1. Nutrition Evaluation and Support
Applied Therapeutics

2. INTRODUCTION
Malnutrition is a consequence of nutrient imbalance resulting from inadequate intake, absorption, or utilization of protein and energy.
Undernutrition can result in changes in subcellular, cellular, or organ function that increase the individual’s risks of morbidity and mortality.

3. CLINICAL EVALUATION
Medical and dietary history should include weight changes within 6 months, dietary intake changes, gastrointestinal (GI) symptoms, functional capacity, and disease states.
Physical examination should focus on assessment of lean body mass (LBM) and physical findings of vitamin, trace element, and essential fatty acid deficiencies.

4. ANTHROPOMETRIC MEASUREMENTS
Anthropometric measurements are physical measurements of the size, weight, and proportions of the human body used to compare an individual with normative population standards.
The most common measurements are weight, stature, head circumference (for children younger than 3 years of age) waist circumference, and measurements of limb size (eg, skinfold thickness and midarm muscle and wrist circumferences), along with bioelectrical impedance analysis (BIA).

5. ANTHROPOMETRIC MEASUREMENTS
Interpretation of actual body weight (ABW) should consider ideal weight (IBW) for height, usual body weight (UBW), fluid status, and age.
Change over time can be calculated as the percentage of UBW. Unintentional weight loss, especially rapid weight loss (5% of UBW in one month or 10% of UBW in 6 months), increases risk of poor clinical outcome in adults.

6. ANTHROPOMETRIC MEASUREMENTS
Body mass index (BMI) is another index of weight-for-height that is highly correlated with body fat. Interpretation of BMI should include consideration of gender, frame size, and age.
BMI values greater than 25 kg/m2 are indicative of overweight, and values less than kg/m2 are indicative of undernutrition. BMI is calculated as follows:
Body weight (kg)/[height (m)]2 

7. ASSESSMENT OF NUTRIENT REQUIREMENTS
Assessment of nutrient requirements must be made in the context of patient-specific factors (eg, age, gender, size, disease state, clinical condition, nutrition status, and physical activity).
To replace recommended dietary allowances, the Food and Nutrition Board created the dietary reference intakes made up of seven nutrient groups.
Adults should consume 45% to 65% of total calories from carbohydrates, 20% to 35% from fat, and 10% to 35% from protein. Recommendations are similar for children, except that infants should consume 40% to 50% of total calories from fat.

8. ENERGY REQUIREMENTS
Energy requirements of individuals can be estimated using published, validated equations or directly measured, depending on factors including severity of illness and resources available.
The simplest method is to use population estimates of calories required per kilogram of body weight.
Healthy adults with normal nutrition status and minimal illness severity require an estimated 20 to 25 kcal ABW/kg/day (84–105 kJ ABW/kg/day). Daily energy requirements for children are approximately 150% of basal metabolic rate with additional calories to support activity and growth.

9. Protein Requirements
Protein requirements are based on age, gender, nutrition status, disease state, and clinical condition. The usual recommended daily protein allowances are 0.8 g/kg for adults, 1.5 g/kg for adults over 60 years of age, 1.5 to 2 g/kg for patients with metabolic stress (eg, infection, trauma, and surgery), and 2.5 to 3 g/kg for patients with burns.

10. Fluid Requirements
Daily adult fluid requirements are approximately 30 to 35 mL/kg, 1 mL/kcal (or per every 4.18 kJ) ingested, or 1500 mL/m2.
Daily fluid requirements for children and preterm infants who weigh less than 10 kg are at least 100 mL/kg. An additional 50 mL/kg should be provided for each kilogram of body weight between 11 and 20 kg, and 20 mL/kg for each kilogram greater than 20 kg.

11. Micronutrients Requirements
Requirements for micronutrients (ie, electrolytes, trace elements, and vitamins) vary with age, gender, route of administration, and underlying clinical conditions.
Sodium, potassium, magnesium, and phosphorus requirements are typically decreased in patients with kidney failure, whereas calcium requirements are increased

12. ENTERAL NUTRITION
Enteral nutrition (EN) delivers nutrients by tube or mouth into the GI tract; we will focus on delivery through a feeding tube.
EN is indicated for the patient who cannot or will not eat enough to meet nutritional requirements and who has a functioning GI tract and a method of enteral access.
Potential indications include neoplastic disease, organ failure, hypermetabolic states, GI disease, and neurologic impairment.

