Bench-to-bedside review: beta2-Agonists and the acute respiratory distress syndrome

Using the sympathetic system, beta blockers and alpha-2 agonists, to address acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) manifests as an acute inflammatory lung injury characterized by persistent hypoxemia, featuring a swift onset, high mortality, and predominantly supportive care as the current therapeutic approach, while effective treatments remain an area of active investigation. Adrenergic receptors (AR) play a pivotal role as stress hormone receptors, extensively participating in various inflammatory processes by initiating downstream signaling pathways. Advancements in molecular biology and pharmacology continually unveil the physiological significance of distinct AR subtypes. Interventions targeting these subtypes have the potential to induce specific alterations in cellular and organismal functions, presenting a promising avenue as a therapeutic target for managing ARDS. This article elucidates the pathogenesis of ARDS and the basic structure and function of AR. It also explores the relationship between AR and ARDS from the perspective of different AR subtypes, aiming to provide new insights for the improvement of ARDS.

Inhaled β2 Adrenergic Agonists and Other cAMP-Elevating Agents: Therapeutics for Alveolar Injury and Acute Respiratory Disease Syndrome?

Inhaled long-acting β-adrenergic agonists (LABAs) and short-acting β-adrenergic agonists are approved for the treatment of obstructive lung disease via actions mediated by β2 adrenergic receptors (β2-ARs) that increase cellular cAMP synthesis. This review discusses the potential of β2-AR agonists, in particular LABAs, for the treatment of acute respiratory distress syndrome (ARDS). We emphasize ARDS induced by pneumonia and focus on the pathobiology of ARDS and actions of LABAs and cAMP on pulmonary and immune cell types. β2-AR agonists/cAMP have beneficial actions that include protection of epithelial and endothelial cells from injury, restoration of alveolar fluid clearance, and reduction of fibrotic remodeling. β2-AR agonists/cAMP also exert anti-inflammatory effects on the immune system by actions on several types of immune cells. Early administration is likely critical for optimizing efficacy of LABAs or other cAMP-elevating agents, such as agonists of other Gs-coupled G protein-coupled receptors or cyclic nucleotide phosphodiesterase inhibitors. Clinical studies that target lung injury early, prior to development of ARDS, are thus needed to further assess the use of inhaled LABAs, perhaps combined with inhaled corticosteroids and/or long-acting muscarinic cholinergic antagonists. Such agents may provide a multipronged, repurposing, and efficacious therapeutic approach while minimizing systemic toxicity. SIGNIFICANCE STATEMENT: Acute respiratory distress syndrome (ARDS) after pulmonary alveolar injury (e.g., certain viral infections) is associated with ∼40% mortality and in need of new therapeutic approaches. This review summarizes the pathobiology of ARDS, focusing on contributions of pulmonary and immune cell types and potentially beneficial actions of β2 adrenergic receptors and cAMP. Early administration of inhaled β2 adrenergic agonists and perhaps other cAMP-elevating agents after alveolar injury may be a prophylactic approach to prevent development of ARDS.

Pharmacological treatment to reduce pulmonary morbidity after esophagectomy

Esophagectomy for esophageal cancer is one of the most invasive procedures in gastrointestinal surgery. An invasive surgical procedure causes postoperative lung injury through the surgical procedure and one-lung ventilation during anesthesia. Lung injury developed by inflammatory response to surgical insults and oxidative stress is associated with pulmonary morbidity after esophagectomy. Postoperative pulmonary complications negatively affect the long-term outcomes; therefore, an effort to reduce lung injury improves overall survival after esophagectomy. Although significant evidence has not been established, various pharmacological treatments for reducing lung injury, such as administration of a corticosteroid, neutrophil elastase inhibitor, and vitamins are considered to have efficacy for pulmonary morbidity. In this review we survey the following topics: mediators during the perioperative periods of esophagectomy and the efficacy of pharmacological therapies for patients with esophagectomy on pulmonary complications.

Transepithelial nasal potential difference in patients with, and at risk of acute respiratory distress syndrome

BACKGROUND

Impaired alveolar fluid clearance, determined in part by alveolar sodium transport, is associated with acute respiratory distress syndrome (ARDS). Nasal sodium transport may reflect alveolar transport. The primary objective of this prospective, observational study was to determine if reduced nasal sodium transport, as measured by nasal potential difference (NPD), was predictive of the development of and outcome from ARDS.

METHODS

NPD was measured in 15 healthy controls and in 88 patients: 40 mechanically ventilated patients defined as 'at-risk' for ARDS, 61 mechanically ventilated patients with ARDS (13 who were previously included in the 'at-risk' group) and 8 ARDS survivors on the ward.

RESULTS

In at-risk subjects, maximum NPD (mNPD) was greater in those who developed ARDS (difference -8.4 mV; 95% CI -13.8 to -3.7; p=0.005) and increased mNPD predicted the development of ARDS before its onset (area under the curve (AUC) 0.75; 95% CI 0.59 to 0.89). In the ARDS group, mNPD was not significantly different for survivors and non-survivors (p=0.076), and mNPD was a modest predictor of death (AUC 0.60; 95% CI 0.45 to 0.75). mNPD was greater in subjects with ARDS (-30.8 mV) than in at-risk subjects (-24.2 mV) and controls (-19.9 mV) (p<0.001). NPD values were not significantly different for survivors and controls (p=0.18).

CONCLUSIONS

Increased NPD predicts the development of ARDS in at-risk subjects but does not predict mortality. NPD increases before ARDS develops, is greater during ARDS, but is not significantly different for controls and survivors. These results may reflect the upregulated sodium transport necessary for alveolar fluid clearance in ARDS. NPD may be useful as a biomarker of endogenous mechanisms to stimulate sodium transport. Larger studies are now needed to confirm these associations and predictive performance.

