Selenium and glutamine supplements: where are we heading? A critical care perspective

Efficacy of selenium on patients undergoing cardiac surgery: a meta-analysis of randomized controlled trials

INTRODUCTION

Postoperative complications pose significant challenges in cardiac surgery and with the evolution of selenium as a potential anti-inflammatory agent, some studies reported its inefficiency. Thus, we conducted our meta-analysis to evaluate the impact of selenium supplementation on cardiac surgery patients.

METHODS

Different databases such as PubMed, Embase, and Cochrane Library from inception till January 2024 were searched identifying a total of seven randomized-controlled trials involving selenium supplementation after cardiac surgery. Risk ratio (RR) and Mean difference (MD) were calculated with a 95% confidence interval (CI).

RESULTS

The selenium intervention significantly raised the incidence of Acute Kidney injury (RR 0.76; 95% CI: 0.59, 0.98; P = 0.04) while significantly reducing the duration of hospital stay (MD -1.33; 95% CI: -2.51, -0.16; P = 0.03) and postoperative CRP levels (SMD -0.18; 95% CI: -0.34, -0.02; P = 0.03). The effect of selenium intervention on days spent in ICU (MD -0.01; 95% CI: -0.28, 0.25; P = 0.92), mortality (RR 1.07; 95% CI: 0.84, 1.37; P = 0.57) and incidence of hospital acquired infections (RR 0.98; 95% CI: 0.76, 1.26; P = 0.88) is insignificant.

CONCLUSION

Selenium supplementation did not significantly reduce major postoperative complications in cardiac surgery patients. However, its ability to modulate inflammation, as reflected in decreased C-reactive protein levels, highlights its potential role in managing the inflammatory response. Future investigations should focus on optimized selenium supplementation strategies in conjunction with other antioxidants to enhance its benefits.

Efficacy and safety of selenium or vitamin E administration alone or in combination in ICU patients: A systematic review and meta-analysis

BACKGROUND

Micronutrient administration that contributes to antioxidant defense has been extensively studied in critically ill patients, but consensus remains elusive. Selenium and vitamin E are two important micronutrients that have synergistic antioxidant effects. This meta-analysis aimed to assess the effect of selenium or vitamin E administration alone and the combination of both on clinical outcomes in patients hospitalized in the ICU.

METHODS

After electronic searches on PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), SinoMed, VIP database and Wanfang data, initially 1767 papers were found, and 30 interventional studies were included in this analysis. We assessed the risk-difference between treatment and control (standard treatment) groups by pooling available data on length of stay (ICU length of stay and hospital length of stay), mortality (ICU mortality, hospital mortality, 28-day mortality, 6-month mortality and all-cause mortality), duration of mechanical ventilation, adverse events and new infections.

RESULTS

By analyzing the included studies, we found no significant effect of selenium administration alone on mortality, mechanical ventilation duration, or adverse events in ICU patients. However, after excluding studies with high heterogeneity, the meta-analysis showed that selenium alone reduced the length of hospital stay (MD: -1.38; 95% CI: -2.52, -0.23; I-square: 0%). Vitamin E administration alone had no significant effect on mortality, duration of mechanical ventilation, or adverse events in ICU patients. However, after excluding studies with high heterogeneity, the meta-analysis showed that vitamin E alone could reduce the length of ICU stay (MD: -1.27; 95% CI: -1.86, -0.67; I-square: 16%). Combined administration of selenium and vitamin E had no significant effect on primary outcomes in ICU patients.

CONCLUSIONS

Selenium administration alone may shorten the length of hospital stay, while vitamin E alone may reduce the length of ICU stay. The putative synergistic beneficial effect of combined administration of selenium and vitamin E in ICU patients has not been observed, but more clinical studies are pending to confirm it further.

