Epidemiology of acute lung injury and acute respiratory distress syndrome in The Netherlands: A survey

What factors predispose patients to acute respiratory distress syndrome?

Sepsis, pneumonia, and shock are the most common conditions predisposing to acute respiratory distress syndrome (ARDS) and certain host genetic variants have been associated with the development of ARDS. Risk modifiers include abuse of alcohol and tobacco, malnutrition, and obesity. The Lung Injury Prediction Score (LIPS) and the simplified Early Acute Lung Injury Score predict ARDS based on clinical and investigational criteria. Hospital-acquired ARDS may result from a medley factors of which high tidal volume ventilation, high oxygen concentration, and plasma transfusion are most commonly implicated. The Checklist for Lung Injury Prevention (CLIP) has been developed to ensure compliance with evidence-based practice that may affect ARDS occurrence. To date, no pharmacologic intervention has been shown to prevent ARDS

Health care utilization and the cost of posttraumatic acute respiratory distress syndrome care

BACKGROUND

Posttraumatic acute respiratory distress syndrome (ARDS) is associated with prolonged mechanical ventilation and longer hospitalizations. The relationship between posttraumatic ARDS severity and financial burden has not been previously studied. We hypothesized that increasing ARDS severity is associated with incrementally higher health care costs.

METHODS

Adults arriving as the highest level of trauma activation were enrolled in an ongoing prospective cohort study. Patients who survived 6 hours or longer are included in the analysis. Blinded review of chest radiographs was performed by two independent physicians for any intubated patient with PaO2:FIO2 ratio of 300 mmHg or lower during the first 8 days of admission. The severity of ARDS was classified by the Berlin criteria. Hospital charge data were used to perform standard costing analysis.

RESULTS

Acute respiratory distress syndrome occurred in 13% (203 of 1,586). The distribution of disease severity was 33% mild, 42% moderate, and 25% severe. Patients with ARDS were older (41 years vs. 35 years, p < 0.01), had higher median Injury Severity Score (30 vs. 10, p < 0.01), more chest injury (Abbreviated Injury Scale score, ≥ 3: 51% vs. 21%, p < 0.01), and blunt mechanisms (85% vs. 53%, p < 0.01). By ARDS severity, there was no significant difference in age, mechanism, or rate of traumatic brain injury. Increasing ARDS severity was associated with higher Injury Severity Score and higher mortality rates. Standardized total hospital charges were fourfold higher for patients who developed ARDS compared with those who did not develop ARDS (US $434,000 vs. US $96,000; p < 0.01). Furthermore, the daily hospital charges significantly increased across categories of worsening ARDS severity (mild, US $20,451; moderate, US $23,994; severe, US $33,316; p < 0.01).

CONCLUSION

The development of posttraumatic ARDS is associated with higher health care costs. Among trauma patients who develop ARDS, total hospital charges per day increase with worsening severity of disease. Prevention, early recognition, and treatment of ARDS after trauma are potentially important objectives for efforts to control health care costs in this population.

LEVEL OF EVIDENCE

Economic and value-based evaluations, level IV.

The tri-peptide GHK-Cu complex ameliorates lipopolysaccharide-induced acute lung injury in mice

The tripeptide-copper complex glycyl-l-histidyl-l-lysine-Cu (II) (GHK-Cu) is involved in wound healing and tissue remodeling. Although GHK-Cu exhibits anti-aging and tissue renewing properties, its roles in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are still unknown. Therefore, we examined the effects of GHK-Cu in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages in vitro and ALI in mice in vivo. GHK-Cu treatment reduced reactive oxygen species (ROS) production, increased superoxide dismutase (SOD) activity while decreased TNF-α and IL-6 production through the suppression of NF-κB p65 and p38 MAPK signaling in vitro and in vivo model of ALI. Moreover, GHK-Cu attenuated LPS-induced lung histological alterations, suppressed the infiltration of inflammatory cells into the lung parenchyma in LPS-induced ALI in mice. Taken together, these findings demonstrate that GHK-Cu possesses a protective effect in LPS-induced ALI by inhibiting excessive inflammatory responses; accordingly it may represent a novel therapeutic approach for ALI/ARDS.

Serial inflammatory biomarkers of the severity, course and outcome of late onset acute respiratory distress syndrome in critically ill patients with or at risk for the syndrome after new-onset fever

AIM

Accurate biomarkers of the acute respiratory distress syndrome (ARDS) may help risk stratification and management. We assessed the relation between several biomarkers and the severity, course and outcome of late onset ARDS in 101 consecutive critically ill patients with new onset fever.

MATERIALS AND METHODS

On study days 0, 1, 2 and 7 we measured angiopoietin-2 (ANG2), pentraxin-3 (PTX3), interleukin-6 (IL-6), procalcitonin (PCT) and midregional proadrenomedullin (proADM). ARDS was defined by the Berlin definition and by the lung injury score (LIS).