Pharmacological management of COVID-19 patients with ARDS (CARDS): A narrative review

Coronavirus disease 2019 (COVID-19) is highly infectious. It has been highlighted that if not expertly and individually managed with consideration of the vasocentric features, a COVID-19 patient with an acute respiratory distress syndrome (CARDS) may eventually develop multiorgan failure. Unfortunately, there is still no definite drug for CARDS that is capable of reducing either short-term or long-term mortality and no specific treatments for COVID-19 exist right now. In this narrative review, based on a selective literature search in EMBASE, MEDLINE, Scopus, The Cochrane Library, Web of Science, and Google Scholar and ClinicalTrials.gov, we have examined the emerging evidence on the possible treatment of CARDS. Although numerous pharmacologic therapies to improve clinical outcomes in CARDS have been studied also in clinical trials, none have shown efficacy and there is great uncertainty about their effectiveness. There is still no recommendation for the therapeutic use of any specific agent to treat CARDS because no drugs are validated to have significant efficacy in clinical treatment of COVID-19 patients in large-scale trials. However, there exist a number of drugs that may be useful at least in some patients. The real challenge now is to link the right patient to the right treatment.

VEGF mediates fat embolism-induced acute lung injury via VEGF receptor 2 and the MAPK cascade

Fat embolism (FE) is a lethal medical emergency often caused by fracture of long bones and amputation of limbs. Vascular endothelial growth factor (VEGF) promotes angiogenesis and increases vascular permeability. We tested the hypothesis that VEGF plays a critical role in FE-induced acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Fat tissues were collected from male Sprague-Dawley rats, and animal oil was extracted and mixed with water to form fatty micelles. The micelles were then injected into the tail vein to produce FE and ALI in rats. Lung weight gain was measured as the index of pulmonary edema. The expression of pulmonary VEGF was evaluated by real-time PCR and western blot analysis. Inducible nitric oxide synthase (iNOS) and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by western blot analyses. Interleukin-1β (IL-1β) was quantified by ELISAs. Hematoxylin and eosin staining was used to evaluate the pathological damage of ALI. In this study, we found that animal oil-induced FE significantly increased pulmonary VEGF expression and MAPK phosphorylation. We also evaluated the inflammatory response after FE and found that iNOS and IL-1β significantly increased after FE. Systemic administration of SU-1498, an antagonist of VEGF receptor 2 (VEGFR-2), significantly attenuated the FE-induced inflammatory response and histological damage. This study suggested that VEGF is involved in FE-induced ARDS via the VEGFR-2 and MAPK cascades, which induce IL-1β release and iNOS upregulation. Blockade of could be used to treat FE-induced pulmonary damage.

Treatments for Pulmonary Ricin Intoxication: Current Aspects and Future Prospects

Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor beans), is one of the most lethal toxins known, particularly if inhaled. Ricin is considered a potential biological threat agent due to its high availability and ease of production. The clinical manifestation of pulmonary ricin intoxication in animal models is closely related to acute respiratory distress syndrome (ARDS), which involves pulmonary proinflammatory cytokine upregulation, massive neutrophil infiltration and severe edema. Currently, the only post-exposure measure that is effective against pulmonary ricinosis at clinically relevant time-points following intoxication in pre-clinical studies is passive immunization with anti-ricin neutralizing antibodies. The efficacy of this antitoxin treatment depends on antibody affinity and the time of treatment initiation within a limited therapeutic time window. Small-molecule compounds that interfere directly with the toxin or inhibit its intracellular trafficking may also be beneficial against ricinosis. Another approach relies on the co-administration of antitoxin antibodies with immunomodulatory drugs, thereby neutralizing the toxin while attenuating lung injury. Immunomodulators and other pharmacological-based treatment options should be tailored according to the particular pathogenesis pathways of pulmonary ricinosis. This review focuses on the current treatment options for pulmonary ricin intoxication using anti-ricin antibodies, disease-modifying countermeasures, anti-ricin small molecules and their various combinations.

The Effects of Inhaled β-Adrenergic Agonists in Transient Tachypnea of the Newborn

Aim. To investigate the efficacy of an inhaled β-adrenergic agonists in transient tachypnea of the newborn (TTN). Method. We retrospectively analyzed a cohort of 51 term infants (Group 1) and 37 term infants (Group 2) monitored in the newborn intensive care unit diagnosed with TTN. Infants in Group 1 received humidified oxygen alone, and infants in Group 2 were administered the inhaled β-2 agonist plus humidified oxygen. Results. TTN clinical respiratory assessment, respiratory rate, oxygen saturation values, need for supplemental oxygen therapy, blood gas PH, PO₂, and duration of hospitalization were significantly improved in infants in Group 2 as compared with infants in Group 1 (P < .05). No statistically significant difference was observed with regard to blood glucose, potassium, heart rate, and PCO₂ (P > .05). Conclusion. Inhaled β-adrenergic agonist added to humidified oxygen was found to improve clinical and laboratory parameters. We believe that further studies should be conducted with larger groups to demonstrate the efficacy of β-2 agonists in TTN patients.

Emerging drugs for acute lung injury

INTRODUCTION

Acute respiratory distress syndromes (ARDS) are devastating disorders of overwhelming pulmonary inflammation and hypoxemia, resulting in high morbidity and mortality.

AREAS COVERED

The main pharmacological treatment strategies have focused on the attempted inhibition of excessive inflammation or the manipulation of the resulting physiological derangement causing respiratory failure. Additionally, such interventions may allow reduced occurence mechanical ventilation injury. Despite promising preclinical and small clinical studies, almost all therapies have been shown to be unsuccessful in large-scale randomized controlled trials. The evidence for pharmacological treatment for ARDS is reviewed. Potential future treatments are also presented.

EXPERT OPINION

We suggest for future clinical trials addressing prevention and early intervention to attenuate lung injury and progression to respiratory failure.

The beta agonist lung injury trial prevention. A randomized controlled trial

RATIONALE

Experimental studies suggest that pretreatment with β-agonists might prevent acute lung injury (ALI).

OBJECTIVES

To determine if in adult patients undergoing elective esophagectomy, perioperative treatment with inhaled β-agonists effects the development of early ALI.

