understanding normal and clinical nutrition, 9th edition, 2012 Special topics Topic 4 Enteral Nutrition Support understanding normal and clinical nutrition, 9th edition, 2012

Introduction Nutrition support: the delivery of nutrients using a feeding tube or intravenous infusions. Enteral (EN-ter-al) nutrition: the provision of nutrients using the GI tract, including the use of tube feedings and oral diets. Parenteral (par-EN-ter-al) nutrition: the intravenous provision of nutrients that bypasses the GI tract.

Some illnesses may interfere with eating, digestion, or absorption to such a degree that conventional foods cannot supply the necessary nutrients. In such cases, nutrition support: the delivery of nutrients using a feeding tube or intravenous infusions can meet a patient’s nutritional needs. Enteral nutrition provides nutrients using the gastrointestinal (GI) tract. Enteral nutrition includes oral diets or supplements, but the term more often refers to the use of tube feedings, which supply nutrients directly to the stomach or intestine via a thin, flexible tube

If gastrointestinal function is normal and a poor appetite is the primary nutrition problem, enteral formulas can be provided as oral supplements to the usual diet. If patients cannot consume enough food or drink enough formula to meet nutrient needs, tube feedings may be used to deliver the required nutrients. Administration of Tube Feedings Safe Handling Initiating and Progressing a Tube Feeding Meeting Water Needs Medication Delivery through Feeding Tubes Tube Feeding Complications Transition to Table Foods

Enteral Formulas Enteral formulas are categorized according to their macronutrient sources. Standard formulas usually contain intact proteins and polysaccharides, whereas elemental formulas contain macronutrients that have been broken down to some extent and require less digestion. Specialized formulas include nutrient combinations that can assist in the treatment of certain illnesses. When an ideal formula is unavailable, a modular formula can be prepared in the hospital pharmacy by combining individual macronutrient preparations (called modules).

Standard Formulas Called polymeric formulas, are provided to individuals who can digest and absorb nutrients without difficulty. They contain intact proteins extracted from milk or soybeans (called protein isolates) or a combination of such proteins. The carbohydrate sources include modified starches, glucose polymers (such as maltodextrin), and sugars. A few formulas, called blenderized formulas, are made from whole foods and derive their protein primarily from pureed meat or poultry.

Elemental Formulas Called hydrolyzed, chemically defined, or monomeric formulas, are prescribed for patients who have compromised digestive or absorptive functions. Elemental formulas contain proteins and carbohydrates that have been partially or fully broken down to fragments that require little (if any) digestion. The formulas are often low in fat and may contain medium chain triglycerides (MCT) to ease digestion and absorption.

Specialized Formulas Called disease-specific formulas, are designed to meet the nutrient needs of patients with particular illnesses. Products have been developed for individuals with liver, kidney, and lung diseases; glucose intolerance; and metabolic stress (later chapters provide details). Specialized formulas are generally expensive, and their effectiveness is controversial

Modular Formulas are sometimes prepared for patients who require specific nutrient combinations to treat their illnesses. Vitamin and mineral preparations are also included in these formulas so that they can meet all of a person’s nutrient needs. In some cases, one or more modules are added to other enteral formulas to adjust their nutrient composition.

Formula Characteristics Formulas vary in their nutrient and energy densities so that they can supply the required nutrients in different volumes of fluid. The fiber content influences intestinal function and blood glucose control. These properties affect the administration of tube feedings, as well as the side effects that patients may experience.

Macronutrient Composition The amounts of protein, carbohydrate, and fat in enteral formulas vary substantially . The protein content of most formulas ranges from 12 to 20 percent of total kcalories; note that protein needs are high in patients with severe metabolic stress, whereas protein restrictions are necessary for patients with chronic kidney disease. Carbohydrate and fat provide most of the energy in enteral formulas; standard formulas generally provide 40 to 60 percent of kcalories from carbohydrate and 30 to 40 percent of kcalories from fat

Energy Density The energy density of enteral formulas ranges from 0.5 to 2.0 kcalories per milliliter of fluid. Standard formulas provide 1.0 to 1.2 kcalories per milliliter and are appropriate for patients with average fluid requirements. Formulas that have higher energy densities can meet energy and nutrient needs in a smaller volume of fluid and therefore benefit patients who have high nutrient needs or fluid restrictions. Individuals with high fluid needs can be given a formula with low energy density or be supplied with additional water via the feeding tube or intravenously.

