Nutritional Support: Macronutrient Formulation (Assessment of Energy and Substrate Requirements) (UPDATE IN PROCESS)

Published 2003

Level 1

There appears to be no advantage to the routine use of calorimetry to determine the caloric requirements of burn patients.

Level 2

  1. For moderately to severely injured patients (ISS 25-30), energy requirements are estimated to be 25-30 total kcal/kg/day or 120% to 140% of predicted BEE (per Harris-Benedict equation).
  2. There appears to be no consistent relationship between ISS and measured resting energy expenditure (MREE) in trauma patients.
  3. For patients with severe head injury (GCS score <8), energy requirements may be met by replacing 140% of MREE (~30 total kcal/kg/day) in non-pharmacologically paralyzed patients and 100% of MREE (~25 kcal/kg/day) in paralyzed patients.
  4. Within the first 2 weeks after spinal cord injury, nutritional support should be delivered at 20-22 total kcal/kg/day (55% to 90% of predicted BEE by Harris-Benedict equation) for quadriplegics and 22-24 total kcal/kg/day (80% to 90% of predicted BEE by Harris-Benedict equation) for paraplegics.
  5. For patients with burns exceeding 20% to 30% TBSA, initial caloric requirements may be estimated by several available formulas.
  6. The Curreri formula (25 kcal/kg + 40kcal/TBSA burn) overestimates caloric needs of the burn patient (as estimated by calorimetry) by 25% to 50%.
  7. The Harris-Benedict formula underestimates the caloric needs of the burn patient (as estimated by calorimetry) by 25% to 50%.
  8. In patients with burns exceeding 50% TBSA, TPN supplementation of enteral feedings to achieve Curreri-predicted caloric requirements is associated with higher mortality and aberrations in T-cell function.
  9. Caloric requirements for major burns fluctuate during the hospital course but appear to follow a biphasic course with energy expenditure declining as the burn wound closes. Therefore, direct measurement of energy expenditure via calorimetry once or twice weekly may be of benefit in adjusting caloric support throughout the hospital course.
  10. Intraoperative enteral feeding of the burn patient is safe and efficacious, leads to fewer interruptions in the enteral feeding regimen, and, therefore, more successful attainment of calorie and protein goals.
  11. Approximately 1.25 grams of protein per kg body weight per day is appropriate for most injured patients.
  12. Up to 2 grams of protein per kg body weight per day is appropriate for severely burned patients.
  13. In the burn patient, energy as carbohydrate may be provided at a rate of up to 5 mg/kg/min (~25 kcal/kg/day); exceeding this limit may predispose patients to the metabolic complications associated with overfeeding. In the non-burn trauma patient, even this rate of carbohydrate delivery may be excessive.
  14. Intravenous lipid or fat intake should be carefully monitored and maintained at <30 percent of total calories. Zero fat or minimal fat administration to burned or traumatically injured patients during the acute phase of injury may minimize the susceptibility to infection and decrease length of stay.
  15. Proteins, fat, and carbohydrate requirements do not appear to vary significantly according to the route of administration, either enterally or parenterally.
  16. Fat or carbohydrate requirements do not appear to vary significantly according to the type of injury, i.e., burned versus traumatically injured.

Level 3

  1. Provision of excess calories to trauma patients may induce hyperglycemia, excess CO2 production, fluid/electrolyte abnormalities, lipogenesis, and hepatic steatosis.
  2. Energy requirements for patients with less than 20% to 30% TBSA burns are similar to those of patients without cutaneous burns.
  3. Protein requirements in burn patients and in those with severe CNS injuries may be significantly greater than anticipated, up to 2.2 grams/kg body weight per day. However, the ability to achieve positive nitrogen balance in a given patient varies according to the phase of injury. Provision of large protein loads to elderly patients or to those with compromised hepatic, renal, or pulmonary function may lead to deleterious outcomes.