METHODS

We conducted a randomized placebo-controlled trial in 12 UK centers (2008-2011). Adult patients undergoing elective esophagectomy were allocated to prerandomized, sequentially numbered treatment packs containing inhaled salmeterol (100 μg twice daily) or a matching placebo. Patients, clinicians, and researchers were masked to treatment allocation. The primary outcome was development of ALI within 72 hours of surgery. Secondary outcomes were ALI within 28 days, organ failure, adverse events, survival, and health-related quality of life. An exploratory substudy measured biomarkers of alveolar-capillary inflammation and injury.

MEASUREMENTS AND MAIN RESULTS

A total of 179 patients were randomized to salmeterol and 183 to placebo. Baseline characteristics were similar. Treatment with salmeterol did not prevent early lung injury (32 [19.2%] of 168 vs. 27 [16.0%] of 170; odds ratio [OR], 1.25; 95% confidence interval [CI], 0.71-2.22). There was no difference in organ failure, survival, or health-related quality of life. Adverse events were less frequent in the salmeterol group (55 vs. 70; OR, 0.63; 95% CI, 0.39-0.99), predominantly because of a lower number of pneumonia (7 vs. 17; OR, 0.39; 95% CI, 0.16-0.96). Salmeterol reduced some biomarkers of alveolar inflammation and epithelial injury.

CONCLUSION

Perioperative treatment with inhaled salmeterol was well tolerated but did not prevent ALI. Clinical trial registered with International Standard Randomized Controlled Trial Register (ISRCTN47481946) and European Union database of randomized Controlled Trials (EudraCT 2007-004096-19).

The effects of salbutamol on epithelial ion channels depend on the etiology of acute respiratory distress syndrome but not the route of administration

Introduction

We investigated the effects of intravenous and intratracheal administration of salbutamol on lung morphology and function, expression of ion channels, aquaporin, and markers of inflammation, apoptosis, and alveolar epithelial/endothelial cell damage in experimental pulmonary (p) and extrapulmonary (exp) mild acute respiratory distress syndrome (ARDS).

Methods

In this prospective randomized controlled experimental study, 56 male Wistar rats were randomly assigned to mild ARDS induced by either intratracheal (n = 28, ARDSp) or intraperitoneal (n = 28, ARDSexp) administration of E. coli lipopolysaccharide. Four animals with no lung injury served as controls (NI). After 24 hours, animals were anesthetized, mechanically ventilated in pressure-controlled mode with low tidal volume (6 mL/kg), and randomly assigned to receive salbutamol (SALB) or saline 0.9% (CTRL), intravenously (i.v., 10 μg/kg/h) or intratracheally (bolus, 25 μg). Salbutamol doses were targeted at an increase of ≈ 20% in heart rate. Hemodynamics, lung mechanics, and arterial blood gases were measured before and after (at 30 and 60 min) salbutamol administration. At the end of the experiment, lungs were extracted for analysis of lung histology and molecular biology analysis. Values are expressed as mean ± standard deviation, and fold changes relative to NI, CTRL vs. SALB.

Results

The gene expression of ion channels and aquaporin was increased in mild ARDSp, but not ARDSexp. In ARDSp, intravenous salbutamol resulted in higher gene expression of alveolar epithelial sodium channel (0.20 ± 0.07 vs. 0.68 ± 0.24, p < 0.001), aquaporin-1 (0.44 ± 0.09 vs. 0.96 ± 0.12, p < 0.001) aquaporin-3 (0.31 ± 0.12 vs. 0.93 ± 0.20, p < 0.001), and Na-K-ATPase-α (0.39 ± 0.08 vs. 0.92 ± 0.12, p < 0.001), whereas intratracheal salbutamol increased the gene expression of aquaporin-1 (0.46 ± 0.11 vs. 0.92 ± 0.06, p < 0.001) and Na-K-ATPase-α (0.32 ± 0.07 vs. 0.58 ± 0.15, p < 0.001). In ARDSexp, the gene expression of ion channels and aquaporin was not influenced by salbutamol. Morphological and functional variables and edema formation were not affected by salbutamol in any of the ARDS groups, regardless of the route of administration.

Conclusion

Salbutamol administration increased the expression of alveolar epithelial ion channels and aquaporin in mild ARDSp, but not ARDSexp, with no effects on lung morphology and function or edema formation. These results may contribute to explain the negative effects of β2-agonists on clinical outcome in ARDS.

Is there a role for adrenaline during cardiopulmonary resuscitation?

PURPOSE OF REVIEW

To critically evaluate the recent data on the influence adrenaline has on outcome from cardiopulmonary resuscitation.

RECENT FINDINGS

Two prospective controlled trials in out-of-hospital cardiac arrest (OHCA) have indicated that adrenaline increases the rate of return of spontaneous circulation (ROSC), but neither was sufficiently powered to determine the long-term outcomes. Several observational studies document higher ROSC rates in patients receiving adrenaline after OHCA, but these also document an association between receiving adrenaline and worse long-term outcomes.

SUMMARY

Appropriately powered prospective, placebo-controlled trials of adrenaline in cardiac arrest are essential if the role of this drug is to be defined reliably.

The effects of inhaled albuterol in transient tachypnea of the newborn

Purpose

Transient tachypnea of the newborn (TTN) is a disorder caused by the delayed clearance of fetal alveolar fluid. β-adrenergic agonists such as albuterol (salbutamol) are known to catalyze lung fluid absorption. This study examined whether inhalational salbutamol therapy could improve clinical symptoms in TTN. Additional endpoints included the diagnostic and therapeutic efficacy of salbutamol as well as its overall safety.

Methods

From January 2010 through December 2010, we conducted a prospective study of 40 newborns hospitalized with TTN in the neonatal intensive care unit. Patients were given either inhalational salbutamol (28 patients) or placebo (12 patients), and clinical indices were compared.

Results

The duration of tachypnea was shorter in patients receiving inhalational salbutamol therapy, although this difference was not statistically significant. The duration of supplemental oxygen therapy and the duration of empiric antibiotic treatment were significantly shorter in the salbutamol-treated group. No adverse effects were observed in either treatment group.

