Nutrition status, severity of illness, and thermogenic response to parenteral nutrition

The effect of the degree of metabolic stress on the thermogenic response to parenteral nutrition was studied in surgical and intensive-care patients. Indirect calorimetry was measured before and 3 h after the start of parenteral nutrition. The following patient groups were studied: depleted ward patients before and after surgery for gastrointestinal malignancy (n = 16), mechanically ventilated sepsis/injury patients (n = 21), and spontaneously breathing intensive-care sepsis/injury patients (n = 8). The patients received either nonprotein energy alone (glucose/fat 30/70%) at a rate corresponding to 1.4-1.6x baseline resting energy expenditure (REE) or amino acids (1.5 g.kg-1.day-1) and hypocaloric glucose. There was no correlation between the thermogenic effect of nutrition and the degree of hypermetabolism or degree of malnutrition. There was no significant thermogenic response to either amino acids or hypercaloric lipids and glucose preoperatively. In the depleted patients, REE increased because of the operation (p < 0.05); postoperatively, only amino acids increased REE significantly (p < 0.05). The operation enhanced the thermogenic response, which was higher to amino acids than to nonprotein energy (27.2 +/- 9 vs. 5.3 +/- 2.2%, means +/- SE, p < 0.05). In the sepsis/trauma patients, REE increased in both nutrition groups (p < 0.05). The thermogenic response (19.7 +/- 6.5 and 8.0 +/- 3.2% in patients receiving amino acids and nonprotein energy, respectively) was similar to that of the depleted patients postoperatively and was similar in sepsis and trauma patients. We conclude that the thermogenic response to parenteral amino acids and nonprotein energy is minor in depleted patients.(ABSTRACT TRUNCATED AT 250 WORDS)