The complexity of prescribing intravenous lipid emulsions

Intravenous lipid emulsions (LEs) are relevant for patients receiving parenteral nutrition because they prevent the depletion of essential fatty acids (FAs) and, as a highly dense energy source, enable the reduction of glucose provision, thereby decreasing the risks of hyperglycemia and hepatic impairment. The prescription of LEs is complex, due mainly to their distinct FA components, which may alter the immune response in different ways and distinctly influence inflammation, oxidative stress and blood coagulation according to their biochemical properties. In addition, an excess of other LE components, such as phospholipids and phytosterols, may be associated with hepatic steatosis and dysfunction. These associations do not represent direct risks or obstacles to LE use in metabolically stable patients but can render the choice of the best LE for hypermetabolic patients difficult. The infusion of LEs according to the available guidelines provides more benefit than harm and should be part of exclusive parenteral nutrition regimens or complement enteral nutrition when appropriate. The patient's metabolic profile should guide the type of FA and amount of lipids that are provided. For critically ill hypermetabolic patients, growing evidence indicates that standard LEs based solely on soybean oil should be avoided in favor of new LEs containing medium-chain triglycerides, olive oil, or fish oil to decrease the provision of potentially oxidative, inflammatory/immunosuppressive, and prothrombotic n-6 FAs. In addition, as sources of eicosapentaenoic and docosahexaenoic acids, LEs containing fish oil may be important for critically ill patients because they allow better modulation of the immune response and likely reduce the length of intensive care unity stay. However, current evidence precludes the recommendation of a specific LE for clinical use in this patient population.