The purpose of this study is to establish the parenteral lysine requirements for neonates.

It is important to identify the appropriate level of lysine requirements for parenterally fed neonates as this amino acid is the limiting amino acid in the diet of neonates. Feeding lysine at requirement improves the likelihood that other amino acids will be utilized appropriately for building proteins. In addition, lysine plays a major role in calcium absorption, development of muscle proteins and in the production of hormones, enzymes and antibodies. We believe that the lysine requirement will be 158 mg/kg/day which is significantly lower than the current 267 and 327 mg/kg/d that is found in the current Trophamine and Primene parenteral solutions.

Inclusion Criteria:

• Clinically stable neonates on TPN
• minimum of 2.5 g/kg/d protein and 85 - 90 kcal/kg/d)
• Post conception age of ≥ 34 weeks gestation and appropriate for gestational age
• Weight of ≥ 1.5 kg
• NPO or ≤10% of total protein requirement consumed enterally

Exclusion Criteria:

• Infants on mechanical ventilators, supplemental oxygen or who are receiving medications that would alter protein or energy metabolism (ie. corticosteroid therapy, etc)