THE ROLE OF OSMOLALITY IN THE ADSORPTION OF A NUTRIENT SOLUTION

Background: Loss of water during enteral nutrition following massive i ntestinal resection may be severe. Low osmolality of oral rehydration solutions has recently been shown to mediate an increase in water abso rption. Aim: To evaluate the effect of osmolality of a nutrient soluti on on the intraluminal duodenojejunal water now, and the net absorptio n rates of total nitrogen and carbohydrate, Methods: Eight healthy vol unteers with a mean age of 27 (range 25-29) years participated in the study. Enteral nutrition (17% protein, 59% carbohydrate, 24% lipid plu s 5 g/L PEG 4000) was infused (5 mL/min 2.64 kcal/min) into the descen ding duodenum either as a hypotonic (160 mOsmol/kg) or as an isotonic solution in a random order. Intestinal samples were aspirated 20 and 4 5 cm distally to the infusion point. Results: Intraluminal water flow rates were significantly lower with the hypotonic solution than with t he isotonic solution, both in the duodenum (4.9 +/- 0.3 vs, 6.7 +/- 0. 5 mL/min; P < 0.02) and the upper jejunum (3.0 +/- 0.1 vs, 3.9 +/- 0.2 mL/min; P < 0.005). The net absorption rates of total nitrogen and ca rbohydrate were similar with both solutions. Conclusion: Low osmolalit y of a nutrient solution decreases intraluminal water now rates in the upper intestine without affecting the absorption rates of total nitro gen and carbohydrate. Compared with an isotonic solution, the use of a hypotonic solution might lower the water loss in patients with extens ive short bowel intestinal resection.