Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support

Safe practice recommendations for prescribing PN solutions – Should be prescribed in total amount

per day (e.g., dextrose 200 g/day, “brand X” amino acids 150 g/day, “brand Y” lipids 50 g/day,

fluid volume 1800 mL/day, sodium chloride 60 mEq/day, potassium acetate 80 mEq/day), NOT by

concentrations (e.g., 20% dextrose, 8% amino acids) or by compounding techniques (e.g., 500 mL

of 50% dextrose in water plus 500 mL of 10% amino acids). Because different brands of amino

acids and ILEs contain different ingredients and have different compatibility and stability profiles,

the brand name of these ingredients should also be noted in the PN prescription and label (JPEN J

Parenter Enteral Nutr 2014;8:296-333).

Glucose requirements

Obligatory requirements for CNS, renal medulla, bone marrow, leukocytes, etc.: Around 130

g/day

ii.

Surgical wound healing requires about 80–150 g/day (based on atrioventricular differences

and blood flow from a burned limb)

iii.

Caloric contribution of glucose: 3.4 kcal/g (as opposed to carbohydrate 4 kcal/g)

iv.

Mean glucose oxidation rate in critically ill patients is around 5 mg/kg/day (or about 25 kcal/

kg/day as glucose). In general, most clinicians avoid exceeding this glucose intake in the acute

phase of critical illness.

SO-ILE products have historically been the main source of ILE in the United States. ILE may

be given separately from the PN admixture or as part of the PN solution. When given separately

from the dextrose/amino acid formulation, the maximum allowable hang time according to the

FDA is 12 hours. Previous recommendations were to consider withholding SO-ILE during the

first week following initiation of PN in critically ill patients (or limiting to 100 g/week during

this time) (JPEN J Parenter Enteral Nutr 2016;40:159-211). This is due to the high omega-6

fatty acid (more pro-inflammatory) content of SO-ILE and limited evidence suggesting worse

outcomes for ICU patients who receive ILE early in their ICU course. However, this evidence

is very limited with several notable design flaws that likely confounded study outcomes (J

Trauma 1997;43:52-60). Several ILE products are now commercially available in the United

States, but owing to the limitations of available evidence, the 2022 ASPEN guidelines for

nutrition support in critically ill patients do not make a recommendation for one ILE product

over another. SMOFlipid consists of 30% soybean oil, 30% medium-chain triglycerides, 25%

olive oil (OO), and 15% fish oil (FO). It may be more advantageous than 100% SO-ILE because

of a decreased propensity to cause elevated serum triglyceride concentrations and decreased

exposure to SO without compromising caloric intake. Additionally, limited data analyses

suggest decreased infections in ICU patients and decreased liver function tests with prolonged

PN use. Daily administration is usually required to meet essential fatty acid requirements (met

only by the SO component). A 100% FO-ILE product is also FDA-approved for use in pediatric

patients in the United States, and an OO,SO-ILE product (80% OO, 20% SO) is also approved

for use in adults. All clinical and practical considerations listed previously should be evaluated

when choosing which ILE product to use for critically ill patients.

ii.

Caloric contribution of ILE 10% = 1.1 kcal/mL (11 kcal/g); 20% = 2 kcal/mL (10 kcal/g);

30% = 3 kcal/mL (10 kcal/g)

iii.

Dosage: About 100–150 g of soybean oil weekly (or 1–1.5 g/kg weekly) is enough to prevent

essential fatty acid deficiency (EFAD). The FDA states a maximum upper limit of 2.5 g/kg/day

in adults, though SO-ILE provision in critically ill patients should generally be maintained at

less than 1 g/kg/day. The recommended dosing for SMOFlipid is 1–2 g/kg/day, and OO,SO-

ILE formulations can be provided at doses of 1–1.5 g/kg/day. However, EFAD requirements

can be met with SMOFlipid doses as low as 12.6% and OO,SO-ILE formulations as low as

12-25% of total calories. (Nutr Clin Pract 2020;35:769-82).