Effects of Vitamin C on Organ Function in Cardiac Surgery Patients: A Systematic Review and Meta-Analysis

Vitamin C for all?

PURPOSE OF REVIEW

Vitamin C can be a potential adjunctive treatment option for critically ill individuals due to its pleiotropic effects as electron donor in many enzymatic reactions throughout the body. Recently, several important randomized controlled trials (RCTs) investigating vitamin C in critically ill patients have been published.

RECENT FINDINGS

Two recent large RCTs administering high-dose vitamin C to patients with sepsis and COVID-19 showed signs of harm. Though performed at high standard, these trials had several limitations. Recent studies in cardiac surgery and burns showed decreased cardiac enzymes and improved clinical outcomes after cardiac surgery, and decreased fluid requirements, reduced wound healing time and in-hospital mortality after burns. Vitamin C may hold benefit in the management of other ischemia/reperfusion injury populations, including postcardiac arrest patients and after solid organ transplantation. Currently, covering basal vitamin C requirements during critical illness is recommended, though the exact dose remains to be determined.

SUMMARY

Future work should address optimal vitamin C timing, since early versus late drug administration are likely distinct, and duration of therapy, where withdrawal-induced injury is possible. Additionally accurate assessment of body stores with determination of individual vitamin requirements is crucial to ascertain patient and subgroups most likely to benefit from vitamin C.

Start Strong, Finish Strong: A Review of Prehabilitation in Cardiac Surgery

Cardiac surgery constitutes a significant surgical insult in a patient population that is often marred by significant comorbidities, including frailty and reduced physiological reserve. Prehabilitation programs seek to improve patient outcomes and recovery from surgery by implementing a number of preoperative optimization initiatives. Since the initial trial of cardiac prehabilitation twenty-four years ago, new data have emerged on how to best utilize this tool for the perioperative care of patients undergoing cardiac surgery. This review will explore recent cardiac prehabilitation investigations, provide clinical considerations for an effective cardiac prehabilitation program, and create a framework for future research studies.

Preoperative and postoperative administration of vitamin C in cardiac surgery patients - settings, dosages, duration, and clinical outcomes: a narrative review

Vitamin C or ascorbic acid is a water-soluble vitamin capable of directly donating electrons to reactive oxygen species, attenuating electrical remodeling, and cardiac dysfunction in patients undergoing cardiac surgery (CS), considered one of the most effective defenses against free radicals in the blood, thus being one of the first antioxidants consumed during oxidative stress. The aim of this review is to assess the effects of perioperative administration of vitamin C in CS patients. A comprehensive literature search was conducted in order to identify prospective cohort studies and/or randomized controlled trials reporting on the perioperative effects of vitamin C among adult patients undergoing CS. Studies published between January 1980 to December 2022 were included in our search, resulting in a total of 31 articles that met all our inclusion criteria. There seems to be a beneficial effect of vitamin C supplementation in arrhythmias such as in postoperative atrial fibrillation, reduction of ICU length of stay, and hospital length of stay, reduction in postoperative ventilation time, in inotropic demand, and in postoperative fatigue. Vitamin C can act as a scavenger of free radicals to decrease the peroxidation of the lipids present in the cell membrane, and to protect the myocardium postoperatively from ischemia/reperfusion injury, thus attenuating oxidative stress and inflammation. It represents a readily available and cost-effective strategy that could improve the outcome of patients undergoing CS, by reducing the risk of serious cardiovascular adverse events, both perioperatively and postoperatively.

The impact of cardiopulmonary bypass time on the Sequential Organ Failure Assessment score after cardiac surgery

OBJECTIVES

Postoperative organ dysfunction is common after cardiac surgery, particularly when cardiopulmonary bypass (CPB) is used. The Sequential Organ Failure Assessment (SOFA) score is validated to predict morbidity and mortality in cardiac surgery. However, the impact of CPB duration on postoperative SOFA remains unclear.

METHODS

This is a retrospective study. Categorical values are presented as percentages. The comparison of SOFA groups utilized the Kruskal-Wallis chi-squared test, complemented by ad hoc Dunn's test with Bonferroni correction. Multinomial logistics regressions were employed to evaluate the relationship between CPB time and SOFA.

RESULTS

A total of 1032 patients were included. CPB time was independently associated with higher postoperative SOFA scores at 24 h. CPB time was significantly higher in patients with SOFA 4-5 (**P = 0.0022) or higher (***P < 0.001) when compared to SOFA 0-1. The percentage of patients with no/mild dysfunction decreased with longer periods of CPB, down to 0% for CPB time >180min (50% of the patients with >180m in of CPB presented SOFA ≥ 10). The same trend is observed for each of the SOFA variables, with higher impact in the cardiovascular and renal systems. Severe dysfunction occurs especially >200 min of CPB (cardiovascular system >100 min; other systems mainly >200 min).

