Table 1.
Composition of a Typical Adult Formulation of Central Venous Parenteral Nutrition.*
| Component | Content |
|---|---|
| Total volume (liters/day) | 1–2 |
| Dextrose (%) | 10–25 |
| Amino acids (%)† | 3–8 |
| Lipids (%)‡ | 2.5–5.0 |
| Electrolytes (mmol/liter) | |
| Sodium | 40–150 |
| Potassium | 30–50 |
| Phosphorus | 10–30 |
| Magnesium | 5–10 |
| Calcium | 1.5–2.5 |
| Trace elements§ | |
| Vitamins¶ |
Electrolytes in parenteral nutrition are adjusted as indicated according to renal function, gastrointestinal losses, and other indicators to maintain serially measured serum levels within the normal range. In the presence of elevated blood levels, lower doses (or elimination) of specific electrolytes, as compared with the typical ranges that are listed, may be indicated until blood levels normalize. Higher dextrose levels typically increase requirements for potassium, magnesium, and phosphorus. The percentage of sodium and potassium salts as chloride is increased to correct metabolic alkalosis, and the percentage of salts as acetate is increased to correct metabolic acidosis. Regular insulin is added to parenteral nutrition as needed to achieve blood glucose goals, and separate intravenous insulin infusions are commonly required in patients with hyperglycemia.
Parenteral nutrition provides all nine essential amino acids and eight nonessential amino acids. Some guidelines recommend the routine addition of glutamine as a conditionally essential amino acid in critically ill adults. The dose of amino acids is adjusted as a function of the respective degrees of renal and hepatic dysfunction.
In the United States, only soybean oil–based fat emulsions are available. Intravenous lipid is provided as a 20% emulsion when given as a separate infusion over a period of 10 to 12 hours per day; when pharmacy parenteral-nutrition compounding machines are used, 20% or 30% lipid emulsions may be mixed with dextrose, amino acids, and micronutrients in the same infusion bag. In European and other countries, intravenous fish oil, mixtures of olive and soybean oils, medium-chain triglyceride–soybean oil mixtures, and combinations of these oils are approved for use in parenteral nutrition.
Trace elements that are added on a daily basis to parenteral nutrition are typically mixtures of chromium, copper, manganese, selenium, and zinc. Minerals can also be supplemented individually.
Vitamins that are added on a daily basis to parenteral nutrition are mixtures of vitamins A1, B1 (thiamine), B2 (riboflavin), B3 (niacinamide), B6 (pyridoxine), B12, C, D, and E; biotin; folate; and pantothenic acid. Vitamin K is added on an individual basis (e.g., in patients with cirrhosis). Specific vitamins can also be supplemented individually.