Infusion time for fish oil-containing parenteral emulsions in surgery: A study on ω-3 fatty acid dynamics in rats.

OBJECTIVES: The aim of this study was to contribute to the design of specialized parenteral nutrition protocols in surgery by evaluating the dynamics of polyunsaturated fatty acid (PUFA) concentrations in different body pools after the infusion of fish oil-containing lipid emulsion (FOLE) in rats that had undergone surgical central venous catheterization (CVC). METHODS: After 5-d adaptation in metabolic cages, 78 male Lewis rats (300-450 g) fed a standard diet were sacrificed (baseline control) or had only CVC (surgical control) or also received a 72-h infusion of a parenteral lipid emulsion with or without fish oil. The catheterized animals were sacrificed 0 (T0), 2 (T2), 6 (T6), and 12 h (T12) after the infusion ended. Gas chromatography was used to determine the concentrations of eicosapentaenoic (EPA), docosahexaenoic (DHA), and arachidonic (ARA) acids and the ω-3 to ω-6 ratio in plasma, liver, and blood leukocytes. Kruskal-Wallis and Wilcoxon tests were applied to plasma and liver data and descriptive analysis to leukocyte data. RESULTS: Plasma, liver, and leukocytes exhibited almost undetectable EPA and DHA and detectable ARA concentrations at baseline. Immediately after FOLE infusion (T0), these PUFAs changed in all pools, resulting in a higher ratio of ω-3 to ω-6 compared with rats with no FOLE infusion (P < 0.05). All these changes decreased over time, with residual effects remaining until T6 in plasma, T12 in liver, and only until T2 in leukocytes. CONCLUSION: Data from this study suggest that ω-3 PUFAs are cleared early after the end of FOLE infusion, mainly in leukocytes. This should be considered when FOLEs are applied for immunomodulatory purposes in surgery.

Is There an Advantage in Enriching Parenteral Lipid Emulsions Containing Fatty Acids From Fish Oil With Medium-Chain Triglycerides? A Study on Body Pool Concentrations of ω-3 Fatty Acids in Lewis Rats.

BACKGROUND: The addition of medium-chain triglycerides (MCTs) into parenteral lipid emulsions rich in fatty acids from fish oil (FOLEs) has been shown to improve their clearance and extrahepatic uptake. We assessed whether this effect could favor the leukocyte uptake of ω-3 polyunsaturated fatty acids (PUFAs) for immunomodulatory purposes METHODS: Following 5-day adaptation in metabolic cages, 42 male Lewis rats fed with AIN-93M chow were killed (baseline control group [BC]) or submitted to central venous catheterization and distributed into (1) surgical control group without parenteral infusion (chow group), (2) test emulsion (MCT/LCT/FO) group with the parenteral infusion of a FOLE containing 40% MCT, and (3) control emulsion group (LCT/FO) with the parenteral infusion of an FOLE without MCT. The 2 FOLEs had similar ω-3 PUFA contents and ω-6/ω-3 PUFA ratios and were infused during 48 and 72 hours. Concentrations of ω-3 and ω-6 PUFAs in plasma, liver, and blood mononuclear and polymorphonuclear leukocytes were assessed by gas chromatography RESULTS: In both FOLE groups, leukocyte concentrations of ω-3 PUFAs peaked after 48 hours' infusion (vs BC). At this time point, plasma concentrations of ω-3 PUFAs were higher in MCT/LCT/FO group than in LCT/FO group and the opposite was found in the liver (P<.05), but no differences in PUFA concentrations were observed between these groups in leukocytes (P>.05) CONCLUSION: The ω-3 PUFAs provided by FOLEs rich in MCT were less incorporated by liver and remained more available for extrahepatic cell delivery, but this did not result in a clear benefit in increasing their incorporation by peripheral leukocytes.

A new swivel model for parenteral and enteral infusion in rats.

BACKGROUND: In experimentation with rats submitted to enteral and parenteral infusions for medium to long periods it is necessary to use swivels. With the objective of developing a new biocompatible, safe, efficient, and low cost swivel, the medical and engineering teams of the University of São Paulo joined forces. MATERIAL AND METHODS: After defining the characteristics and criteria for the mechanical design, the new swivel was developed and bench tested for flow, rotation and sealing. Later it was evaluated on rats, after catheterization of jugular vein and stomach (by gastrostomy) for infusion of different solutions at certain concentrations and infusion rates (mean 6.73 days of infusion). RESULTS: The new swivel consisted of two sections of common plastic syringes for injection, together with the rubber seals, a plunger, and a hypodermic needle. The syringe with a slightly smaller diameter rotates inside the larger diameter syringe interconnected with a needle sealed by their respective rubber rings. The bench and animal tests did not reveal any functional defects. There were no blockages or leaks in the swivel and it was reused three times without losing its mechanical properties, after being hygienized and sterilized with ethylene oxide. The cost of producing this swivel is estimated to be no more than $3 US. CONCLUSION: The cooperation between the departments of medical research and mechanical engineering enabled the development of a swivel that is simple and inexpensive to make, yet fully meets the needs of parenteral and enteral infusion in rats. The authors present detailed instructions for the construction of this new swivel.