Enteral Zinc to Improve Growth in Infants at Risk for Bronchopulmonary Dysplasia

Multiple factors contribute to growth failure in infants with BPD, including poor nutrient
stores, inadequate intake, increased losses, and increased needs. Furthermore, compared to
infants without BPD, those with BPD have increased resting metabolic rates and energy
expenditure. Growth deficits manifest as lower weight, length, and head circumference, as
well as changes in body composition. These deficits precede the development of BPD and
persist post-discharge. While similar rates of growth are observed in very low birth weight
infants with and without BPD once receiving equal calories, catch up growth does not occur in
the BPD group. Thus, early growth deficits remained uncompensated.

After iron, zinc is the most metabolically active trace element in the human body. It has a
critical role in growth, through its actions on growth hormone, IGF-1, IGFBP-3, and bone
metabolism. Prematurity is a risk factor for zinc deficiency, as 60% of zinc accretion occurs
in the third trimester. Impaired intake and absorption or excess excretion can further
increase this risk. Finally, periods of rapid growth, as seen in preterm infants, increase
the need for zinc.

Biochemically, zinc deficiency is defined by a serum zinc level less than 55mcg/dl. However,
while zinc depletion is associated with deficiency, the opposite may not be true. For
example, in starving patients, clinical symptoms of zinc deficiency occur during re-feeding,
suggesting overall requirements are related to needs, regardless of overall zinc status. This
may be the case in preterm infants, who may have a subclinical deficiency despite serum zinc
level. Thus, zinc deficiency should be considered in infants with poor growth despite
receiving adequate protein and calories.

The objective of this study is to determine whether enteral zinc supplementation leads to
improved growth in infants at risk for bronchopulmonary dysplasia (BPD). The investigator's
hypothesis is that enteral zinc supplementation in very preterm infants at high risk for BPD
will significantly improve growth compared to standard of care.