The intraoperative decrease of selenium is associated with the postoperative development of multiorgan dysfunction in cardiac surgical patients*:

Update on antioxidant micronutrients in the critically ill

PURPOSE OF REVIEW

To evaluate recent evidence on pharmaconutrition with antioxidant micronutrients, for different populations of adult critically ill patients.

RECENT FINDINGS

Over the last few years, different studies have shown that high-dose trace elements and vitamins, especially parenteral selenium and zinc, may be able to improve relevant clinical outcomes in the most seriously ill patients. High-dose selenite monotherapy reduces mortality, particularly when a pharmacological loading dose is given in the early stage of severe sepsis and septic shock. Notwithstanding, the recently published REducing Deaths due to OXidative Stress study using an antioxidant cocktail and parenteral selenite, in addition to standard enteral nutrition, was unable to show any benefits for patients with multiple organ failure.

SUMMARY

There is evidence supporting the concept of pharmaconutrition with high-dose micronutrients. Selenium therapy may be able to decrease infections and reduce mortality in sepsis, but more research is needed to better understand pharmacokinetics, optimal composition, timing, duration, and dose of antioxidant cocktails for the critically ill.

Plasma selenium status in a group of Australian blood donors and fresh blood components

The purpose of this study was to assess plasma selenium levels in an Australian blood donor population and measure extra-cellular selenium levels in fresh manufactured blood components. Selenium levels were measured using graphite furnace atomic absorption spectrometry with Zeeman background correction. The mean plasma selenium level in healthy plasmapharesis donors was 85.6±0.5 μg/L and a regional difference was observed between donors in South East Queensland and Far North Queensland. Although participants had selenium levels within the normal range (55.3-110.5 μg/L), 88.5% had levels below 100 μg/L, a level that has been associated with sub-optimal activity of the antioxidant enzyme glutathione peroxidase (GPx). Extra-cellular selenium levels in clinical fresh frozen plasma (cFFP) and apheresis-derived platelets (APH Plt) were within the normal range. Packed red blood cells (PRBC) and pooled buffy coat-derived platelets (BC Plt) had levels at the lower limit of detection, which may have clinical implications to the massively transfused patient.

Insulin alleviates posttrauma cardiac dysfunction by inhibiting tumor necrosis factor-α-mediated reactive oxygen species production

OBJECTIVE

Clinical evidence indicates that intensive insulin treatment prevents the incidence of multiple organ failures in surgical operation and severe trauma, but the mechanisms involved remain elusive. This study was designed to test the hypothesis that insulin may exert anti-inflammatory and antioxidative effects and thus alleviate cardiac dysfunction after trauma.

DESIGN

Prospective, randomized experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Sprague Dawley rats.

INTERVENTIONS

Anesthetized rats were subjected to 200 revolutions at a rate of 35 rpm in Noble-Collip drum to induce a nonlethal mechanical trauma and were randomized to receive vehicle, insulin, and insulin + wortmannin treatments. An in vitro study was performed on cultured cardiomyocytes subjected to sham-traumatic serum (SS), traumatic serum (TS), SS + tumor necrosis factor (TNF)-α, SS + H2O2, TS + neutralizing anti-TNF-α antibody, or TS + tempol treatments.

MEASUREMENTS AND MAIN RESULTS

Immediate cardiac dysfunction occurred 0.5 hr after trauma without significant cardiomyocyte necrosis and apoptosis, while serum TNF-α and cardiac reactive oxygen species (ROS) production was increased. Importantly, incubation of cardiomyocytes with TS or SS + TNF-α significantly increased ROS generation together with dampened cardiomyocyte contractility and Ca transient, all of which were rescued by TNF-α antibody. Administration of insulin inhibited TNF-α and ROS overproduction and alleviated cardiac dysfunction 2 hours after trauma. Scavenging ROS with tempol also attenuated cardiac dysfunction after trauma, whereas insulin combined with tempol failed to further improve cardiac functional recovery compared with insulin treatment alone. Moreover, the aforementioned anti-TNF-α, antioxidative, and cardioprotective effects afforded by insulin were almost abolished by the phosphatidylinositol 3-kinase inhibitor wortmannin.

CONCLUSIONS

These results demonstrate for the first time that mechanical trauma induces a significant increase in TNF-α and ROS production, resulting in immediate cardiac dysfunction. Early posttrauma insulin treatment alleviates cardiac dysfunction by inhibiting TNF-α-mediated ROS production via a phosphatidylinositol 3-kinase/Akt-dependent mechanism.

The effect of selenium therapy on mortality in patients with sepsis syndrome: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Patients with sepsis syndrome commonly have low serum selenium levels. Several randomized controlled trials have examined the efficacy of selenium supplementation on mortality in patients with sepsis.

OBJECTIVE

To determine the efficacy and safety of high-dose selenium supplementation compared to placebo for the reduction of mortality in patients with sepsis.

SOURCES OF DATA

We searched Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, SciFinder, and Clinicaltrials.gov.

SELECTION CRITERIA

Randomized controlled parallel group trials comparing selenium supplementation in doses greater than daily requirement to placebo on the outcome of mortality in patients with sepsis syndrome.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied eligibility criteria, assessed quality, and extracted data. The primary outcome was mortality; secondary outcomes were ICU length of stay, nosocomial pneumonia, and adverse events. Trial authors were contacted for additional or clarifying information.

RESULTS

Nine trials enrolling a total of 792 patients were included. Selenium supplementation in comparison to placebo was associated with lower mortality (odds ratio, 0.73; 95% CI, 0.54, 0.98; p = 0.03; I = 0%). Among patients receiving and not receiving selenium, there was no difference in ICU length of stay (mean difference, 2.03; 95% CI, -0.51, 4.56; p = 0.12; I = 0%) or nosocomial pneumonia (odds ratio, 0.83; 95% CI, 0.28, 2.49; p = 0.74; I = 56%). Significant heterogeneity among trials in adverse event reporting precluded pooling of results.

CONCLUSIONS

In patients with sepsis, selenium supplementation at doses higher than daily requirement may reduce mortality. We observed no impact of selenium on ICU length of stay or risk of nosocomial pneumonia.

Hemorrhagic shock and surgical stress alter distribution of labile zinc within high- and low-molecular-weight plasma fractions

Zinc ions (Zn) are essential for tissue repair following injury or stress. We hypothesize that during such stresses Zn is redistributed to labile pools in plasma components. Here we tested this hypothesis using a novel assay to monitor labile Zn in plasma in hemorrhagic shock. Adult rats in the shock group (S group) underwent hemorrhage and resuscitation. Blood samples were drawn at baseline and at 1, 4, and 24 h. The surgical control group (SC group) was anesthetized and instrumented, but not bled. Albumin, total Zn, and labile Zn levels were assayed in plasma. Binding capacity for Zn was assessed in high- and low-molecular-weight pools. Significant decreases in total Zn were observed by 24 h, in both S and SC groups. Albumin levels were significantly reduced in the S group at 1 and 4 h but restored at 24 h; significant changes were not observed in other groups. In whole plasma, labile Zn levels were stable initially in the S and SC groups, but declined at 24 h. In the high-molecular-weight pool, marked and significant impairment of binding was noted throughout all time periods following the shock period in the S group. Such changes were observed in the SC group of less intensity and duration. These experiments suggest that shock alters affinity of plasma proteins for Zn, promoting delivery to peripheral tissues during periods of increased Zn utilization.

Lower whole blood selenium level is associated with higher operative risk and mortality following cardiac surgery

PURPOSE

The authors intended to test their hypothesis that a low blood selenium level is associated with higher mortality, morbidity, and increased inflammatory response following cardiac surgery.

METHODS

A single-center clinical survey was conducted on 197 consecutive patients undergoing on-pump operation in Debrecen, Hungary. Blood samples for whole blood selenium analysis were taken immediately before the surgery. Their risk profiles were evaluated according to the EuroSCORE. The outcome parameters were as follows: 30-day mortality, incidence of systemic inflammatory response syndrome, and cardiac and renal dysfunction. The main laboratory outcome variables were the postoperative concentrations of C-reactive protein and cardiac troponin I.

RESULTS

The mean blood selenium level was significantly lower in non-survivors 102.2 ± 19.5 μg/L compared with survivors 111.1 ± 16.9 μg/L (p = 0.047), and the mean age, EuroSCORE values, and troponin concentrations were significantly higher in the non-survivors. To exclude these potential confounders a logistic regression model was fitted to our data, with mortality as the outcome and the EuroSCORE, the degree of troponin elevation, and selenium concentration as explanatory variables. This model revealed that a lower selenium level was a minor but apparently existing risk factor for postoperative mortality.

CONCLUSION

Further examinations are required to clarify the question that remained unanswered in this study: the role of low selenium in the causality chain leading to higher postoperative mortality.

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.

High postoperative blood levels of macrophage migration inhibitory factor are associated with less organ dysfunction in patients after cardiac surgery

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that exerts protective effects during myocardial ischemia/reperfusion injury. We hypothesized that elevated MIF levels in the early postoperative time course might be inversely associated with postoperative organ dysfunction as assessed by the simplified acute physiology score (SAPS) II and sequential organ failure assessment (SOFA) score in patients after cardiac surgery. A total of 52 cardiac surgical patients (mean age [± SD] 67 ± 10 years; EuroScore: 7) were enrolled in this monocenter, prospective observational study. Serum levels of MIF and clinical data were obtained after induction of anesthesia, at admission to the intensive care unit (ICU), 4 h after admission and at the first and second postoperative day. To characterize the magnitude of MIF release, we compared blood levels of samples from cardiac surgical patients with those obtained from healthy volunteers. We assessed patient outcomes using the SAPS II at postoperative d 1 and SOFA score for the first 3 d of the eventual ICU stay. Compared to healthy volunteers, patients had already exhibited elevated MIF levels prior to surgery (64 ± 50 versus 13 ± 17 ng/mL; p < 0.05). At admission to the ICU, MIF levels reached peak values (107 ± 95 ng/mL; p < 0.01 versus baseline) that decreased throughout the observation period and had already reached preoperative values 4 h later. Postoperative MIF values were inversely correlated with SAPS II and SOFA scores during the early postoperative stay. Moreover, MIF values on postoperative d 1 were related to the calculated cardiac power index (r = 0.420, p < 0.05). Elevated postoperative MIF levels are inversely correlated with organ dysfunction in patients after cardiac surgery.

Nutrition intervention in the critically ill cardiothoracic patient

Despite acute myocardial infarction and cardiac surgery accounting for 2 of the most common reasons patients are admitted to the intensive care unit, little attention and investigation have been directed specifically for these patients. This patient population therefore deserves special attention as they are often malnourished but require emergent interventions, making nutrition intervention challenging. This article reviews current medical interventions implemented in critically ill cardiothoracic patients and discusses evidence-based nutrition therapy, including enteral and parenteral feeding, glycemic control, and antioxidant provision.

Blood levels of macrophage migration inhibitory factor after successful resuscitation from cardiac arrest

INTRODUCTION

Ischemia-reperfusion injury following cardiopulmonary resuscitation (CPR) is associated with a systemic inflammatory response, resulting in post-resuscitation disease. In the present study we investigated the response of the pleiotropic inflammatory cytokine macrophage migration inhibitory factor (MIF) to CPR in patients admitted to the hospital after out-of-hospital cardiac arrest (OHCA). To describe the magnitude of MIF release, we compared the blood levels from CPR patients with those obtained in healthy volunteers and with an aged- and gender-matched group of patients undergoing cardiac surgery with the use of extracorporeal circulation.

METHODS

Blood samples of 17 patients with return of spontaneous circulation (ROSC) after OHCA were obtained upon admission to the intensive care unit, and 6, 12, 24, 72 and 96 h later. Arrest and treatment related data were documented according to the Utstein style.

RESULTS

In patients after ROSC, MIF levels at admission (475.2±157.8 ng/ml) were significantly higher than in healthy volunteers (12.5±16.9 ng/ml, p<0.007) and in patients after cardiac surgery (78.2±41.6 ng/ml, p<0.007). Six hours after admission, MIF levels were decreased by more than 50% (150.5±127.2 ng/ml, p<0.007), but were not further reduced in the subsequent time course and remained significantly higher than the values observed during the ICU stay of cardiac surgical patients. In this small group of patients, MIF levels could not discriminate between survivors and non-survivors and were not affected by treatment with mild therapeutic hypothermia.

CONCLUSION

MIF shows a rapid and pronounced increase following CPR, hence allowing a very early assessment of the inflammatory response. Further studies are warranted in larger patient groups to determine the prognostic significance of MIF.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01412619.