The Effects of Surgery on the Nitrogen Metabolism of Parenterally Fed Human Neonates

Abstract

ABSTRACT. Nitrogen retention and rates of whole body whole body protein synthes~s, we hypothesized that giving inamino nitrogen flux, protein synthesis, and breakdown were creased amounts of exogenous amino acids as precursor might measured in 18 neonates during the 72 h immediately reverse this process and improve net prot~in synthesis. We therepostsurgery. The infants were all intravenously fed with a fore studied neonates receiving either 2.5 g or 4.0 g/kg/day of crystalline amino acid source (Vamin), glucose, and Intra-amino acids immediately postoperatively. lipid The infants were divided into two groups based on amino acid intake: either 2.3 S D 0.4 g or 3.9 S D 0.5 g/kg/ day. Nonprotein energy intakes were similar and averaged MATERIALS AND METHODS g1 kcal/kg/day-A (n = 11) retained 145 SD 11°Eighteen newborn infants were studied in the Neonatal Intenmg N/kg/day, group (n = 7, retained 315 SD 93 sive Care Unit of The Montreal Children's Hospital. The subjects mg N/kg/day ( p < 0-001)-There were differences seen were divided randomly into two groups on the basis of the level in flux, synthesis or breakdown. However, group B had of amino acid received. The clinical characteristics of the two significantly higher net protein synthesis rates (synthesis-diet are shown in ~~b l~ 1. ~1 1 infants received amino breakdown) (P < 0.01). The improved nitrogen utilization acid/glucose solutions with complete mineral and vitamin addiin group was achieved principally by a in tions similar to those we have previously reported (6). The amino endogenous protein breakdown. There were no differences acid source chosen was a crystalline amino acid mixture patbetween the two groups in urinary creatinine or 3-methyl-terned on egg albumin (vamin; vitrurn co., stockholm, swehistidine excretion. Since these two parameters reflect den). ~h~ amino acid glucose solutions were infused in combiskeletal muscle turnover the differences between groups in nation with a 10% soy bean lipid emulsion (~~~~~l i~i d vitrum nitrogen retention and turnover appear to be mediated Co.). The studies were approved by the Human Experimentation Committee of The Montreal Children's Hospital and informed, Abbreviation written consent was obtained from the parents. The infants were N, nitrogen randomly allocated to one of the two total parenteral nutrition regimes, either 2.5 g amino acid or 4 g amino acid/kg/day. Parenteral nutrition was started within 24 h postoperatively. Seventy-two-hour N balance, whole body protein turnover, and urine 3-methylhistidine excretion studies were canied out also It has been known for many years that surgery results in an starting within 24 h after surgery. Our balance techniques have increased urinary urea excretion and often a negative N balance. been previously described (7). All studies were performed with Several investigators using isotopically labeled amino acids have the neonate in a standard servocontrolled incubator. The surgical shown that this "catabolic" loss of nitrogen appeared to be a procedures the infants ...

Intravenous insulin decreases protein breakdown in infants on extracorporeal membrane oxygenation

“…Exogenous protein and caloric provisions through parenteral nutrition help to increase the synthesis of new protein but have little effect on the body's increased protein degradation. 4,5 Excessive caloric allotments may increase CO 2 production rates and thereby exacerbate the ventilatory burden of the child. 6 One study of ECMO neonates has shown a possible paradoxical increase in protein breakdown with the administration of increased carbohydrate regimens.…”

“…The increased allotment of protein in parenteral nutrition regimens serves to increase the synthesis of new protein but has little effect on elevated rates of protein breakdown. 4,5 Excessive carbohydrate provisions may worsen respiratory failure, 6 and a recent study of ECMO neonates has correlated increased carbohydrate intake with further increases in protein breakdown. 7 Therefore, investigation into an alternate means to alter protein metabolism in this cohort is clinically relevant.…”

Special Nutrition of the Surgical Neonate

“…Neonates have high protein turnover rates of about 6 to 12 g/kg per day, in contrast to adults (3.5 g/kg per day). 25,26 Fortunately, amino acid supplementation is shown to improve protein balance in children and surgical patients by promoting protein synthesis. 21 In neonates with cardiopulmonary failure requiring ECMO, the protein turnover rate is doubled compared with stable patients.…”

Enhancing Parenteral Nutrition Therapy for the Neonate

“…7,49 TrophAmine has also been associated with a decreased incidence and degree (level of serum direct bilirubin concentration) of PN-associated cholestasis. 50 The United States patent for TrophAmine expired in 2003, at which time Premasol (Baxter Healthcare Corp, Deerfield, IL) became available.…”