Parenteral Nutrition

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Where possible, the enteral route should be used in preference to parenteral nutrition
In general, the risk outweighs the benefit if PN is provided for <5 days

Anticipation of undernutrition (<50% metabolic requirements achieved enterally for >7 days)
Severely undernourished patients who will be unable to meet oral requirements prior to surgery, chemotherapy or radiotherapy
Patients with gastrointestinal disorders requiring gastrointestinal rest e.g. ulcerative colitis
Patients with gastrointestinal disorders precluding normal absorption e.g. short gut syndrome
Post-operative patients in whom enteral feeding is not possible (e.g. bowel obstruction) or has failed after 5 days

Overall, there isn't a robust evidence bsae suggesting PN is superior to EN for all-comers, and so recommendations for its use are typically for when EN has failed or isn't possible

The daily requirements for any given patient will vary, but the estimated requirements can be found on the page on nutritional support
The goal of PN is to match these requirements as closely as possible
Total parenteral nutrition supplies all daily nutritional requirements to the patient, although other sources of calories may need to be taken into account e.g. propofol infusions, citrate

Nutritional element	Notes
Total energy	Typically 25-30kcal/kg
Carbohydrate	As glucose, with concentration ranging from 40% to 70% Max. infusion rate 5mg/kg/min
Protein	All essential amino acids
Lipid	As triglycerides, about 40% non-protein calories Max. 1.5kg/day
Electrolytes
Vitamins

Increased demand in critical illness may outstrip synthetic capabilities
These are arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine
Unclear whether supplementation of these conditional amino acids provides benefit
Data from some small trials suggests benefit to supplementing glutamine and arginine, but others demonstrate no effect or even harm
Routine supplementation is not recommended

Vitamins and trace elements are not necessarily contained in PN solutions due to instability
They require separate supplementation, including:

Mg²⁺, Ca²⁺, Cu²⁺, Zn, Na⁺, K⁺, Cl^-, Se, Cr, Co, Mn, Fl, I, Mo, V & acetate
Vitamins A, C, D, E, K, folate and the B vitamins thiamine, niacin and pyridoxine

Evidence does not support administration of doses beyond minimum requirements (SIGNET, VITdAL-ICU) as it may be harmful

Administer through a dedicated port of a central venous catheter including PICC, Hickman and Portacath lines

Unless contraindicated, 10 - 30ml/hr of enteral feed should be administered to reduce villous atrophy and maintain gastrointestinal integrity

Related to nutrition

Related to central venous catheters

The incidence of bacterial or fungal infection is higher in patients who receive PN vs. those who don't