Personalized Nutritional Formula for ICU Patients: A Study on Prognosis and Multidimensional Health Markers

Inclusion Criteria: Critically ill patients admitted to the intensive care unit (ICU) who meet the indications for enteral nutrition support. Age ≥ 18 years. APACHE II score \> 8 at ICU admission. Expected ICU length of stay \> 7 days. Exclusion Criteria: Age \< 18 years. Pregnancy or lactation. Known allergy to any component of the enteral nutrition formula. Gastrointestinal bleeding, incomplete intestinal obstruction, or other conditions precluding full enteral nutrition. Known severe thyroid dysfunction (e.g., thyrotoxic crisis, myxedema coma, or uncontrolled hyperthyroidism/hypothyroidism). Chronic end-stage organ failure, including: New York Heart Association (NYHA) Class IV heart failure, Child-Pugh Class C cirrhosis, or Stage 5 chronic kidney disease (CKD). Primary intestinal diseases (e.g., Crohn's disease, ulcerative colitis, or intestinal malignancies), short bowel syndrome, or history of extensive small bowel resection (residual small intestine \< 100 cm). Metabolic disorders that significantly affect nutritional metabolism (e.g., Sheehan's syndrome, or other conditions with major metabolic consequences) as determined by the investigator.