Fiber Content Fiber-containing formulas can be helpful for improving fecal bulk and colonic function, treating diarrhea or constipation, and maintaining blood glucose control. Conversely, fiber-containing formulas are avoided in patients with acute intestinal conditions or pancreatitis, and before or after some intestinal examinations and surgeries.

Osmolality Refers to the moles of osmotically active solutes (or osmoles) per kilogram of solvent. An enteral formula with an osmolality similar to that of blood serum (about 300 milliosmoles per kilogram) is an isotonic formula, whereas a hypertonic formula has an osmolality greater than that of blood serum. Most enteral formulas have osmolalities between 300 and 700 milliosmoles per kilogram; generally, elemental formulas and nutrient-dense formulas have higher osmolalities than standard formulas. Most people are able to tolerate both isotonic and hypertonic feedings without difficulty. When medications are infused along with enteral feedings, however, the osmotic load increases substantially and may contribute to the diarrhea experienced by many tube-fed patients.

Formula Selection Generally, the best formula is one that meets the patient’s medical and nutrient needs with the lowest risk of complications and the lowest cost. The vast majority of patients can use standard formulas. A person with a functional, but impaired, GI tract may require an elemental formula. Factors that influence formula selection include:

Nutrient and energy needs Nutrient and energy needs. As with patients consuming regular diets, an adjustment in macronutrient and energy intakes may be necessary for tubefed patients. For example, patients with diabetes may need to control carbohydrate intake, critical-care patients may have high protein and energy requirements, and patients with chronic kidney disease may need to limit their intakes of protein and several minerals. Fluid requirements. High nutrient needs must be met using the volume of formula a patient can tolerate. If fluids are restricted, the formula should have adequate nutrient content and energy density to deliver the required nutrients in the volume prescribed.

The need for fiber modifications The need for fiber modifications. The choice of formulas is narrower if fiber intake needs to be high or low. Formulas that provide fiber may be helpful for managing diarrhea, constipation, or hyperglycemia in some patients; other patients may need to avoid fiber due to an increased risk of GI obstructions. Individual tolerances ( food allergies and sensitivities). Most formulas are lactose- free, because many patients who need enteral formulas have some degree of lactose intolerance. Many formulas are also gluten-free and can accommodate the needs of individuals with celiac disease (gluten sensitivity).

Enteral Nutrition in Medical Care A person with a functional GI tract who cannot meet nutrient needs with conventional foods alone may be a candidate for enteral nutrition support. Enteral feedings are preferred over parenteral nutrition because they help to stimulate or maintain gut function, cause fewer complications, and are less costly. Similarly, oral feedings are preferred to tube feedings when the person is able to drink enteral formulas, because drinking the formulas prevents the stress, complications, and expense associated with tube feedings

Oral Use of Enteral Formulas As mentioned previously, enteral formulas can fully meet a person’s nutritional needs. In most cases, however, patients drink enteral formulas to supplement their diets when they are unable to consume enough food to meet their needs. Enteral formulas provide a reliable source of nutrients and add energy and protein to the diets of malnourished patients. Those who are weak or debilitated may also find it easier to manage formulas than meals.

When a patient drinks a formula, taste becomes an important consideration. Allowing patients to sample different products and flavors and to select the ones they prefer helps to promote acceptance. The “How To” above offers additional suggestions for helping patients to accept and enjoy oral formulas. Several enteral products are sold in pharmacies and grocery stores for home use. These products are sometimes used as nutrition supplements or convenient meal replacements by healthy individuals. The products are available in ready-to-drink liquid form or in powdered forms that must be reconstituted with water or milk

Indications for Tube Feedings Tube feedings are typically recommended for patients at risk of protein-energy malnutrition who are unable to consume adequate food or formula for at least seven days.8 The following medical conditions may indicate the need for tube feedings: Severe swallowing disorders Impaired motility in the upper GI tract Gastrointestinal obstructions and fistulas that can be bypassed with a feeding tube Certain types of intestinal surgeries

Mechanical ventilation Extremely high nutrient requirements Little or no appetite for extended periods, especially if the patient is malnourished Mental incapacitation due to confusion, neurological disorders, or coma Contraindications for tube feedings include severe GI bleeding, high-output fistulas, intractable vomiting or diarrhea, complete intestinal obstruction, and severe malabsorption.

