Effects of parenteral nutrients on gastrointestinal motility and secretion

The stimulation of gastrointestinal motility and secretion during nutrient digestion is generally divided into a cephalic, gastric and intestinal phase. Little is known about the effects of macronutrients on gastrointestinal function during the postabsorptive or circulatory phase of digestion.

Review of studies investigating the effects of circulating macro-nutrients such as fat, amino acids and glucose on gastrointestinal motility and secretion.

Intravenous infusion of fat emulsions delays gastric emptying and interrupts the interdigestive intestinal motor pattern. Intravenous amino acids, administered in high doses, stimulate gastric acid secretion, pancreatic secretion, gallbladder contraction, and intestinal motility. Patients receiving total parental nutrition (TPN) have inert gallbladders and are at risk of developing gallbladder sludge and stones. Administering a proportion of the daily amino acid requirement by rapid intravenous infusion may prove useful in the prevention of sludge and stone formation during TPN by promoting gallbladder contraction. Intravenous infusion of glucose, already at physiological postprandial plasma levels, inhibits gastrointestinal motility and secretion. The inhibitory effect of glucose is dose-dependent, that is, more pronounced at higher plasma glucose levels. Recent studies have indicated that in patients with diabetes mellitus alterations in gastrointestinal function are related to the degree of hyperglycaemia.

Nutrients during the circulatory phase of digestion influence gastrointestinal motility and secretion. Knowledge of these effects is relevant for conditions with increased plasma levels of macro-nutrients such as in patients with diabetes mellitus or during total parenteral nutrition.