Quirin Notz, Zheng-Yii Lee, Johannes Menger, Gunnar Elke, Aileen Hill, Peter Kranke, Daniel Roeder, Christopher Lotz, Patrick Meybohm, Daren K. Heyland, Christian Stoppe

• Background Parenteral lipid emulsions in critical care are traditionally based on soybean oil (SO) and rich in pro-inflammatory omega-6 fatty acids (FAs). Parenteral nutrition (PN) strategies with the aim of reducing omega-6 FAs may potentially decrease the morbidity and mortality in critically ill patients. Methods A systematic search of MEDLINE, EMBASE, CINAHL and CENTRAL was conducted to identify all randomized controlled trials in critically ill patients published from inception to June 2021, which investigated clinical omega-6 sparingBackground Parenteral lipid emulsions in critical care are traditionally based on soybean oil (SO) and rich in pro-inflammatory omega-6 fatty acids (FAs). Parenteral nutrition (PN) strategies with the aim of reducing omega-6 FAs may potentially decrease the morbidity and mortality in critically ill patients. Methods A systematic search of MEDLINE, EMBASE, CINAHL and CENTRAL was conducted to identify all randomized controlled trials in critically ill patients published from inception to June 2021, which investigated clinical omega-6 sparing effects. Two independent reviewers extracted bias risk, treatment details, patient characteristics and clinical outcomes. Random effect meta-analysis was performed. Results 1054 studies were identified in our electronic search, 136 trials were assessed for eligibility and 26 trials with 1733 critically ill patients were included. The median methodologic score was 9 out of 14 points (95% confidence interval [CI] 7, 10). Omega-6 FA sparing PN in comparison with traditional lipid emulsions did not decrease overall mortality (20 studies; risk ratio [RR] 0.91; 95% CI 0.76, 1.10; p = 0.34) but hospital length of stay was substantially reduced (6 studies; weighted mean difference [WMD] − 6.88; 95% CI − 11.27, − 2.49; p = 0.002). Among the different lipid emulsions, fish oil (FO) containing PN reduced the length of intensive care (8 studies; WMD − 3.53; 95% CI − 6.16, − 0.90; p = 0.009) and rate of infectious complications (4 studies; RR 0.65; 95% CI 0.44, 0.95; p = 0.03). When FO was administered as a stand-alone medication outside PN, potential mortality benefits were observed compared to standard care. Conclusion Overall, these findings highlight distinctive omega-6 sparing effects attributed to PN. Among the different lipid emulsions, FO in combination with PN or as a stand-alone treatment may have the greatest clinical impact.…