Decisions About Formulas

Osmolality

Volume

Complete or Standard Formulas

Elemental Formulas

Home-Prepared Formulas

Modular Products

Specialized Formulas

School and Tube Feeding

A variety of commercial formulas are available for tube feeding. Infants under 12 months should be given breast milk, a standard infant formula or a special infant formula. For most children 1-10 years of age, pediatric enteral formulas such as Pediasure, Resource or Kindercal are designed specifically to meet their nutrient requirements. These formulas are complete and balanced. About 1000-1300 ml will meet 100% of the DRI for vitamins and minerals. These formulas are isotonic and easily tolerated by most children. An adult formula may be used for the older child. However the adult formula may not meet the child's vitamin and mineral needs. The protein and fiber content of adult formulas are higher than a child may require, so special attention is needed to make sure a child has adequate fluid. Formula must supply adequate nutrients in a form and volume that the child can tolerate. In selecting an appropriate formula, the factors to consider include the following:

- Protein and calorie requirements
- Age and medical condition
- History of food intolerance or allergy
- Intestinal function
- Route of delivery
- Formula characteristics (e.g., osmolality, viscosity, nutrient content, convenience, and cost)

The osmolality of a formula has a direct influence on the gastrointestinal (GI) side effects that occur with enteral feeding. Osmolality refers to the concentration of osmotically-active particles per liter solution of formula, expressed as mOsm/L. The osmolality of a formula is affected by the concentration of amino acids, carbohydrates, and electrolytes. Formula with a higher osmolality than that of normal body fluids produces an osmotic effect in the stomach and small intestine; this hyperosmolality draws water into the GI tract to dilute the concentration of the formula.

An influx of water into the GI tract may cause diarrhea, nausea, cramping, and distention. Isotonic formulas are designed to alleviate these problems. The osmolality of full-strength isotonic formulas is similar to the osmolality of normal body fluids, approximately 300 mOsm/L.

For infants, volume of formula is determined by calculating protein to meet child's needs. If additional energy is needed, fat and/or calories can be added. Water must be provided to meet fluid requirements. Another method to determine formula volume for children is to calculate amount of formula needed to meet energy needs, then add supplements to meet other nutrient needs. Try to minimize addition of supplements for ease of preparation, improved tolerance and decreased risk of error.

Sometimes parents feel that because enteral formulas are not solid food, they are not feeding their child enough. They may be tempted to add fruit juice, baby foods or blenderized foods through the feeding tube. Parents need reassurance that their child is not going hungry and their nutrient needs can be met by formula only.

Complete, or standard formulas, available from a number of companies, are nutritionally complete and made of complex proteins, fats, carbohydrates, vitamins, and minerals. Complete formulas are designed for patients who have normal digestion, but cannot orally consume adequate calories and nutrients. The advantages of complete formulas are that they have low osmolality and they are usually lactose-free, palatable, easy to use, and sterile. Some complete formulas have added fiber to promote regular bowel movements.

Elemental formulas are made from predigested nutrients including amino acids or hydrolyzed protein, carbohydrate, and fat in the form of medium-chain triglycerides or essential fatty acids. They contain all the essential vitamins and minerals.

The major advantages of elemental formulas are that little or no digestion is required, stool volume is low and the stimulation of bile and pancreatic secretions is minimal. On the other hand, elemental formulas are hyperosmolar and, if infused too rapidly, may cause cramping and osmotic diarrhea. They are more expensive than standard formulas and offer no advantage to a child whose gut is relatively intact.

Clinical indications for the use of elemental formulas include the following: short gut syndrome, malabsorption syndromes, inflammatory bowel disease, gastrointestinal fistulas, nonspecific maldigestive and malabsorptive states.

Home-prepared formulas are much less expensive than commercial formulas. Although they are cheaper, blenderized home-prepared formulas are also more time consuming. Extra time is needed to make sure sanitary methods are used to prevent contamination of the formula. Because there is a tendency to dilute calories and add extra protein to the formula, the content should be analyzed carefully by a nutritionist. When using a home-blended formula, supplements may be necessary to meet nutrient requirements. Milk or infant formula can serve as a base for the blenderized diet, which can contain a variety of foods. Home-blended formulas are best delivered through a gastrostomy tube because these feedings are viscous and may clog a narrow nasogastric tube.

Modular formulas are not complete formulas. They contain only specific nutrients, which can be added to commercial or home-prepared formulas to meet special nutrient needs. Examples of modular formulas are the following:

- Medium-chain triglycerides (e.g., MCT Oil), which are fats in an easy-to-digest form used for additional calories
- Readily-digested carbohydrates (e.g., Moducal or Polycose) used for additional calories
- Protein and specific amino acid preparations (e.g., Casec or ProMod)

Specialized formulas are available for children with special needs, such as prematurity renal failure or inborn errors of metabolism. The formula should be selected by a physician or a dietitian who is familiar with the products and their particular uses.

Children with gastrostomies are considered children with special needs and are eligible for expanded nutrition services in schools through Public Law 99-457 and the American Disabilities Act. This presents understandable concern for educators. Enteral feeds can be given as a routine activity at school. A team of a nutritionist, special educator, nurse and the family can help facilitate feeding in the school. The objective is to use the same feeding routine, positioning and oral-motor stimulation at home and school. Physician orders, an individualized education plan and instruction about when to call parent or physician may be required.

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Page reviewed: March 24, 2015