Immunonutrition in critically ill patients: a systematic review and analysis of the literature

Background: The role of immuno-modulating diets (IMDs) in critically ill patients is controversial. Objective: The goal of this meta-analysis was to determine the impact of IMD's on hospital mortality, nosocomial infections and length of stay (LOS) in critically ill patients. Outcome was stratified according to type of IMD and patient setting. Data sources: MEDLINE, Embase, Cochrane Register of Controlled Trials. Study selection: RCT's that compared the outcome of critically ill patients randomized to an IMD or a control diet. Data synthesis: Twenty-four studies (with a total of 3013 patients) were included in the meta-analysis; 12 studies included ICU patients, 5 burn patients and 7 trauma patients. Four of the studies used formulas supplemented with arginine, two with arginine and glutamine, nine with arginine and fish oil (FO), two with arginine, glutamine and FO, six with glutamine alone and three studies used a formula supplemented with FO alone. Overall IMD's had no effect on mortality or LOS, but reduced the number of infections (OR 0.63; 95% CI 0.47-0.86, P = 0.004, I-2 = 49%). Mortality, infections and LOS were significantly lower only in the ICU patients receiving the FO IMD (OR 0.42, 95% CI 0.26-0.68; OR 0.45, 95% CI 0.25-0.79 and WMD -6.28 days, 95% CI -9.92 to -2.64, respectively). Conclusion: An IMD supplemented with FO improved the outcome of medical ICU patients (with SIRS/sepsis/ARDS). IMDs supplemented with arginine with/without additional glutamine or FO do not appear to offer an advantage over standard enteral formulas in ICU, trauma and burn patients.