Gastroenterology & Nutrition | Parenteral Nutrition

TPN Constituents

• Glucose
• Amino acids
• Vitamins
  • Weight-based vitamin additives
  • Weight-based trace metal additives
• Intravenous lipid
• Osmolarity

Glucose

Glucose provides the major energy source of parenteral nutrition. Although any concentration of glucose may be selected, certain concentrations provide for easier calculations and sufficient calories when employed with common infusion rates. Glucose provides 4 kcal/gm. Strictly speaking, glucose in PN solutions is hydrated and thus provides only 3.4 kcal/gm of actual hydrated weight. To simplify calculations, however, glucose is commonly estimated to provide its actual 4 kcal/gm. Thus, a 10% glucose or dexstrose solution supplies 40 kcal/100ml or 0.4 kcal/ml. A 20% glucose solution provides 0.8 kcal/ml.

For PN solutions infused via peripheral vein, glucose concentration should not exceed 12.5%. Higher concentrations of glucose produce PN solutions of sufficiently high osmolarity that venous endothelium may be damaged, resulting in venous thrombosis and sclerosis.

For PN solutions infused via central vein, the high venous flow rate rapidly dissipates the high osmolarity. Although a 20% glucose concentration is standard, concentrations as high as 40% can be employed if required by fluid restrictions.

Amino Acids

Cyrstalline amino acids provide the building blocks for protein in PN. Standard commercially produced mixtures of essential and non-essential amino acids are available for compounding PN. Trophamine and Travasol are the two formulations most commonly employed at SLCH. Trophamine was designed for term and premature infants up to age 3 months. Trophamine infusion replicates the serum amino acid concentrations of a breast-fed infant. Travasol was designed for adults, but experience indicates that it meets the nutritional needs of children. Specialized formulations have been designed for patients with renal and hepatic disease, but evidence is lacking to demonstrate that these mixtures are more efficacious in those disorders.

Vitamins in PN

Weight-based Vitamin Additives

The exact amount of MVI-Ped added to a PN solution depends on the patient's weight.

Weight-based Trace Metal Additives

Intravenous Lipid

Intravenous lipid provides essential fatty acids and supplemental calories. Intralipid is the standard commercial form of intravenous lipid.

Intralipid Constituents

Osmolarity of Usual PN Solutions