PN delivers a complete nutritional regimen directly into the bloodstream in the form of crystalline amino acids, dextrose, triglyceride emulsions, minerals (calcium, phosphate, magnesium, and zinc), electrolytes, and micronutrients. Because of its high osmolarity (>1200 mOsm/L) and often large volume, PN is infused into a central vein in adults. Ready-to-use PN admixtures typically containing 4-7% hydrous amino acids and 20-25% dextrose (with or without electrolytes) are available in two-chamber (amino acids and dextrose) or three-chamber (amino acids, dextrose, and lipid) bags that are intermixed, and vitamins, trace minerals, and additional electrolytes added just prior to infusion. Although convenient and cost-effective, these products have fixed nutrient composition and thus are dosed according to the volume required to meet calorie requirements.

The risks of parenteral therapy include mechanical complications from insertion of the infusion catheter, catheter sepsis, fluid overload, hyperglycemia, electrolyte disorders, acid-base and electrolyte imbalance, cholestasis, metabolic bone disease, and micronutrient deficiencies.

The following parameters should be monitored in all pts receiving supplemental nutrition, whether enteral or parenteral:

• Fluid balance (weight, intake vs. output)
• Glucose, electrolytes, BUN (daily until stable, then 2× per week)
• Serum creatinine, albumin, phosphorus, calcium, magnesium, Hb/Hct, WBC (baseline, then 2× per week)
• International normalized ratio (INR) (baseline, then weekly)
• Micronutrient tests as indicated