Pharmacotherapy of acute respiratory distress syndrome

Personalized pharmacological therapy for ARDS: a light at the end of the tunnel

Introduction: Pharmacotherapy for the acute respiratory distress syndrome (ARDS) has been tested in preclinical and clinical studies. However, to date, no pharmacological interventions have proven effective. This may be attributed to lack of proper identification of different ARDS phenotypes.Areas covered: We designed inclusive search strings and searched four bibliographic databases (Cochrane Database of Systematic Reviews, PubMed, Web of Science, and clinicaltrials.gov) to identify relevant research. Search results were mainly restricted to papers published from 2009 through 2019. ARDS is a heterogeneous syndrome, and its different phenotypes - defined according to clinical, radiological, and biological parameters - may affect response to therapy. The most promising pharmacological approaches to date have been based on ARDS pathophysiology. They focus on reducing inflammation and pulmonary edema, promoting selective vasodilation, and repairing alveolar epithelial and endothelial cells.Expert opinion: Pharmacotherapeutic approaches targeting ARDS pathophysiology have failed to exert beneficial effects. Personalized medicine targeting the different ARDS phenotypes has emerged as an option to improve survival. Identification of specific ARDS patient phenotypes that respond to specific therapies seems to be the most important challenge for the next decade. Additional research is warranted before personalized medicine approaches can be applied at bedside for ARDS patients.

Long-Term Quality of Life After Extracorporeal Membrane Oxygenation in ARDS Survivors: Systematic Review and Meta-Analysis

PURPOSE

Extracorporeal membrane oxygenation (ECMO) is an increasingly prevalent treatment for acute respiratory failure (ARF). To evaluate the impact of ECMO support on long-term outcomes for critically ill adults with ARF.

METHODS

We searched electronic databases 1948 through to November 30 2016; selected controlled trials or observational studies of critically ill adults with acute respiratory distress syndrome, examining long-term morbidity specifically health-related quality of life (HRQL); 2 authors independently selected studies, extracted data, and assessed methodological quality.

ANALYSIS

Of the 633 citations, 1 randomized controlled trial and 5 observational studies met the selection criteria. Overall quality of observational studies was moderate to high (mean score on Newcastle-Ottawa scale, 7.2/9; range, 6-8). In 3 studies (n = 245), greater decrements in HRQL were seen for survivors of ECMO when compared to survivors of conventional mechanical ventilation (CMV) as measured by the Short Form 36 (SF-36) scores ([ECMO-CMV]: 5.40 [95% confidence interval, CI, 4.11 to 6.68]). As compared to CMV survivors, those who received ECMO experienced significantly less psychological morbidity (2 studies; n = 217 [ECMO-CMV]: mean weighted difference [MWD], -1.31 [95% CI, -1.98 to -0.64] for depression and MWD, -1.60 [95% CI, -1.80 to -1.39] for anxiety).

CONCLUSIONS

Further studies are required to confirm findings and determine prognostic factors associated with more favorable outcomes in survivors of ECMO.

Neuroimmune regulation of ventilator-induced lung injury

RATIONALE

Ventilator-induced lung injury (VILI) contributes to the mortality in patients with acute lung injury by increasing inflammation. Recent evidence suggests that stimulation of the cholinergic antiinflammatory pathway may be an attractive way to attenuate inflammatory injury.

OBJECTIVES

To determine the role of vagus nerve signaling in VILI and establish whether stimulation of the vagus reflex can mitigate VILI.

METHODS

We performed bilateral vagotomy in a mouse model of high-tidal volume-induced lung injury. We performed pharmacological and electrical vagus nerve stimulation in a rat model of VILI following ischemia/reperfusion injury. To determine the contribution of the alpha 7 acetylcholine nicotinic receptor to pulmonary cell injury, we exposed human bronchial epithelial cells to cyclic stretch in the presence of specific agonist or antagonist of the alpha 7 receptor.

