Initiating parenteral nutrition

Step	Calculations and considerations
Assess medical status and determine nutrition goals	Does the patient meet indications for PN? Is anticipated duration of PN >2 weeks? Will PN be used to provide full or partial nutritional requirements?
Assess venous access	Does the patient require central venous access to meet nutritional needs (as for most patients requiring PN)? If central venous access is necessary, consider type of catheter and number of lumens needed to accommodate PN and any other therapies. Verify that catheter is centrally placed prior to starting PN using radiography.
Determine weight	Consider which weight measure will be used to determine the patient's nutritional targets (eg, actual body weight, dry weight, ideal body weight, usual body weight, or an adjusted body weight).
Calculate fluid requirements/volume of PN to be provided	Review patient's fluid status, intake/output balance, gastrointestinal losses, etc. Use Holliday-Segar formula to estimate initial fluid requirements and then adjust as needed based on the patient's individual needs. The estimated fluid requirement determines the approximate total volume available for PN. Most patients can tolerate fluid administration at 30 to 50% above maintenance needs.
Assess total energy requirements and approximate targets for carbohydrate, fat, and protein intake	Estimate energy (caloric) needs for PN at approximately 80% of enteral requirements. Provide 40 to 60% of calories from dextrose, 20 to 50% of calories from fat, and 10 to 20% of calories from protein/amino acid.
Assess protein requirements	Assess whether the patient has increased protein needs (eg, due to gastrointestinal protein losses, wound healing, etc). Calculate total grams of protein in g/kg, g/day, and g/L.
Calculate grams of fat or mL of lipid	20% lipid emulsion provides 20 g fat per 100 mL solution, or 2 kcal/mL. Energy from fat (kcal/day) ÷ 2 kcal/mL = mL/day of lipid.
Calculate grams of dextrose	Energy to be provided from dextrose ÷ 3.4 kcal/g of dextrose = g dextrose.
Calculate GIR	GIR (mg/kg/min) = g dextrose/kg × 1000 mg/g ÷ minutes of infusion. Minutes of infusion = 1440 minutes if given for 24 hours.
Assess electrolyte requirements	Determine mEq per kilogram and total mEq/L. Refer to table describing electrolyte requirements.
Assess vitamin/mineral and trace element requirements	Check with pharmacist to see which products are available and what concentrations are compatible.
Calculate osmolality of solution (if intravenous access is peripheral)	mOsm/L = (g amino acid/L × 10) + (g dextrose × 5) + [(mEq Na + K + Ca/L) × 2]. Solution must be <900 mOsm/L for peripheral administration.
Determine rate of infusion	Total volume to be infused in mL ÷ hours of infusion time = rate mL/hour. If infusion is to be cycled (ie, given over <24 hours), refer to UpToDate content on cycling PN in children.

PN: parenteral nutrition; GIR: glucose infusion rate; mEq: milliequivalents; mOsm: milliosmoles.

Modified with permission from: Pediatric Parenteral Nutrition, Baker RD, Baker SS, Davis AM (Eds), Aspen Publishers, Inc, Gaithersburg 2001. Copyright © 2001 Robert D Baker, MD, PhD; Susan S Baker, MD, PhD; and Anne M Davis, RD, CNSD.

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Initiating parenteral nutrition