1. From the Department of Pediatrics, Section of Critical Care (L.O., P.P., S.S., A.B.) and Department of Pediatrics, Section of Cardiology (P.P., J.G., A.B.), University of Arkansas for Medical Sciences, Arkansas Children's Hospital, Little Rock, and Department of Anesthesia and Critical Care, University of Pennsylvania School of Medicine, Children's Hospital of Philadelphia, Philadelphia (R.B., V.N.).