Low birth weight (LBW) is defined by a birth weight of less than 2,500 grams (5.5 pounds), regardless of gestational age. It has two subcategories: very low birth weight (VLBW), which is less than 1,500 grams; and extremely low birth weight (ELBW), which is less than 1,000 grams.
The risk factors of LBW include young age, multiple pregnancies, previous LBW infants, poor nutrition, heart disease, hypertension, drug addiction, alcohol abuse, insufficient prenatal care, smoking, lead exposure, or other types of air pollutions.
So far, there have been four pathways recognized for preterm birth: precocious fetal endocrine activation, decidual bleeding and intrauterine inflammation or infection. Based on a report from the Agency for Health Care Research and Quality (AHRQ), 6.1 percent of the 3.8 million births in 2011 in the U.S. were diagnosed with LBW and 1.3 percent with VLBW.
Premature infants are highly susceptible to extra-uterine growth restriction. Due to limited nutrient stores, preterm infants are at risk of nutrient deficit, leading to a potential poor growth and neurodevelopment. Therefore, it is critical to provide adequate nutritional support early enough in order to avoid nutrition deficits of energy and protein.
Parenteral nutrition (PN) has been widely used to provide a relatively safe nutrient input for preterm infants. Although there have been many studies confirming the benefits of short-term parenteral nutrition in VLBW and ELBW, not many trials have been conducted for its long-term utility.
Once PN becomes the sole source of nutrition, micronutrient requirements have to be carefully assessed for each infant. In most cases, the recommendations include: 3.5-4.0 g/kg/day protein (mainly amino acids), 3-4 g/kg/day lipids, and equal of 90-110 kcal/kg/day carbohydrate. If there is no nutrient osmolality problem, a peripheral venous access will suffice. However, in many cases a central venous access line would be required to take care of osmolality issues.
Some of the inherent problems that may occur in PN include:
- increased incidence of bacterial and fungal sepsis
- mechanical complications due to venous line placement
- nutrient dosage miscalculations
- manufacturing, supply or administration errors
- metabolic derangements
- hepatic dysfunction
- aluminum contamination risk during manufacturing
In general, there might be an increased risk of aluminum toxicity in patients receiving long-term PN. This toxicity can lead to metabolic bone disease, aluminum-associated encephalopathy and impaired neurological development in preterm infants. Measurement of bone turnover markers provides a minimally invasive approach to measure metabolic bone disease.
In order to address these complications, many solutions have been proposed, some of which include
- administration of PN in units with high standards of quality control
- applying strict aseptic methodologies in its manufacturing and administration
- multidisciplinary team involvement in its application and monitoring
It is important to adjust the focus of PN therapy on proper nutrient need calculation for individuals and to continuously assess the PN therapy success. Further large-scale studies need to be designed to assess the long-term effects of PN on this population.
