The goal of this clinical trial is o determine the feasibility and efficacy of high enteral protein in critically ill postoperative children. It will also learn about the safety of high enteral protein for critically ill postoperative children. The main questions it aims to answer are:

Does high enteral protein improve nitrogen balance in critically ill postoperative children? Does high enteral protein reduce levels of Intestinal Fatty Acid Binding Protein (I-FABP) in critically ill postoperative children?

Researchers will compare high enteral protein to a standard enteral protein to see if high enteral protein works to improve nitrogen balance and reduces levels of Intestinal Fatty Acid Binding Protein (I-FABP) in critically ill postoperative children.

Participants will:

Take high enteral protein or standard enteral protein for 72 hours The nitrogen balance and I-FABP levels will be assessed both before and after enteral feeding.

Monitoring and reporting of adverse events and serious adverse events will be conducted in accordance with good clinical practice guidelines.

Postoperative care in critically ill children often involves careful attention to nutritional support to optimize recovery and outcomes. Among the various nutritional interventions, high protein enteral nutrition has gained significant attention for its potential benefits in this population. Adequate protein intake is essential for wound healing, immune function, and muscle preservation, all of which are crucial aspects of recovery following surgery in critically ill children.

High protein enteral nutrition offers a targeted approach to meet the increased protein requirements during the postoperative period. By providing a concentrated source of protein directly into the gastrointestinal tract, it bypasses potential barriers associated with oral intake and facilitates nutrient absorption in a controlled manner. Additionally, enteral nutrition is preferred over parenteral nutrition due to its lower risk of complications and potential to maintain gut integrity and function.

Despite its theoretical advantages, the clinical efficacy of high protein enteral nutrition in critically ill postoperative children remains an area of ongoing research. Studies investigating its impact on nitrogen balance, muscle protein synthesis, immune function, and clinical outcomes are essential for guiding nutritional practices in this vulnerable population.

This study aim to evaluate the effect of high protein enteral nutrition on critically ill postoperative children, with a focus on assessing nitrogen balance and intestinal fatty acid binding protein levels. Through comprehensive analysis, potential benefits and challenges associated with this nutritional intervention will be identified, ultimately informing evidence-based nutritional strategies for optimizing postoperative care in critically ill pediatric patients.

Inclusion Criteria:

1. Critically ill postoperative children (age 1 to 5 years of age)
2. Hemodynamically stable within 48 hours postoperative
3. The patient receives enteral nutrition within 48 hours postoperative
4. The patient can undergo observation and examination for up to 72 hours after enteral nutrition therapy
5. The parents/guardians are willing to participate in the study by signing the informed consent

Exclusion Criteria:

1. Patients with absolute contraindications (paralytic/mechanical ileus, gastrointestinal obstruction, gastrointestinal perforation) or relative contraindications (gastrointestinal dysmotility, necrotizing enterocolitis, toxic megacolon, extensive peritonitis, gastrointestinal bleeding, gastrointestinal fistula) to enteral nutrition administration.
2. Patients with a history of cow's milk allergy or using special formula milk.
3. Patients still receiving breast milk (breastfeeding).
4. Patients at high risk of refeeding syndrome according to ASPEN consensus
5. Patients with acute or chronic kidney disorders.
6. Patients with liver disorders.
7. Patients with diabetes mellitus.
8. Patients with inborn errors of metabolism.
9. Patients receiving total parenteral nutrition.
10. Patients requiring continuous life support devices such as continuous renal replacement therapy (CRRT) or extracorporeal membrane oxygenation (ECMO).
11. Nitrogen balance cannot be measured (patients with drainage production >1 ml/kg/hour or bleeding >10% of total blood volume at the time of enteral nutrition initiation).

Subjects were recruited through consecutive sampling until the required number of participants was reached. They were then randomly assigned into study groups using block randomization. The randomization process was conducted online via https://www.sealedenvelope.com/, overseen by the methodology team. Results were stored securely, inaccessible to researchers. Allocation concealment was ensured with sequentially numbered sealed opaque envelopes, indicating standard or high-protein enteral nutrition. These were handed to a designated nutritionist coordinator, independent of the research team, responsible for storage, preparation, and distribution. Research assistants informed the coordinator of subjects, who then prepared the assigned nutrition accordingly. High-protein enteral nutrition resembled standard nutrition to maintain blindness. Researchers, patients, families, nurses, and physicians remained unaware of the nutrition type.