EFFECTS OF PARENTERAL NUTRIENTS ON GASTROINTESTINAL MOTILITY AND SECRETION

Background: The stimulation of gastrointestinal motility and secretion during nutrient digestion is generally divided into a cephalic, gastr ic and intestinal phase. Little is known about the effects of macronut rients on gastrointestinal function during the postabsorptive or circu latory phase of digestion. Methods: Review of studies investigating th e effects of circulating macro-nutrients such as fat, amino acids and glucose on gastrointestinal motility and secretion. Results: Intraveno us infusion of fat emulsions delays gastric emptying and interrupts th e interdigestive intestinal motor pattern. Intravenous amino acids, ad ministered in high doses, stimulate gastric acid secretion, pancreatic secretion, gallbladder contraction and intestinal motility. Patients receiving total parental nutrition (TPN) have inert gallbladders and a re 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 format ion during TPN by promoting gallbladder contraction. Intravenous infus ion of glucose, already at physiological postprandial plasma levels, i nhibits gastrointestinal motility and secretion. The inhibitory effect of glucose is dose-dependent, that is, more pronounced at higher plas ma glucose levels. Recent studies have indicated that in patients with diabetes mellitus alterations in gastrointestinal function are relate d to the degree of hyperglycaemia. Conclusions: Nutrients during the c irculatory 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 di abetes mellitus or during total parenteral nutrition.