The effect of continuous versus intermittent delivery of enteral feeding on glycaemic control and gastrointestinal response in critically ill patients (CGM-ICU)

CGM-ICU study aims to assess the impact of nutrient delivery pattern (continuous versus intermittent) over a 24-hour period on glycaemic control and gastrointestinal function in enterally fed critically ill patients. A total of 60 ICU patients will be included from the intensive care unit at the Royal Adelaide Hospital. Participants will be randomised to receive a total of 1200 mL of enteral nutrition (EN) gastrically either as intermittent (4 boluses per 24 hours, therefore one bolus of 300 mL/hr every 6 hours; INT) or continuous (total volume spread evenly per hour over 24 hours, therefore 50 mL/hr for 24 hours; CON). Throughout the study arterial blood samples will be collected every 6 hours via an arterial line present for standard care (t=0, 6, 12, and 24 h relative to the initiation of the study). Continuous interstitial glucose concentrations will be measured using a subcutaneous continuous glucose monitor. Postprandial responses will be determined from blood samples taken every 6 hours to assess plasma amino acid profiles, glucose and insulin concentrations, and key gut related-hormone concentrations (GLP-1, GIP, PYY, CCK, C-peptide, glucagon, leptin, and ghrelin). On the following day, 20 of the included patients will be assessed in a sub study (duration 4 hours), to measure gastric emptying and nutrient absorption following 24 hours of either INT or CON feeding. Patients will be selected if they meet the additional inclusion criteria: Expected to remain ventilated and receiving enteral nutrition, not receiving gastro-kinetic drugs, no prior upper gastrointestinal surgery and no gastrointestinal surgery on this admission. The 4 hour sub study involves measurement of Gastric Emptying (GE), using bedside scintigraphy, and glucose absorption (3-OMG concentrations). Patients will be provided with a 100 mL dose of enteral formulation (same EN as CON and INT feeding) labelled with 20 MBq 99mTc-calcium phytate colloid, and 3g of 3-O-Methyl-D-gluco-pyranose (3-OMG) (a non-absorbable glucose analogue). Scintigraphic images will be acquired at 1-min intervals for 60 min, and 3-min intervals thereafter for a total of 4 hours. Arterial blood samples will be taken starting at t= -5 mins, then every 15 minutes for the first hour (t= 15, 30, 45, 60 min), and half hourly for the remaining 3 hours (t= 90min – 240min).