[1] Univ Maryland, Sch Med, Dept Emergency Med, Baltimore, MD 21201 USA
[2] Univ Maryland, Sch Med, Dept Med, Baltimore, MD 21201 USA
[3] Stanford Univ, Dept Surg, Div Emergency Med, Stanford, CA 94305 USA
[4] Univ Virginia, Sch Med, Dept Emergency Med, Charlottesville, VA 22908 USA
[5] Univ Virginia, Sch Med, Dept Med, Charlottesville, VA 22908 USA