MEASUREMENTS AND MAIN RESULTS

Vagotomy exacerbates lung injury from VILI in mice as demonstrated by increased wet-to-dry ratio, infiltration of neutrophils, and increased IL-6. Vagal stimulation attenuates lung injury in rats after ischemia/reperfusion injury ventilated with high-volume strategies. Treatment of both mice and rats with the vagus mimetic drug semapimod resulted in decreased lung injury. Vagotomy also increased pulmonary apoptosis, whereas vagus stimulation (electrical and pharmacological) attenuated VILI-induced apoptosis. In vitro studies suggest that vagus-dependent effects on inflammation and apoptosis are mediated via the α7 nicotinc acetylcholine receptor-dependent effects on cyclic stretch-dependent signaling pathways c-jun N-terminal kinase and tumor necrosis factor receptor superfamily, member 6.

CONCLUSIONS

Stimulation of the cholinergic antiinflammatory reflex may represent a promising alternative for the treatment of VILI.

From oxygen sensing to heart failure: role of thioredoxin

Oxidative stress has been widely recognized to be involved in the pathogenesis of cardiopulmonary disorders. In ischemic heart diseases, it is involved not only in the development of atherosclerosis but also in ongoing ischemic injury, especially in the reperfusion process. Cardiomyopathy is another cardiac disorder in which oxidative stress is involved. In diabetic cardiomyopathy, homocysteine, a well-known source of oxidative stress, is believed to play major roles in its development. Thioredoxin (TRX) is a redox-acting protein ubiquitously present in the human body. It also is inducible by a wide variety of oxidative stresses. TRX is a multifunctional protein and has anti-inflammatory and antiapoptotic effects, as well as antioxidative effects. It is therefore feasible to think that TRX is a potential therapy for cardiac disease. Moreover, serum TRX is a well-recognized biomarker of various diseases involving oxidative stress, and this is also the case for cardiac disorders. Here we discuss how TRX is useful as a biomarker of and therapeutic agent for cardiopulmonary disorders, especially focusing on ischemic heart disease, myocarditis and oxygen sensing, and acute respiratory distress syndrome.

Effect of nitric oxide on oxygenation and mortality in acute lung injury: systematic review and meta-analysis

OBJECTIVE

To review the literature on the use of inhaled nitric oxide to treat acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and to summarise the effects of nitric oxide, compared with placebo or usual care without nitric oxide, in adults and children with ALI or ARDS.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, CINAHL, Embase, and CENTRAL (to October 2006), proceedings from four conferences, and additional information from authors of 10 trials.

REVIEW METHODS

Two reviewers independently selected parallel group randomised controlled trials comparing nitric oxide with control and extracted data related to study methods, clinical and physiological outcomes, and adverse events.

MAIN OUTCOME MEASURES

Mortality, duration of ventilation, oxygenation, pulmonary arterial pressure, adverse events.

RESULTS

12 trials randomly assigning 1237 patients met inclusion criteria. Overall methodological quality was good. Using random effects models, we found no significant effect of nitric oxide on hospital mortality (risk ratio 1.10, 95% confidence interval 0.94 to 1.30), duration of ventilation, or ventilator-free days. On day one of treatment, nitric oxide increased the ratio of partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2 ratio) (13%, 4% to 23%) and decreased the oxygenation index (14%, 2% to 25%). Some evidence suggested that improvements in oxygenation persisted until day four. There was no effect on mean pulmonary arterial pressure. Patients receiving nitric oxide had an increased risk of developing renal dysfunction (1.50, 1.11 to 2.02).

CONCLUSIONS

Nitric oxide is associated with limited improvement in oxygenation in patients with ALI or ARDS but confers no mortality benefit and may cause harm. We do not recommend its routine use in these severely ill patients.

Is there a role for beta-adrenoceptor agonists in the management of acute lung injury and the acute respiratory distress syndrome?

Despite improvements in general supportive care and ventilatory strategies designed to limit lung injury, no specific pharmacological therapy has yet proven to be efficacious in the management of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Based on experimental studies, as well as studies of the ex-vivo human lung, pulmonary edema fluid clearance from the alveolar space can be augmented by both inhaled and systemic beta2-adrenoceptor agonists (beta2-agonists). Additionally, in the presence of lung injury, beta2-agonists may reduce lung vascular permeability. Treatment with beta2-agonists may also increase the secretion of surfactant and have anti-inflammatory effects. In view of these potentially beneficial effects, beta2-agonist therapy should be evaluated for the treatment of lung injury in humans, particularly because they are already in wide clinical use and do not seem to have serious adverse effects in critically ill patients.

