The Effect of Lipid Emulsions on Reticuloendothelial System Function in the Injured Animal

Abstract

Use of intravenous lipid emulsions in trauma and sepsis still remains controversial. In order to examine the impact lipid emulsions have on host defense against bacterial infection during total parenteral nutrition (TPN), 56 male Sprague-Dawley rats underwent jugular cannulation and were randomly divided into three groups, each receiving one of three TPN regimens. All regimens delivered approximately 250 kcal/kg X body weight/day, of which 12.5 g were as amino acids. Group 1 received 100% of the nonprotein calories as glucose (AA + G). Group 2 was given 50% of the nonprotein calories as a longchain triglyceride emulsion (100% LCT). Group 3 received 50% of nonprotein calories as a mixed lipid system, composed of medium- and long-chain triglycerides (75% MCT/25% LCT). After 24 hr on intravenous nutrition, all animals received bilateral septic femur fractures and were continued on TPN for 3 days. On the last day, the level of bacteremia and the in vivo response to an intravenous challenge of 59Fe-labeled Escherichia coli were examined. Three days following the septic injury, animals given MCT as part of their lipid calories were not bacteremic, whereas the other groups had greater than 10(2) cfu/ml of blood. Animals receiving TPN with MCT sequestered a greater percentage of exogenously administered bacteria in the liver and sequestered less in the lung compared to animals given 100% LCT (p less than 0.05). From these data, we conclude that parenteral nutrition formulas where LCT has been partially replaced with MCT may better support host bactericidal capacity than similar regimens comprised of LCT as the sole lipid source.

Medium- and long-chain triglycerides have different effects on the synthesis of tumor necrosis factor by human mononuclear cells in patients under total parenteral nutrition.

“…The effect of MCT on the immune system seems to be beneficial compared to LCT, especially in severely stressed and septic patients. MCT have been found to support host bactericidal capacity and improve reticuloendothelial system function better than LCTs [22]. They also seem to have no effect on T-helper/T-suppressor cell ratio, while LCT resulted in a significant decrease of this ratio [23].…”

Lipid Injectable Emulsions: Pharmacopeial and Safety Issues

“…On a Fmicroscopic_ scale, the clearance of large fat globules is greatly accelerated, and they most likely accumulate in RES organs where they can cause increased oxidative stress and possible organ injury. With respect to the role of the RES in the clearance of lipid injectable emulsions, previous animal data (43,44) and human data (45,46) would suggest that the liver is the principal organ injured by the infusion of unstable lipid injectable emulsions, as originally described by Geyer (40).…”

Effects of Long‐Chain Triglyceride Emulsions on Reticuloendothelial System Function in Humans

“…2). Presented in Figure 3 is the set of curves for patient 13 3 (Appendix) and the model shown in Figure 4. ance rates between those obtained before and after lipid emulsion administration.…”