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Burns: Nutritional Considerations

Nutritional support is a key component of burn care. Elevations in metabolic rate ranging between 118% and 210% of that predicted by the Harris–Benedict equation occur in adults with a burn covering 25% of TBSA. Resting metabolic rate (RMR) is approximately 180% of basal rate during acute admission in these patients, and their calorie needs may exceed 5,000 kcal/day.5 Patients with a surface burn of 40% can lose 25% of preadmission weight in 3 weekswithout nutrition support;5 losses exceeding 10% are associated with significantly poorer outcome, including impaired immunity and delayed healing.6

Energy and Macronutrient Support

Significant weight loss is preventable with nutritional support. Recommended daily energy intake is as follows:5 for adults, 25 calories per kilogram plus 40 calories per each percent of burn area; for children, 1,800 calories plus 2,200 calories per m2 of burn area. Individualized nutrition assessment is recommended for patients with burns on >20% of TBSA.7

Enteral nutrition support with a high–protein, high–carbohydrate diet is recommended, and timing may be critical. Feedings started within ~ 4 to 36 hours following injury appear to have advantages over delayed (> 48 hours) feedings. If patients are hemodynamically stable (a prerequisite for prevention of bowel ischemia), these benefits include reductions in sepsis associated with gut permeability and clinical infection, as well as significantly shortened hospital stays.8 Enteral support can reduce the burn–related increase in secretion of catabolic hormones and help maintain gut mucosal integrity. The duodenal route is better tolerated than gastric feeding, due to an 18% failure rate in the latter from regurgitation.6 Total parenteral nutrition (TPN) is not recommended, due to its ineffectiveness in preventing the catabolic response to burns.6 TPN also impairs immunity and liver function and increases mortality, when compared with enteral nutrition.5

High–carbohydrate, low–fat diets for burn patients result in less proteolysis and more improvement in lean body mass, compared with high–fat diets,5 and may reduce infectious morbidity and shorten hospitalization time, when compared with a high–fat regimen.7 However, the benefit of a high–carbohydrate formula must be balanced against the risk for hyperglycemia, which can negatively influence the outcome of critically ill patients.6 Nearly all burn patients experience insulin resistance as part of their hypermetabolic response and will need to be placed on an insulin drip to maintain tight control of their blood glucose level.

Protein and fluid needs must also be considered carefully. Protein oxidation rates are 50% higher in burn patients, and protein needs are ~1.5 to 2.0 grams/kg.5 Water loss can be as much as 4 liters/m2/day,5 and a range of 30 to 50 ml/hour is given depending on urine output.9

Micronutrient Support

Additional vitamin–mineral supplements may be indicated. Levels of the fat–soluble vitamins A and E and carotenoids fall below normal in burn injury patients.10 Vitamin E treatment reduced elevation in lipid peroxide levels in burn patients, although improved outcome was not noted as a result.11 Vitamin D synthesis is impaired in the skin of burn patients, both acutely and long–term. Blood levels appear to continue to fall, are below the normal range several years after recovery, and may negatively affect lumbar spine bone mineral density. Consequently, supplementation with the recommended dietary allowance of 400 IU per day has been suggested for patients with significant burns.12

Patients with major burns also suffer acute trace–element deficiencies, at least partly because of large exudative losses through the burned areas.13 A lack of certain trace elements (eg, selenium and zinc) can exacerbate poor immunity, and burns are the second–leading cause of immunodeficiency, after HIV infection.5 Although a role for free radicals and lipid peroxides in burn trauma has been established,14 little research has been done on the effects of antioxidant supplements in human burn injury. However, the addition of selenium, zinc, and copper to a standard trace element formula and enteral nutrition was associated with a significant decrease in the number of bronchopneumonia infections and with a shorter hospital stay.13

The response of burn patients to their nutritional intake should be evaluated weekly or biweekly. However, standard measures of nutritional repletion, such as visceral proteins (eg, albumin, pre–albumin), are influenced not only by nutritional status, but also by inflammatory processes. When low concentrations are observed, the simultaneous concentrations of acute phase reactants, such as C reactive protein, must be compared with their own reference standard to separate nutritional from inflammatory effects.15

Orders

Diet: Low–fat, high–protein, high–carbohydrate, enteral tube feedings with appropriate caloric content. Weekly or biweekly assessments of nutritional status.

Nutrition consultation, as appropriate.

Physical therapy, occupational therapy, and mental health consultations, as appropriate.

What to Tell the Family

Burn injury can be very traumatic. It is important for the family to know that the patient may need a great deal of support, especially for deep partial–thickness (2nd  degree) and full–thickness (3rd or 4th degree) burns. In severe burns, the patient may be physically incapacitated and emotionally traumatized. In general, a burn patient will be in the hospital 1 to 2 days for each percent of total body surface area burned. The family can play an essential role supporting the patient.

 

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