[1] Univ Montreal, Dept Pediat, Div Emergency Med, Montreal, PQ H3C 3J7, Canada
[2] Childrens Hosp Philadelphia, Div Emergency Med, Philadelphia, PA 19104 USA
[3] Childrens Hosp Philadelphia, Div Crit Care Med, Philadelphia, PA 19104 USA
[4] Univ Montreal, Dept Pediat, Div Emergency Med, Montreal, PQ H3C 3J7, Canada