13. ENTERAL NUTRITION
Distal mechanical intestinal obstruction, bowel ischemia, active peritonitis, uncorrectable coagulopathy, and necrotizing enterocolitis are contraindications to EN.
Conditions that challenge the success of EN include severe diarrhea, protracted vomiting, enteric fistulas, severe GI hemorrhage, hemodynamic instability, and intestinal dysmotility.

14. ENTERAL NUTRITION
EN has replaced parenteral nutrition (PN) as the preferred method for the feeding of critically ill patients requiring specialized nutrition support.
Advantages of EN over PN include maintaining GI tract structure and function; fewer metabolic, infectious, and technical complications; and lower costs.

15. ACCESS of ENTERAL NUTRITION
EN can be administered through four routes, which have different indications, tube placement options, advantages, and disadvantages.
The choice depends on the anticipated duration of use and the feeding site (ie, stomach vs small bowel).
The stomach is generally the least expensive and least labor-intensive access site; however, patients who have impaired gastric emptying are at risk for aspiration and pneumonia.
Long-term access should be considered when EN is anticipated for more than 4 to 6 weeks.

16. Options and Considerations in the Selection of Enteral Access
Nasogastric or orogastric:
Short term, Normal gastric emptying
Nasojejunal or orojejunal:
Short term, Impaired gastric motility or emptying
Gastrostomy:
Long term, Normal gastric emptying
Jejunostomy:
Long term, Impaired gastric motility or emptying

17. ADMINISTRATION METHODS
EN can be administered by continuous, cyclic, bolus, and intermittent methods.
The choice depends on the location of the feeding tube tip, patient’s clinical condition, intestinal function, and tolerance to tube feeding.

18. COMPLICATIONS AND MONITORING
Monitor patients for metabolic, GI, and mechanical complications of EN.
Metabolic complications associated with EN are similar to those of parenteral nutrition (PN), but the occurrence is lower.
GI complications include nausea, vomiting, abdominal distention, cramping, aspiration, diarrhea, and constipation. Gastric residual volume is thought to increase the risk of vomiting and aspiration.
Mechanical complications include tube occlusion or malposition and inadvertent nasopulmonary intubation.

19. PARENTERAL NUTRITION
Parenteral nutrition (PN) provides macro- and micronutrients by central or peripheral venous access to meet specific nutritional requirements of the patient.
PN should be considered when a patient cannot meet nutritional requirements through use of the GI tract.
Consider PN after suboptimal nutritional intake for 1 day in preterm infants, 2 to 3 days in term infants, 3 to 5 days in critically injured children, 5 to 7 days in other children, and 7 to 14 days in older children and adults.

20. COMPONENTS OF PARENTERAL NUTRITION
Macronutrients (ie, water, protein, dextrose, and fat) are used for energy (dextrose and fat) and as structural substrates (protein and fat).
Protein is provided as crystalline amino acids (CAAs). When oxidized, 1 g of protein yields 4 calories (~17 J). Including the caloric contribution from protein in calorie calculations is controversial; therefore, PN calories can be calculated as either total or nonprotein calories.

21. SPECIFICS OF PARENTERAL NUTRITION
The patient’s clinical condition determines whether PN is administered through a peripheral or central vein.
Peripheral parenteral nutrition (PPN) candidates do not have large nutritional requirements, are not fluid restricted, and are expected to regain GI tract function within 10 to 14 days. Solutions for PPN have lower final concentrations of amino acid (3% – 5%), dextrose (5% –10%), and micronutrients as compared with central parenteral nutrition (CPN).
Primary advantages of PPN include a lower risk of infectious, metabolic, and technical complications.

22. SPECIFICS OF PARENTERAL NUTRITION
CPN is useful in patients who require PN for more than 7 to 14 days and who have large nutrient requirements, poor peripheral venous access, or fluctuating fluid requirements.
CPN solutions are highly concentrated hypertonic solutions that must be administered through a large central vein.
The choice of venous access site depends on factors including patient age and anatomy.
Peripherally inserted central catheters (PICCs) are often used for both short- and long-term central venous access in acute or home care settings.

23. Assessment of Nutrition Status and Nutrition Requirements