Deterioration of Nutritional Status and Need for Support

Caloric Requirements

Even previously healthy patients may lose nutritional ground rapidly once they are hospitalized. Surgery and the stress of disease increase caloric requirements. The amount of these increases can be calculated using one of a number of predictive equations for determining resting metabolic rate (RMR) in kilocalories per day (kcal/day), which is the largest component of overall calorie expenditure. One frequently used model is the Harris-Benedict equation (1919), as follows: For men:

RMR = 66.47 + (13.75 X Weight [kg]) + (5.0 X Height [cm])- (6.75 X Age [yr])

For women:

RMR = 665.09 + (9.56 X Weight [kg]) + (1.84 X Height [cm ])- (4.67 X Age [yr])

Frankenfield and colleagues (2005) compared validation studies on several equations and found that the Mifflin-St. Jeor equation performed best in terms of predicting RMR compared with calorimetry. Although all the equations are less accurate for obese subjects, the following Mifflin-St. Jeor equation is least affected by obesity. For men:

RMR =(9.99 X Weight [kg]) + (6.25 X Height [cm ])- (4.92 X Age [yr ])+ 5

For women:

RMR = (9.99 XWeight [kg]) + (6.25 XHeight [cm])-(4.92XAge [yr])- 161

(See Web Resources for resting metabolic rate/basal metabolic rate and resting energy energy/basal energy expenditure calculators.)

These predictive equations do have weaknesses. They have not been validated in all subsets of the population, such as the elderly and nonwhite ethnic groups. Chronic illness can affect the relationship between RMR and body size, with loss of lean body mass in chronic illness.

These equations predict the resting metabolic rate, and caloric requirements increase beyond this figure, based on the patient's illness and other metabolic demands. The resting energy expenditure (REE) is 1.2 to 1.3 multiplied by the RMR. This figure is further altered by the level of stress. An example is to multiply REE by 1.1

by the number of degrees (Celsius) above normal in a patient with fever. Other multiples are 1.2 for mild stress, 1.4 for moderate stress, and 1.6 for severe stress. It is important to remember that all these calculations only estimate caloric requirements and should be considered as a starting point in nutrition repletion rather than the goal (Table 37-9).

Macronutrient Requirements

Hospitalized patients, and especially surgery and trauma patients, often suffer from protein-calorie malnutrition (PCM). It is important that patients in the hospital receive adequate calories to meet energy needs and adequate protein to maintain cellular integrity. Caloric requirement can be estimated by a formula, as noted earlier. Protein should make up 1.5 to 2 g/kg/day of that caloric requirement. Specific amino acids (e.g., glutamine, arginine) may be especially important in catabolic states (e.g., cancer, burns). These amino acids are therefore called conditionally essential amino acids. Carbohydrates make up about 70% of the total caloric requirement and lipids about 30%.

When to Start Nutritional Supplementation

There is a general trend to delay nutritional supplementation in hospitalized patients in the belief that oral intake will improve imminently, but this may exacerbate the existing malnutrition. The decision to initiate supplemental feeding (over what the patient willingly consumes at meals) must be individualized according to the patient's overall health and likely clinical outcome.

Calorie counts can be obtained for patients receiving oral nutrition. If the patient is falling short on caloric or protein intake, oral supplements are appropriate, given one to three times daily. The commercially available, canned oral supplements provide about 250 kcal and 9 g of protein per can.

For a variety of reasons, hospitalized patients are often unable to consume the calories and protein required to maintain nutrition. At some point, a patient may require enteral or parenteral nutrition. The American Society for Enteral and Parenteral Nutrition has published evidence-based guidelines for assessment and management of supplemental

Table 37-9 Estimated Caloric Need (kcal/kg)

Level of Activity or Severity of Illness

Table 37-9 Estimated Caloric Need (kcal/kg)

Level of Activity or Severity of Illness

Weight Goal

Low kcal/kg

Moderate kcal/kg

High kcal/kg

Lose weight

is

20

2s

Maintain weight

20

2s

30

Gain weight

2s

30

35

Examples: A 165-pound woman (height 5'2"; BMI 30.2) needs to lose weight but does not want to do any physical activity (low activity, lose weight); 165 lb = 75 kg, 75 X 15 = 1125 kcal estimated. A 200-pound man (height 6'4"; BMI 24.3) is hospitalized with sepsis and needs to maintain his weight (moderate activity, maintain weight); 200 lb = 91 kg, 91 X 25 = 2275 kcal estimated.