Feeding Routes The feeding route chosen depends on the patient’s medical condition, the expected duration of tube feeding, and the potential complications of a particular route. Gastrointestinal Access: When a patient is expected to be tube fed for less than four weeks, a nasogastric or nasoenteric route is generally chosen; for these routes, the feeding tube is passed into the GI tract via the nose. The patient is frequently awake during transnasal (through-the-nose) placement of a feeding tube.

While the patient is in a slightly upright position with head tilted, the tube is inserted into a nostril and passed into the stomach (nasogastric placement), duodenum (nasoduodenal placement), or jejunum (nasojejunal placement). If the patient is awake and alert, he or she can swallow water to ease the tube’s passage. The final position of the feeding tube tip is verified by abdominal X-ray or other means.

In infants, orogastric placement, in which the feeding tube is passed into the stomach via the mouth, is sometimes preferred over transnasal routes; this placement allows the infant to breathe more normally during feedings. When a patient will be tube fed for longer than four weeks or if the nasoenteric route is inaccessible due to an obstruction or other medical reasons, a direct route to the stomach or intestine may be created by passing the tube through an enterostomy, an opening in the abdominal wall that leads to the stomach (gastrostomy) or jejunum (jejunostomy). An enterostomy can be made by either surgical incision or needle puncture.

Transnasal access is usually preferred when the tube feeding duration is expected to be less than four weeks, and enterostomies are often appropriate when tube feedings are planned for longer periods. Gastric feedings (nasogastric and gastrostomy routes) are preferred whenever possible. These feedings are more easily tolerated and less complicated to deliver than intestinal feedings because the stomach controls the rate at which nutrients enter the intestine. Gastric feedings are not possible, however, if patients have gastric obstructions or motility disorders that interfere with the stomach’s ability to empty

Gastric feedings are often avoided in patients at high risk of aspiration, a common complication in which formula or GI secretions enter the lungs, possibly from the backflow of stomach contents. Aspiration pneumonia, a lung disease that is sometimes fatal, may result. Although health practitioners frequently administer nasoenteric feedings to minimize the possibility of aspiration, studies have not consistently shown that gastric feedings are associated with increased aspiration risk.

Feeding Tubes Are made from soft, flexible materials (usually silicone, polyurethane, or polyvinyl) and come in a variety of lengths and diameters. The tube selected largely depends on the patient’s age and size, the feeding route, and the formula’s viscosity. In many cases, the tube selected is the smallest diameter tube through which the formula will flow without clogging. The outer diameter of a feeding tube is measured in French units, in which each unit equals 1/3 millimeter; thus, a “12 French” feeding tube has a 4-millimeter diameter.

The inner diameter depends on the thickness of the tubing material The inner diameter depends on the thickness of the tubing material. Double-lumen tubes are also available; these allow a single tube to be used for both intestinal feedings and gastric decompression, a procedure in which the stomach contents of patients with motility disorders are removed by suction.

Feeding Systems Formulas are available in open feeding systems and closed feeding systems. With an open feeding system, the formula needs to be transferred from its original packaging to a feeding container. Examples include formulas that are packaged in cans or bottles, concentrates that need to be diluted, and powders that require reconstitution. In a closed feeding system, the formula is prepackaged in a container that can be connected directly to a feeding tube.

Closed systems are less likely to become contaminated, require less nursing time, and can hang for longer periods of time than open systems. Although closed systems cost more initially, they may be less expensive in the long run because they prevent bacterial contamination and thus avoid the costs of treating infections.