Conclusions

Inhalational salbutamol therapy reduced the duration of supplemental oxygen therapy and the duration of empiric antibiotic treatment, with no adverse effects. However, the time between salbutamol therapy and clinical improvement was too long to allow definitive conclusions to be drawn. Further studies examining a larger number of patients with strict control over dosage and frequency of salbutamol inhalations are necessary to better direct the treatment of TTN.

Effect of phenylephrine on alveolar fluid clearance in ventilator-induced lung injury

OBJECTIVE

To investigate the effect of phenylephrine (an α-adrenergic agonist) on alveolar fluid clearance (AFC) in ventilator-induced lung injury and the possible mechanism involved.

METHODS

A total of 170 male Wistar rats were randomly allocated into 17 groups (n=10) using random number tables. Short-term (40 minutes) mechanical ventilation with high tidal volume (HVT) was performed to induce lung injury, impair active Na+ transport and lung liquid clearance in the rats. Unventilated rats served as controls. To demonstrate the effect of phenylephrine on AFC, phenylephrine at different concentrations (1×10(-5), 1×10(-6), 1×10(-7), 1×10(-8), and 1×10(-9) mol/L) was injected into the alveolar space of the HVT ventilated rats. To identify the influence of adrenergic antagonists, Na(+) channel, and microtubular system on the effect of phenylephrine, phenylephrine at 1×10(-5) mol/L combined with prazosin (an α1-adrenergic antagonist, 1×10(-4) mol/L), yohimbine (an α2-adrenergic antagonist, 1×10(-4) mol/L), atenolol (a β1- adrenergic antagonist, 1×10(-5) mol/L), ICI-118551 (an β2-adrenergic antagonist, 1×10(-5) mol/L), amiloride (a Na+ channel blocker, 5×10(-4) mol/L), ouabain (a Na(+)/K(+)-ATPase blocker, 5×10(-4) mol/L), colchicine (a microtubular disrupting agent, 0.25 mg/100 g body weight), or β-lumicolchicine (an isomer of colchicine, 0.25 mg/100 g body weight) were perfused into the alveolar space of the rats ventilated with HVT for 40 minutes. AFC and total lung water content were measured.

RESULTS

Basal AFC in control rats was (17.47±2.56)%/hour, which decreased to (9.64± 1.32)%/hour in HVT ventilated rats (P=0.003). The perfusion of phenylephrine at 1×10(-8), 1×10(-7), 1×10(-6), and 1×10(-5) mol/L significantly increased the AFC in HVT ventilated rats (all P<0.05). This effect of phenylephrine on AFC was suppressed by prazosin, atenolol, and ICI-118551 in HVT ventilated rats by 53%, 31%, and 37%, respectively (all P<0.05). The AFC-stimulating effect of phenylephrine was lowered by 33% and 42% with amiloride and ouabain, respectively (both P<0.05). Colchicine significantly inhibited the effect of phenylephrine (P=0.031).

CONCLUSION

Phenylephrine could increase the AFC in HVT-ventilated rats and accelerate the absorption of pulmonary edema.

Anti-inflammatory effects of β2 adrenergic receptor agonists in experimental acute lung injury

These studies were undertaken to extend emerging evidence that β(2) adrenergic receptor (β(2)AR) agonists, in addition to their bronchorelaxing effects, may have broad anti-inflammatory effects in the lung following onset of experimental acute lung injury (ALI). Young male C57BL/6 mice (25 g) developed ALI following airway deposition of bacterial LPS or IgG immune complexes in the absence or presence of appropriate stereoisomers (enantiomers) of β(2)AR agonists, albuterol or formoterol. Endpoints included albumin leak into lung and buildup of polymorphonuclear neutrophils and cytokines/chemokines in bronchoalveolar fluids. Both β(2)AR agonists suppressed lung inflammatory parameters (IC(50)=10(-7) M). Similar effects of β(2)AR agonists on mediator release were found when mouse macrophages were stimulated in vitro with LPS. The protective effects were associated with reduced activation (phosphorylation) of JNK but not of other signaling proteins. Collectively, these data suggest that β(2)AR agonists have broad anti-inflammatory effects in the setting of ALI. While β(2)AR agonists suppress JNK activation, the extent to which this can explain the blunted lung inflammatory responses in the ALI models remains to be determined.

Effect of intravenous β-2 agonist treatment on clinical outcomes in acute respiratory distress syndrome (BALTI-2): a multicentre, randomised controlled trial

BACKGROUND

In a previous randomised controlled phase 2 trial, intravenous infusion of salbutamol for up to 7 days in patients with acute respiratory distress syndrome (ARDS) reduced extravascular lung water and plateau airway pressure. We assessed the effects of this intervention on mortality in patients with ARDS.

METHODS

We did a multicentre, placebo-controlled, parallel-group, randomised trial at 46 UK intensive-care units between December, 2006, and March, 2010. Intubated and mechanically ventilated patients (aged ≥16 years) within 72 h of ARDS onset were randomly assigned to receive either salbutamol (15 μg/kg ideal bodyweight per h) or placebo for up to 7 days. Randomisation was done by a central telephone or web-based randomisation service with minmisation by centre, pressure of arterial oxygen to fractional inspired oxygen concentration (PaO(2)/F(I)O(2)) ratio, and age. All participants, caregivers, and investigators were masked to group allocation. The primary outcome was death within 28 days of randomisation. Analysis was by intention-to-treat. This trial is registered, ISRCTN38366450 and EudraCT number 2006-002647-86.

FINDINGS

We randomly assigned 162 patients to the salbutamol group and 164 to the placebo group. One patient in each group withdrew consent. Recruitment was stopped after the second interim analysis because of safety concerns. Salbutamol increased 28-day mortality (55 [34%] of 161 patients died in the salbutamol group vs 38 (23%) of 163 in the placebo group; risk ratio [RR] 1·47, 95% CI 1·03-2·08).

INTERPRETATION

Treatment with intravenous salbutamol early in the course of ARDS was poorly tolerated. Treatment is unlikely to be beneficial, and could worsen outcomes. Routine use of β-2 agonist treatment in ventilated patients with this disorder cannot be recommended.

