Critically Ill Patients Who Are Not Allowed to Eat Orally But Can Initiate Enteral Nutrition Within 48 Hours of ICU

When the subjects are admitted to the department, the researchers will monitor potential biomarkers of gastrointestinal injury before administering enteral nutrition (a small amount of blood is drawn, serum is separated by centrifugation, and the serum sample is frozen for final centralized biomarker detection), and measure the antral movement index under ultrasound (300ml of warm water is injected into the stomach before measurement, and then the antral movement is observed for 6 minutes) Then, monitor whether the patient has developed feeding intolerance within 7 days of the ICU