CONCLUSIONS

CPB time may predict the probability of postoperative SOFA categories. Patients with extended CPB durations exhibited higher SOFA scores (overall and for each variable) at 24 h, with higher proportion of moderate and severe dysfunction with increasing times of CPB.

Effect of high-dose vitamin C on renal ischemia-reperfusion injury

Acute kidney injury frequently occurs after cardiac surgery, and is primarily attributed to renal ischemia-reperfusion (I/R) injury and inflammation from surgery and cardiopulmonary bypass. Vitamin C, an antioxidant that is often depleted in critically ill patients, could potentially mitigate I/R-induced oxidative stress at high doses. We investigated the effectiveness of high-dose vitamin C in preventing I/R-induced renal injury. The ideal time and optimal dosage for administration were determined in a two-phase experiment on Sprague-Dawley rats. The rats were assigned to four groups: sham, IRC (I/R + saline), and pre- and post-vitC (vitamin C before and after I/R, respectively), with vitamin C administered at 200 mg/kg. Additional groups were examined for dose modification based on the optimal timing determined: V100, V200, and V300 (100, 200, and 300 mg/kg, respectively). Renal I/R was achieved through 45 min of ischemia followed by 24 h of reperfusion. Vitamin C administration during reperfusion significantly reduced renal dysfunction and tubular damage, more than pre-ischemic administration. Doses of 100 and 200 mg/kg during reperfusion reduced oxidative stress markers, including myeloperoxidase and inflammatory responses by decreasing high mobility group box 1 release and nucleotide-binding and oligomerization domain-like receptor 3 inflammasome. Overall beneficial effect was most prominent with 200 mg/kg. The 300 mg/kg dose, however, showed no additional benefits over the IRC group regarding serum blood urea nitrogen and creatinine levels and histological evaluation. During reperfusion, high-dose vitamin C administration (200 mg/kg) significantly decreased renal I/R injury by effectively attenuating the major triggers of oxidative stress and inflammation.

Risk of Hypovitaminosis and Vitamin C Deficiency in Pediatric Patients Undergoing Cardiopulmonary Bypass

Vitamin C levels are known rapidly decrease in adult critical illness. Vitamin C scavenges free radicals, provides critical protection of the endothelial barrier, and improves endothelial responsiveness to catecholamines. Children with congenital heart disease and undergoing cardiac surgery might be at increased risk for low circulating vitamin C levels. A prospective single-center observational study investigated perioperative changes in vitamin C levels in critically ill Children who underwent congenital heart surgery using CPB. Vitamin C serum levels were collected preoperatively and postoperatively (upon admission to the ICU, 24 and 72 h). Linear mixed-effect model was used to estimate mean circulating concentration of vitamin C and to estimate changes in concentration over time. Primary outcome was change in circulating levels of vitamin C before and after CPB. Secondary outcomes were hospital length of stay (LOS), acute kidney injury (AKI), and illness severity. Forty-one patients with a median age of 4.5 [interquartile range (IQR) 2.6-65.6] months at the time of surgery were consented and enrolled. Median CPB duration was 130 [90-175] minutes, and hospital LOS was 9.1 [5.2-19] days. Mean vitamin C levels (μmol/L) before CPB, at PICU admission, 24 h, and 72 h were 82.0 (95% CI 73.4-90.7), 53.4 (95% CI 44.6,62.0), 55.1 (95% CI 46.3,63.8), and 59.2 (95% CI 50.3,68.1), respectively. Upon postoperative admission to the PICU, vitamin C levels decreased by 28.7 (95% CI 20.6-36.8; p < 0.001) μmol/L, whereas levels at 24 and 72 h recovered and did not differ substantially from concentrations reported upon PICU admission (p > 0.15). Changes in vitamin C concentration were not associated with CPB time, STAT mortality category, age, or PIM3. Three patients had post-CPB hypovitaminosis C or vitamin C deficiency. Reduction in vitamin C levels was not associated with hospital LOS (p = 0.673). A 25 μmol/L decrease in vitamin C levels upon PICU admission was associated with developing AKI (aOR = 3.65; 95% CI 1.01-18.0, p = 0.049). Pediatric patients undergoing cardiac surgery with CPB showed decreased vitamin C levels during the immediate postoperative period. Effects of hypovitaminosis C and vitamin C deficiency in this population remain unclear.

