Selenium Supplementation in the Critically Ill

Abstract

Selenium (Se) is an essential trace element with antioxidant, immunological, and anti-inflammatory properties, which are attributed to its presence in selenoproteins, as the 21st amino acid selenocysteine. These selenoenzymes are involved in redox signaling, antioxidant defense, thyroid hormone metabolism, and immune responses. Dietary intakes differ considerably between geographical regions, due to variability of the Se food content, leading to differences in dietary reference intakes and toxicity cautions. Critical illness with systemic inflammatory response syndrome (SIRS) is characterized by Se depletion with high morbidity and mortality. Se status correlates well with clinical outcome in SIRS and may be useful as an early predictor of survival. Several investigators have evaluated the benefits of Se supplementation for the critically ill, either as monotherapy or in an antioxidant micronutrient combination. Pharmaconutrition, with high-dose Se (from 500-1600 µg/d) involving an initial loading bolus, followed by continuous infusion, appears to be safe and efficacious, with evidence that it can improve clinical outcome by reducing illness severity, infectious complications, and decreasing mortality in the intensive care unit (ICU). We now have a clearer understanding of the pharmacokinetics of the initial and transient pro-oxidant effect of an intravenous bolus of selenite and the antioxidant effect of continuous infusion. Better biomarkers to ascertain optimum Se requirements for individual patients are now needed, and clinical practice guidelines need improvement. Nevertheless, sufficient evidence is available to consider initiating high-dose intravenous Se therapy routinely in critically ill SIRS patients, immediately on admission to the ICU.

Increased plasma selenium is associated with better outcomes in children with systemic inflammation

“…It should be emphasized, however, that plasma selenium concentrations do not ultimately represent the amounts of tissue selenium, as there is only 0.2 mg selenium in plasma for 20 to 40 mg in the whole body [26]. Moreover, plasma selenium concentrations decrease during the acute-phase response, likely due to endothelial injury leading to transcapillary escape of selenium proteins [9,27]. Although reflecting short-term selenium status and responding rapidly to selenium supplementation, it may not accurately reflect tissue selenium content or seleno-enzyme activity in the presence of systemic inflammation [25,27].…”

“…In intensive care, the growing interest in studying the effect of selenium supplementation in critically ill adults stems from the evidence of the association between its deficiency and poor clinical outcome [7,8] and also from the beneficial role of selenium in immune and antioxidant systems. The reduction in circulating and tissue concentrations of antioxidant enzymes observed in these patients has been associated with disease severity, progression of organ dysfunction and mortality [7][8][9], which have favored its supplementation in certain specific situations [9][10][11].…”

A Randomized Trial of Glutamine and Antioxidants in Critically Ill Patients

“…The laboratory substudy of North American patients did not reveal the selenium deficiency consistently observed in European and South American trials of selenium status in critically ill and healthy persons. 16,17 These differences may reflect the considerable depletion of selenium in soil observed in parts of Europe but not throughout North America. 18 We may have prescribed an insufficient dose of selenium or used an ineffective dosing schedule, since a higher-thannormal level of selenium in the blood may be associated with the best outcome 19 and an initial bolus of selenium might have been more effective than the continuous administration we used.…”

Can dietary selenium intake increase the risk of toxicity in healthy children?

“…The essential trace element selenium has antioxidant, anti-inflammatory and immunomodulatory effects 1 . Recent research has focussed on chronic dietary intakes and the potential role of selenium as a protective agent against some cancers, cardiac disease, fertility disorders, and cognitive decline 2 .…”