Prolonged glucocorticoid treatment and secondary prevention in acute respiratory distress syndrome

Effectiveness of Glucocorticoids in Acute Respiratory Distress Syndrome: An Umbrella Review

Objectives. Acute respiratory distress syndrome is a very challenging condition that is associated with high morbidity and mortality. This review was intended to evaluate evidence on the effectiveness of glucocorticoid treatment for acute respiratory distress syndrome. Method. A comprehensive search strategy was conducted on PubMed/Medline, Cochrane Library, Science Direct, and LILACS. Data extraction was carried out by two independent reviewers using a customized checklist. The quality of each systematic review was assessed by two independent reviewers using an AMSTAR tool, and the overall quality of evidence was generated with online GRADEpro GDT software for primary and secondary outcomes. Results. The umbrella review included nine systematic reviews and meta-analysis and one narrative review with 8491 participants. The methodological quality of the included studies was moderate-to-high quality. The overall quality of evidence and recommendations varied form high to very low. Conclusion. There is high-to-moderate quality evidence that early low-dose prolonged glucocorticoid therapy reduces mortality in ARDS. However, randomized controlled trials with large sample sizes to address ventilator-free days, the incidence of infection, and other glucocorticoid-associated adverse events are required as the quality of evidence for these secondary outcomes which were low to very low. Registration. This umbrella review was registered in PROSPERO, the International Prospective Register of Systematic Reviews (CRD42019130539).

Regulation of inflammatory biomarkers by intravenous methylprednisolone in pediatric ARDS patients: Results from a double-blind, placebo-controlled randomized pilot trial

OBJECTIVE

A double-blind, randomized controlled trial showed that low-dose glucocorticoid therapy in pediatric ARDS patients is feasible and may improve both ventilation and oxygenation indices in these patients. However, the molecular mechanisms underlying potential changes in outcomes remain unclear. Based on these clinical findings, this study was designed to examine the effects of intravenous methylprednisolone on circulating inflammatory biomarkers in pediatric ARDS patients.

DESIGN

Double-blind, placebo-controlled randomized trial with blood collection on study entry and day 7.

SETTING

Tertiary care children's hospital.

PATIENTS

Children (0-18years) with ARDS undergoing mechanical ventilation.

INTERVENTIONS

35 children were randomized within 72h of mechanical ventilation. The glucocorticoid group received methylprednisolone 2mg/kg loading dose followed by 1mg/kg/day continuous infusion from days 1 to 7. Both groups were ventilated following the ARDSnet recommendations. WBC and differential cell counts, plasma cytokines and CRP levels, and coagulation parameters were analyzed on days 0 and 7.

RESULTS

At study entry, the placebo group had higher IL-15 and basophil levels. On day 7, in comparison to study entry, the placebo group had lower IL-1α, IFN-γ and IL-10 levels. The glucocorticoid group had lower INF-α, IL-6, IL-10, MCP-1, G-CSF and GM-CSF levels, and higher IL-17α levels on day 7 in comparison to study entry. Total and differential cell counts remained unchanged within the placebo group between days 0 and 7, whereas in the glucocorticoid group total WBC and platelets counts were increased on day 7. Pearson's correlation studies within the placebo and glucocorticoid groups revealed positive and negative correlations between cytokine levels, cell counts, coagulation parameters and relevant clinical parameters of disease severity identified in our previous study. Multiple regression models identified several cytokines as predictors for alterations in clinical parameters of disease severity.

CONCLUSION

This pilot study shows the feasibility of simultaneously measuring multiple inflammatory cytokines, cell counts and coagulation parameters in pediatric ARDS patients. We report statistical models that may be useful for future, larger trials to predict ARDS severity and outcomes.

Mechanical Stress and the Induction of Lung Fibrosis via the Midkine Signaling Pathway

RATIONALE

Lung-protective ventilatory strategies have been widely used in patients with acute respiratory distress syndrome (ARDS), but the ARDS mortality rate remains unacceptably high and there is no proven pharmacologic therapy.

OBJECTIVES

Mechanical ventilation can induce oxidative stress and lung fibrosis, which may contribute to high dependency on ventilator support and increased ARDS mortality. We hypothesized that the novel cytokine, midkine (MK), which can be up-regulated in oxidative stress, plays a key role in the pathogenesis of ARDS-associated lung fibrosis.

METHODS

Blood samples were collected from 17 patients with ARDS and 10 healthy donors. Human lung epithelial cells were challenged with hydrogen chloride followed by mechanical stretch for 72 hours. Wild-type and MK gene-deficient (MK(-/-)) mice received two-hit injury of acid aspiration and mechanical ventilation, and were monitored for 14 days.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of MK were higher in patients with ARDS than in healthy volunteers. Exposure to mechanical stretch of lung epithelial cells led to an epithelial-mesenchymal transition profile associated with increased expression of angiotensin-converting enzyme, which was attenuated by silencing MK, its receptor Notch2, or NADP reduced oxidase 1. An increase in collagen deposition and hydroxyproline level and a decrease in lung tissue compliance seen in wild-type mice were largely attenuated in MK(-/-) mice.

