Effect of Critical Illness on Triglyceride Absorption

Background: Adequate nutrition support for critically ill patients optimizes outcome, and enteral feeding is the preferred route of nutrition. Small intestinal glucose absorption is frequently impaired in critical illness. Despite lipid being a major constituent of liquid nutrient administered, there is little information about lipid absorption during critical illness. Objectives: To determine small intestinal lipid, as well as glucose, absorption in critical illness compared with health. Materials and Methods: Twenty-nine mechanically ventilated critically ill patients and 16 healthy volunteers were studied. Liquid nutrient (60 mL, 1 kcal/mL), containing 200 μL ¹³C-triolein and 3 g 3-O-methyl-glucose (3-OMG), was infused directly into the duodenum at a rate of 2 kcal/min. Exhaled ¹³CO² and serum 3-OMG concentrations were measured at timed intervals over 360 minutes. Lipid absorption was measured as the cumulative percentage dose (cPDR) of ¹³CO² recovered at 360 minutes. Glucose absorption was measured as the area under the 3-OMG concentration curve. Data are median (range) and analyzed using the Mann-Whitney U and Pearson correlation tests. Results: Lipid absorption was markedly less in the critically ill (cPDR¹³CO²: patients, 22.6% [0%-100%] vs healthy participants, 40.7% [5.3%-84.7%]; P =.018). While glucose absorption was less at 60 minutes in the critically ill (3-OMG⁶⁰: 13.2 [3.5-29.5] vs 21.1 [9.3-31.9] mmol/L·min; P =.003), this was not apparent at 360 minutes (3-OMG³⁶⁰: 92.7 [54.5-147.9] vs 107.9 [64.0-168.7] mmol/L·min; P =.126). There was no relationship between lipid and glucose absorption. Conclusion: Small intestinal absorption of lipid is diminished during critical illness.