Pharmacological therapies for acute respiratory distress syndrome

Unraveling the impact of nitric oxide, almitrine, and their combination in COVID-19 (at the edge of sepsis) patients: a systematic review

Introduction: During the coronavirus disease 2019 (COVID-19) pandemic, a large number of critically ill and severe COVID-19 patients meet the diagnostic criteria for sepsis and even septic shock. The treatments for COVID-19 patients with sepsis are still very limited. For sepsis, improving ventilation is one of the main treatments. Nitric oxide (NO) and almitrine have been reported to improve oxygenation in patients with "classical" sepsis. Here, we conducted a systematic review and meta-analysis to evaluate the efficacy and safety of NO, almitrine, and the combination of both for COVID-19 (at the edge of sepsis) patients. Method: A systematic search was performed on Embase, PubMed, the Cochrane Library, the Web of Science, Wanfang Data, and China National Knowledge Infrastructure. Randomized clinical trials, cohort studies, cross-sectional studies, case-control studies, case series, and case reports in COVID-19 patients with suspected or confirmed sepsis were performed. Study characteristics, patient demographics, interventions, and outcomes were extracted from eligible articles. Results: A total of 35 studies representing 1,701 patients met eligibility criteria. Inhaled NO did not affect the mortality (OR 0.96, 95% CI 0.33-2.8, I2 = 81%, very low certainty), hospital length of stay (SMD 0.62, 95% CI 0.04-1.17, I2 = 83%, very low certainty), and intubation needs (OR 0.82, 95% CI 0.34-1.93, I2 = 56%, very low certainty) of patients with COVID-19 (at the edge of sepsis). Meanwhile, almitrine did not affect the mortality (OR 0.44, 95% CI 0.17-1.13, low certainty), hospital length of stay (SMD 0.00, 95% CI -0.29-0.29, low certainty), intubation needs (OR 0.94, 95% CI 0.5-1.79, low certainty), and SAEs (OR 1.16, 95% CI 0.63-2.15, low certainty). Compared with pre-administration, the PaO2/FiO2 of patients with NO (SMD-0.87, 95% CI -1.08-0.66, I2 = 0%, very low certainty), almitrine (SMD-0.73, 95% CI-1.06-0.4, I2 = 1%, very low certainty), and the combination of both (SMD-0.94, 95% CI-1.71-0.16, I2 = 47%, very low certainty) increased significantly. Conclusion: Inhaled NO, almitrine, and the combination of the two drugs improved oxygenation significantly, but did not affect the patients' mortality, hospitalization duration, and intubation needs. Almitrine did not significantly increase the patients' SAEs. Well-designed high-quality studies are needed for establishing a stronger quality of evidence. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=367667, identifier CRD42022367667.

Unraveling the protective mechanisms of Chuanfangyihao against acute lung injury: Insights from experimental validation

Chuanfangyihao (CFYH) is an effective treatment for acute lung injury (ALI) in clinical practice; however, its underlying mechanism of action remains unclear. Therefore, the aim of the present study was to elucidate the pharmacological mechanism of action of CFYH in ALI through experimental validation. First, a rat model of ALI was established using lipopolysaccharide (LPS). Next, the pathological changes in the lungs of the rats and the pathological damage were scored. The wet/dry weight ratios were measured, and ROS content was detected using flow cytometry. ELISA was used to examine IL-6, TNF-α, IL-1β, IL-18, and LDH levels. Immunohistochemistry was used to detect Beclin-1 and NLRP3 expression. Western blotting was performed to analyze the expression of HMGB1, RAGE, TLR4, NF-κB p65, AMPK, p-AMPK, mTOR, p-mTOR, Beclin-1, LC3-II/I, p62, Bcl-2, Bax, Caspase-3, Caspase-1, and GSDMD-NT. The mRNA levels of HMGB1, RAGE, AMPK, mTOR, and HIF-1α were determined using reverse transcription quantitative PCR. CFYH alleviated pulmonary edema and decreased the expression of IL-6, TNF-α, TLR4, NF-κB p65, HMGB1/RAGE, ROS, and HIF-1α. In addition, pretreatment with CFYH reversed ALI-induced programmed cell death. In conclusion, CFYH alleviates LPS-induced ALI, and these findings provide a preliminary clarification of the predominant mechanism of action of CFYH in ALI.

