Pediatric Randomized Trial Of Amino Acid Therapy Evaluating the Incidence of New Onset AKI

The goal of this clinical trial is to learn whether giving amino acids through an IV during and after heart surgery can protect the kidneys of children with congenital heart disease. Many children who have heart surgery using a heart-lung (bypass) machine develop a sudden decrease in kidney function, called acute kidney injury (AKI). AKI can lead to a longer hospital stay and other complications, and over time it may raise the risk of long-term kidney disease. Children with congenital heart disease often need more than one heart surgery, so their kidneys may face this risk several times. There is currently no treatment proven to prevent AKI in children after heart surgery. Amino acids are the building blocks of protein. Giving amino acids through an IV increases blood flow and oxygen delivery to the kidneys. In adults having heart surgery, this treatment lowered the chance of kidney injury, but it has not been tested in children. The amino acid solution used in this study, TrophAmine, is already used routinely in children's hospitals as part of IV nutrition. The main questions this study aims to answer are: * Does IV amino acid treatment reduce how severe and long-lasting kidney injury is in the first week after heart surgery? * Does IV amino acid treatment reduce signs of damage to the kidney's cells, measured in urine samples? * Researchers will compare children who receive the amino acid solution with children who receive a placebo (Lactated Ringer's, a standard IV fluid that does not contain amino acids). Neither the families nor the medical team will know which solution a child receives. About 270 children younger than 18 years undergoing certain higher-risk heart surgeries will take part at three hospitals: Cincinnati Children's Hospital Medical Center, UPMC Children's Hospital of Pittsburgh, and Nationwide Children's Hospital. Participants will: * Be assigned by chance (like flipping a coin) to receive either the amino acid solution or the placebo * Receive the study solution through an IV for 72 hours, starting in the operating room * Have routine blood tests during the first week after surgery to check kidney function * Give urine samples before surgery, 6 to 12 hours after surgery, and on the first and second days after surgery * Have their health followed for 90 days after surgery, including kidney function, time on a breathing machine, and time in the hospital.