[Molecular biology studies of a multicenter phase III study (SIC Study)]

Selenium supplementation for critically ill adults

BACKGROUND

Selenium is a trace mineral essential to health and has an important role in immunity, defence against tissue damage and thyroid function. Improving selenium status could help protect against overwhelming tissue damage and infection in critically ill adults. This Cochrane review was originally published in 2004 updated in 2007 and again 2015.

OBJECTIVES

The primary objective was to examine the effect of nutrition supplemented with selenium or ebselen on mortality in critically ill patients.The secondary objective was to examine the relationship between selenium or ebselen supplementation and number of infections, duration of mechanical ventilation, length of intensive care unit stay and length of hospital stay.

SEARCH METHODS

In this update, we searched the current issue of the Cochrane Central Register of Controlled Trials, the Cochrane Library (2014, Issue 5); MEDLINE (Ovid SP, to May 20, 2014), EMBASE (Ovid SP, to May 20, 2014), CAB, BIOSIS and CINAHL. We handsearched the reference lists of the newest reviews and cross-checked with our search in MEDLINE. We contacted the main authors of included studies to request any missed, unreported or ongoing studies. The latest search was performed up to 21 May 2014. The search is now from inception until 21 May 2014.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) irrespective of publication status, date of publication, blinding status, outcomes published or language. We contacted the trial investigators and authors in order to retrieve relevant and missing data.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and we resolved any disagreements by discussion. Our primary outcome measure was all-cause mortality. We performed several subgroup and sensitivity analyses to assess the effects of selenium in critically ill patients. We presented pooled estimates of the effects of intervention as risk ratios (RRs) with 95% confidence intervals (CIs). We assessed the risk of bias through assessment of trial methodological components and the risk of random error through trial sequential analysis.

MAIN RESULTS

We included six new RCTs in this review update. In total we included 16 RCTs (2084 participants) in this review. Most trials were at high risk of bias. The availability of outcome data was limited and trials involving selenium supplementation were, with the exception of one trial, small regarding sample size. Thus the results must be interpreted with caution.Thirteen trials of intravenous sodium selenite showed a statistically significant reduction in overall mortality (RR 0.82, 95% CI 0.72 to 0.93, 1391 participants, very low quality of evidence). However, the overall point estimate on mortality is primarily influenced by trials of high risk of bias. Meta-analysis of three trials of ebselen had a RR of 0.83 (95% CI 0.52 to 1.34, 693 participants, very low quality of evidence).Nine trials of intravenous sodium selenite were analysed for 28 days mortality with no statistically significant difference (RR 0.84, 95% CI 0.69 to 1.02, 1180 participants, very low quality of evidence) while three trials were analysed for 90 days mortality with similar findings (RR 0.96, 95% Cl 0.78 to 1.18, 614 participants, very low quality of evidence).Two trials of ebselen were analysed for 90 days mortality and were not found to yield any benefit (RR 0.72, 95% Cl 0.42 to 1.22, 588 participants, very low quality of evidence).For mortality among intensive care patients selenium supplementation failed to indicate any statistically significant advantage (RR 0.88, 95% CI 0.77 to 1.01, nine trials, 1168 participants, very low quality of evidence).Six trials of intravenous sodium selenite found no statistically significant difference for participants developing infection (RR 0.96, 95% CI 0.75 to 1.23, 934 patients, very low quality of evidence). Similarly, three trials of ebselen provided data for participants developing infections (pyrexia, respiratory infections or meningitis) with no obvious benefit (RR 0.60, 95% CI 0.36 to 1.02, 685 participants, very low quality of evidence).Our analyses showed no effect of selenium or ebselen on adverse events (Selenium: RR 1.03, 95% Cl 0.85 to 1.24; six trials, 925 participants ; Ebselen: RR 1.16, 95% CI 0.40 to 3.36; two trials, 588 participants, very low quality of evidence).No clear evidence emerged in favour of selenium supplementation for outcomes such as number of days on a ventilator (mean difference (MD) -0.86, 95% CI -4.39 to 2.67, four trials, 191 participants, very low quality of evidence), length of intensive care unit stay (MD 0.54, 95% CI -2.27 to 3.34, seven trials, 934 participants, very low quality of evidence) or length of hospital stay (MD -3.33, 95% Cl -5.22 to -1.44, five trials, 693 participants, very low quality of evidence).The quality of trial methodology was low. Due to high risk of bias in the included trials, results must be interpreted with caution.