Successful Application of Argatroban During VV-ECMO in a Pregnant Patient Complicated With ARDS due to Severe Tuberculosis: A Case Report and Literature Review

Severe tuberculosis during pregnancy may progress to acute respiratory distress syndrome (ARDS), and venovenous (VV) extracorporeal membrane oxygenation (ECMO) should be considered if conventional lung-protective mechanical ventilation fails. However, thrombocytopenia often occurs with ECMO, and there are limited reports of alternative anticoagulant therapies for pregnant patients with thrombocytopenia during ECMO. This report describes the first case of a pregnant patient who received argatroban during ECMO and recovered. Furthermore, we summarized the existing literature on VV-ECMO and argatroban in pregnant patients. A 31-year-old woman at 17 weeks of gestation was transferred to our hospital with ARDS secondary to severe tuberculosis. We initiated VV-ECMO after implementing a protective ventilation strategy and other conventional therapies. Initially, we selected unfractionated heparin anticoagulant therapy. However, on ECMO day 3, the patient’s platelet count and antithrombin III (AT-III) level declined to 27 × 103 cells/μL and 26.9%, respectively. Thus, we started the patient on a 0.06 μg/kg/min argatroban infusion. The argatroban infusion maintenance dose ranged between 0.9 and 1.2 μg/kg/min. The actual activated partial thromboplastin clotting time and activated clotting time ranged from 43 to 58 s and 220–260 s, respectively, without clinically significant bleeding and thrombosis. On day 27, the patient was weaned off VV-ECMO and eventually discharged. VV-ECMO may benefit pregnant women with refractory ARDS, and argatroban may be an alternative anticoagulant for pregnant patients with thrombocytopenia and AT-III deficiency during ECMO.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Investigating the effect of TRPV4 inhibition on pulmonary-vascular barrier permeability following segmental endotoxin challenge

BACKGROUND

Acute Respiratory Distress Syndrome (ARDS) is associated with increased pulmonary-vascular permeability. In the lung, transient receptor potential vanilloid 4 (TRPV4), a Ca²⁺-permeable cation channel, is a regulator of endothelial permeability and pulmonary edema. We performed a Phase I, placebo-controlled, double-blind, randomized, parallel group, proof-of-mechanism study to investigate the effects of TRPV4 channel blocker, GSK2798745, on pulmonary-vascular barrier permeability using a model of lipopolysaccharide (LPS)-induced lung inflammation.

METHODS

Healthy participants were randomized 1:1 to receive 2 single doses of GSK2798745 or placebo, 12 h apart. Two hours after the first dose, participants underwent bronchoscopy and segmental LPS instillation. Total protein concentration and neutrophil counts were measured in bronchoalveolar lavage (BAL) samples collected before and 24 h after LPS challenge, as markers of barrier permeability and inflammation, respectively. The primary endpoint was baseline adjusted total protein concentration in BAL at 24 h after LPS challenge. A Bayesian framework was used to estimate the posterior probability of any percentage reduction (GSK2798745 relative to placebo). Safety endpoints included the incidence of adverse events (AEs), vital signs, 12-lead electrocardiogram, clinical laboratory and haematological evaluations, and spirometry.

RESULTS

Forty-seven participants were dosed and 45 completed the study (22 on GSK2798745 and 23 on placebo). Overall, GSK2798745 was well tolerated. Small reductions in mean baseline adjusted BAL total protein (~9%) and neutrophils (~7%) in the LPS-challenged segment were observed in the GSK2798745 group compared with the placebo group; however, the reductions did not meet pre-specified success criteria of at least a 95% posterior probability that the percentage reduction in the mean 24-h post LPS BAL total protein level (GSK2798745 relative to placebo) exceeded zero. Median plasma concentrations of GSK2798745 were predicted to inhibit TRPV4 on lung vascular endothelial cells by ~70-85% during the 24 h after LPS challenge; median urea-corrected BAL concentrations of GSK2798745 were 3.0- to 8.7-fold higher than those in plasma.

CONCLUSIONS

GSK2798745 did not affect segmental LPS-induced elevation of BAL total protein or neutrophils, despite blood and lung exposures that were predicted to be efficacious. CLINICALTRIALS.

GOV IDENTIFIER

NCT03511105.

