Effects of three intravenous lipid emulsions on the survival and mononuclear phagocyte function of septic rats

The immunosuppressive effects of intravenous lipid emulsions are a matter of great concern and debate. In a rat model of gram-negative bacteremia, we assessed whether the use of three intravenous lipid emulsions with different triacylglycerol compositions could influence mortality, bacterial clearance, and prostaglandin E 2 (PGE 2) levels and compared these groups with groups of orally fed rats and rats that received a small amount of calories in form of glucose without enteral feeding (starvation). Rats were assigned to one of five groups: group 1 (control, n = 15) received rodent chow ad libitum and saline infusion; group 2 (starvation group, n = 12) had no access to chow and received an infusion of 5% glucose; group 3 ( n = 17) received total parenteral nutrition (TPN) with long-chain triacylglycerols; group 4 ( n = 12) received TPN with medium- and long-chain triacylglycerols; and group 5 ( n = 15) received TPN with its emulsion based on olive oil. Animals received isonitrogenous and isocaloric TPN. After 2 d of TPN, a dose of 10 8 colony-forming units of Escherichia coli was introduced via the venous catheter; 2 d later the animals were killed. Blood, spleen, liver, and lungs were cultured. Circulating levels of PGE 2 were measured. Bacterial growth in the liver and lungs were significantly higher in groups 3 and 4 than in group 1, with no differences among the other groups. Rates of bacteremia were significantly higher in groups 3 and 4 than in group 1, with no differences among the other groups. Plasma levels of PGE 2 did not differ, and mortality was unaffected. Bacterial clearance clearly was preserved in orally fed, control rats when compared with rats on TPN with long-chain triacylglycerols or medium- plus long-chain triacylglycerols. However, the use of a lipid emulsion enriched intravenously with oleic acid was a valid way of reducing this disturbance, although plasma levels of PGE 2 and survival were not modified.