Chapter 7: Nutrition

                     _____NPO

                     _____high protein and high calorie with milk   

                               shakes

                     _____INFANT FORMULA__________________________                     

                     _____tube feedings

                     _____feeding tube placement________________

                     _____enteral product desired________________

                   MONITORING

                     _____calorie count

                     _____DAILY WEIGHTS

                     _____INDIRECT CALORIMETRY

                     _____24-HOUR URINE FOR URINE UREA NITROGEN

                     _____prealbumin weekly

I.  PATHOPHYSIOLOGY

1. There is a postburn hypermetabolic response due to multiple factors such as increased levels of circulating catecholamines, glucagon, and cortisol.  The metabolic rates of patients with burns greater then 40% TBSA are 100-150% greater than their basal metabolic rate. 

2. Similar to resuscitation formulae, the prescription for caloric requirements is at best an estimate.  It is not possible to accurately calculate these requirements, which vary with environmental temperatures and humidity, inhalation injury, extent and depth of burn, activity level, and surgery. 

3. Enteral feedings given within the first 24 hours postburn have been shown to decrease hyper-metabolism, decrease the release of catabolic hormones, improve nitrogen balance, maintain gut mucosal integrity, and decrease the incidence of diarrhea.[i]^,[ii],[iii] In addition, enteral feedings have been shown to increase intestinal blood flow, preserve gastrointestinal function, and minimize bacterial translocation from the gut.[iv]^,[v]

D.  Adult Requirement

1.      The modified Harris Benedict formula is used to calculate the daily Basal Energy of Expenditure (BEE) in kilocalories:

BEE (male) = [66 + (13.7 x  wt. in kg) + (5 x ht. in cm) - (6.8 x age)]  x [IF]

BEE (female) = [655 + (9.6 x wt in kg) + (1.8 x ht. in cm) - (4.7 x age)]  x [IF]

Where IF= injury factor

                                                                           Table I Injury Factor[vi]

2.      Protein needs of the burn patient are increased, due to the loss of nitrogen through burn wound exudates in addition to urinary nitrogen losses.  Increased proteolysis raises amino acid substrate demand.  

Protein Need= 20% of total kilocalories

E. Pediatric Requirements

1.         Children have an increased surface area to weight ratio, necessitating greater caloric requirements than adults. 

2.            Daily Caloric Requirements

a.    BEE= [55 - (2 x age in yrs)] x wt in kg x GF x IF

Where GF= growth factor; 1.5 over 1 yr of age; 2.0 under 1 yr of age

           IF= injury factor; 2 for >10% TBSA; 1.5 for <10%TBSA

2. The BEE should always be compared to the Recommended Daily Allowance (RDA).  These values are often similar because the increased caloric requirements due to the burn injury are balanced by the decreased activity of the child.  Never give less than the RDA (see Table II).

Table II Recommended Daily Allowances[vii]

3.         Protein needs in children are 11-15% of total kiloccalorie requirements.  There are 4 kcal of energy per gram of protein. 

II.  Nothing by mouth (NPO)

Patients who are scheduled for immediate surgery should have feedings held.

All other patients should begin nutritional supplementation as soon as possible. 

III.  HIGH PROTEIN, HIGH CALORIE DIET WITH MILK SHAKES

Smaller burns (<25% TBSA) with no associated facial injuries or inhalational injury can receive a high protein/ high calorie diet with milk shake supplements along with daily calorie counts by the dietitian.

IV.  TUBE FEEDINGS

A.    Patients with larger surface area burns are usually unable to meet their nutritional requirements by the oral route only.  Therefore, these patients should receive continuous tube feedings. 

B.    A nasogastric (NG) tube is first passed upon admission.  A softer Keofed feeding tube later replaces the NG tube. 

C.    If the patient is not tolerating tube feedings, as evidenced by nausea or emesis, the Keofed should be placed into the duodenum.

D.   Patients with high gastric residuals should have both a duodenal tube and a nasogastric tube for gastric decompression.

E.    Feedings are started at full strength at 20 cc/hr and increased slowly (by 10 cc/4 hrs) or rapidly (by 20 cc/4hrs) as tolerated until the goal hourly rate is achieved. 

F.     Tube feedings are weaned as the patient increases oral intake.  When the oral intake is 20-25% of caloric needs, tube feedings may be administered during the nighttime only to stimulate appetite and increase daytime oral intake.  When the patient can eat 80-90% of his caloric needs, tube feedings may be discontinued.

G.   Complications of Tube feedings

1.                  Gastric ileus is common in the patients with burns to the trunk or abdomen.  If a patient with a feeding tube with its tip in the stomach does not tolerate feedings, the tube may be passed into the duodenum or jejunum.  This method reduces the risk of tube feeding aspiration, and even allows feedings during surgery.[viii]  Placement of feeding tubes within the small intestine can be accomplished via the use of weighted-tipped tubes, by positioning the patient with the right side down, and with promotility drugs such as metoclopramide (Reglan), by endoscopy or fluoroscopy.  All of these techniques require radiographic confirmation of placement in the small bowel.  Percutaneous endoscopic gastrostomy (PEG) or percutaneous endoscopic jejunostomy (PEJ) feeding tubes are designed for extended periods. 

2.                  Aspiration - The incidence of documented aspiration varies from 1 to 44%.[ix]  Food coloring added to the tube feedings can detect aspiration by the change in color of respiratory secretions.

3.                  Diarrhea - occurs in 10 to 20% of patients receiving enteral tube feedings.  This is caused by both osmotic forces and by malabsorption.  Tube feedings should not be stopped, as this will further aggravate the diarrhea and will halt nutritional supplementation.  For small intestinal feedings, the rate should be cut in half and slowly increased as tolerated.  Discontinue any magnesium-containing antacids or other medications that can promote diarrhea.