The protective effect of hyperin on LPS-induced acute lung injury in mice

Hyperin, a flavonoid compound found in natural plants, has been reported that it have anti-inflammatory properties. However, the protective effects and mechanisms of hyperin on acute lung injury have not been reported so far. This research was designed to investigate the protective effects of hyperin on lipopolysaccharide-induced acute lung injury (ALI) in mice. The mice were stimulated with LPS in the presence or absence of hyperin and the MPO activity, lung wet/dry ratio, inflammatory cells in BALF, and cytokines, as well as NF-κB expression were assessed in lung tissue. Results showed that hyperin significantly inhibited LPS-induced histological changes, inflammatory cell infiltration, MPO activity and lung wet/dry ratio. Additionally, hyperin distinctly reduced the production of TNF-α, IL-1β and IL-6 and the activation of NF-κB signaling pathways in LPS-induced ALI in mice. In conclusion, hyperin is an effective suppressor of inflammation and may be a promising potential therapeutic reagent for ALI treatment.

25-Hydroxycholesterol protects against acute lung injury via targeting MD-2

Acute lung injury (ALI) is mainly caused by uncontrolled inflammatory response, and it remains without effective therapeutic options. 25‐hydroxycholesterol (25HC) has been reported to be a potent regulator of inflammation. The aim of this study was to investigate the effects of 25HC on lipopolysaccharide (LPS)‐induced ALI. C57BL/6 mice were pretreated with 25HC intraperitoneally before intratracheal exposure to LPS. Our results showed that 25HC pretreatment improved survival rate, attenuated the pathological changes of the lung and decreased the release of inflammatory cytokines in mice. Consistently, 25HC reduced expression of Toll‐like receptor (TLR4)‐mediated inflammatory cytokines in vitro. These effects of 25HC were obtained by preventing LPS binding to TLR4 via interaction with myeloid differentiation protein 2 (MD‐2). Crystal structure analysis suggested that 25HC could bind MD‐2 with high affinity into its hydrophobic pocket. Furthermore, LPS‐induced activation of Akt/NF‐κB pathway was partially down‐regulated by 25HC pretreatment. In summary, this study demonstrates that 25HC could inhibit the overwhelming inflammatory response through MD‐2 interaction, which suppresses Akt/NF‐κB signalling pathway. These findings suggest 25HC may be a promising candidate for ALI prevention.

In vitro evaluation of lysophosphatidic acid delivery via reverse perfluorocarbon emulsions to enhance alveolar epithelial repair

BACKGROUND

Alveolar drug delivery is needed to enhance alveolar repair during acute respiratory distress syndrome. However, delivery of inhaled drugs is poor in this setting. Drug delivery via liquid perfluorocarbon emulsions could address this problem through better alveolar penetration and improved spatial distribution. Therefore, this study investigated the efficacy of the delivery of lysophosphatidic acid (LPA) growth factor to cultured alveolar epithelial cells via a perfluorocarbon emulsion.

METHODS

Murine alveolar epithelial cells were treated for 2 h with varying concentrations (0-10 μM) of LPA delivered via aqueous solution or PFC emulsion. Cell migration was evaluated 18 h post-treatment using a scratch assay. Barrier function was evaluated 1 h post-treatment using a permeability assay. Proliferation was evaluated 72 h post-treatment using a viability assay.

RESULTS

Partially due to emulsion creaming and stability, the effects of LPA were either diminished or completely hindered when delivered via emulsion versus aqueous. Migration increased significantly following treatment with the 10 μM emulsion (p < 10^-3), but required twice the concentration to achieve an increase similar to aqueous LPA. Both barrier function and proliferation increased following aqueous treatment, but neither were significantly affected by the emulsion.

CONCLUSIONS

The availability and thus the biological effect of LPA is significantly blunted during emulsified delivery in vitro, and this attenuation depends on the specific cellular function examined. Thus, the cellular level effects of drug delivery to the lungs via PFC emulsion are likely to vary based on the drug and the effect it is intended to create.

Adjunctive therapies during veno-venous extracorporeal membrane oxygenation

Veno-venous extracorporeal membrane oxygenation (VV ECMO) restores gas exchanges in severely hypoxemic patients. The need for adjunctive therapies usually originates either from refractory hypoxemia during ECMO (defined as the persistence of low blood oxygen levels despite extracorporeal support) or from the attempt to give a specific therapy for acute respiratory distress syndrome (ARDS). In this review, therapeutic strategies to treat refractory and persistent hypoxemia during ECMO are evaluated. In the second part, therapies that can be added on top of VV ECMO to address inflammation and altered vascular permeability in ARDS are examined. The therapies currently available often allow for an effective treatment of hypoxemia during ECMO. ARDS is still lacking a specific therapy, with low-grade evidence sustaining the majority of currently used drugs.