Perioperative selenium administration in cardiac surgery patients, a way out to reduce post surgical adversities? A meta analysis

Introduction

The oxidative damage suffered in cardiac surgery is associated with declining trace elements which lead to the development of multi organ dysfunction (MOD), acute kidney injury (AKI), or increased length of hospital stay (LOS). Recent evidence shows the cardioprotective role of the trace element selenium as it mitigates worsening outcomes post cardiac surgery. Hence, this meta analysis aims to investigate the role of selenium in lowering cardiac surgery related adverse outcomes.

Methods

Literature search of five electronic databases was performed from the inception of the paper till 29th July, 2023. Eligibility criteria included; (a) randomized clinical trials with Adult patients (≥18 years) undergoing cardiac surgery (b) intervention with selenium pre or/and postoperatively; (c) a control group of a placebo, normal saline, or no selenium. Outcomes of interest include postoperative mortality, LOS in the hospital and Intensive Care Unit (ICU), AKI, troponin I, and Creatinine Kinase-MB (CK-MB). The Cochrane bias assessment tool was used to evaluate the risk of bias. Outcomes were pooled with the Mantel-Haenszel Random-effects model using Review Manager.

Results

Seven RCTs with 2,521 patients and 65% of males were included in this paper. No noticable differences were observed between selenium and control groups in terms of postoperative AKI, mortality, LOS in hospital and ICU, troponin I, and CK-MB levels. All studies had a low risk of bias on quality assessment.

Discussion

Our meta analysis demonstrated no discernible effects of selenium infusion on post operative complications among patients undergoing cardiac surgery. Further large scale multi centered studies comparing the protective role of selenium with combined therapy of other bioactive agents are needed to provide convincing explanations.

Systematic Review Registration

PROSPERO Identifier: 424920.

Association between Plasma Ascorbic Acid Levels and Postoperative Delirium in Older Patients Undergoing Cardiovascular Surgery: A Prospective Observational Study

BACKGROUND

The incidence of delirium is high in older patients undergoing cardiovascular surgery with cardiopulmonary bypass (CPB). Intraoperative tissue hypoperfusion and re-reperfusion injury, which generate reactive oxygen species (ROS), are suggested to induce delirium. Ascorbic acid is an excellent antioxidant and may reduce organ damage by inhibiting the production of ROS. This prospective observational study aimed to measure pre- and postoperative plasma ascorbic acid levels and examine their association with delirium.

METHODS

Patients older than 70 years of age scheduled for elective cardiovascular surgery using CPB were enrolled. From September 2020 to December 2021, we enrolled 100 patients, and the data of 98 patients were analyzed.

RESULTS

In total, 31 patients developed delirium, while 67 did not. Preoperative plasma ascorbic acid levels did not differ between the non-delirium and delirium groups (6.0 ± 2.2 vs. 5.5 ± 2.4 µg/mL, p = 0.3). Postoperative plasma ascorbic acid levels were significantly different between the groups (2.8 [2.3-3.5] vs. 2.3 [1.6-3.3] µg/mL, p = 0.037).

CONCLUSIONS

In patients who undergo cardiovascular surgery with CPB, lower postoperative plasma ascorbic acid levels may be associated with the development of delirium.

Alteration of Blood Oxidative Stress Status in Patients with Thoracic Aortic Dissection: A Pilot Study

BACKGROUND

Thoracic aortic dissection (TAD) is a life-threatening condition which usually occurs on an aneurysmal aortic wall. Although increasing data have shown that inflammation and oxidative stress play an important role in the patho-physiology of dissection, systemic oxidative stress status (OSS) has not been clearly determined in patients suffering from TAD.

METHODS

A cohort of 115 patients presenting type A or B TAD were admitted to our center from 2013 to 2017. Out of this cohort, 46 patients were included in a study on dissected aorta (LIege study on DIssected Aorta: LIDIA). In 18 out of the 46 patients, systemic OSS parameters were evaluated after TAD diagnosis by determination of eight different antioxidants, four trace elements, two markers of oxidative lipid damage and two inflammatory markers.

RESULTS

The 18 TAD patients included 10 men and 8 women (median age: 62 years; interquartile range: 55-68) diagnosed with type A (N = 8) or B (N = 10) TAD. Low plasma levels of vitamin C, β-carotene, γ-tocopherol, thiol proteins, paraoxonase and selenium were observed in these 18 patients. By contrast, the concentration of copper and total hydroperoxides, copper/zinc ratio, as well as inflammatory markers, were higher than the reference intervals. No difference was observed in oxidative stress biomarker concentrations between type A and B TAD patients.

CONCLUSIONS

This pilot study, limited to 18 TAD patients, revealed a heightened systemic OSS, determined at 15.5 days (median) after the initial diagnosis, in those TAD patients without complications (malperfusion syndrome and aneurysm formation). Larger studies on biological fluids are needed to better characterize the oxidative stress and interpret its consequence in TAD disease.

