The purpose of this study is to analyze if the infants who received Primene solution, have lower serum levels of methionine and cysteine and higher serum levels of taurine, we also analyze if the infants who received Primene solution develop TPN-associated cholestasis in a smaller proportion than those who received Trophamine solution.

Total parenteral nutrition is an essential component of the care of premature and ill infants. Prolonged parenteral nutrition is associated with complications affecting the hepatobiliary system, such as cholelithiasis, cholestasis, and steatosis. The most common of these is total parenteral nutrition-associated cholestasis (TPNAC), that occurs because of reduced bile flow from the liver into the duodenum. Cholestasis causes liver damage and in some cases, death. Infant and neonate are at particular risk for this complication. The incidence of TPNAC ranges from 7.4 to 84%.

Animal studies have implicated amino acids in the production of cholestasis; whereas studies in human neonates suggest a direct effect of amino acid infusions on the hepatocyte canalicular membrane. An appropriate amino acid solution might compensate for the metabolic immaturity of infants and perhaps reduce total parenteral nutrition associated complications such as cholestasis. Therefore, is important to compare the frequency of cholestasis and blood amino acid concentration during Primene and Trophamine use.

Inclusion Criteria:

• Newborns greater than 1500 g who enter the Intensive Care Unit and their pathology requiring total parenteral nutritional support (necrotizing enterocolitis, intestinal atresia, short bowel syndrome).
• Gestational age greater than 30 weeks
• Patients with normal liver function tests for their age, prior to the initiation of total parenteral nutrition.
• Authorization from both parents or legal guardian for recruiting of the child into the study with consent signed form after the purpose and procedures have been explained

Exclusion Criteria:

• Patients with acute renal failure
• Congenital liver disease, end-stage liver disease
• Patients with liver damage secondary to viral or bacterial infection
• Patients with liver damage secondary to drugs