FUNDING

UK Medical Research Council, UK Department of Health, UK Intensive Care Foundation.

Beta Agonist Lung Injury TrIal-2 (BALTI-2) trial protocol: a randomised, double-blind, placebo-controlled of intravenous infusion of salbutamol in the acute respiratory distress syndrome

BACKGROUND

The acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure in critically ill patients. Experimental studies suggest that treatment with beta agonists may be helpful in ARDS. The Beta Agonist Lung Injury TrIal (BALTI-2) is a multicentre, pragmatic, randomised, double-blind, placebo-controlled clinical trial which aims to determine if sustained treatment with intravenous (IV) salbutamol will improve survival in ARDS.

METHODS/DESIGN

Patients fulfilling the American-European Consensus Conference Definition of ARDS will be randomised in a 1:1 ratio to receive an IV infusion either of salbutamol (15 μg kg ideal body weight-1 hr-1) or placebo (0.9% sodium chloride solution), for a maximum of seven days. Allocation to randomised groups will use minimisation to ensure balance with respect to hospital of recruitment, age group (<64, 65-84, >85 years) and PaO2/FiO2 ratio (≤6.7, 6.8- 13.2, ≥13.3 kPa). Data will be recorded by participating ICUs until hospital discharge, and all surviving patients will be followed up by post at six and twelve months post randomisation. The primary outcome is mortality at 28 days after randomisation; secondary outcomes are mortality in ICU, mortality in hospital, number of ventilator-free days, number of organ failure-free days, mortality at twelve months post-randomisation, quality of life at six and twelve months, length of stay in ICU, length of stay in hospital, adverse effects (tachycardia, arrhythmia or other side effects sufficient to stop treatment drug). 1,334 patients will be recruited from about fifty ICUs in the UK. An economic evaluation will be conducted alongside the trial.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN38366450.

The Beta Agonist Lung Injury TrIal (BALTI)--prevention trial protocol

BACKGROUND

Acute lung injury complicates approximately 25-30% of subjects undergoing oesophagectomy. Experimental studies suggest that treatment with beta agonists may prevent the development of acute lung injury by decreasing inflammatory cell infiltration, activation and inflammatory cytokine release, enhancing basal alveolar fluid clearance and improving alveolar capillary barrier function.

METHODS/DESIGN

The Beta Agonist Lung Injury TrIal (prevention) is a multi-centre, randomised, double blind, placebo-controlled trial. The aim of the trial is to determine in patients undergoing elective transthoracic oesphagectomy, if treatment with inhaled salmeterol 100 mcg twice daily started at induction of anaesthesia and continued for 72 hours thereafter compared to placebo affect the incidence of early acute lung injury and other clinical, resource and patient focused outcomes. The primary outcome will be the development of acute lung injury within 72 hours of oesophagectomy. The trial secondary outcomes are the development of acute lung injury during the first 28 days post operatively; PaO2: FiO2 ratio; the number of ventilator and organ failure free days, 28 and 90 day survival; health related quality of life and resource utilisation. The study aims to recruit 360 patients from 10 UK centres.

TRIAL REGISTRATION NUMBER

Current Controlled Trials ISRCTN47481946.

Nasal potential difference to detect Na+ channel dysfunction in acute lung injury

Pulmonary fluid clearance is regulated by the active transport of Na(+) and Cl(-) through respiratory epithelial ion channels. Ion channel dysfunction contributes to the pathogenesis of various pulmonary fluid disorders including high-altitude pulmonary edema (HAPE) and neonatal respiratory distress syndrome (RDS). Nasal potential difference (NPD) measurement allows an in vivo investigation of the functionality of these channels. This technique has been used for the diagnosis of cystic fibrosis, the archetypal respiratory ion channel disorder, for over a quarter of a century. NPD measurements in HAPE and RDS suggest constitutive and acquired dysfunction of respiratory epithelial Na(+) channels. Acute lung injury (ALI) is characterized by pulmonary edema due to alveolar epithelial-interstitial-endothelial injury. NPD measurement may enable identification of critically ill ALI patients with a susceptible phenotype of dysfunctional respiratory Na(+) channels and allow targeted therapy toward Na(+) channel function.

Year in review 2009: Critical Care--shock

The research papers on shock that have been published in Critical Care throughout 2009 are related to four major subjects: first, alterations of heart function and, second, the role of the sympathetic central nervous system during sepsis; third, the impact of hemodynamic support using vasopressin or its synthetic analog terlipressin, and different types of fluid resuscitation; as well as, fourth, experimental studies on the treatment of acute respiratory distress syndrome. The present review summarizes the key results of these studies together with a brief discussion in the context of the relevant scientific and clinical background published both in this and other journals.

Protective effect of carbon monoxide inhalation on lung injury after hemorrhagic shock/resuscitation in rats

BACKGROUND

Hemorrhagic shock and resuscitation (HSR) induces pulmonary inflammation that leads to acute lung injury. Carbon monoxide (CO), a by-product of heme catalysis, was shown to have potent cytoprotective and anti-inflammatory effects. The aim of this study was to examine the effects of CO inhalation at low concentration on lung injury induced by HSR in rats.

METHODS

Rats were subjected to HSR by bleeding to achieve mean arterial pressure of 30 mm Hg for 60 minutes followed by resuscitation with shed blood and saline as needed to restore blood pressure. HSR animals were either maintained in room air or were exposed to CO at 250 ppm for 1 hour before and 3 hours after HSR.

RESULTS

HSR caused an increase in the DNA binding activity of nuclear factor-kappaB and activator protein-1 in the lung followed by the up-regulation of pulmonary gene expression of tumor necrosis factor-alpha, inducible nitric oxide synthase, and interleukin (IL)-10. HSR also resulted in an increase in myeloperoxidase activity and wet weight to dry weight ratio in the lung, and more prominent histopathologic changes including congestion, edema, cellular infiltration, and hemorrhage. In contrast, CO inhalation significantly ameliorated these inflammatory events as judged by fewer histologic changes, less up-regulation of inflammatory mediators, and less activation of nuclear factor-kappaB and activator protein-1. Interestingly, the protective effects against lung injury afforded by CO were associated with further increases in mRNA expression of IL-10 in the lung.

