Enteral nutrition in hypermetabolic surgical patients

Enteral nutrition is usually administered with premixed formulas and in a volume determined by the estimated total caloric need of the patient. The present study was undertaken to evaluate the nutritional outcome when isocaloric amounts of three commercial products were given as enteral nutrition in hypermetabolic surgical ICU patients. To qualify for the study, the patients had to be hypermetabolic and must have received and retained the volume of enteral formula estimated to meet energy and nutritional requirements for at least eight consecutive days. Caloric needs were defined as 30 to 35 total cal/kg.day. All data were prospectively collected; all patients had moderate to high-level metabolic stress after surgical intervention. Thirty-five patients participated in the study: 18 received a formula that was 23% amino acids, 20% fat, and had a nonprotein calorie/nitrogen (NPC/N) ratio of 97:1; ten patients received a formula with NPC/N 125:1 that was 17.5% protein and 35% fat; and seven patients received a formula with an NPC/N of 149:1 that was 15.3% amino acids and 2.5% fat. All formulas were given via nasoduodenal tube by continuous pump technique. Patients who received the low NPC/N had significantly greater N retention (p less than .05), increased plasma transferrin levels (p less than .05), and a lower RQ (p less than .05). There was a strong correlation between NPC/N and N retention and the increase in plasma transferrin levels. Thus, dosing enteral nutrition by total estimated caloric need does not presume optimal nutritional outcome. Formula composition is an important determinant of nutritional effect; formulas that have a lower NPC/N with more N and reduced calories as glucose demonstrate better nutritional results.