Is total parenteral nutrition immunosuppressive?

Total parenteral nutrition (TPN) has been a major advance in patient therapeutics, particularly for critically ill patients. Incorrect administration of TPN, however, primarily through excessive use of energy, either as dextrose or lipid, is an underappreciated risk factor that leads to serious complications in nutritional support. Even a modest degree of uncontrolled hyperglycemia induced by TPN appears to increase the risk of infection, usually to a level that can nullify any potential benefit of feeding. Rapid and/or excessive lipid administration can interfere with the reticuloendothelial system function, which may also predispose the patient to serious infection. The goals of nutritional support in the critically ill are to provide ample protein at 1.5 to 2.0 g/kg body weight/day, while limiting calories to approximately the patient's resting energy expenditure, which optimally supports the metabolic response to injury. Repleting the critically ill, malnourished patient with calories in excess of the patient's energy expenditure is not effective, but rather increases the likelihood of an adverse outcome.