Impact of intravenous vitamin C as a monotherapy on mortality risk in critically ill patients: A meta-analysis of randomized controlled trials with trial sequential analysis

Background

This meta-analysis aimed at investigating the pooled evidence regarding the effects of intravenous vitamin C (IVVC) on mortality rate in critically ill patients.

Methods

Databases including Medline, Embase, and Cochrane Library were searched from inception to October, 2022 to identify RCTs. The primary outcome was the risk of overall mortality. Subgroup analyses were performed based on IVVC dosage (i.e., cut-off value: 100 mg/kg/day or 10000 mg/day). Trial sequential analysis (TSA) was used to examine the robustness of evidence.

Results

A total of 12 trials including 1,712 patients were analyzed. Although meta-analysis demonstrated a lower risk of mortality in patients with IVVC treatment compared to those without [risk ratio (RR): 0.76, 95% CI: 0.6 to 0.97, p = 0.02, I2 = 36%, 1,711 patients), TSA suggested the need for more studies for verification. Moreover, subgroup analyses revealed a reduced mortality risk associated with a low IVVC dosage (RR = 0.72, p = 0.03, 546 patients), while no beneficial effect was noted with high IVVC dosage (RR = 0.74, p = 0.13, I2 = 60%, 1,165 patients). The durations of vasopressor [mean difference (MD): −37.75 h, 404 patients) and mechanical ventilation (MD: −47.29 h, 388 patients) use were shorter in the IVVC group than those in the controls, while there was no significant difference in other prognostic outcomes (e.g., length of stay in intensive care unit/hospital) between the two groups.

Conclusion

Although intravenous vitamin C as a monotherapy reduced pooled mortality, durations of vasopressor use and mechanical ventilation, further research is required to support our findings and to identify the optimal dosage of vitamin C in the critical care setting.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022371090.

Overview of oxidative stress and the role of micronutrients in critical illness

Inflammation and oxidative stress represent physiological response mechanisms to different types of stimuli and injury during critical illness. Its proper regulation is fundamental to cellular and organismal survival and are paramount to outcomes and recovery from critical illness. A proper maintenance of the delicate balance between inflammation, oxidative stress, and immune response is crucial for resolution from critical illness with important implications for patient outcome. The extent of inflammation and oxidative stress under normal conditions is limited by the antioxidant defense system of the human body, whereas the antioxidant capacity is commonly significantly compromised, and serum levels of micronutrients and vitamins significantly depleted in patients who are critically ill. Hence, the provision of antioxidants and anti-inflammatory nutrients may help to reduce the extent of oxidative stress and therefore improve clinical outcomes in patients who are critically ill. As existing evidence of the beneficial effects of antioxidant supplementation in patients who are critically ill is still unclear, actual findings about the most promising anti-inflammatory and antioxidative candidates selenium, vitamin C, zinc, and vitamin D will be discussed in this narrative review. The existing evidence provided so far demonstrates that several factors need to be considered to determine the efficacy of an antioxidant supplementation strategy in patients who are critically ill and indicates the need for adequately designed multicenter prospective randomized control trials to evaluate the clinical significance of different types and doses of micronutrients and vitamins in selected groups of patients with different types of critical illness.

An update of the effects of vitamins D and C in critical illness

Many critically ill patients are vitamin D and vitamin C deficient and the current international guidelines state that hypovitaminoses should be compensated. However, uncertainty about optimal dosage, timing and indication exists in clinical routine, mainly due to the conflicting evidence. This narrative review discusses both micronutrients with regards to pathophysiology, clinical evidence of benefits, potential risks, and guideline recommendations. Evidence generated from the most recent clinical trials are summarized and discussed. In addition, pragmatic tips for the application of these vitamins in the clinical routine are given. The supplementations of vitamin D and C represent cost-effective and simple interventions with excellent safety profiles. Regarding vitamin D, critically ill individuals require a loading dose to improve 25(OH)D levels within a few days, followed by a daily or weekly maintenance dose, usually higher doses than healthy individuals are needed. For vitamin C, dosages of 100-200 mg/d are recommended for patients receiving parenteral nutrition, but needs may be as high as 2-3 g/d in acutely ill patients.

