Increasing glucose intake during total parenteral nutrition increases norepinephrine excretion in trauma and sepsis

Total Parenteral Nutrition (TPN) was given to 15 traumatized or infected patients with all of the non-protein calories, either as intravenous glucose (Glucose System), or as 50% glucose + 50% intravenous fat (Lipid System). Before the administration of TPN, mean urinary excretion of unconjugated norepinephrine was 2.37 +/- 0.52 (SEM) microgram/kg/day, which is significantly higher than for normal subjects (0.62 +/- 0.04 microgram/kg/day; n = 56). TPN with the Glucose System for 4-6 days significantly increased the norepinephrine excretion from 1.95 +/- 0.47 to 6.77 +/- 0.95 microgram/kg/day (P less than 0.01). When TPN with the Lipid System was given the increase (from 3.05 +/- 0.89 to 4.26 +/- 0.70 microgram/kg/day) was not statistically significant. A modest increase in resting energy expenditure was seen with the Glucose System but not with the Lipid System. The administration of high glucose loads during TPN, in addition to providing nutritional support, may exert a metabolic stress as reflected by increased metabolic rate and increased catecholamine excretion. These metabolic changes are reduced when intravenous fat emulsions are substituted for a major part of glucose calories.