[1] Univ Pittsburgh, Sch Med, Dept Neurol Surg, Pittsburgh, PA 15213 USA
[2] Univ Pittsburgh, Sch Med, Dept Crit Care Med, Pittsburgh, PA 15213 USA
[3] Univ Pittsburgh, Sch Med, Dept Pediat, Safar Ctr Resuscitat Res, Pittsburgh, PA 15213 USA
[4] Childrens Hosp Pittsburgh, Pittsburgh, PA 15213 USA