Energy and protein requirements and the metabolic response to starvation and stress

At a glance

• Total energy expenditure is basal metabolic rate (60 to 70%), the thermic effect of food (about 10%) and activity. Most hospital patients need 25 to 30 kcal/kg/day; critically ill patients early on need less than their measured expenditure.
• Indirect calorimetry is the reference method in the ICU. ESPEN ranks ventilator VCO2 (or VO2 from a pulmonary artery catheter) next. Predictive equations (Harris-Benedict, Schofield) are often wrong by 20% or more in sick patients.
• Starvation runs in three phases: glycogenolysis (first 24 hours), gluconeogenesis from amino acids, glycerol and lactate (days 1 to 3), then ketoadaptation, which spares muscle.