Iowa Neonatology Handbook: Feeding

Enteral Feedings

Ekhard E. Ziegler, MD, and Susan J. Carlson, MMSc, RD, CSP, LD, CNSD
Peer Review Status: Internally Peer Reviewed

Feeding the Gut (Trophic Feedings)

The provision of small amounts of feedings starting soon after birth aims at preventing atrophy of the gut. A number of studies in recent years have demonstrated the general feasibility of this approach as well as beneficial clinical effects, with no recognizable increase in the risk of necrotizing enterocolitis. Although we have no formal protocol for the use of trophic feedings, such feedings are being used increasingly and their use is encouraged. Colostrum/human milk should be used whenever available. Otherwise, preemie formula should be used. The use of dilute formula, although practiced widely, has no rational basis and no demonstrated benefits, except that the larger volume may improve gastric emptying. Trophic feedings should be initiated at a volume not to exceed 15 ml/kg/d. These feedings are traditionally given in small boluses of 1 - 3 ml/kg per feeding. Trophic feedings should continue until the infant's respiratory and cardiac status have stabilized. Older preterm infants (i.e. > 27 weeks) and infants with minimal respiratory compromise may bypass trophic feeds and begin feedings using a nutritive feeding regimen.

Feeding the Baby (Nutritive Feedings)

When feedings begin in earnest in the stable baby, feedings should be advanced slowly. The rate of increase should not exceed 20 ml/kg/day except in situations where feedings were held and are being restarted. Feeding volume is increased first by reducing the interval between feeds to q 3 hrs or q 4 hrs and subsequently by increasing the bolus volume. Infants less than 1200 g may tolerate larger volumes with continuous (3 hr on, 1 hr off) feedings than bolus feedings.

Intestinal motility is often impaired in the infant in the Special Care Nursery due to immaturity, sedation, or critical illness and thus feeding aspirates are common. Aspirates should be checked but, as a rule, should be refed, except when they are clearly bilious or when there are other clear signs of bowel obstruction. Aspirates greater than 2 ml, especially if they contain mostly milk or formula rather than gastric juice, should prompt a physical examination of the infant, and subsequent aspirates as well as the infant's medical condition should be monitored closely.

Human Milk

Milk provided by the infant's mother is, of course, the feeding of choice. Fresh milk that has not been frozen is preferred when available. Freezing entails some loss of nutrients, but, with the exception of live neutrophils and lymphocytes, all the protective components of breast milk remain essentially intact. Expressed, stored milk should always be fed in the order in which it was obtained. In this way, the infant receives the colostrum first, which is most protective, followed by transitional and mature milk. If mother's milk is not available, donor milk from the Mother's Milk Bank of Iowa may be substituted. Donor milk is mature human milk and likely contains less protein and sodium than mother's preterm milk but still confers most of the immunological and nutritional benefits of human milk.

¹"Preterm" milk at 2 weeks of lactation

Because human milk does not contain protein and minerals in amounts needed by the growing preterm infant, fortification is necessary. Table 3 indicates the estimated nutrient requirements ("Advisable Intakes") of preterm infants and contrasts these with the composition of unfortified and fortified human milk. It is evident that fortified milk comes close to meeting the needs of larger infants, but that the needs of smaller infants are met only partially. Fortification should be started when milk feeds of approximately 50 - 80 ml/kg/day are achieved. The composition of the Enfamil Human Milk Fortifier is indicated in Table 4. Standard fortification is one envelope per 25 ml of human milk.

Fortified milk has a caloric density of 80 kcal/dl (24 kcal/oz), assuming caloric density of native breast milk to be 67 kcal/dl. Expressed breast milk is frequently low in fat content and thus contains fewer calories than the assumed 67/dl. Use of calories to quantify breast milk is a convenient practice, but we must always remember that the actual intake of calories is likely to be less than the stated value.

In selected cases it may be beneficial to increase fortification by decreasing the volume of milk to which one envelope is added (e.g., to 15 ml). Situations where this might be indicated include very small infants, infants on fluid restrictions, or any infant who fails to gain satisfactorily in spite of receiving what appears to be an adequate intake. The addition of extra fortifier to human milk substantially increases calcium and phosphorus intake, particularly in infants receiving >120 kcal/kg/d from feeds. Routine monitoring of ionized calcium and phosphorus are indicated to prevent the development of hypercalcemia or hyperphosphatemia. The iron content of human milk is negligible. The iron content of Enfamil Human Milk Fortifier will provide a daily iron intake of 2.2 mg/kg/d in infants fed 120 kcal/kg/d. This level of intake is sufficient to meet the iron needs of growing premature infants.

Formula

The composition of a typical premature infant formula is included in Table 3. Premature formula has a caloric density of 80 kcal/dl (24 cal/oz). As Table 3 shows, the formula meets the protein needs of larger infants but not of smaller infants. Infants requiring concentrated feedings will receive premature formula mixed with term formula concentrate. Please contact the dietitian if concentrated feedings are required. The addition of carbohydrate and/or lipid is not a suitable means of increasing caloric density of feedings for premature infants as protein and mineral density of the premature formula is significantly reduced.

Feedings at Discharge

Fortified Human Milk and Premature Formula should be used until the infant is feeding ad libitum or a weight of 3000 g has been reached, whichever comes first. Prior to discharge the infant must be transitioned to an appropriate homegoing regimen. Selection of the appropriate feeding for discharge depend on a number of factors including infant weight, degree of growth failure, need for fluid restriction, and oral feeding skills. The use of Preterm Discharge Formulas (e.g. Enfacare, Neosure) as formula, or mixed with breast milk, may enhance growth in preterm infants discharged to home before reaching term size. Preterm Discharge Formulas are routinely prepared at 22 kcal/oz and have a higher protein and mineral content than term formulas. Concentrated term formula (24, 27 kcal/oz) may be indicated for larger infants (e.g. >2500 g) with inadequate oral feeding skills. Vitamin D and iron supplements are indicated for infants breastfeeding at discharge. No additional vitamin or iron supplements are needed for the formulas fed infant. Table 5 lists guidelines for selection of an appropriate discharge feeding regimen.

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