CONCLUSIONS

These findings suggest that inhaled CO at a low concentration ameliorated HSR-induced lung injury and attenuated inflammatory cascades by up-regulation of anti-inflammatory IL-10.

Increased cardiac index due to terbutaline treatment aggravates capillary-alveolar macromolecular leakage in oleic acid lung injury in dogs

Introduction

We assessed the in vivo effects of terbutaline, a beta2-agonist assumed to reduce microvascular permeability in acute lung injury.

Methods

We used a recently developed broncho-alveolar lavage (BAL) technique to repeatedly measure (every 15 min. for 4 hours) the time-course of capillary-alveolar leakage of a macromolecule (fluorescein-labeled dextran) in 19 oleic acid (OA) lung injured dogs. BAL was performed in a closed lung sampling site, using a bronchoscope fitted with an inflatable cuff. Fluorescein-labeled Dextran (FITC-D70) was continuously infused and its concentration measured in plasma and BAL fluid. A two-compartment model (blood and alveoli) was used to calculate KAB, the transport rate coefficient of FITC-D70 from blood to alveoli. KAB was estimated every 15 minutes over 4 hours. Terbutaline intra-venous perfusion was started 90 min. after the onset of the injury and then continuously infused until the end of the experiment.

Results

In the non-treated injured group, the capillary-alveolar leakage of FITC-D70 reached a peak within 30 minutes after the OA injury. Thereafter the FITC-D70 leakage decreased gradually until the end of the experiment. Terbutaline infusion, started 90 min after injury, interrupted the recovery with an aggravation in FITC-D70 leakage.

Conclusions

As cardiac index increased with terbutaline infusion, we speculate that terbutaline recruits leaky capillaries and increases FITC-D70 leakage after OA injury. These findings suggest that therapies inducing an increase in cardiac output and a decrease in pulmonary vascular resistances have the potential to heighten the early increase in protein transport from plasma to alveoli within the acutely injured lung.

A Scandinavian survey of drug administration through inhalation, suctioning and recruitment maneuvers in mechanically ventilated patients

BACKGROUND

The aim was to describe current practices for drug administration through inhalation, endotracheal suctioning and lung recruitment maneuvers in mechanically ventilated patients in Scandinavian intensive care units (ICUs).

METHODS

We invited 161 ICUs to participate in a web-based survey regarding (1) their routine standards and (2) current treatment of ventilated patients during the past 24 h. In order to characterize the patients, the lowest PaO(2) with the corresponding highest FiO(2), and the highest PaO(2) with the corresponding lowest FiO(2) during the 24-h study period were recorded.

RESULTS

Eighty-seven ICUs answered and reported 186 patients. Positive end-expiratory pressure (PEEP) levels (cmH(2)O) were 5-9 in 65% and >10 in 31% of the patients. Forty percent of the patients had heated humidification and 50% received inhalation of drugs. Endotracheal suctioning was performed >7 times during the study period in 40% of the patients, of which 23% had closed suction systems. Twenty percent of the patients underwent recruitment maneuvers. The most common recruitment maneuver was to increase PEEP and gradually increase the inspiratory pressure. Twenty-six percent of the calculated PaO(2)/FiO(2) ratios varied >13 kPa for the same patient.

CONCLUSION

Frequent use of drug administration through inhalation and endotracheal suctioning predispose to derecruitment of the lungs, possibly resulting in the large variations in PaO(2)/FiO(2) ratios observed during the 24-h study period. Recruitment maneuvers were performed only in one-fifth of the patients during the day of the survey.

Effects of salbutamol on exhaled breath condensate biomarkers in acute lung injury: prospective analysis

Introduction

The benefits of β-adrenergic stimulation have been described in acute lung injury (ALI), but there is still no evidence of its anti-inflammatory effect in these patients. Biomarkers in exhaled breath condensate (EBC) were used to study the effects of salbutamol on lung inflammation in mechanically ventilated patients with ALI.

Methods

EBC was collected before and 30 minutes after administration of inhaled salbutamol (800 μg). The following parameters were measured in the samples: volume obtained, conductivity, pH after helium deaeration, and concentration of nitrites, nitrates and 8-isoprostane. The leukotriene B₄ concentration was measured after sample lyophilization and reconstitution. Results are expressed as the median (interquartile range).

Results

EBC was obtained from six ALI patients, with a median age of 56 (46 to 76) years. At the time of EBC collection, the Lung Injury Score was 3 (2.3 to 3.1) and the PaO₂/F_IO₂ ratio was 133 (96 to 211) mmHg. A significant increase in deaerated EBC pH was observed after salbutamol administration (7.66 (7.58 to 7.75) versus 7.83 (7.67 to 7.91), P = 0.028). Trends toward decreased nitrosative species (18.81 (13.33 to 49.44) μM versus 21.21 (8.07 to 29.83) μM, P = 0.173) and decreased 8-isoprostane concentration (11.64 (7.17 to 17.13) pg/ml versus 6.55 (4.03 to 9.99) pg/ml, P = 0.068) were detected. No changes in leukotriene B₄ concentration were found (1.58 (0.47 to 3.57) pg/ml versus 2.06 (1.01 to 3.01) pg/ml, P = 0.753).

Conclusion

EBC analysis is a noninvasive technique that can be used to monitor ventilated patients. In EBC from a small cohort of patients with ALI, inhaled salbutamol significantly decreased airspace acidosis, a marker of inflammation, and was associated with a trend toward decreased markers of nitrosative and oxidative stress.

