Measurements: Indirect calorimetry on Days 3, 4, 9 (twice). Primary endpoints = glucose and leucine metabolism On days 4 and 9-10: isotopic investigation of glucose metabolism, and immune and inflammatory responses// Day 9-10: isotopic investigation of protein (leucine) metabolism Secondary endpoints: Insulin requirements, area under the curve (AUC) of blood Glucose, infections after day 9, overall complications, length of mechanical ventilation, of ICU and hospital stay.