Histopathologic heterogeneity of acute respiratory distress syndrome revealed by surgical lung biopsy and its clinical implications

BACKGROUND/AIMS

Diffuse alveolar damage (DAD) is the histopathologic hallmark of acute respiratory distress syndrome (ARDS). However, there are several non-DAD conditions mimicking ARDS. The purpose of this study was to investigate the histopathologic heterogeneity of ARDS revealed by surgical lung biopsy and its clinical relevance.

METHODS

We retrospectively analyzed 84 patients with ARDS who met the criteria of the Berlin definition and underwent surgical lung biopsy between January 2004 and December 2013 in three academic hospitals in Korea. We evaluated their histopathologic findings and compared the clinical outcomes. Additionally, the impact of surgical lung biopsy on therapeutic alterations was examined.

RESULTS

The histopathologic findings were highly heterogeneous. Of 84 patients undergoing surgical lung biopsy, DAD was observed in 31 patients (36.9%), while 53 patients (63.1%) did not have DAD. Among the non-DAD patients, diffuse interstitial lung diseases and infections were the most frequent histopathologic findings in 19 and 17 patients, respectively. Although the mortality rate was slightly higher in DAD (71.0%) than in non-DAD (62.3%), the difference was not significant. Overall, the biopsy results led to treatment alterations in 40 patients (47.6%). Patients with non-DAD were more likely to change the treatment than those with DAD (58.5% vs. 29.0%), but there were no significant improvements regarding the mortality rate.

CONCLUSIONS

The histopathologic findings of ARDS were highly heterogeneous and classic DAD was observed in one third of the patients who underwent surgical lung biopsy. Although therapeutic alterations were more common in patients with non-DAD-ARDS, there were no significant improvements in the mortality rate.

[Acute respiratory distress syndrome : Basic principles and treatment]

Even after many years of intensive research acute respiratory distress syndrome (ARDS) is still associated with a high mortality. Epidemiologically, ARDS represents a central challenge for modern intensive care treatment. The multifactorial etiology of ARDS complicates the clear identification and evaluation of new therapeutic interventions. Lung protective mechanical ventilation and adjuvant therapies, such as the prone position and targeted extracorporeal lung support are of particular importance in the treatment of ARDS, depending on the severity of the disease. In order to guarantee an individualized and needs-adapted treatment, ARDS patients benefit from treatment in specialized centers.

Extracorporeal membrane oxygenation (ECMO) during pregnancy and postpartum

Extracorporeal membrane oxygenation (ECMO) can provide respiratory support (VV-ECMO) or both respiratory and circulatory support (VA-ECMO). The use of ECMO has increased dramatically as a result of simpler technology. No level I evidence is yet available reflecting improved outcomes with ECMO. The use of this technology during pregnancy may be indicated in very select cases and should be delivered in centers with dedicated ECMO specialized units.

Intratracheal instillation of alveolar type II cells enhances recovery from acute lung injury in rats

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by excess production of inflammatory factors. Alveolar type II (ATII) cells help repair damaged lung tissue, rapidly proliferating and differentiating into alveolar type I cells after epithelial cell injury. In ALI, the lack of viable ATII favors progression to more severe lung injury. ATII cells regulate the immune response by synthesizing surfactant and other anti-inflammatory proteins and lipids. Cross-talk between ATII and other cells such as macrophages may also be part of the ATII function. The aim of this study was to test the anti-inflammatory and reparative effects of ATII cells in an experimental model of ALI.

METHODS

In this study ATII cells (2.5 × 10⁶ cells/animal) were intratracheally instilled in rats with HCl and lipopolysaccharide (LPS)-induced ALI and in healthy animals to check for side effects. The specific effect of ATII cells was compared with fibroblast transplantation.

RESULTS

ATII cell transplantation promoted recovery of lung function, decrease mortality and lung inflammation of the animals with ALI. The primary mechanisms for benefit were paracrine effects of prostaglandin E₂ (PGE₂) and surfactant protein A (SPA) released from ATII cells that modulate alveolar macrophages to an anti-inflammatory phenotype. To our knowledge, these data are the first to provide evidence that ATII cells secrete PGE₂ and SPA, reducing pro-inflammatory macrophage activation and ALI.

