Glutamine and antioxidants: status of their use in critical illness

Many studies in critically ill patients have addressed enteral or parenteral supplementation of glutamine and antioxidants to counteract assumed deficiencies and induce immune-modulating effects to reduce infections and improve outcome. Older studies showed marked reductions in mortality, infectious morbidity and length of stay. Recent studies no longer show beneficial effects and in contrast even demonstrated increased mortality. This opiniating review focuses on the latest information and the consequences for the use of glutamine and antioxidants in critically ill patients.

Positive effects in systematic reviews and meta-analyses are based on results from older, smaller and mainly single-centre studies. New information has challenged the conditional deficiency hypothesis concerning glutamine in critically ill patients. The recent REDOXS and MetaPlus trials studying the effects of glutamine, selenium and other antioxidants have shown no benefits and increased mortality.

Given that the first dictum in medicine is to do no harm, we cannot be confident that immune-modulating nutrient supplementation with glutamine and antioxidants is effective and well tolerated for critically ill patients. Until more data are available, it is probably better not to routinely administer glutamine and antioxidants in nonphysiological doses to mechanically ventilated critically ill patients.