RESULTS

At baseline, 48% had ARDS according to the Berlin definition and 86% according to the LIS. Baseline markers poorly predicted maximum Berlin categories attained within 7 days, whereas ANG2 best predicted maximum LIS. Depending on the ARDS definition, the day-by-day area under the receiver operating characteristic curves suggested greatest monitoring value for IL-6 and PCT, followed by ANG2. ANG2 and proADM predicted outcome, independently of disease severity.

CONCLUSION

Whereas IL-6 and PCT had some disease monitoring value, ANG2 was the only biomarker capable of both predicting the severity, monitoring the course and predicting the outcome of late onset ARDS in febrile critically ill patients, irrespective of underlying risk factor, thereby yielding the most specific ARDS biomarker among those studied.

Albumin rather than C-reactive protein may be valuable in predicting and monitoring the severity and course of acute respiratory distress syndrome in critically ill patients with or at risk for the syndrome after new onset fever

BACKGROUND

We studied the value of routine biochemical variables albumin, C-reactive protein (CRP) and lactate dehydrogenase (LDH) to improve prediction and monitoring of acute respiratory distress syndrome (ARDS) severity in the intensive care unit.

METHODS

In 101 critically ill patients, with or at risk for ARDS after new onset fever, data were collected on days (D) 0, 1, 2, and 7 after inclusion. ARDS was defined by the Berlin definition and lung injury score (LIS).

RESULTS

At baseline, 48 patients had mild to severe ARDS according to Berlin and 87 according to LIS (Rs = 0.54, P < 0.001). Low baseline albumin levels were moderately associated with maximum Berlin and LIS categories within 7 days; an elevated CRP level was moderately associated with maximum Berlin categories only. The day-by-day Berlin and LIS categories were inversely associated with albumin levels (P = 0.01, P < 0.001) and directly with CRP levels (P = 0.02, P = 0.04, respectively). Low albumin levels had monitoring value for ARDS severity on all study days (area under the receiver operating characteristic curve, AUROC, 0.62-0.82, P < 0.001-0.03), whereas supranormal CRP levels performed less . When the Berlin or LIS category increased, albumin levels decreased ≥1 g/L (AUROC 0.72-0.77, P = 0.001) and CRP increased ≥104 mg/L (only significant for Berlin, AUROC 0.69, P = 0.04). When the LIS decreased, albumin levels increased ≥1 g/L (AUROC 0.68, P = 0.02). LDH was higher in 28-day non-survivors than survivors (P = 0.007).

CONCLUSIONS

Overall, albumin may be of greater value than CRP in predicting and monitoring the severity and course of ARDS in critically patients with or at risk for the syndrome after new onset fever. Albumin levels below 20 g/L as well as a decline over a week are associated with ARDS of increasing severity, irrespective of its definition. LDH levels predicted 28-day mortality.

Early increase in alveolar macrophage prostaglandin 15d-PGJ2 precedes neutrophil recruitment into lungs of cytokine-insufflated rats

Early detection and prevention is an important goal in acute respiratory distress syndrome research. We determined the concentration of the anti-inflammatory 15-deoxy-Δ(12,14)-prostaglandin-J2 (15d-PGJ2) and other components of the cyclopentenone prostaglandin cascade in relation to lung inflammation in cytokine (IL-1/LPS)-insufflated rats. We found that 15d-PGJ2 levels increase in the bronchoalveolar lavage (BAL) fluid of rats insufflated with cytokines 2 h before. BAL 15d-PGJ2 increases preceded neutrophil recruitment, lung injury, and oxidative stress in the lungs of cytokine-insufflated rats. 15d-PGJ2 was localized in alveolar macrophages that decreased following cytokine insufflation. 15d-PGJ2 may constitute an early biomarker of lung inflammation and may reflect an endogenous attempt to regulate ongoing inflammation in macrophages and elsewhere after cytokine insufflation.

Recombinant human activated protein C in the treatment of acute respiratory distress syndrome: a randomized clinical trial

RATIONALE

Pulmonary coagulopathy may play a pathogenetic role in acute respiratory distress syndrome (ARDS), by contributing to alveolocapillary inflammation and increased permeability. Recombinant human activated protein C (rh-APC) may inhibit this process and thereby improve patient outcome.

METHODS

A prospective randomized, saline-controlled, single-blinded clinical trial was performed in the intensive care units of two university hospitals, and patients with ARDS were included within 24 h after meeting inclusion criteria.

INTERVENTION

A 4-day course of intravenous rh-APC (24 mcg/kg/h) (n = 33) versus saline (n = 38).

OUTCOMES

The primary outcome parameter was the pulmonary leak index (PLI) of 67Gallium-transferrin as a measure of alveolocapillary permeability and secondary outcomes were disease severity scores and ventilator-free days, among others.

RESULTS

Baseline characteristics were similar; in 87% of patients the PLI was above normal and in 90% mechanical or non-invasive ventilation was instituted at a median lung injury score of 2.5. There was no evidence that Rh-APC treatment affected the PLI or attenuated lung injury and sequential organ failure assessment scores. Mean ventilator-free days amounted to 14 (rh-APC) and 12 days (saline, P = 0.35). 28-day mortality was 6% in rh-APC- and 18% in saline-treated patients (P = 0.12). There was no difference in bleeding events. The study was prematurely discontinued because rh-APC was withdrawn from the market.

