1Department of Cardiology and Cardiac Surgery, Pediatric Cardiac Intensive Care Unit, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy. 2Nephrology and Dialysis Unit, Meyer Children's Hospital, Florence, Italy. 3Department of Pediatric Neuroanesthesia/NeuroICU and Pediatric Trauma Center, Meyer Children's Hospital, Florence, Italy. 4Department of Health Science, Section of Anesthesiology and Intensive Care, University of Florence, Florence, Italy. 5Davidson School of Biomedical Engineering, Purdue University, West Lafayette, IN. 6Center for Acute Care Nephrology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH. 7Department of Nephrology Dialysis & Transplantation, International Renal Research Institute (IRRIV), San Bortolo Hospital, Vicenza, Italy.