aDivision of Emergency Medicine, Children's National Hospital, Washington, DC, USA

bPediatric Emergency Medicine, Department of Paediatrics, Schulich School of Medicine & Dentistry, London, Ontario, Canada

cEmergency Department, Lyell McEwin Hospital, Elizabeth Vale, South Australia, Australia

Correspondence to Camilo E. Gutiérrez, MD, Division of Emergency Medicine, Children's National Hospital. George Washington University School of Medicine and Health Sciences, 111 Michigan Ave, NW, Washington, DC 20010, USA. Tel: +1 202 476 4177; fax: +1 202 476 3573; e-mail: [email protected]