4.                  Tube obstruction - Feeding tubes become obstructed in about 10% of patients,[x] usually from feedings that has formed an occlusive plug.  Usually the tube can be prevented by flushing with warm water before and after each infusion.[xi]  Unplugging a clotted tube can be achieved by flushing with Coke, Mountain Dew, meat tenderizer, or Viokase.¹⁶

V.    ENTERAL PRODUCTS

Table III

A.    The Osmolite products are the most commonly used formulae in our adult patients.  They are identical to Jevity, but without the fiber.  The Osmolite HNâ (High Nitrogen) product is used in patients with normal renal function.

B.    Jevityâ is used for patients with diarrhea and loose stools due to its increased fiber content.

C.    Additives such as pectin flakes and free water to decrease feed strength are not recommended due to risk of contamination. 

D.   Glucernaâ has low carbohydrate and higher fat content, and is recommended for patients with poorly controlled blood sugars. 

E.    The moderate proetin concentration of Neproâ makes it useful in patients with poor renal function.

F.     Pediasureâ is the standard feeding formula for pediatric patients.

G.   Total parenteral nutrition (TPN) is seldom used and is reserved for patients with very prolonged digestive tract dysfunction.  Immunosuppression and increased mortality was shown in patients with burns greater than 50% TBSA randomized to receive intravenous feeding versus enteral calories alone.[xii]

VI. MONITORING

A.    Calorie counts are the most important determination of adequate nutrition.

B.    Body weight is also useful, since changes in weight from admission allow an assessment of fluid balance[xiii] and nutrition.[xiv]  Body weight within 10% of the admission weight indicates adequate nutrition.[xv]

C.    Indirect calorimetry is measured weekly.

a.     Metabolism can be assessed by measurement of : oxygen consumption (uO₂), carbon dioxide production (uCO₂), and energy expenditure with the production of water and heat.  Because heat and water production is not easy to measure, uO₂ and uCO₂ are used as indirect measures of the metabolic energy expenditure, forming the basis for “indirect calorimetry.”  The uO₂ and uCO₂ are determined by measuring the concentration of O₂  and CO₂  in inhaled and exhaled gas.  The daily resting energy expenditure (REE) is calculated by the formula:

REE (kcal/day)= 3.94 (uO₂) + 1.1(uCO₂) X 1440

The REE is increased by 20% to account for daily activity.  The REE is similar to the basal daily energy requirements but includes the thermal effect of food.

b.     Indirect calorimetry also allows for the calculation of the Respiratory Quotient (RQ) which is the ratio of uCO₂ to uO₂ (RQ=uCO₂/uO₂).  Glucose has the highest RQ (1.0) and fat has the lowest (0.7).  The RQ from indirect calorimetry will measure the average contribution from carbohydrate and fat and will provide an index of the major fuel source in the patient.  An overall RQ above 0.9 indicates excess carbohydrate calories in the diet.[xvi]  The amount of carbohydrates given to the patient with an RQ at this level should be reduced to bring the RQ below 0.9, especially in patients with respiratory failure, to limit the tendency for CO₂ retention. 

D.   The 24-hour urine urea nitrogen is performed once per week with the indirect calorimetry measurements.  The purpose is to determine whether the patient is in positive or negative nitrogen balance.  Negative nitrogen balance implies a catabolic state.

E.    Prealbumin has a normal range of 17-40 mg/dl and a half-life of 1.9 days, compared to the traditional nutritional marker, albumin, which has a half-life of 21 days. Therefore, by monitoring with prealbumin, a response to therapy will be seen much sooner. Serum albumin may be within the normal range while prealbumin indicates declining nutritional status. Prealbumin is also less affected by changes in hydration status and liver and renal function than other testing methods.

VI. EXAMPLES

A.  Adult patient  - a 30 year-old man who weighs 70kg, is 6 feet tall, and has a 50% TBSA burn

1.                  Calculate caloric needs using the Harris Benedict formula:

66+ (13.7 x 70) + (5 x 183) – (6.8 x 30) = BEE of 1736 Cals (1 Cal=1 kcal)

2.                  Multiply Cals by the Injury Factor (IF).  For a 50% burn the IF is 2.  Therefore the 24-hour caloric need is 3472 Cals.

3.                  Determine the amount of protein needed.  Protein should account for 20% of the total calories, or 694 Cals.  Since there are 4 Cals per gram of protein, the patient needs 174 grams of protein/day.

4.                  Feeding rates are based on a 21 hour day, since tube feedings are

            temporarily stopped to allow dressing changes, physical therapy, etc.  For this patient, Osmolite HN will be used (1.06 Cal/ml).  Thus, his goal-feeding rate is 155 cc/hr.

B.                 Pediatric patient – a 2 year-old child who weighs 13kg with a 30% TBSA burn

1.                  Calculate caloric needs using the pediatric formula:

            [55- (2 x 2)] x 13 = 663 Cals

2.                  Multiply Cals by the Growth Factor (GF), which in this patient is 1.5, and by the Injury Factor (IF), which in this patient is 2.  Thus the patient’s 24-hour caloric need is 1989 Cals.

3.                  Compare this with the RDA caloric needs, which for this child is 102 kcal/kg or 1326 Cals.  Feedings should at minimum provide this amount of calories.

4.                  Determine the amount of protein needed.  Since protein in a child should account for 11 to 15% of the total calories, this patient should receive at most 219 to 298 Cals from protein, or 55 to 75 grams of protein. 

5.                  The patient will receive Pediasure (1 Cal/cc) over a 21 hour feeding day.  Since it is safer from a fluid standpoint, use the RDA to calculate caloric needs (i.e. 1326 Cals) to arrive at a starting feeding rate of 63 cc/hr.