Chapter 10: Nutritional Support of the Critically ill Neonate

INTRODUCTION

Over the last 30 years, survival rates have improved among preterm infants of all gestational ages.¹ With increasing survival rates, it has become evident that neonatal nutrition is important to prevent postnatal growth restriction, achieve appropriate body composition, and prevent neurodevelopmental impairment.² Nutrition previously provided by the placenta can now be provided as parenteral or enteral support in an effort to allow these infants to mimic intrauterine growth as closely as possible. Studies have shown growth velocity alone to be associated with developmental outcomes, emphasizing the importance of appropriate nutrition for the neonatal population.^2,3 Providing the best nutrition for any high-risk, critically ill neonate is an evolving field, and determining how to deliver the best nutrition for gut maturation as well as effective nutrient absorption is still debated. Previous nutritional strategies emphasized catch-up growth through increased calories, with an emphasis on carbohydrate and lipid intake. This nutritional plan led to late catch-up growth, with infants that were shorter and fatter than term infants at the same corrected gestational age.⁴ In addition to providing higher calories, new data have shown protein to be an important component for lean muscle mass synthesis and linear growth.⁵ Appropriate nutrition is also important to prevent anemia of prematurity and osteopenia of prematurity, and appears to play an important role in prevention of necrotizing enterocolitis (NEC).⁶

GOALS FOR GROWTH AND NUTRITION ASSESSMENT

The goal set forth by the American Academy of Pediatrics is to provide neonatal nutrition to best mimic fetal accretion rates for the appropriate gestational age of each infant.⁷ These intrauterine growth rates are estimated to be 20 to 30 grams per day, increasing with gestational age nearing a full-term fetus. Postnatal growth rate goals for preterm infants range from 16 to 18 g/kg per day.⁸ Goal increase for length is 1.1 cm per week, while goal increase for head circumference is 0.7 to 1 cm per week. Once infants near term-corrected gestational age, a goal of 20 to 30 grams per day is appropriate, and infants should follow the trajectory of growth in the World Health Organization charts.7

Intrauterine growth rates are often not achieved until near the time of discharge from the neonatal intensive care unit (NICU), while needed catch-up growth does not occur until after discharge.¹ When growth mimicking fetal rates are achieved, infants are often found to be shorter than their term counterparts.⁹ Achievement of appropriate postnatal growth will reduce the risks of developing morbidities such as cardiovascular disease and neurodevelopment impairment.¹⁰

Assessment of Neonatal Nutritional Status

Assessment of nutritional status can be difficult in the preterm infant where normative standardized data are limited, especially among the extremely low birth weight (ELBW) (<1500 gm) and very low birth weight (VLBW) (<1000 gm) populations. Anthropometric analysis remains the standard ...