Selenium in Cardiac Surgery

Selenium (Se) is an essential trace element that plays a pivotal role in many of the body's regulatory and metabolic functions, especially during times of stress. After uptake, Se is incorporated into several Se-dependent proteins, which have potent anti-inflammatory and antioxidant capacities. Several observational clinical studies have demonstrated that Se deficiency can cause chronic cardiovascular diseases and aggravate organ dysfunction after cardiac surgery and that low levels of Se may be independently associated with the development of organ dysfunction after cardiac surgery. Based on these findings, several studies have investigated the effects of a perioperative Se supplementation strategy. Therefore, the present review describes in depth the pathophysiology and harmful stimuli during cardiac surgery, how Se may counteract these injuries, the different types of Se supplementation strategies that have been evaluated, and current evidence of its clinical significance.

Selenium supplementation in the critically ill

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.

Glycemic control and nutritional strategies in the cardiothoracic surgical intensive care unit--2010: state of the art

Patients in the cardiothoracic surgical intensive care unit are generally critically ill and undergoing a systemic inflammatory response to cardiopulmonary bypass, ischemia/reperfusion, and hypothermia. This presents several metabolic challenges: hyperglycemia in need of intensive insulin therapy, catabolism, and uncertain gastrointestinal tract function in need of nutritional strategies. Currently, there are controversies surrounding the standard use of intensive insulin therapy and appropriate glycemic targets as well as the use of early enteral nutrition ± parenteral nutrition. In this review, an approach for intensive metabolic support in the cardiothoracic surgical intensive care unit is presented incorporating the most recent clinical evidence. This approach advocates an IIT blood glucose target of 80-110 mg/dL if, it can be implemented safely, with early nutrition support (using parenteral nutrition as needed) to prevent a critical energy debt.

Selenium in human health and disease

This review covers current knowledge of selenium in the environment, dietary intakes, metabolism and status, functions in the body, thyroid hormone metabolism, antioxidant defense systems and oxidative metabolism, and the immune system. Selenium toxicity and links between deficiency and Keshan disease and Kashin-Beck disease are described. The relationships between selenium intake/status and various health outcomes, in particular gastrointestinal and prostate cancer, cardiovascular disease, diabetes, and male fertility, are reviewed, and recent developments in genetics of selenoproteins are outlined. The rationale behind current dietary reference intakes of selenium is explained, and examples of differences between countries and/or expert bodies are given. Throughout the review, gaps in knowledge and research requirements are identified. More research is needed to improve our understanding of selenium metabolism and requirements for optimal health. Functions of the majority of the selenoproteins await characterization, the mechanism of absorption has yet to be identified, measures of status need to be developed, and effects of genotype on metabolism require further investigation. The relationships between selenium intake/status and health, or risk of disease, are complex but require elucidation to inform clinical practice, to refine dietary recommendations, and to develop effective public health policies.

Amino acid composition in parenteral nutrition: what is the evidence?

PURPOSE OF REVIEW

Complete parenteral nutrition solutions contain mixed amino acid products providing all nine essential amino acids and a varying composition of nonessential amino acids. Relatively little rigorous comparative efficacy research on altered parenteral nutrition amino acid composition has been published in recent years.

RECENT FINDINGS

Limited data from randomized, double-blind, adequately powered clinical trials to define optimal doses of total or individual amino acids in parenteral nutrition are available. An exception is the growing number of studies on the efficacy of glutamine supplementation of parenteral nutrition or given as a single parenteral agent. Parenteral glutamine appears to confer benefit in selected patients; however, additional data to define optimal glutamine dosing and the patient subgroups who may most benefit from this amino acid are needed. Although some promising studies have been published, little data are available in the current era of nutrition support on the clinical efficacy of altered doses of arginine, branched chain amino acids, cysteine, or taurine supplementation of parenteral nutrition.

SUMMARY

Despite routine use of parenteral nutrition, surprisingly little clinical efficacy data are available to guide total or specific amino acid dosing in adult and pediatric patients requiring this therapy. This warrants increased attention by the research community and funding agencies to better define optimal amino acid administration strategies in patient subgroups requiring parenteral nutrition.