AUTHORS' CONCLUSIONS

Despite publication of a number of trials, the current evidence to recommend supplementation of critically ill patients with selenium or ebselen remains disputed. Trials are required which overcome the methodological inadequacies of the reviewed studies, particularly in relation to sample size, design and outcomes.

The β-SiC nanowires (~100 nm) induce apoptosis via oxidative stress in mouse osteoblastic cell line MC3T3-E1

Silicon carbide (SiC), a compound of silicon and carbon, with chemical formula SiC, the beta modification ( β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperature below 1700°C. β-SiC will be the most suitable ceramic material for the future hard tissue replacement, such as bone and tooth. The in vitro cytotoxicity of β-SiC nanowires was investigated for the first time. Our results indicated that 100 nm long SiC nanowires could significantly induce the apoptosis in MC3T3-E1 cells, compared with 100 μm long SiC nanowires. And 100 nm long SiC nanowires increased oxidative stress in MC3T3-E1 cells, as determined by the concentrations of MDA (as a marker of lipid peroxidation) and 8-OHdG (indicator of oxidative DNA damage). Moreover, transmission electron microscopy (TEM) was performed to evaluate the morphological changes of MC3T3-E1 cells. After treatment with 100 nm long SiC nanowires, the mitochondria were swelled and disintegrated, and the production of ATP and the total oxygen uptake were also decreased significantly. Therefore, β-SiC nanowires may have limitations as medical material.

Selenium supplementation for critically ill adults

BACKGROUND

Selenium is a trace mineral essential to human health, which has an important role in the immune response, defence against tissue damage and thyroid function. Improving selenium status could help protect against overwhelming tissue damage and infection in critically ill adults.

OBJECTIVES

This review assessed the effects of selenium supplementation including the selenium-containing compound, ebselen, on adults recovering from critical illness.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library, Issue 2, 2003), MEDLINE, (1966 to July 2003), EMBASE (1980 to Week 30 2003),CAB NAR (1973 to March 2003), BIOSIS (1985 to July 2003), CINAHL (1982 to July 2003), HEALTHSTAR (1975 to September 2002), Current Controlled Trials, and reference lists. We contacted investigators, and handsearched four journals. Date of the most recent search: December 2003.

SELECTION CRITERIA

Randomized trials of selenium or ebselen supplementation by any route, in adults with critical illness (including burns, head injury, brain haemorrhage, cerebrovascular accident and surgery).

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. We sought additional information as required from trialists. We also undertook pooling of data for outcomes and selected exploratory analyses were undertaken.

MAIN RESULTS

Seven randomized trials involving813participants were included. The quality of trials, as reported, was poor, particularly for allocation concealment. The availability of outcome data was limited and trials involving selenium supplementation, were small. Thus the results must be interpreted with caution. Because of heterogeneity, results are presented for the random effects models. Four selenium trials showed no statistically significant difference in mortality (relative risk (RR) 0.52, 95% confidence interval (CI) 0.20 to 1.34). Three trials of ebselen also showed no statistically significant difference in mortality (RR 0.83, 95% CI 0.51 to 1.35). One trial of selenium found no statistically significant difference between groups for participants developing infection (RR 1.33, 95% CI 0.55 to 3.24). Three trials of ebselen provided data for participants developing infections (pyrexia, respiratory infections or meningitis), which was not statistically significant (RR 0.60, 95% CI 0.36 to 1.02). No clear evidence emerged for the benefits of selenium or ebselen supplementation for the outcomes of days on a ventilator, length of intensive care unit stay, length of hospital stay or quality of life.

REVIEWERS' CONCLUSIONS

There is insufficient evidence to recommend supplementation of critically ill patients with selenium or ebselen. Trials are required which overcome the defects of the reviewed studies, particularly inadequate size and methodology. This review will be updated when four ongoing trials are completed.