The immuno-inflammatory response to trauma

The systemic inflammatory response syndrome is a well recognized physiological entity being part of our homeostatic mechanisms. It represents the cascade of inflammatory reactions initiated in the immediate aftermath following trauma reflecting the state of alertness that our body undergoes in order to fight for survival. A variety of inflammatory mediators and cellular elements are involved during this process interacting amongst each other. This allows communication between the different organ systems and thus regulating local and systemic responses. We have just begun to characterize and quantify the immuno-inflammatory response to trauma and this has opened new horizons in the way we understand the pathophysiological response to injury. As our knowledge evolves new therapeutic agents and innovative treatment plans will be developed contributing to increased survival rates in patients with multiple injuries.

Pharmacologic therapies for adults with acute lung injury and acute respiratory distress syndrome

BACKGROUND

Multiple pharmacologic treatments have been studied for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

OBJECTIVES

Our objective was to determine the effects of pharmacologic treatments on clinical outcomes in adults with ALI or ARDS.

SEARCH STRATEGY

We searched OVID versions of CENTRAL (The Cochrane Library Issue 3, 2003), MEDLINE (1966 to week 2, January 2004), EMBASE (1980 to week 4, 2004), CINAHL (1982 to week 2, January 2004), and HEALTHSTAR (1995 to December 2003); proceedings from four conferences (1994 to 2003); and bibliographies of review articles and included studies.

SELECTION CRITERIA

Randomized controlled trials of pharmacologic treatments compared to no therapy or placebo for established ALI or ARDS in adults admitted to an intensive care unit, with measurement of early mortality (primary outcome), late mortality, duration of mechanical ventilation, ventilator-free days to day 28, or adverse events. We excluded trials of nitric oxide, partial liquid ventilation, fluid and nutritional interventions, oxygen, and trials in other populations reporting outcomes in subgroups of patients with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened titles and abstracts, rated studies for inclusion, extracted data and assessed methodologic quality of included studies. Disagreements were resolved by consensus in consultation with a third reviewer. For each pharmacologic therapy, we quantitatively pooled the results of studies using random effects models where permitted by the available data. We contacted study authors when clarification of the primary outcome was required.

MAIN RESULTS

Thirty three trials randomizing 3272 patients met our inclusion criteria. Pooling of results showed no effect on early mortality of prostaglandin E1 (seven trials randomizing 697 patients; relative risk [RR] 0.95, 95% confidence interval [CI] 0.77 to 1.17), N-acetylcysteine (five trials randomizing 239 patients; RR 0.89, 95% CI 0.65 to 1.21), early high-dose corticosteroids (two trials randomizing 187 patients; RR 1.12, 95% CI 0.72 to 1.74), or surfactant (nine trials randomizing 1441 patients; RR 0.93, 95% CI 0.77 to 1.12). Two interventions were beneficial in single small trials; corticosteroids given for late phase ARDS reduced hospital mortality (24 patients; RR 0.20, 95% CI 0.05 to 0.81), and pentoxifylline reduced one-month mortality (RR 0.67, 95% CI 0.47 to 0.95) in 30 patients with metastatic cancer and ARDS. Individual trials of nine additional interventions failed to show a beneficial effect on prespecified outcomes.

REVIEWERS' CONCLUSIONS

Effective pharmacotherapy for ALI and ARDS is extremely limited, with insufficient evidence to support any specific intervention.

Inflammation and the acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of non-cardiogenic pulmonary oedema associated with bilateral pulmonary infiltrates, stiff lungs and refractory hypoxaemia. ARDS is characterized by an explosive acute inflammatory response in the lung parenchyma, leading to alveolar oedema, decreased lung compliance and, ultimately, hypoxaemia. Although our understanding of the causes and pathophysiology of ARDS has increased, the mortality rate remains in the range of 30-50%. No major advances in pharmacological therapy have been achieved. Mechanical ventilation is the main therapeutic intervention in the management of ARDS. The only approach that has been shown to reduce the inflammatory response and mortality is the use of lung-protective ventilatory strategy with a low tidal volume and high positive-end expiratory pressure. This chapter will review the current state of the literature on the pathogenesis of ARDS and ventilatory and pharmacotherapy approaches to its management.