CONCLUSION

ATII cells and their secreted molecules have shown an ability to resolve ALI, thereby highlighting a potential novel therapeutic target.

Pilot Feasibility Study of Therapeutic Hypothermia for Moderate to Severe Acute Respiratory Distress Syndrome

OBJECTIVES

Prior studies suggest hypothermia may be beneficial in acute respiratory distress syndrome, but cooling causes shivering and increases metabolism. The objective of this study was to assess the feasibility of performing a randomized clinical trial of hypothermia in patients with acute respiratory distress syndrome receiving treatment with neuromuscular blockade because they cannot shiver.

DESIGN

Retrospective study and pilot, prospective, open-label, feasibility study.

SETTING

Medical ICU.

PATIENTS

Retrospective review of 58 patients with acute respiratory distress syndrome based on Berlin criteria and PaO2/FIO2 less than 150 who received neuromuscular blockade. Prospective hypothermia treatment in eight acute respiratory distress syndrome patients with PaO2/FIO2 less than 150 receiving neuromuscular blockade.

INTERVENTION

Cooling to 34-36°C for 48 hours.

MEASUREMENTS AND MAIN RESULTS

Core temperature, hemodynamics, serum glucose and electrolytes, and P/F were sequentially measured, and medians (interquartile ranges) presented, 28-day ventilator-free days, and hospital mortality were calculated in historical controls and eight cooled patients. Average patient core temperature was 36.7°C (36-37.3°C), and fever occurred during neuromuscular blockade in 30 of 58 retrospective patients. In the prospectively cooled patients, core temperature reached target range less than or equal to 4 hours of initiating cooling, remained less than 36°C for 92% of the 48 hours cooling period without adverse events, and was lower than the controls (34.35°C [34-34.8°C]; p < 0.0001). Compared with historical controls, the cooled patients tended to have lower hospital mortality (75% vs 53.4%; p = 0.26), more ventilator-free days (9 [0-21.5] vs 0 [0-12]; p = 0.16), and higher day 3 P/F (255 [160-270] vs 171 [120-214]; p = 0.024).

CONCLUSIONS

Neuromuscular blockade alone does not cause hypothermia but allowed acute respiratory distress syndrome patients to be effectively cooled. Results support conducting a randomized clinical trial of hypothermia in acute respiratory distress syndrome and the feasibility of studying acute respiratory distress syndrome patients receiving neuromuscular blockade.

Clinical practice of acute respiratory distress syndrome in Japan: A nationwide survey and scientific evidences

BACKGROUND

There has been limited information about epidemiology and clinical practice of acute respiratory distress syndrome (ARDS) in Japan.

METHODS

An invitation letter to the web-based survey was mailed to all 871 board certified hospitals of the Japanese Respiratory Society. The questionnaires were designed to collect data on epidemiology and clinical practice of ARDS, including diagnostic measures and therapeutics.

RESULTS

Within 4 months of the survey period, valid responses were obtained from 296 (34%) hospitals. The incidence of ARDS was estimated to be 3.13 cases/100 hospital beds or 1.91 cases/ICU bed per year. The most frequent underlying disease was pneumonia (34%), followed by sepsis (29%). In hospitals with fewer ICU beds, pulmonologists tended to be in charge of management of ARDS patients. Routine diagnostic measures included computed tomography of the chest (69.6% of the hospitals) and Swan-Ganz catheterization was rarely performed for diagnosis. In 87.4% of the hospitals, non-invasive ventilation was applied to management of ARDS patients, especially those with mild disease. Prone positioning and extracorporeal membrane oxygenation (ECMO) for ARDS patients was more widely adopted in hospitals with larger numbers of ICU beds and intensivists. In 58.2% of the responding hospitals, corticosteroid was considered as a treatment option for ARDS, among which pulse therapy was routinely introduced to ARDS patients in 35.4%.

CONCLUSIONS

The incidence of ARDS in Japan was estimated to be lower than that in the recent international study. The scale and equipment of hospitals and the number of intensivists might influence clinical practice of ARDS.

Inhibition of TNF Receptor p55 By a Domain Antibody Attenuates the Initial Phase of Acid-Induced Lung Injury in Mice

BACKGROUND

Tumor necrosis factor-α (TNF) is strongly implicated in the development of acute respiratory distress syndrome (ARDS), but its potential as a therapeutic target has been hampered by its complex biology. TNF signals through two receptors, p55 and p75, which play differential roles in pulmonary edema formation during ARDS. We have recently shown that inhibition of p55 by a novel domain antibody (dAb™) attenuated ventilator-induced lung injury. In the current study, we explored the efficacy of this antibody in mouse models of acid-induced lung injury to investigate the longer consequences of treatment.

