Respiratory Changes Induced by the Large Glucose Loads of Total Parenteral Nutrition

Total parenteral nutrition (TPN) using glucose as nonprotein calories was associated with increases in O2 consumption (VO2) and CO2 production (VCO2). The magnitude of the changes was a function of the patient's clinical state and glucose load. Depleted patients showed a minimal increase in VO2, while VCO2 increased 23%. Minute ventilation (VE) increased 32%. Hypermetabolic patients (major trauma, sepsis) had a 30% increase in VO2 and a 57% increase in VCO2, while VE increased 71%. Patients with mild to moderate injuries (energy expenditure +/- 15% of normal) showed a 21% increase in VO2 and a 53% increase in VCO2, while VE increased 121%. Large carbohydrate intakes were associated with increases in CO2 production in all patients, while increases in O2 consumption were seen primarily in hypermetabolic patients. These changes suggest that the high glucose loads of TPN may be a physiologic stress.