Certain nutrients have been associated with improved outcomes. Surgery and anesthesia are well-recognized inducers of inflammation, produc-ing changes in local (near the wound) and plasma concentrations of neurohormones, cytokines, and other mediators. Many investigators have hypoth-esized that adverse neurohormonal and inflam-matory responses to surgery and anesthesia can be ameliorated through specific diets. Several clini-cal trials (and a recent meta-analysis) suggest that the addition of “immunomodulating” nutrients (specifically arginine and “fish” oil) to EN may reduce the risk of infection and reduce the length of hospital stay in high-risk surgical patients. Simi-larly, current guidelines for perioperative PN also advocate the inclusion of n-3 fatty acids. There is some evidence that inclusion of long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), long-chain monounsaturated fatty acids (found in olive oil), or medium-chain fatty acids may be preferable to the use of solutions (such as soy bean-derived lipids) that are rich in longer chain n-6 PUFA. However, such solutions (although widely available outside of the United States) are not approved for use in the United States.
In the past, it was customary to individualize TPN solutions for each patient. Currently, there is little evidence that this is necessary, except in patients who cannot handle a sodium load (eg, those with severe heart failure). Adjustments may also be made in patients requiring renal replacement ther-apy; however, in most cases, this is not necessary. Similarly, except in patients who are already suffer-ing from hepatic encephalopathy, most patients with liver disease can safely receive standard amino acid solutions. Thus, most patients receiving EN and PN can be safely managed with standardized nutritional formulations. Both EN and PN standardized for-mulations are available in ready-to-use formats that decrease preparation times and reduce contamina-tion risks during formulation.