Vitamin C supplementation attenuates oxidative stress and improves erythrocyte deformability in cardiac surgery with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) depletes endogenous Vitamin C and generates oxidative stress in cardiac surgery. This study aimed to clarify whether Vitamin C supplementation reduces oxidant production and improves erythrocyte deformability in cardiac surgery with CPB. In a randomized and controlled design, 30 eligible patients undergoing cardiac surgery with hypothermic CPB were equally assigned to the Vitamin C group and control group. Subjects of the Vitamin C group and control group received an intravenous infusion of Vitamin C 20 mg·kg^-1 and a placebo during rewarming period of CPB, respectively. We measured the plasma level of reactive oxygen species (ROS) and phosphorylation levels of non-muscle myosin IIA (NMIIA) in erythrocyte membrane, as an index of erythrocyte deformability, before and after CPB. Vitamin C supplementation attenuated the surge in plasma ROS after CPB, mean 1.661 ± standard deviation 0.801 folds in the Vitamin C group and 2.743 ± 1.802 in the control group. The tyrosine phosphorylation level of NMIIA after CPB was upregulated in the Vitamin C group compared to the control group, 2.159 ± 0.887 folds and 1.384 ± 0.445 (P = 0.0237). In addition, the phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and focal adhesion kinase (FAK) in erythrocytes was concurrently enhanced in the Vitamin C group after CPB. The phosphorylation level of endothelial nitric oxide synthase in erythrocytes was significantly increased in the Vitamin C group (1.734 ± 0.371 folds) compared to control group (1.102 ± 0.249; P = 0.0061). Patients receiving Vitamin C had lower intraoperative blood loss and higher systemic vascular resistance after CPB compared to controls. Vitamin C supplementation attenuates oxidative stress and improves erythrocyte deformability via VASP/FAK signaling pathway in erythrocytes during CPB.

Sequential Organ Failure Assessment Score in the ICU As a Predictor of Long-Term Survival After Cardiac Surgery

OBJECTIVES:

The Sequential Organ Failure Assessment (SOFA) score is a predictor of mortality in ICU patients. Although it is widely used and has been validated as a reliable and independent predictor of mortality and morbidity in cardiac ICU, few studies correlate early postoperative SOFA with long-term survival.

DESIGN:

Retrospective observational cohort study.

SETTING:

Tertiary academic cardiac surgery ICU.

PATIENTS:

One-thousand three-hundred seventy-nine patients submitted to cardiac surgery.

INTERVENTIONS:

SOFA 24 hours, SOFA 48 hours, mean, and highest SOFA scores were correlated with survival at 12 and 24 months. Wilcoxon tests were used to analyze differences in variables. Multivariate logistic regressions and likelihood ratio test were used to access the predictive modeling. Receiver operating characteristic curves were used to assess accuracy of the variables in separating survivor from nonsurvivors.

MEASUREMENTS AND MAIN RESULTS:

Lower SOFA scores have better survival rates at 12 and 24 months. Highest SOFA and SOFA at 48 hours showed to be better predictors of outcome and to have higher accuracy in distinguishing survivors from nonsurvivors than initial SOFA and mean SOFA. A decreasing score during the first 48 hours had mortality rates of 4.9%, while an unchanged or increased score was associated with a mortality rate of 5.7%.

CONCLUSIONS:

SOFA score in the ICU after cardiac surgery correlated with survival at 12 and 24 months. Patients with lower SOFA scores had higher survival rates. Differences in survival at 12 months were better correlated with the absolute value at 48 hours than with its variation. SOFA score may be useful to predict long-term outcomes and to stratify patients with higher probability of mortality.

Perioperative micronutrients, macroscopic benefits?

'Micronutrients' are vitamins and minerals vital for healthy metabolic function, wound healing and disease and infection prevention. Micronutrients may play a role in significantly improving postoperative recovery and indices of patient comfort; however, minimal research exists for surgical patients. Furthermore, current guidelines on perioperative nutrition have a macronutrient focus which may fail to guide detection and treatment of the subclinical micronutrient deficiency in a patient who is not obviously malnourished. Limited research into supplementation of some micronutrient deficiencies shows favourable results; however, given the financial implications of wound care, the prevalence of micronutrient deficiency and possible benefits from attention to micronutrition for postoperative recovery, further research into this area is urgently warranted. Interventions to guide optimal future clinical practice are suggested.

Inflammation and Oxidative Stress in the Context of Extracorporeal Cardiac and Pulmonary Support

Extracorporeal circulation (ECC) systems, including cardiopulmonary bypass, and extracorporeal membrane oxygenation have been an irreplaceable part of the cardiothoracic surgeries, and treatment of critically ill patients with respiratory and/or cardiac failure for more than half a century. During the recent decades, the concept of extracorporeal circulation has been extended to isolated machine perfusion of the donor organ including thoracic organs (ex-situ organ perfusion, ESOP) as a method for dynamic, semi-physiologic preservation, and potential improvement of the donor organs. The extracorporeal life support systems (ECLS) have been lifesaving and facilitating complex cardiothoracic surgeries, and the ESOP technology has the potential to increase the number of the transplantable donor organs, and to improve the outcomes of transplantation. However, these artificial circulation systems in general have been associated with activation of the inflammatory and oxidative stress responses in patients and/or in the exposed tissues and organs. The activation of these responses can negatively affect patient outcomes in ECLS, and may as well jeopardize the reliability of the organ viability assessment, and the outcomes of thoracic organ preservation and transplantation in ESOP. Both ECLS and ESOP consist of artificial circuit materials and components, which play a key role in the induction of these responses. However, while ECLS can lead to systemic inflammatory and oxidative stress responses negatively affecting various organs/systems of the body, in ESOP, the absence of the organs that play an important role in oxidant scavenging/antioxidative replenishment of the body, such as liver, may make the perfused organ more susceptible to inflammation and oxidative stress during extracorporeal circulation. In the present manuscript, we will review the activation of the inflammatory and oxidative stress responses during ECLP and ESOP, mechanisms involved, clinical implications, and the interventions for attenuating these responses in ECC.

Circulating Lipopolysaccharides and Impaired Antioxidant Status in Patients With Atrial Fibrillation. Data From the ATHERO-AF Study

Objectives: Atrial fibrillation (AF) is characterized by an oxidative imbalance, which is associated with an increased risk of cardiovascular events (CVEs). It is unclear whether low grade endotoxemia may contribute to the impaired antioxidant status in AF patients. We investigated the relationship between circulating lipopolysaccharides (LPS) and antioxidant status in AF patients.

Patients and Methods:Post-hoc analysis from the ongoing prospective observational cohort ATHERO-AF study including 907 patients. Antioxidant status was evaluated by the activity of glutathione peroxidase 3 (GPx3) and superoxide dismutase (SOD). Patients were divided into two groups to evaluate the risk of CVEs: (1) LPS below median and GPx3 above median (n = 254); (2) LPS above median and GPx3 below median (n = 263).

Results: The mean age was 73.5 ± 8.3 years, and 43.1% were women. Median LPS and GPx3 were 50.0 pg/ml [interquartile range (IQR) 15–108] and 20.0 U/ml (IQR 10.0–34.0), respectively. Patients of Groups 2 were older, with a higher prevalence of heart failure. LPS above the median was associated with reduced GPx3 [Odds Ratio for LPS 1.752, 95% Confidence Interval (CI) 1.344–2.285, p < 0.001] and SOD (OR 0.525, 95%CI 0.403–0.683) activity after adjustment for CHA₂DS₂VASc score. In a mean follow-up of 54.0 ± 36.8 months, 118 CVEs occurred, 42 in Group 1 and 76 in Group 2 (Log-Rank test p = 0.001). At multivariable Cox regression analysis, Group 2 was associated with a higher risk of CVEs [Hazard Ratio (HR) 1.644, 95%CI 1.117–2,421, p = 0.012], along with age ≥ 75 years (HR 2.035, 95%CI 1.394–2.972, p < 0.001), diabetes (HR 1.927, 95%CI 1.280–2.900, p = 0.002), and previous cerebrovascular disease (HR 1.895, 95%CI 1.251–2.870, p = 0.003) and previous cardiovascular disease (HR 1.708, 95%CI 1.149–2.538, p = 0.008).

Conclusions: Our study indicates that circulating LPS may contribute to impaired antioxidant status in patients with AF. Patients with coincidentally high LPS and reduced GPx3 activity showed the highest risk of CVEs.

Early high-dose vitamin C in post-cardiac arrest syndrome (VITaCCA): study protocol for a randomized, double-blind, multi-center, placebo-controlled trial

BACKGROUND

High-dose intravenous vitamin C directly scavenges and decreases the production of harmful reactive oxygen species (ROS) generated during ischemia/reperfusion after a cardiac arrest. The aim of this study is to investigate whether short-term treatment with a supplementary or very high-dose intravenous vitamin C reduces organ failure in post-cardiac arrest patients.

METHODS

This is a double-blind, multi-center, randomized placebo-controlled trial conducted in 7 intensive care units (ICUs) in The Netherlands. A total of 270 patients with cardiac arrest and return of spontaneous circulation will be randomly assigned to three groups of 90 patients (1:1:1 ratio, stratified by site and age). Patients will intravenously receive a placebo, a supplementation dose of 3 g of vitamin C or a pharmacological dose of 10 g of vitamin C per day for 96 h. The primary endpoint is organ failure at 96 h as measured by the Resuscitation-Sequential Organ Failure Assessment (R-SOFA) score at 96 h minus the baseline score (delta R-SOFA). Secondary endpoints are a neurological outcome, mortality, length of ICU and hospital stay, myocardial injury, vasopressor support, lung injury score, ventilator-free days, renal function, ICU-acquired weakness, delirium, oxidative stress parameters, and plasma vitamin C concentrations.

DISCUSSION

Vitamin C supplementation is safe and preclinical studies have shown beneficial effects of high-dose IV vitamin C in cardiac arrest models. This is the first RCT to assess the clinical effect of intravenous vitamin C on organ dysfunction in critically ill patients after cardiac arrest.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03509662. Registered on April 26, 2018. https://clinicaltrials.gov/ct2/show/NCT03509662 European Clinical Trials Database (EudraCT): 2017-004318-25. Registered on June 8, 2018. https://www.clinicaltrialsregister.eu/ctr-search/trial/2017-004318-25/NL.

Novel Combined Antioxidant Strategy against Hypertension, Acute Myocardial Infarction and Postoperative Atrial Fibrillation

Reactive oxygen species (ROS) play a physiological role in the modulation of several functions of the vascular wall; however, increased ROS have detrimental effects. Hence, oxidative stress has pathophysiological impacts on the control of the vascular tone and cardiac functions. Recent experimental studies reported the involvement of increased ROS in the mechanism of hypertension, as this disorder associates with increased production of pro-oxidants and decreased bioavailability of antioxidants. In addition, increased ROS exposure is found in ischemia-reperfusion, occurring in acute myocardial infarction and cardiac surgery with extracorporeal circulation, among other settings. Although these effects cause major heart damage, at present, there is no available treatment. Therefore, it should be expected that antioxidants counteract the oxidative processes, thereby being suitable against cardiovascular disease. Nevertheless, although numerous experimental studies agree with this notion, interventional trials have provided mixed results. A better knowledge of ROS modulation and their specific interaction with the molecular targets should contribute to the development of novel multitarget antioxidant effective therapeutic strategies. The complex multifactorial nature of hypertension, acute myocardial infarction, and postoperative atrial fibrillation needs a multitarget antioxidant strategy, which may give rise to additive or synergic protective effects to achieve optimal cardioprotection.

A meta-analysis of randomized clinical trials on the impact of oral vitamin C supplementation on first-year outcomes in orthopedic patients

This meta-analysis aimed at investigating the impact of oral vitamin C supplementation on the post-procedural recovery of orthopedic patients, including functional outcomes and complex regional pain syndrome type I (CRPS I). Literature search using the Medline, Cochrane Library, and Embase databases from inception till March 2021 identified seven eligible randomized controlled trials with 1,361 participants. Forest plot revealed no significant difference in the functional outcomes at 6-12 months [standardized mean difference (SMD) = -0.00, 95% CI - 0.19 to 0.18, 467 patients], risk of overall complications (RR = 0.98, 95% CI 0.68 to 1.39, 426 patients), and pain severity at 3-6 months (SMD = - 0.18, 95% CI - 0.49 to 0.12, 486 patients) between patients with and without oral vitamin C supplementation. Pooled analysis showed that vitamin C treatment reduced the risk of CRPS I regardless of dosage (RR = 0.46, 95% CI 0.25 to 0.85, 1143 patients). In conclusion, the current meta-analysis demonstrated that oral vitamin C supplementation may reduce the risk of complex regional pain syndrome type I but did not improve the functional outcomes in orthopedic patients. Nevertheless, because of the small number of trials included in the present study, further large-scale clinical studies are warranted to support our findings.

The efficacy of intravenous vitamin C in critically ill patients: A meta-analysis of randomized controlled trials

BACKGROUND & AIMS

A large number of clinical studies have shown that intravenous vitamin C supplementation is beneficial for critically ill patients, but current research conclusions are controversial. This meta-analysis included high-quality randomized controlled trials (RCTs) to evaluate the efficacy of intravenous vitamin C in critically ill patients.

METHODS

We searched PubMed, EMBASE and the Cochrane Library from inception to August 15, 2020 to identify published reports of RCTs evaluating the role of intravenous vitamin C in critically ill patients. Risk ratios values (RRs) and 95% confidence intervals (CIs) were calculated by random-effects meta-analysis. Trial sequential analysis (TSA), meta-regression, subgroup analyses and sensitivity analyses were also performed.

RESULTS

Our meta-analysis included 18 RCTs involving 2001 patients (1005 with vitamin C treatment and 996 control treatment). Intravenous vitamin C administration reduced the intensive care unit (ICU) length of stay (LOS) (MD = -0.36, 95% CI: -0.60 to -0.11, P = 0.004) and hospital LOS (MD = -1.50, 95% CI: -2.64 to -0.35, P = 0.01) but had no significant effect on the longest follow-up mortality, hospital or ICU mortality and change in Sequential Organ Failure Assessment (SOFA) score. TSAs for mortality, ICU and hospital LOS were inconclusive.