TEZOSENTAN COUNTERACTS ENDOTOXIN-INDUCED PULMONARY EDEMA AND IMPROVES GAS EXCHANGE

Sepsis-induced acute lung injury is still associated with high morbidity and mortality. The pathophysiology is complex, and markers of injury include increased extravascular lung water. To evaluate the effects of the novel dual endothelin receptor antagonist tezosentan on endotoxin-induced changes in extravascular lung water and gas exchange, 16 pigs were anaesthetized and catheterized. Twelve animals were subjected to 5 h of endotoxemia. After 2 h, six of these animals received a bolus of tezosentan 1 mg kg(-1) followed by a continuous infusion of 1 mg kg(-1) h(-1) to the end of the experiment at 5 h. Conventional pulmonary and hemodynamic parameters were measured. Extravascular lung water was determined in these pigs after 5 h of endotoxemia, as well as in the four additional nonendotoxemic sham animals. Tezosentan in the current dosage counteracted the deterioration of lung function caused by endotoxin, as measured by dead space, venous admixture, and compliance. In addition, pulmonary hypertension was attenuated. Tezosentan had a marked effect on the endotoxin-induced increase in extravascular lung water that was reduced to levels observed in nonendotoxemic sham animals. These results suggest that endothelin is involved in endotoxin-induced lung injury and the development of pulmonary edema. Dual endothelin receptor antagonism may be of value in the treatment of sepsis-related acute lung injury.

Pharmacologic Treatments for Acute Respiratory Distress Syndrome and Acute Lung Injury

BACKGROUND

Multiple pharmacologic treatments have been studied for patients with acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Our objective was to systematically evaluate this literature to determine the effects of these interventions on important clinical outcomes.

METHODS

We searched OVID versions of CENTRAL (The Cochrane Library Issue 3, 2003), MEDLINE (1966-week 2, January 2004), EMBASE (1980-week 4, 2004), CINAHL (1982-week 2, January 2004), and HEALTHSTAR (1995-December 2003); proceedings from four conferences (1994-2003); and bibliographies of review articles and included studies. We included randomized controlled trials (RCTs) of pharmacologic treatments compared with no therapy or placebo for established ARDS and ALI in adults admitted to an intensive care unit, with measurement of early mortality, late mortality, duration of ventilation, ventilator-free days, non-pulmonary organ dysfunction, or adverse events. We excluded trials in other populations incorporating subgroup analyses of patients with ARDS and ALI and studies of nitric oxide, partial liquid ventilation, and fluid and nutritional interventions. Two reviewers independently screened studies and abstracted data from studies included in the analysis. Data were pooled using random effects models where appropriate.

RESULTS

We retrieved 75 potentially relevant articles and abstracts, of which 33 trials randomizing 3272 patients met our selection criteria. Meta-analysis showed no effect on early mortality for alprostadil ([prostaglandin E(1)] seven studies; 693 patients; relative risk [RR] 0.95; 95% confidence interval [CI], 0.77, 1.17), acetylcysteine (five studies; 235 patients; RR 0.89; 95% CI, 0.65, 1.21), early high-dose corticosteroids (two studies; 180 patients; RR 1.12; 95% CI, 0.72, 1.74), or surfactant therapy (nine studies; 1418 patients; RR 0.93; 95% CI, 0.77, 1.12). Most trials of alprostadil, early high-dose corticosteroids, and surfactant therapy showed more adverse events in the active therapy arm. Single small RCTs demonstrated lower hospital mortality (24 patients, RR 0.20; 95% CI, 0.05, 0.81) with corticosteroids for late phase ARDS and lower 1-month mortality (30 patients, RR 0.67; 95% CI, 0.47, 0.95) with pentoxifylline for patients with metastatic cancer and ARDS. Individual trials of nine additional interventions failed to show beneficial effects on prespecified outcomes.

CONCLUSIONS

Effective pharmacotherapy for ARDS is extremely limited. Corticosteroids for late phase ARDS and pentoxifylline for patients with metastatic cancer and ARDS reduced mortality in single small studies. However, further research is required to investigate their potential benefit in the treatment of ALI/ARDS.