Nonventilatory interventions in the acute respiratory distress syndrome

Acute respiratory distress syndrome was first described in 1967. Acute respiratory distress syndrome and acute lung injury are diseases the busy intensivist treats almost daily. The etiologies of acute respiratory distress syndrome are many. A significant distinction is based on whether the insult to the lung was direct, such as in pneumonia, or indirect, such as trauma or sepsis. Strategies for managing patients with acute respiratory distress syndrome/acute lung injury can be subdivided into 2 large groups, those based in manipulation of mechanical ventilation and those based in nonventilatory modalities. This review focuses on the nonventlilatory strategies and includes fluid restriction, exogenous surfactant, inhaled nitric oxide, manipulation of production, or administration of eicosanoids, neuromuscular blocking agents, prone position ventilation, glucocorticoids, extracorporeal membrane oxygenation, and administration of beta-agonists. Most of these therapies either have not been studied in large trials or have failed to show a benefit in terms of long-term patient mortality. Many of these therapies have shown promise in terms of improved oxygenation and may therefore be beneficial as rescue therapy for severely hypoxic patients. Recommendations regarding the use of each of these strategies are made, and an algorithm for implementing these strategies is suggested.

Advances in critical care for the nephrologist: acute lung injury/ARDS

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are a major cause of acute respiratory failure in the critically ill patient. ALI and ARDS are characterized by the acute onset of severe hypoxemia and bilateral pulmonary infiltrates in the absence of clinical evidence for left atrial hypertension. These conditions are differentiated from one another by the ratio of the partial pressure of oxygen in the arterial blood to the inspired fraction of oxygen; ARDS requires a more severe oxygenation defect. ALI and ARDS may occur in association with a number of clinical disorders, including sepsis, pneumonia, aspiration, trauma including inhalational injury, and blood transfusions. The mortality rate remains high, in the range of 25% to 40%. The pathophysiology of ALI/ARDS involves resident lung cells, including endothelial and epithelial cells, as well as neutrophils, monocytes/macrophages, and platelets. When ALI/ARDS is complicated by acute kidney injury, mortality increases substantially. Several supportive and pharmacologic therapies have been tested in clinical trials. Of these, a low tidal volume, lung protective ventilation strategy is the only strategy that has been demonstrated in a large, multicenter randomized clinical trial to reduce mortality for patients with ALI/ARDS. Based on a recent randomized trial, a conservative fluid management strategy reduces the duration of mechanical ventilation without increasing the incidence of renal failure. Pharmacologic strategies and other ventilator management strategies have not been successful to date; however, several randomized, placebo controlled treatment trials are ongoing.

Salmeterol enhances pulmonary fibrinolysis in healthy volunteers

OBJECTIVE

Various lung diseases are associated with local activation of coagulation and concurrent inhibition of fibrinolysis. Although salmeterol, a beta2-adrenoceptor agonist with profound bronchodilatory properties, has been studied extensively, the effects of this compound on the pulmonary hemostatic balance are not elucidated.

DESIGN

A single-blinded, placebo-controlled study.

SETTING

University hospital and laboratory.

SUBJECTS

A total of 32 human volunteers.

INTERVENTIONS

Subjects inhaled 100 microg of salmeterol or placebo (t = -30 mins) followed by 100 microg of lipopolysaccharide (LPS) or normal saline (t = 0 mins; n = 8 per group).

MEASUREMENTS AND MAIN RESULTS

Measurements were performed in bronchoalveolar lavage fluid obtained 6 hrs postchallenge. Inhalation of LPS enhanced pulmonary coagulation as determined by an increase in the concentrations of thrombin-antithrombin complexes, factor VIIa, and soluble tissue factor in bronchoalveolar lavage fluid (all p < .05 vs. saline). LPS concurrently inhibited pulmonary fibrinolysis, as reflected by a decrease in bronchoalveolar lavage fluid plasminogen activator activity together with an increase in plasminogen activator inhibitor type 1 (both p < .05 vs. saline). Moreover, LPS inhalation was associated with a suppression of the anticoagulant protein C pathway, as indicated by an increase in soluble thrombomodulin and decreases in protein C and activated protein C levels in bronchoalveolar lavage fluid (all p < .05 vs. saline). Salmeterol, either with or without LPS inhalation, enhanced fibrinolysis (plasminogen activator activity and tissue-type and urokinase-type plasminogen activator levels) but did not influence LPS-induced changes in coagulation or the protein C pathway.

CONCLUSIONS

Salmeterol has profibrinolytic properties in the normal lung and when applied in a model of sterile pulmonary inflammation.

Lungenversagen

Das akute Lungenversagen ist eine schwere diffuse entzündliche Erkrankung der Lunge. Nach der „American-European Consensus Conference“ (Bernard et al., 1994) wird zwischen einem ARDS — acute respiratory distress syndrom und einem ALI — acute lung injury unterschieden.

In vitro and in vivo effects of salbutamol on neutrophil function in acute lung injury

BACKGROUND

Intravenous salbutamol (albuterol) reduces lung water in patients with the acute respiratory distress syndrome (ARDS). Experimental data show that it also reduces pulmonary neutrophil accumulation or activation and inflammation in ARDS.

AIM

To investigate the effects of salbutamol on neutrophil function.

METHODS

The in vitro effects of salbutamol on neutrophil function were determined. Blood and bronchoalveolar lavage (BAL) fluid were collected from 35 patients with acute lung injury (ALI)/ARDS, 14 patients at risk from ARDS and 7 ventilated controls at baseline and after 4 days' treatment with placebo or salbutamol (ALI/ARDS group). Alveolar-capillary permeability was measured in vivo by thermodilution (PiCCO). Neutrophil activation, adhesion molecule expression and inflammatory cytokines were measured.

RESULTS

In vitro, physiological concentrations of salbutamol had no effect on neutrophil chemotaxis, viability or apoptosis. Patients with ALI/ARDS showed increased neutrophil activation and adhesion molecule expression compared with at risk-patients and ventilated controls. There were associations between alveolar-capillary permeability and BAL myeloperoxidase (r = 0.4, p = 0.038) and BAL interleukin 8 (r = 0.38, p = 0.033). In patients with ALI/ARDS, salbutamol increased numbers of circulating neutrophils but had no effect on alveolar neutrophils.

