Different enteral nutrition formulas are tested on their effect on glucose homeostasis in critically ill medical patients.

To assess whether enteral nutrition fomulas based either on fat or glucose influence glucose homeostasis differently in critically ill medical patients. All patients are admitted to a tertiary ICU and require mechanical ventilation.

Resting energy expenditure is assessed at baseline in the fasting state by indirect calorimetry. Total energy demand is calculated and patients are randomized to receive fat-based or glucose-based nutrition which is administered continously for 7 days. Indirect calorimetry is repeated on days 3 and 7 under continous nutrition. During the study period, various parameters of glucose homeostasis are assessed. Daily, there will be at least 3 measurements of blood glucose, more if the treating physician deems it necessary. Daily average glucose, daily glucose variability, overall area under the curve for glucose are calculated. Furthermore, energy intake by nutrition, medications (i.e. propofol), and glucose infusion, as well as substrate intake, and insulin demand per 24hrs are determined daily. Adverse effects such as episodes of hyper- or hypoglycemia, cholestasis, hypertriglyceridemia, diarrhea, vomiting, and the amount of gastric residual volume are noted.

Inclusion Criteria:

• medical patient with need for mechanical ventilation
• FiO2 requirement < 60%
• need for nutritional support

Exclusion Criteria:

• contraindications against nutritional therapy
• hemodynamic shock (lactate of ≥ 4 mmol/l)
• severe hypertriglyceridemia (≥ 450 mg/dl)
• contraindications against enteral nutrion (intestinal obstruction, disruption or severe bleeding of upper gastrointestinal tract)