The impact of antioxidant supplementation on clinical outcomes in the critically ill: A metaanalysis

Background. Critical illness is associated with increased oxidative stress that can influence outcome. Many studies have investigated the effects of exogenous antioxidant supplementation, without showing significance owing to the small patient populations.Methodology. A systematic review and meta-analysis of the English literature was performed to determine the effect of antioxidant micronutrient supplementation on clinically important outcomes in the critically ill. Pubmed, Google Scholar and Science Direct electronic databases were searched for papers published between January 1990 and June 2010.Selection criteria. Randomised controlled trials were selected for inclusion if they investigated the effects of antioxidant supplementation in the critically ill and reported on clinically significant endpoints.Data collection and analysis. The data were analysed using a random effects model in Comprehensive Meta-analysis Version 2 (Biostat, USA) to obtain the odds ratio (OR) with a 95% confidence interval (CI) and statistical significance of p<0.05.Results. Twelve studies met the inclusion criteria. Selenium supplementation was associated with a trend towards decreased mortality (OR=0.717, p=0.106, CI 0.48 - 1.07). Mixed antioxidant supplementation was associated with reduced hospital length of stay (OR= 0.710, p=0.002, CI 0.57 - 0.83), reduced infectious complications (OR=0.494, p=0.024, CI 0.28 - 0.98) and reduced mechanical ventilation (OR=0.259, p=0.023, CI 0.08 - 0.83).Conclusion. A combination of antioxidant micronutrients might be associated with improved clinical outcome in the critically ill