During the last years the most widely used lipid emulsion for parenteral nutrition has been based on soybean oil. This first generation of lipid emulsions used in TPN contained w-6 series polyunsaturated long-chain fatty acids (LCT) from soy, maize, sunflower and safflower oil. LCT contain an excess of linoleic acid which, when metabolised, produce large quantities of arachidonic acid and its metabolites. Although the generally used doses seem safe (1-2 g/kg/day by continuous perfusion), alterations in pulmonary function in patients with acute adult respiratory distress syndrome have been described, as have alterations in platelet function, hepatic function and haemodynamics, which are attributed to the excess of said metabolites. However, the most important side effect of the LCT lipid infusions is its influence on the immune response. Experimental and clinical studies show that LCT can interfere with various stages of the immune response such as the production of antibodies, complement synthesis, granulocytic and lymphocytic activity and the reticuloendothelial system. Various hypotheses have been formulated to explain the modulator effect of the polyunsaturated fatty acids on immune function: changes in the permeability of the cellular membrane, modifications in the synthesis of eicosanoids and the presence of peroxides derived from the oxidation of polyunsaturated fatty acids.~In summary, although linoleic acid as a dietary essential fatty acid is important, its excessive intake is associated with undesirable immunological and inflammatory events. Thus it is recommended that soybean oil should be partly replaced by other lipids.~To avoid these side effects the second generation lipid emulsions were developed. These contain a combination of medium- and long-chain fatty acids (MCT/LCT) with lower w-6 fatty acid content. MCT/LCT lipid emulsions are safe and do not produce biochemical or metabolic alterations or gaseous exchange in patients with ARDS. MCT/LCT combinations seem to reduce the generation of eicosanoids and do not alter the immune response in in-vitro and experimental studies. The impact of these differences on the nosocomial infection and the clinical prognosis of the patients has not been studied sufficiently despite the fact that some studies show reduced mortality and morbidity using MCT/LCT emulsions when compared with the use of pure LCT emulsions. MCT/LCT emulsions are normally used in clinical practice on patients that have required parenteral nutrition for 20 years.~Recently, the clinical use in artificial nutrition of omega-3 series polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) present in many fish oils has been significant. EPA is a precursor to certain eicosanoid series that compensate the proinflammatory effects of the eicosanoids in arachidonic acid (omega-6 series). The objective is immunomodulation to attenuate the inflammatory response of patients without negatively impacting on the immune function. The use of enteral diets enriched with omega-3 series fatty acids (fish oil) in post-operation cancer patients showed a reduction in the number of days in hospital and infectious complications.~The use of fish oil or fat emulsions enriched with fish oil (omega-3) in parenteral nutrition has already been the subject of various studies: where modulation of the inflammatory response markers has been shown, reduces the stay in hospital and the need for mechanical ventilation in patients undergoing major abdominal surgery, reduces the stay in hospital in patients undergoing digestive surgery… So, w-3 lipids exhibit strong immunologic properties. They offer the possibility to counterbalance the negative effects of conventional w-6 fatty acids. Recent studies exhibit positive effects of intravenous use of fish oil on immunologic functions and clinical parameters in surgical and septic patients~The purpose of this study is to analyse the effect of two total parenteral nutrition diets with lipid emulsions of different compositions on the incidence of nosocomial infection in critical patients. One diet will contain an MCT/LCT emulsion concentrated to 20% (50:50 ratio) (w3:w6 is 1:7) and the other will comprise an MCT/LCT/fish oil emulsion (50:40:10 ratio) (w3:w6 is 1:2,7). The secondary objective of this study is to analyse mortality in hospital and up to 6 months after discharge.
This study aims to analyse the effect of two total parenteral nutrition diets with lipid emulsions of different compositions on the incidence of nosocomial infection in critical patients. One diet will contain an MCT/LCT emulsion concentrated to 20% (50:50 ratio) and the other will comprise an MCT/LCT/fish oil emulsion (50:40:10 ratio). The secondary objective of this study is to analyse mortality in hospital and up to 6 months of discharge.