METHODS

We employed two acid-induced injury models, an acute ventilated model and a resolving spontaneously breathing model. C57BL/6 mice were pretreated intratracheally or intranasally with p55-targeting dAb or non-targeting "dummy" dAb, 1 or 4 h before acid instillation.

RESULTS

Acid instillation in the dummy dAb group caused hypoxemia, increased respiratory system elastance, pulmonary inflammation, and edema in both the ventilated and resolving models. Pretreatment with p55-targeting dAb significantly attenuated physiological markers of ARDS in both models. p55-targeting dAb also attenuated pulmonary inflammation in the ventilated model, with signs that altered cytokine production and leukocyte recruitment persisted beyond the very acute phase.

CONCLUSION

These results demonstrate that the p55-targeting dAb attenuates lung injury and edema formation in models of ARDS induced by acid aspiration, with protection from a single dose lasting up to 24 h. Together with our previous data, the current study lends support toward the clinical targeting of p55 for patients with, or at risk of ARDS.

Mechanical Ventilation as a Therapeutic Tool to Reduce ARDS Incidence

Trauma, hemorrhagic shock, or sepsis can incite systemic inflammatory response syndrome, which can result in early acute lung injury (EALI). As EALI advances, improperly set mechanical ventilation (MV) can amplify early injury into a secondary ventilator-induced lung injury that invariably develops into overt ARDS. Once established, ARDS is refractory to most therapeutic strategies, which have not been able to lower ARDS mortality below the current unacceptably high 40%. Low tidal volume ventilation is one of the few treatments shown to have a moderate positive impact on ARDS survival, presumably by reducing ventilator-induced lung injury. Thus, there is a compelling case to be made that the focus of ARDS management should switch from treatment once this syndrome has become established to the application of preventative measures while patients are still in the EALI stage. Indeed, studies have shown that ARDS incidence is markedly reduced when conventional MV is applied preemptively using a combination of low tidal volume and positive end-expiratory pressure in both patients in the ICU and in surgical patients at high risk for developing ARDS. Furthermore, there is evidence from animal models and high-risk trauma patients that superior prevention of ARDS can be achieved using preemptive airway pressure release ventilation with a very brief duration of pressure release. Preventing rather than treating ARDS may be the way forward in dealing with this recalcitrant condition and would represent a paradigm shift in the way that MV is currently practiced.

Personalized medicine for ARDS: the 2035 research agenda

In the last 20 years, survival among patients with acute respiratory distress syndrome (ARDS) has increased substantially with advances in lung-protective ventilation and resuscitation. Building on this success, personalizing mechanical ventilation to patient-specific physiology for enhanced lung protection will be a top research priority for the years ahead. However, the ARDS research agenda must be broader in scope. Further understanding of the heterogeneous biology, from molecular to mechanical, underlying early ARDS pathogenesis is essential to inform therapeutic discovery and tailor treatment and prevention strategies to the individual patient. The ARDSne(x)t research agenda for the next 20 years calls for bringing personalized medicine to ARDS, asking simultaneously both whether a treatment affords clinically meaningful benefit and for whom. This expanded scope necessitates standard acquisition of highly granular biological, physiological, and clinical data across studies to identify biologically distinct subgroups that may respond differently to a given intervention. Clinical trials will need to consider enrichment strategies and incorporate long-term functional outcomes. Tremendous investment in research infrastructure and global collaboration will be vital to fulfilling this agenda.

Inhaled nitric oxide therapy and risk of renal dysfunction: a systematic review and meta-analysis of randomized trials

INTRODUCTION

Inhaled nitric oxide (iNO) is an important therapy for acute respiratory distress syndrome (ARDS), pulmonary hypertension and pediatric hypoxemic respiratory failure. Safety concerns regarding iNO and renal dysfunction have been reported; however, there are currently no systematic reviews on this issue. Our objective was to evaluate published randomized controlled trials (RCTs) to ascertain the risk of renal dysfunction associated with iNO therapy in patients with and without ARDS.

METHODS

A systematic review of databases was performed to identify RCTs which compared iNO with controls up to September 2014. Effect estimates for risk ratio (RR) of acute kidney injury (AKI) were pooled using a random-effects model.

