Parenteral Nutrition
Indications and formulation
Parenteral nutrition (PN) is for patients who cannot meet needs enterally. It contains dextrose, amino acids, electrolytes, vitamins, trace elements, and often lipids as a separate emulsion or in a total nutrient admixture. Peripheral PN is limited to roughly 10% dextrose and about 900 mOsm/L; higher osmolarity requires a central catheter.
Safety during administration
Use a dedicated line whenever possible, or a dedicated lumen in a multi-lumen catheter; never interrupt PN for routine medication administration or blood draws if a dedicated lumen exists. Use an in-line filter - 1.2 micron for lipid-containing admixtures, 0.22 micron for lipid-free formulations. Hang times are limited (typically 24 hours for a compounded bag, and lipid emulsions per manufacturer/policy), and the bag and tubing are changed on schedule to limit contamination.
Monitoring
Monitor glucose, electrolytes, renal function, triglycerides, and weight. Rapid initiation in a malnourished patient risks refeeding syndrome - hypophosphatemia, hypokalemia, hypomagnesemia, fluid shifts, and cardiac or respiratory failure - so start at a lower rate and advance gradually. Abrupt discontinuation of high-rate PN can cause hypoglycemia; taper or overlay dextrose per policy, and monitor glucose after stopping.
Trap: questions that treat PN as a fluid resuscitation route or that permit piggybacking medications into the PN line. Neither is acceptable.
Worked example: A patient on PN for 24 hours develops a blood glucose of 310 mg/dL. First actions: check the infusion rate against the order, verify pump programming, and notify the provider - do not simply adjust the bag.
Rule of thumb: if the osmolarity exceeds what a peripheral vein can tolerate, the patient needs a central catheter, not a slower rate.