CONCLUSIONS

Intravenous vitamin C administration may shorten ICU LOS and hospital LOS. It had no effect on mortality and organ failure. All TSAs were inconclusive, and the value of vitamin C for critically ill patients needs to be demonstrated in more high-quality RCTs.

Correction: Hill, A.; et al. Effects of Vitamin C on Organ Function in Cardiac Surgery Patients: A Systematic Review and Meta-Analysis. Nutrients 2019, 11, 2103

The authors thank the readers for pointing out the issues [...].

Reactive Oxygen Species (ROS)-Responsive Nanomedicine for Solving Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a severe condition for most organs, which could occur in various tissues including brain, heart, liver, and kidney, etc. As one of the major hazards, reactive oxygen species (ROS) is excessively generated after IRI, which causes severe damage inside tissues and further induces the following injury via inflammatory response. However, current medical strategies could not thoroughly diagnose and prevent this disease, eventually leading to severe sequelae by missing the best time point for therapy. In the past decade, various nanoparticles that could selectively respond to ROS have been developed and applied in IRI. These advanced nanomedicines have shown efficient performance in detecting and treating a series of IRI (e.g., acute kidney injury, acute liver injury, and ischemic stroke, etc.), which are well-summarized in the current review. In addition, the nano-platforms (e.g., anti-IL-6 antibody, rapamycin, and hydrogen sulfide delivering nanoparticles, etc.) for preventing IRI during organ transplantation have also been included. Moreover, the development and challenges of ROS-responsive nanomedicine are systematically discussed for guiding the future direction.

Vitamin C for Cardiac Surgery Patients: Several Errors in a Published Meta-Analysis. Comment on "Effects of Vitamin C on Organ Function in Cardiac Surgery Patients: A Systematic Review and Meta-Analysis. Nutrients 2019, 11, 2103"

We recently published a meta-analysis on vitamin C and the length of intensive care unit [ICU] stay [...].

Vitamin C may reduce the duration of mechanical ventilation in critically ill patients: a meta-regression analysis

BACKGROUND

Our recent meta-analysis indicated that vitamin C may shorten the length of ICU stay and the duration of mechanical ventilation. Here we analyze modification of the vitamin C effect on ventilation time, by the control group ventilation time (which we used as a proxy for severity of disease in the patients of each trial).

METHODS

We searched MEDLINE, Scopus, and the Cochrane Central Register of Controlled Trials and reference lists of relevant publications. We included controlled trials in which the administration of vitamin C was the only difference between the study groups. We did not limit our search to randomized trials and did not require placebo control. We included all doses and all durations of vitamin C administration. One author extracted study characteristics and outcomes from the trial reports and entered the data in a spreadsheet. Both authors checked the data entered against the original reports. We used meta-regression to examine whether the vitamin C effect on ventilation time depends on the duration of ventilation in the control group.

RESULTS

We identified nine potentially eligible trials, eight of which were included in the meta-analysis. We pooled the results of the eight trials, including 685 patients in total, and found that vitamin C shortened the length of mechanical ventilation on average by 14% (P = 0.00001). However, there was significant heterogeneity in the effect of vitamin C between the trials. Heterogeneity was fully explained by the ventilation time in the untreated control group. Vitamin C was most beneficial for patients with the longest ventilation, corresponding to the most severely ill patients. In five trials including 471 patients requiring ventilation for over 10 h, a dosage of 1-6 g/day of vitamin C shortened ventilation time on average by 25% (P < 0.0001).

CONCLUSIONS

We found strong evidence that vitamin C shortens the duration of mechanical ventilation, but the magnitude of the effect seems to depend on the duration of ventilation in the untreated control group. The level of baseline illness severity should be considered in further research. Different doses should be compared directly in future trials.

The Pharmacokinetics of Vitamin C

The pharmacokinetics of vitamin C (vitC) is indeed complex. Regulated primarily by a family of saturable sodium dependent vitC transporters (SVCTs), the absorption and elimination are highly dose-dependent. Moreover, the tissue specific expression levels and subtypes of these SVCTs result in a compartmentalized distribution pattern with a diverse range of organ concentrations of vitC at homeostasis ranging from about 0.2 mM in the muscle and heart, and up to 10 mM in the brain and adrenal gland. The homeostasis of vitC is influenced by several factors, including genetic polymorphisms and environmental and lifestyle factors such as smoking and diet, as well as diseases. Going from physiological to pharmacological doses, vitC pharmacokinetics change from zero to first order, rendering the precise calculation of dosing regimens in, for example, cancer and sepsis treatment possible. Unfortunately, the complex pharmacokinetics of vitC has often been overlooked in the design of intervention studies, giving rise to misinterpretations and erroneous conclusions. The present review outlines the diverse aspects of vitC pharmacokinetics and examines how they affect vitC homeostasis under a variety of conditions.