CONCLUSIONS

Mechanical stretch can induce an epithelial-mesenchymal transition phenotype mediated by the MK-Notch2-angiotensin-converting enzyme signaling pathway, contributing to lung remodeling. The MK pathway is a potential therapeutic target in the context of ARDS-associated lung fibrosis.

Impact of Corticosteroids on Mortality in Patients with Acute Respiratory Distress Syndrome: A Systematic Review and Meta-analysis

OBJECTIVE

The impact of corticosteroids on acute respiratory distress syndrome (ARDS) mortality remains controversial following the publication of numerous trials, observational studies and meta-analyses. An updated meta-analysis is warranted, as a few original studies on this topic have been published since the last meta-analysis.

METHODS

We searched for eligible articles using four databases. In particular, we included full-length original articles providing sufficient data for evaluating the impact of corticosteroid treatment on adult ARDS mortality in the form of odds ratios. A fixed model with the confidence interval method was used. An assessment of publication bias and sensitivity analyses were also conducted.

RESULTS

We included 11 of 185 articles. The pooled odds ratio for corticosteroids with respect to all-cause mortality involving 949 patients was 0.77 [95% confidence interval (CI): 0.58-1.03, p=0.079] with strong heterogeneity(I2=70%, p<0.001). The results of the sensitivity analysis, Begg-Kendall test (τ=0.53, p=0.024)and funnel plot consistently suggested the existence of strong publication bias. After six potentially unpublished cohorts were filled using Duval's trim and fill method, the pooled odds ratio shifted to 1.11 (95% CI0.86-1.44, p=0.427). In addition, the sensitivity analyses suggested that corticosteroid treatment has a different impact on mortality depending on the comorbidities and trigger events.

CONCLUSION

We were unable to confirm, based on the data of published studies, the favorable impact of corticosteroid therapy on mortality in overall ARDS cases. Published articles exhibit strong publication bias,and previous meta-analyses may be affected by this publication bias. Further research focusing on pathophysiology- or trigger event-specific ARDS is anticipated.

Mechanical ventilation-associated lung fibrosis in acute respiratory distress syndrome: a significant contributor to poor outcome

One of the most challenging problems in critical care medicine is the management of patients with the acute respiratory distress syndrome. Increasing evidence from experimental and clinical studies suggests that mechanical ventilation, which is necessary for life support in patients with acute respiratory distress syndrome, can cause lung fibrosis, which may significantly contribute to morbidity and mortality. The role of mechanical stress as an inciting factor for lung fibrosis versus its role in lung homeostasis and the restoration of normal pulmonary parenchymal architecture is poorly understood. In this review, the authors explore recent advances in the field of pulmonary fibrosis in the context of acute respiratory distress syndrome, concentrating on its relevance to the practice of mechanical ventilation, as commonly applied by anesthetists and intensivists. The authors focus the discussion on the thesis that mechanical ventilation-or more specifically, that ventilator-induced lung injury-may be a major contributor to lung fibrosis. The authors critically appraise possible mechanisms underlying the mechanical stress-induced lung fibrosis and highlight potential therapeutic strategies to mitigate this fibrosis.

To ventilate, oscillate, or cannulate?

Ventilatory management of acute respiratory distress syndrome has evolved significantly in the last few decades. The aims have shifted from optimal gas transfer without concern for iatrogenic risks to adequate gas transfer while minimizing lung injury. This change in focus, along with improved ventilator and multiorgan system management, has resulted in a significant improvement in patient outcomes. Despite this, a number of patients develop hypoxemic respiratory failure refractory to lung-protective ventilation (LPV). The intensivist then faces the dilemma of either persisting with LPV using adjuncts (neuromuscular blocking agents, prone positioning, recruitment maneuvers, inhaled nitric oxide, inhaled prostacyclin, steroids, and surfactant) or making a transition to rescue therapies such as high-frequency oscillatory ventilation (HFOV) and/or extracorporeal membrane oxygenation (ECMO) when both these modalities are at their disposal. The lack of quality evidence and potential harm reported in recent studies question the use of HFOV as a routine rescue option. Based on current literature, the role for venovenous (VV) ECMO is probably sequential as a salvage therapy to ensure ultraprotective ventilation in selected young patients with potentially reversible respiratory failure who fail LPV despite neuromuscular paralysis and prone ventilation. Given the risk profile and the economic impact, future research should identify the patients who benefit most from VV ECMO. These choices may be further influenced by the emerging novel extracorporeal carbon dioxide removal devices that can compliment LPV. Given the heterogeneity of acute respiratory distress syndrome, each of these modalities may play a role in an individual patient. Future studies comparing LPV, HFOV, and VV ECMO should not only focus on defining the patients who benefit most from each of these therapies but also consider long-term functional outcomes.

