Omega-6 sparing effects of parenteral lipid emulsions—an updated systematic review and meta-analysis on clinical outcomes in critically ill patients

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 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. Trial registration PROSPERO international prospective database of systematic reviews (CRD42021259238). GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13054-022-03896-3.