Acute lower gastrointestinal dysfunction is a kind of much common complication which occurred in critically ill patients. Once it developed, enteral nutrition would be disturbed. In this study, investigators suppose that early application of a sufficient amount of pectin ahead of enteral nutrition, may promote recovery of acute lower gastrointestinal dysfunction in critically ill patients, and exert its good effect on early EN support.

Investigators designed this prospective randomized controlled trial to test and evaluates the effect whether EN feeding with or without a pectin start would be safe or with advanced clinical outcomes.

Gastrointestinal function (GI) is an important determinant in the outcome of critically ill patients, with up to 62% of patients exhibiting at least one GI symptom for at least 1 day. Unlike the upper gastrointestinal dysfunction, which can be diagnosed early because of abdominal distension, nausea, and feeding intolerance, acute lower gastrointestinal dysfunction (ALGID) is a kind of more common complication which more easily neglected due to atypical symptoms. Once ALGID developed, critical patients could not get enteral nutrition (EN) normally, as early EN support is often essential and standard on critically ill patients when feasible. It also causes colonic bacteria reflux to the ileum and jejunum, leads to ischemic necrosis or colon perforation, and increases the incidence of various adverse events.

Dietary fiber (DF) plays an important and helpful role in GI. It undergoes partial or total fermentation in the distal small bowel and colon, leading to the production of short chain fatty acids (SCFA) and gas. It also helps to conduct slower and delayed gastroenterology absorption, and reduce luminal flow. To date, many research and evidences exist for DF-supplemented EN reduces the incidence of colonic dysfunction in non-intensive care unit studies. However, until recently, it still lacks guidelines on how to conduct DF-supplemented EN rationally in critically ill patients.

Pectin, a representative DF, is a gelatinous substance derived from the cell walls of fruits and some plants and contains galacturonan, consisting of mostly long-chain D-galacturonic acids combined into units by α-1,4 linkages. As a kind of soluble dietary fiber, pectin has been proved of controlling glucose and blood lipids. It slows rapid infusion of the liquid meal into the gut by delaying gastric emptying. Studies showed that 90% of ingested pectin can be found in the terminal ileum. In view of all the former studies data and on the basis of investigators' clinical observation, investigators postulate that early application of a sufficient amount of pectin ahead of EN, may promote ALGID recovery in critically ill patients, and exert its effect.

Investigators designed this prospective randomized controlled trial to test whether EN feeding with or without a pectin start would be safe or with advanced clinical outcomes. Investigators speculated that pectin start EN could nourish the digestive tract in critically ill patients, and it is superior to traditional EN feeding for the delivery of early nutritional support.

Inclusion Criteria:：

• Adult ICU patients who were at least 18 years old if they were expected to require EN support within 36 hours after an unplanned ICU admission.

Exclusion Criteria:

• Could not be fed through enteral route,
• Had received EN in the past 2 months,
• Had a colectomy or jejunostomy in situ,
• Had severe colonic disease such as ulcerative colitis and Crohn's,
• Had pregnant,
• Had EN taboo crowd.