Is prolonged low-dose glucocorticoid treatment beneficial in community-acquired pneumonia?

Community-acquired pneumonia (CAP) has a significant impact on public health in terms of short-term and long-term morbidity and mortality. Irrespective of microbiological etiology, the host's inability to fully downregulate systemic inflammation is the dominant pathogenetic process contributing to acute and long-term morbidity and mortality in CAP. Glucocorticoids are the natural regulators of inflammation, and their production increases during infection. There is consistent evidence that downregulation of systemic inflammation with prolonged low-dose glucocorticoid treatment in patients with severe sepsis and acute respiratory distress syndrome improves cardiovascular and pulmonary organ physiology. A recent meta-analysis of pooled controlled small trials (n = 970) of patients admitted with CAP found improved short-term mortality in the subgroup with severe CAP and/or receiving >5 days of glucocorticoid treatment. We have expanded on this meta-analysis by including patients with CAP recruited in trials investigating prolonged low-dose glucocorticoid treatment in septic shock and/or early acute respiratory distress syndrome (n = 1,206). Our findings confirm a survival advantage for severe CAP (RR 0.66, 95% confidence interval 0.51-0.84; p = .001). A large randomized trial is in progress to confirm the aggregate findings of these small trials and to evaluate the long-term effect of this low-cost treatment.

Induction of alternatively activated macrophages enhances pathogenesis during severe acute respiratory syndrome coronavirus infection

Infection with severe acute respiratory syndrome coronavirus (SARS-CoV) causes acute lung injury (ALI) that often leads to severe lung disease. A mouse model of acute SARS-CoV infection has been helpful in understanding the host response to infection; however, there are still unanswered questions concerning SARS-CoV pathogenesis. We have shown that STAT1 plays an important role in the severity of SARS-CoV pathogenesis and that it is independent of the role of STAT1 in interferon signaling. Mice lacking STAT1 have greater weight loss, severe lung pathology with pre-pulmonary-fibrosis-like lesions, and an altered immune response following infection with SARS-CoV. We hypothesized that STAT1 plays a role in the polarization of the immune response, specifically in macrophages, resulting in a worsened outcome. To test this, we created bone marrow chimeras and cell-type-specific knockouts of STAT1 to identify which cell type(s) is critical to protection from severe lung disease after SARS-CoV infection. Bone marrow chimera experiments demonstrated that hematopoietic cells are responsible for the pathogenesis in STAT1(-/-) mice, and because of an induction of alternatively activated (AA) macrophages after infection, we hypothesized that the AA macrophages were critical for disease severity. Mice with STAT1 in either monocytes and macrophages (LysM/STAT1) or ciliated lung epithelial cells (FoxJ1/STAT1) deleted were created. Following infection, LysM/STAT1 mice display severe lung pathology, while FoxJ1/STAT1 mice display normal lung pathology. We hypothesized that AA macrophages were responsible for this STAT1-dependent pathology and therefore created STAT1/STAT6(-/-) double-knockout mice. STAT6 is essential for the development of AA macrophages. Infection of the double-knockout mice displayed a lack of lung disease and prefibrotic lesions, suggesting that AA macrophage production may be the cause of STAT1-dependent lung disease. We propose that the control of AA macrophages by STAT1 is critical to regulating immune pathologies and for protection from long-term progression to fibrotic lung disease in a mouse model of SARS-CoV infection.

Predictors and outcome of patients with acute respiratory distress syndrome caused by miliary tuberculosis: a retrospective study in Chongqing, China

Background

Miliary tuberculosis (TB) is an uncommon cause of acute respiratory distress syndrome (ARDS) with a high mortality. The aim of the present study was to evaluate the clinical characteristics, predictors and outcome of patients with ARDS caused by miliary TB.

Methods

A retrospective study was conducted among patients with a diagnosis of ARDS with miliary TB in four hospitals from 2006 to 2010. Medical records and laboratory examinations of these patients were taken during the first 24 h of admission.

Results

Eighty-five patients with miliary TB developed ARDS, 45 of whom survived (52.9%). The median age was 36.6 ± 12.5 years with 38 males (44.7%). Diabetes mellitus (DM) was the most common underlying disease (18.8%).ICU mortality was 47.1%. The time from admission to anti-tuberculosis therapy was 4.5 ± 2.0 days. Mean duration of mechanical ventilation was 8.5 ± 3.0 days in all patients. Duration of time to diagnosis, time from diagnosis to mechanical ventilation, and time to anti-tuberculosis therapy were significantly shorter in survivors than those in non-survivors. Diabetes mellitus (OR 5.431, 95%CI 1.471-20.049; P = 0.005), ALT (70-100U/L, OR 10.029, 95%CI 2.764-36.389; P = 0.001), AST (>94U/L,OR 8.034, 95%CI 2.200-29.341; P = 0.002), D-dimer (>1.6mg/L, OR 3.167, 95%CI 0.896-11.187; P = 0.042), hemoglobin (<90g/L, OR 14.824, 95%CI 3.713-59.179; P = 0.001), albumin (<25g/L, OR 15.896, 95%CI 3.975-63.566; P = 0.001) were independent predictors of ARDS development in the setting of miliary TB.

Conclusions

Accurate diagnosis, early initiation of anti-tuberculosis therapy and mechanical ventilation are important for the outcome of patients with ARDS caused by miliary TB. DM, ALT, AST, D-dimer, hemoglobin, and albumin are independent predictors of ARDS development in patients with miliary TB.

Use of extracorporeal life support in adults with severe acute respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a recognized and accepted therapeutic option in the treatment of neonatal and pediatric respiratory failure. However, early studies in adults did not demonstrate a survival benefit associated with the utilization of ECMO for severe acute respiratory failure. Despite this historical lack of benefit, use of ECMO in adult patients has seen a recent resurgence. Local successes and a recently published randomized trial have both demonstrated promising results in an adult population with high baseline mortality and limited therapeutic options. This article will review the history of ECMO use for respiratory failure; investigate the driving forces behind the latest surge in interest in ECMO for adults with refractory severe acute respiratory failure; and describe potential applications of ECMO that will likely increase in the near future.

Pathophysiology of acute respiratory distress syndrome. Glucocorticoid receptor-mediated regulation of inflammation and response to prolonged glucocorticoid treatment

Based on molecular mechanisms and physiologic data, a strong association has been established between dysregulated systemic inflammation and progression of ARDS. In ARDS patients, glucocorticoid receptor-mediated down-regulation of systemic inflammation is essential to restore homeostasis, decrease morbidity and improve survival and can be significantly enhanced with prolonged low-to-moderate dose glucocorticoid treatment. A large body of evidence supports a strong association between prolonged glucocorticoid treatment-induced down-regulation of the inflammatory response and improvement in pulmonary and extrapulmonary physiology. The balance of the available data from controlled trials provides consistent strong level of evidence (grade 1B) for improving patient-centered outcomes. The sizable increase in mechanical ventilation-free days (weighted mean difference, 6.58 days; 95% CI, 2.93 -10.23; P<0.001) and ICU-free days (weighted mean difference, 7.02 days; 95% CI, 3.20-10.85; P<0.001) by day 28 is superior to any investigated intervention in ARDS. The largest meta-analysis on the subject concluded that treatment was associated with a significant risk reduction (RR=0.62, 95% CI: 0.43-0.91; P=0.01) in mortality and that the in-hospital number needed to treat to save one life was 4 (95% CI 2.4-10). The balance of the available data, however, originates from small controlled trials with a moderate degree of heterogeneity and provides weak evidence (grade 2B) for a survival benefit. Treatment decisions involve a tradeoff between benefits and risks, as well as costs. This low cost highly effective therapy is familiar to every physician and has a low risk profile when secondary prevention measures are implemented.

New modalities in treating pneumococcal pneumonia

Despite the availability of effective antibiotics and intensive medical care, pneumococcal pneumonia is still associated with substantial mortality. Early diagnosis is becoming increasingly possible. This article reviews several adjunctive measures that might be instituted at or soon after admission in patients who are hospitalized for community-acquired pneumonia that is found to be due to Streptococcus pneumoniae. Available data favor the use of a macrolide together with a β-lactam antibiotic for treatment, based largely on immunomodulatory activity of macrolides. Two large subgroup analyses from a single major study suggest that activated protein C (eg, drotrecogin) should be considered for patients with severe sepsis, organ failure, and an Acute Physiology and Chronic Health Evaluation II score > 25 due to pneumococcal pneumonia. Statins exert an anti-inflammatory effect and several retrospective studies suggest that their use might ameliorate the adverse effects of pneumonia. Because inflammation elsewhere in the body is associated with inflammation in coronary arteries and because pneumococcal pneumonia has been shown to precipitate myocardial infarction, statins might be of further benefit by decreasing the likelihood of associated myocardial infarction. Aspirin, which inhibits platelet aggregation in inflamed coronary arteries, might also be considered for initial therapy. One reason that the association between myocardial infarction and pneumonia was not previously recognized is that aspirin was widely used in the past when people had acute febrile conditions. The literature on the benefits of corticosteroids in pneumonia is not convincing, and a particularly well-done, very recent study shows no benefit with corticosteroid use in patients with pneumococcal pneumonia, and perhaps even a worse outcome. No clinical data favor the use of platelet-activating factor antagonists.