RESULTS

Ten RCTs involving 1363 participants were included. Inhaled nitric oxide significantly increased the risk of AKI compared with controls (RR, 1.4, 95%CI, 1.06 to 1.83, p = 0.02). In the stratified analysis, a high cumulative-dose of iNO significantly increased the risk of AKI (RR, 1.52, 95%CI, 1.14 to 2.02, p = 0.004), whereas medium and low cumulative-doses did not (RR, 0.64, 95%CI, 0.23 to 1.81 and RR, 0.56, 95%CI, 0.11 to 2.86 respectively). In subgroup analysis by study population, an increased risk of AKI was observed in patients with ARDS (RR, 1.55, 95%CI, 1.15 to 2.09, p = 0.005) but not in those without (RR, 0.90, 95%CI, 0.49 to 1.67, p = 0.75).

CONCLUSIONS

The available data show that iNO therapy may increase the risk of renal dysfunction, especially with prolonged use and in patients with ARDS. The risk in pediatric population is unknown owing to limited data. We suggest monitoring renal function during iNO therapy, and that future trials of iNO should evaluate renal safety.

CXCR4 receptor overexpression in mesenchymal stem cells facilitates treatment of acute lung injury in rats

Novel therapeutic regimens for tissue renewal incorporate mesenchymal stem cells (MSCs) as they differentiate into a variety of cell types and are a stem cell type that is easy to harvest and to expand in vitro. However, surface chemokine receptors, such as CXCR4, which are involved in the mobilization of MSCs, are expressed only on the surface of a small proportion of MSCs, and the lack of CXCR4 expression may underlie the low efficiency of homing of MSCs toward tissue damage, which results in a poor curative effect. Here, a rat CXCR4 expressing lentiviral vector was constructed and introduced into MSCs freshly prepared from rat bone marrow. The influence of CXCR4 expression on migration, proliferation, differentiation, and paracrine effects of MSCs was examined in vitro. The in vivo properties of CXCR4-MSCs were also investigated in a model of acute lung injury in rats induced by lipopolysaccharide. Expression of CXCR4 in MSCs significantly enhanced the chemotactic and paracrine characteristics of the cells in vitro but did not affect self-renewal or differentiation into alveolar and vascular endothelial cells. In vivo, CXCR4 improved MSC homing and colonization of damaged lung tissue, and furthermore, the transplanted CXCR4-MSCs suppressed the development of acute lung injury in part by modulating levels of inflammatory molecules and the neutrophil count. These results indicated that efficient mobilization of MSCs to sites of tissue injury may be due to CXCR4, and therefore, increased expression of CXCR4 may improve their therapeutic potential in the treatment of diseases where tissue damage develops.

Clinical utility of the neutrophil elastase inhibitor sivelestat for the treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome is a serious condition that can arise following direct or indirect lung injury. It is heterogeneous and has a high mortality rate. Supportive care is the mainstay of treatment and there is no definitive pharmacological treatment as yet. Sivelestat is a neutrophil elastase inhibitor approved in Japan and the Republic of Korea for acute lung injury, including acute respiratory distress syndrome in patients with systemic inflammatory response syndrome. The aim of this review is to examine the clinical utility of sivelestat in different disease states, using data from nonclinical and clinical studies. In nonclinical studies, sivelestat appears to show benefit in acute lung injury without inhibiting the host immune defense in cases of infection. Clinical studies do not yet provide a clear consensus. Phase III and IV Japanese studies have shown improvements in pulmonary function, length of intensive care unit stay, and mechanical ventilation, but a non-Japanese multicenter study did not demonstrate sivelestat to have an effect on ventilator-free days or 28-day all-cause mortality. Evidence of improvement in various parameters, including duration of stay in intensive care, mechanical ventilation, the ratio of partial pressure of arterial oxygen and fraction of inspired oxygen (PaO₂/F_IO₂ ratio) ratio, and lung injury scores, has been shown in patients with sepsis or gastric aspiration, and following the surgical treatment of esophageal cancer. To date, there are no particular concerns regarding adverse events, and the available data do not suggest that sivelestat might worsen infections. One study has analyzed cost-effectiveness, finding that sivelestat may reduce costs compared with standard care. The currently available evidence suggests that sivelestat may show some benefit in the treatment of acute lung injury/acute respiratory distress syndrome, although large, randomized controlled trials are needed in specific pathophysiological conditions to explore these potential benefits.