1 Pediatric Intensive Care Unit Hospital, Universitario Infantil La Paz, Madrid, Spain, and Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain Pediatric Intensive Care Unit, Hospital Universitario Infantil La Paz, Madrid, Spain Pediatric Intensive Care Unit, Hospital Universitario Niño Jesús, Madrid, Spain Pediatric Intensive Care Unit, Hospital Universitario Ramón y Cajal, Madrid, Spain Pediatric Intensive Care Unit, Hospital Universitario Carlos Haya, Málaga, Spain Pediatric Intensive Care Unit, Hospital Clínico Universitario, Valencia, Spain Pediatric Intensive Care Unit, Hospital Universitario 12 de Octubre, Madrid, Spain, and Department of Pediatrics, Universidad Complutense de Madrid, Madrid, Spain Pediatric Intensive Care Unit, Hospital Universitario Reina Sofía, Cordoba, Spain.