[1] WakeMed Hlth & Hosp, Clin Res Unit, Emergency Serv Inst, Raleigh, NC 27610 USA
[2] Univ Ottawa, Dept Pediat, Ottawa, ON K1N 6N5, Canada
[3] Univ Ottawa, Dept Emergency Med, Ottawa, ON, Canada
[4] Childrens Hosp Philadelphia, Dept Anesthesia & Crit Care Med, Philadelphia, PA 19104 USA
[5] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA