Vitamin C Administration to the Critically Ill: A Systematic Review and Meta-Analysis

Vitamin C, an enzyme cofactor and antioxidant, could hasten the resolution of inflammation, oxidative stress, and microvascular dysfunction. While observational studies have demonstrated that critical illness is associated with low levels of vitamin C, randomized controlled trials (RCTs) of vitamin C, alone or in combination with other antioxidants, have yielded contradicting results. We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials (inception to December 2017) for RCTs comparing vitamin C, by enteral or parenteral routes, with placebo or none, in intensive care unit (ICU) patients. Two independent reviewers assessed study eligibility without language restrictions and abstracted data. Overall mortality was the primary outcome; secondary outcomes were incident infections, ICU length of stay (LOS), hospital LOS, and duration of mechanical ventilation (MV). We prespecified 5 subgroups hypothesized to benefit more from vitamin C. Eleven randomized trials were included. When 9 RCTs (n = 1322) reporting mortality were pooled, vitamin C was not associated with reduced risk of mortality (risk ratio [RR] 0.72, 95% confidence interval [CI]: 0.43-1.20, P = .21). No effect was found on infections, ICU or hospital LOS, or duration of MV. In multiple subgroup comparison, no statistically significant subgroup effects were observed. However, we did observe a tendency towards a mortality reduction (RR 0.21; 95% CI: 0.04-1.05; P = .06) when intravenous high-dose vitamin C monotherapy was administered. Current evidence does not support supplementing critically ill patients with vitamin C. A moderately large treatment effect may exist, but further studies, particularly of monotherapy administration, are warranted.

Vitamin D in the ICU: More sun for critically ill adult patients?

Critical illness in patients is characterized by systemic inflammation and oxidative stress. Vitamin D has a myriad of biological functions relevant to this population, including immunomodulation by the alteration of cytokine production and nuclear factor loop amplification. Low serum levels have consistently been found in observational studies conducted on critically ill patients, but the causality with mortality and worse outcomes has not been confirmed. The current focus is on interventional trials, whereas the pharmacokinetic profile of vitamin D administration remains sparse and the optimal strategy has not been confirmed. So far, high-dose oral or enteral supplementation is the most studied strategy. The largest randomized controlled trial published so far, the VITdAL-ICU (Effect of High-dose Vitamin D3 on Hospital Length of Stay in Critically Ill Patients with Vitamin D Deficiency) trial, showed no benefits on mortality in its primary analysis. However, secondary analysis suggested improvement in those patients with severe deficiency (i.e., 25-dihydroxyvitaminD <12 ng/mL). Smaller trials investigated intramuscular and intravenous administration and found interesting intermediate biochemical findings, including increased cathelicidins, but were not powered to investigate relevant clinical outcomes in the critically ill. The latest meta-analysis, which was recently published, does not support benefits of vitamin D supplementation in the heterogeneous population of critically ill patients. The European guidelines, published in the last year, suggest supplementing severely deficient patients with levels <12.5 ng/mL within the first week after ICU admission. However, other societies do not support such supplementation in their older recommendations. Large trials are currently recruiting ICU patients and could elucidate potential clinical benefits of vitamin D therapy in the critically ill.

Vitamin C for the critically ill: Is the evidence strong enough?

Vitamin C exhibits interesting properties in the context of critical illness, with benefits described in neurologic, cardiovascular, renal, and hematologic systems, both in in vitro and in animal models. Through direct effects on bacterial replication, immunomodulation, and antioxidant reserve of the organism, vitamin C directly affects the pathophysiological process of sepsis, trauma, burn, and systemic inflammation. Even if several observational trials have linked vitamin C deficiency to worse outcomes, the evidence is not such as to provide us with a distinction between causality effects or simple epiphenomenon, and the current focus is on interventional trials. Pharmacokinetic data suggest that a minimal supplementation of 3 g/d intravenously is required to restore normal serum values in critically ill patients with known deficiency. According to these data, only five trials, including a retrospective analysis, studied pharmacologic dose: three as an antioxidant cocktail and two as monotherapy. The largest trial, conducted in 2002, reported reduced incidence of multiorgan failure and duration of mechanical ventilation. Recently a retrospective analysis reported impressive results after administration of vitamin C, thiamine, and hydrocortisone. The two most recent trials reported improved clinical outcomes, including improved mortality, but contained significant methodological limitations. A recent systematic review did not find clinical benefits with the most-studied low-dose oral supplementation, potentially because of suboptimal or insufficient repletion. Current guidelines do not support the administration of high-dose vitamin C in critically ill patients. Future larger trials are required to support any therapy, but the low cost and safety profile can justify supplementation in the meantime. Metabolomics study will further help understand biological effect.

Retroclavicular approach vs infraclavicular approach for plexic bloc anesthesia of the upper limb: study protocol randomized controlled trial

Background

The coracoid approach is recognized as the simplest approach to perform brachial plexus anaesthesia, but needle visualization needs to be improved. With a different needle entry point, the retroclavicular approach confers a perpendicular angle between the ultrasound and the needle, which theoretically enhances needle visualization. This trial compares these two techniques. The leading hypothesis is that the retroclavicular approach is comparable to the infraclavicular coracoid approach in general aspects, but needle visualization is better with this novel approach.

Methods

We designed a multicentre, randomized, non-inferiority trial. Patients eligible for the study are older than 18 years, able to consent, will undergo urgent or elective upper limb surgery distal to the elbow and are classified with American Society of Anaesthesiologists risk score (ASA) I-III. They will be excluded if they meet contraindicated criteria to regional anaesthesia, have affected anatomy of the clavicle or are pregnant. Randomization will be done by a computer-generated randomization schedule stratified for each site and in 1:1 ratio, and concealment will be maintained with opaque, sealed envelopes in a locked office. The primary outcome, the performance time, will be analyzed using non-inferiority analysis while secondary outcomes will be analyzed with superiority analysis. Needle visualization will be ranked on a Likert scale of 1–5 that is subjective and represents a pitfall. Two separate persons will rank needle visualization to compensate this pitfall. According to previous studies, 49 patients per group are required for statistical power of 0.90 and one-sided type I error of 0.05.

Discussion

The conduct of this study will bring clear answers to our questions and, if our hypothesis is confirmed, will confer an anatomic alternative to difficult coracoid infraclavicular brachial blocks or could even become a standard for brachial plexus anaesthesia.

Trial registration

ClinicalTrials.gov, NCT02913625. Registered on 12 September 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2086-1) contains supplementary material, which is available to authorized users.

Probiotic and synbiotic therapy in critical illness: a systematic review and meta-analysis

Background

Critical illness is characterized by a loss of commensal flora and an overgrowth of potentially pathogenic bacteria, leading to a high susceptibility to nosocomial infections. Probiotics are living non-pathogenic microorganisms, which may protect the gut barrier, attenuate pathogen overgrowth, decrease bacterial translocation and prevent infection. The purpose of this updated systematic review is to evaluate the overall efficacy of probiotics and synbiotic mixtures on clinical outcomes in critical illness.

Methods

Computerized databases from 1980 to 2016 were searched. Randomized controlled trials (RCT) evaluating clinical outcomes associated with probiotic therapy as a single strategy or in combination with prebiotic fiber (synbiotics). Overall number of new infections was the primary outcome; secondary outcomes included mortality, ICU and hospital length of stay (LOS), and diarrhea. Subgroup analyses were performed to elucidate the role of other key factors such as probiotic type and patient mortality risk on the effect of probiotics on outcomes.

Results

Thirty trials that enrolled 2972 patients were identified for analysis. Probiotics were associated with a significant reduction in infections (risk ratio 0.80, 95 % confidence interval (CI) 0.68, 0.95, P = 0.009; heterogeneity I² = 36 %, P = 0.09). Further, a significant reduction in the incidence of ventilator-associated pneumonia (VAP) was found (risk ratio 0.74, 95 % CI 0.61, 0. 90, P = 0.002; I² = 19 %). No effect on mortality, LOS or diarrhea was observed. Subgroup analysis indicated that the greatest improvement in the outcome of infections was in critically ill patients receiving probiotics alone versus synbiotic mixtures, although limited synbiotic trial data currently exists.

Conclusion

Probiotics show promise in reducing infections, including VAP in critical illness. Currently, clinical heterogeneity and potential publication bias reduce strong clinical recommendations and indicate further high quality clinical trials are needed to conclusively prove these benefits.

Hyponatremia in the neurocritical care patient: An approach based on current evidence

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

Pharmaconutrition with selenium in critically ill patients: what do we know?

Selenium is a component of selenoproteins with antioxidant, anti-inflammatory, and immunomodulatory properties. Systemic inflammatory response syndrome (SIRS), multiorgan dysfunction (MOD), and multiorgan failure (MOF) are associated with an early reduction in plasma selenium and glutathione peroxidase activity (GPx), and both parameters correlate inversely with the severity of illness and outcomes. Several randomized clinical trials (RCTs) evaluated selenium therapy as monotherapy or in antioxidant cocktails in intensive care unit (ICU) patient populations, and more recently several meta-analyses suggested benefits with selenium therapy in the most seriously ill patients. However, the largest RCT on pharmaconutrition with glutamine and antioxidants, the REducing Deaths due to Oxidative Stress (REDOXS) Study, was unable to find any improvement in clinical outcomes with antioxidants provided by the enteral and parenteral route and suggested harm in patients with renal dysfunction. Subsequently, the MetaPlus study demonstrated increased mortality in medical patients when provided extra glutamine and selenium enterally. The treatment effect of selenium may be dependent on the dose, the route of administration, and whether administered with other nutrients and the patient population studied. Currently, there are few small studies evaluating the pharmacokinetic profile of intravenous (IV) selenium in SIRS, and therefore more data are necessary, particularly in patients with MOD, including those with renal dysfunction. According to current knowledge, high-dose pentahydrate sodium selenite could be given as an IV bolus injection (1000-2000 µg), which causes transient pro-oxidant, cytotoxic, and anti-inflammatory effects, and then followed by a continuous infusion of 1000-1600 µg/d for up to 10-14 days. Nonetheless, the optimum dose and efficacy still remain controversial and need to be definitively established.

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.

[Pharmaconutrition with parenteral selenium in sepsis]

Critical illness is characterized by oxidative stress which leads to multiple organ failure, and sepsis-related organ dysfunction remains the most common cause of death in the intensive care unit. Over the last 2 decades, different antioxidant therapies have been developed to improve outcomes in septic patients. According to recent evidence, selenium therapy should be considered the cornerstone of the antioxidant strategies. Selenium given as selenious acid or sodium selenite should be considered as a drug or pharmaconutrient with prooxidant and cytotoxic effects when a loading dose in intravenous bolus form is administered, particularly in the early stage of severe sepsis/septic shock. To date, several phase ii trials have demonstrated that selenium therapy may be able to decrease mortality, improve organ dysfunction and reduce infections in critically ill septic patients. The effect of selenium therapy in sepsis syndrome must be confirmed by large, well designed phase iii clinical trials. The purpose of this review is to discuss current evidence on selenium pharmaconutrition in sepsis syndrome.