Assessment of Nutrient Absorption in Enterally Fed Post-intensive Care Unit Patients Using Bomb Calorimetry: do the Calories Stick

This study investigates the absorption efficiency of enteral nutrition in patients recovering from an intensive care unit (ICU) stay. Nutritional support is critical in the recovery of ICU patients, and enteral feeding is commonly used due to its benefits in preserving gut integrity and reducing infection risks. However, there is limited data on the actual absorption of nutrients in these patients, particularly in terms of how much of the provided energy is utilized versus excreted. The primary focus of this study is to quantify the caloric intake and the caloric content of excreted stool to determine the efficiency of nutrient absorption in post-ICU patients. This will be done using bomb calorimetry, which measures the energy content in stool samples, and indirect calorimetry to assess the patients' resting energy expenditure (REE). The study design is prospective, interventional, and single-center, involving 20 post-ICU patients who meet the inclusion criteria. Detailed tracking of caloric intake, including both enteral feeding and supplemental infusion calories, will be performed daily. Stool samples will be collected for three days, with the nonabsorbable blue dye marker method used to track the specific stool produced during this period. These stool samples will be freeze-dried, formed into pellets, and analyzed using the Parr 6200 Isoperibol Calorimeter to measure their energy content. The secondary objective is to evaluate the sustainability of enteral feeding practices by assessing the amount of waste generated, such as unused nutritional formulas and tubing. This includes quantifying food waste in the hospital, focusing on nutrition that is not consumed, absorbed, or excreted. By understanding the actual energy absorption in ICU survivors, this study aims to provide insights that will optimize nutritional strategies, improve patient recovery, and contribute to cost-effective, environmentally sustainable healthcare practices.