Chapter 11: Enteral Nutrition

INTRODUCTION

The enteral route is the most physiologic and natural way of administering nutrients to humans, and attaining full enteral feedings can often be challenging to clinicians who care for preterm infants. Establishing enteral feedings should be one of the most important goals, especially in very low birth weight (VLBW) infants. The utilization of the gastrointestinal tract provides these patients with multiple benefits, which include enhanced growth and neurodevelopment, improved immunologic functions with decreased infections, and acceleration of intestinal adaptation and maturation with a subsequent increase in the absorption of nutrients. Despite the numerous advances made to date in the area of nutrition for preterm infants, such as the use of parenteral solutions with more proteins, the majority of these infants are discharged weighing less than the 10th percentile for age.^1,2 The early initiation of parenteral nutritional support in preterm infants is a trend now widely supported by neonatologists, but often, enteral nutrition is underutilized, delayed, or totally withheld for prolonged times because of concerns of feeding intolerance or the fear for the development of necrotizing enterocolitis (NEC), which remains the most common devastating gastrointestinal complication of the preterm infant. The principles that should be considered to prevent “metabolic shock” and to optimize nutrition in the preterm infant should include the following:

1. Clinicians should be aware that metabolic and nutritional requirements do not stop with birth.

2. That hours, not days, are the longest periods this group of infants should be allowed to face without receiving either enteral or parenteral nutrition (PN).

3. That the metabolic and nutritional requirements of the newborn are equal to or greater than those of the fetus.

In this chapter, we review characteristics of the developing intestine as they relate to enteral nutritional strategies for the preterm infant.

The Developing Intestine

The intestine not only serves as a nutrient digestive absorptive organ but also is one of the largest immune organs of the body and serves a significant endocrine and exocrine role in humans. The intestine has neural tissue in amounts equivalent to that of the entire spinal cord. As the fetal intestine develops, the increase in its total surface area is significant, largely because of the villus and microvillus growth during this period of development.

In many neonatal intensive care units (NICUs), because of concerns of feeding intolerance and NEC, the gastrointestinal tract of the critically ill, low birth weight infant either is not exposed to nutrients at all for prolonged periods after birth or is provided only “minimal enteral nutrition,” and most nutrients are only provided parenterally. The PN solutions are lifesaving nutritional medical interventions in the preterm infant, but ideally, the approach should be to provide most of the nutrients via the enteral route as soon as safely possible to promote intestinal growth and normal physiology. As illustrated in Figure 11-1, the lack or absence ...