Examples: A 165-pound woman (height 5'2"; BMI 30.2) needs to lose weight but does not want to do any physical activity (low activity, lose weight); 165 lb = 75 kg, 75 X 15 = 1125 kcal estimated. A 200-pound man (height 6'4"; BMI 24.3) is hospitalized with sepsis and needs to maintain his weight (moderate activity, maintain weight); 200 lb = 91 kg, 91 X 25 = 2275 kcal estimated.

nutrition in patients with various disease states and surgical procedures (Albina et al., 2002; also available through the National Guideline Clearinghouse, www.guideline.gov). Depending on the disease state, these guidelines recommend that hospitalized patients begin specialized nutrition support (SNS) (enteral or parenteral feeding) when it is anticipated that patients will not otherwise be able to meet their nutritional needs for 7 to 10 days.

Enteral Nutrition

Most experts agree that when SNS is required, enteral feeding is the most appropriate method as long as the GI tract is competent (ADA, 2006; SORT A). This is partly because enteral feeding can supply complex nutrients such as fiber and intact proteins that parenteral nutrition cannot supply. Also, evidence indicates that enteral feeding has beneficial effects on the GI mucosa. Some cells lining the GI tract rely on lumi-nal nutrients to flourish, and enteral feeding maintains the absorptive capacity of the epithelial cells. Enteral feeding also stimulates the immune function of the gut. Enteral feeding is usually safer and less expensive than parenteral feeding.

Delivery Methods

Nasogastric feeding is the least invasive form of enteral feeding and is appropriate when there is no gastric outlet obstruction, delayed gastric emptying, or elevated risk for aspiration. If a patient does not tolerate gastric feeding, has one of the previous contraindications, or requires prolonged nutritional supplementation, as is often the case with head and neck cancers, a postpyloric feeding method such as duodenal or jejunal tube placement is appropriate. Jejunal tubes are preferred to duodenal tubes because the latter still pose a reasonably high risk for aspiration.

Formulas

One type of tube-feeding formula is blenderized food, which can be any type of food that can be successfully liquefied. There are also nutritionally complete commercial formulas that are sterile, easy to use, and appropriate for patients with normal digestive and absorptive function. Elemental formulas contain predigested, chemically formulated nutrients in low-molecular-weight form and may be useful in patients with a stressed GI tract that cannot digest and absorb nutrients in a more complex form. Specialized modular formulas are available for specific disease states, such as a formula appropriate for a patient with chronic kidney or lung disease.

Complications

Clinicians should be aware of the potential complications of enteral feeding, such as aspiration (especially with gastric feeding), gut perforation, and functional problems, such as gastric distention, nausea, vomiting, and diarrhea. Serum electrolyte and glucose level abnormalities are common in patients receiving enteral nutrition, and monitoring of these parameters is important.

Parenteral Nutrition

Most hospitals now use multidisciplinary teams to help plan and implement parenteral nutrition when it is deemed appropriate. Peripheral parenteral nutrition

(PPN), using a peripheral vein, is appropriate for short-term administration of nutrients (7-10 days) when the GI tract is not functional. Total parenteral nutrition (TPN) is administered through a more central vein and is used longer term (>10 days). TPN may be used to administer higher concentrations of glucose and protein than PPN, as well as for infusion of lipids.

Complications

The complications of PPN and TPN include phlebitis and other local reactions to infusion, maintenance of venous access, infection, air embolism, and refeeding syndrome. The refeeding syndrome is more common with TPN and may result in sudden death, more often affecting severely malnourished patients as they transition suddenly from deriving energy from stored fat to obtaining energy from infused glucose. This can cause a sudden depletion of phosphate stores, resulting in cardiac dysfunction. Patients who have lost more than 30% of their body weight should undergo gradual repletion of nutrients, with a slow increase in the rate of TPN over several days.

EVIDENCE-BASED SUMMARY

• To determine total daily calorie needs, multiply the basal metabolic rate (BMR) by the appropriate activity factor: Sedentary (little or no exercise; mild stress): BMR x 1.2

Light activity (light exercise, sports 1-3 days/wk; moderate stress): BMR x 1.4

Moderately active (moderate exercise, sports 3-5 days/wk; severe stress): BMR x 1.6

Very active (hard exercise, sports 6-7 days/wk): BMR x 1.725 Extra active (very hard exercise, sports + physical job or cross-training): BMR x 1.9

• To determine the BMR or basal energy expenditure (BEE), use the on-line calculator (http://www.calculator.org/bmr.html).

• Whenever possible, nutritional supplementation should be through the enteral route rather than parenteral.

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