gastroenterology, Department of Emergency Medicine, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Pediatrics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ontario, Canada. Department of Emergency Medicine, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ontario, Canada. CHEO Research Institute, Ottawa, Ontario, Canada. Department of Pediatrics, Alberta Children's Hospital, Calgary, Alberta, Canada. Department of Emergency Medicine, Alberta Children's Hospital, Calgary, Alberta, Canada. Department of Physiology & Pharmacology, Alberta Children's Hospital, Calgary, Alberta, Canada. Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Pediatric Emergency Medicine, Centre Hospitalier Universitaire Sainte-Justine, Montréal, Quebec, Canada. Department of Pediatrics, Université de Montréal, Montréal, Quebec, Canada. Department of Social and Preventive Medicine, Université de Montréal, Montréal, Quebec, Canada. Department of Pediatrics, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada. Department of Emergency Medicine, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada. Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada. Department of Pediatrics, Stollery Children's Hospital, University of Alberta, Edmonton, Alberta, Canada. Department of Emergency Medicine, Stollery Children's Hospital, University of Alberta, Edmonton, Alberta, Canada. Department of Pediatrics, Clinical Research Services, Sick Kids Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada. Division of Respiratory Medicine, Sick Kids Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Division of Pediatric Emergency Medicine, British Columbia Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada. Department of Pediatrics and Child Health, Division of Pediatric Emergency Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. Children's Hospital Research Institute of Manitoba, Winnipeg, Manitoba, Canada. Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.