CONCLUSION

At the onset of ALI/ARDS, there is increased neutrophil recruitment and activation. Physiological concentrations of salbutamol did not alter neutrophil chemotaxis, viability or apoptosis in vitro. In vivo, salbutamol increased circulating neutrophils, but had no effect on alveolar neutrophils or on neutrophil activation. These data suggest that the beneficial effects of salbutamol in reducing lung water are unrelated to modulation of neutrophil-dependent inflammatory pathways.

Inhaled beta-2 agonist salbutamol and acute lung injury: an association with improvement in acute lung injury

INTRODUCTION

Beta2 agonists have several properties that could be beneficial in acute lung injury (ALI). We therefore chose to study the effect of inhaled beta2 agonist use (salbutamol) on duration and severity of ALI.

METHODS

We undertook a retrospective chart review of 86 consecutive mechanically ventilated patients with ALI, who had varying exposure to inhaled salbutamol. The cohort was divided into two groups according to the average daily dose of inhaled salbutamol they received ('high dose' > or = 2.2 mg/day and 'low dose' < 2.2 mg/day). Severity of ALI and non-pulmonary organ dysfunction was compared between the groups by calculating the days alive and free of ALI and other organ dysfunctions.

RESULTS

The high dose and low dose groups received a mean of 3.72 mg and 0.64 mg salbutamol per day, respectively. The high dose salbutamol group had significantly more days alive and free of ALI than the low dose group (12.2 +/- 4.4 days versus 7.6 +/- 1.9 days, p = 0.02). There were no associations between dose of beta agonist and non-pulmonary organ dysfunctions. High dose salbutamol (p = 0.04), APACHE II score (p = 0.02), and cause of ALI (p = 0.02) were independent variables associated with number of days alive and free of ALI in a multivariate linear regression model.

CONCLUSION

Our retrospective study suggests that salbutamol, an inhaled beta2 agonist, is associated with a shorter duration and lower severity of ALI. A dose greater than 2.2 mg/day of inhaled salbutamol could be a minimal effective dose to evaluate in a randomized controlled trial.

The beta-agonist lung injury trial (BALTI): a randomized placebo-controlled clinical trial

RATIONALE

Experimental data suggest that manipulation of alveolar fluid clearance with beta-agonists can accelerate the resolution of alveolar edema and improve survival.

OBJECTIVE

To determine if a sustained infusion of intravenous salbutamol (albuterol) would accelerate the resolution of alveolar edema in adult patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS).

METHODS

This was a single-center, double-blind, randomized controlled trial. Patients with ALI/ARDS were randomized to treatment with intravenous salbutamol (15 microg kg(-1) h(-1)) or placebo for 7 d. The primary endpoint was extravascular lung water measured by thermodilution (PiCCO) at Day 7.

MEASUREMENTS AND MAIN RESULTS

Sixty-six patients were screened; of these, 40 met the inclusion criteria and were enrolled during 2001-2003. Patients in the salbutamol group had significantly lower lung water at Day 7 than the placebo group (9.2 +/- 6 vs. 13.2 +/- 3 ml kg(-1); 95% confidence interval difference, 0.2-8.3 ml kg(-1); p = 0.038). Plateau airway pressure was lower at Day 7 in the salbutamol group (23.9 +/- 3.8 cm H2O) versus placebo (29.5 +/- 7.2 cm H2O; p = 0.049). There was a trend toward lower Murray lung injury score at Day 7 in the salbutamol group (1.7 +/- 0.9) versus placebo (2.0 +/- 0.6; p = 0.2). Patients in the salbutamol group had a higher incidence of supraventricular arrhythmias (26 vs. 10%; p = 0.2).

CONCLUSION

Although further research is required to confirm the efficacy and safety of intravenous salbutamol in ALI/ARDS, this trial provides the first proof of principle that, in humans with ALI/ARDS, sustained treatment with intravenous beta-agonists reduces extravascular lung water.

Taming the neutrophil: calcium clearance and influx mechanisms as novel targets for pharmacological control

Neutrophils are relatively insensitive to the anti-inflammatory actions of conventional chemotherapeutic agents, including corticosteroids, emphasizing the requirement for novel pharmacological strategies to control the potentially harmful proinflammatory activities of these cells. In the case of commonly-occurring inflammatory diseases of the airways, the neutrophil is the primary mediator of inflammation in conditions such as chronic obstructive pulmonary disease, cystic fibrosis, acute respiratory distress syndrome, bronchiectasis and non-eosinophilic bronchial asthma. Recent insights into the mechanisms utilized by neutrophils to restore Ca(2+) homeostasis following activation with Ca(2+)-mobilizing, proinflammatory stimuli have facilitated the identification of novel targets for anti-inflammatory chemotherapy in these cells. The most amenable of these from a chemotherapeutic perspective, is the cyclic AMP-dependent protein kinase-modulated endomembrane Ca(2+)-ATPase which promotes clearance of the cation from the cytosol of activated neutrophils. Second generation type 4 phosphodiesterase inhibitors and adenosine receptor agonists operative at the level of subtype A2A adenosine receptors, which are currently undergoing clinical and preclinical assessment respectively, hold promise as pharmacologic modulators during the restoration of Ca(2+) homeostasis. If this promise is realized, it may result in novel chemotherapeutic strategies for the control of hyperacute and chronic inflammatory conditions in which neutrophils are primary offenders. Alternative, potential future targets include the Na(+), Ca(2+)-exchanger and store-operated Ca(2+) channels, which cooperate in the refilling of intracellular Ca(2+) stores.

Fas/FasL interaction: a novel immune therapy approach with immobilized biologicals

Systemically applied agents to modulate the Fas/FasL system, e.g., by stimulation of Fas on activated leukocytes or tumor cells failed as strategies in immune therapy due to severe toxic effects in the host. Recently, a novel strategy has been developed by using immobilized immune active biologicals in a medical device that may allow immune management without expensive systemic therapy. This review reports on the potential role of Fas/FasL in immune therapy and summarizes current experimental and clinical data with the leukocyte inhibition module (LIM), an immobilized anti-Fas antibody containing device yet used in extracorporeal blood circulation. This proof of principal may stimulate the development of other devices based on the regulation of Fas/FasL or other targets relevant for immune disorders.