CONCLUSION

There is no evidence that treatment with intravenous rh-APC during 4 days for infectious or inflammatory ARDS ameliorates increased alveolocapillary permeability or the clinical course of ARDS patients. We cannot exclude underpowering.

TRIAL REGISTRATION

Nederlands Trial Register ISRCTN 52566874.

Penetrating thorax injury leads to mild systemic activation of neutrophils without inflammatory complications

INTRODUCTION

Trauma is one of the major causes of morbidity and mortality. Thoracic injuries are associated with inflammatory complications such as ARDS. The pathogenesis of this complication after pulmonary injury is incompletely understood, but neutrophils are thought to play a pivotal role. The aim of this project was to gain more insight in the role of thoracic injuries in the pathophysiological processes that link systemic neutrophil activation with inflammatory complications after trauma.

METHODS

In this prospective cohort study fifty-five patients with isolated penetrating thoracic injury were included at a level one Trauma Unit. Blood samples were analysed for neutrophil phenotype with the use of flowcytometry within 3 h of trauma and repeated six and 24 h after injury. The presence of inflammatory complications (e.g. ARDS or sepsis/septic shock) was assessed during admission, and this was related to the neutrophil phenotpe.

RESULTS

The clinical follow-up of fifty-three patients was uneventful. Only two patients developed an inflammatory complication. Within 3 h after trauma, neutrophils showed a decreased expression of FcγRII (p=0.007) and FcγRIII (p=0.001) compared to healthy individuals. After 6 h, expression of active FcγRII (p=0.017), C5aR (p=0.004) and CAECAM8 (p=0.043) increased, whereas L-selectin (p=0.002) decreased. After 24 h also CXCR-2 (CD182) expression increased compared to healthy individuals (p=0.001).

CONCLUSIONS

Penetrating thoracic trauma leads to a distinct primed activation status of circulating neutrophils within hours. In addition to activation of cells, both young and reverse migrated neutrophils are released into the circulation. This degree of systemic inflammation does not exceed a threshold of inflammation that is needed for the development of inflammatory complications like ARDS.

Alcohol screening scores and 90-day outcomes in patients with acute lung injury

OBJECTIVES

The effects of excess alcohol consumption (alcohol misuse) on outcomes in patients with acute lung injury have been inconsistent, and there are no studies examining this association in the era of low tidal volume ventilation and a fluid conservative strategy. We sought to determine whether validated scores on the Alcohol Use Disorders Identification Test that correspond to past-year abstinence (zone 1), low-risk drinking (zone 2), mild to moderate alcohol misuse (zone 3), and severe alcohol misuse (zone 4) are associated with poor outcomes in patients with acute lung injury.

DESIGN

Secondary analysis.

SETTING

The Acute Respiratory Distress Syndrome Network, a consortium of 12 university centers (44 hospitals) dedicated to the conduct of multicenter clinical trials in patients with acute lung injury.

SUBJECTS

Patients meeting consensus criteria for acute lung injury enrolled in one of three recent Acute Respiratory Distress Syndrome Network clinical trials.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 1,133 patients enrolled in one of three Acute Respiratory Distress Syndrome Network studies, 1,037 patients had an Alcohol Use Disorders Identification Test score available for analysis. Alcohol misuse was common with 70 (7%) of patients having Alcohol Use Disorders Identification Test scores in zone 3 and 129 (12%) patients in zone 4. There was a U-shaped association between validated Alcohol Use Disorders Identification Test zones and death or persistent hospitalization at 90 days (34% in zone 1, 26% in zone 2, 27% in zone 3, 36% in zone 4; p < 0.05 for comparison of zone 1 to zone 2 and zone 4 to zone 2). In a multiple logistic regression model, there was a significantly higher odds of death or persistent hospitalization in patients having Alcohol Use Disorders Identification Test zone 4 compared with those in zone 2 (adjusted odds ratio 1.70; 95% confidence interval 1.00, 2.87; p = 0.048).

CONCLUSIONS

Severe but not mild to moderate alcohol misuse is independently associated with an increased risk of death or persistent hospitalization at 90 days in acute lung injury patients.

Activated protein C attenuates pulmonary coagulopathy in patients with acute respiratory distress syndrome

OBJECTIVE

Acute respiratory distress syndrome (ARDS) frequently complicates critical illness. We hypothesized that an infusion of recombinant human activated protein C (rh-APC), a natural anticoagulant, would attenuate pulmonary coagulopathy and injury.

METHODS

In this sub study of a multicenter open-label randomized controlled trial of patients with ARDS, we compared an intravenous (i.v.) infusion of rh-APC (24 mcg kg(-1)  h(-1) for 96 h) with placebo. Patients with sepsis or septic shock were excluded.

RESULTS

In 27 patients serial non-directed bronchoalveolar lavage fluid (NBLF) samples were obtained: 16 patients were treated with rh-APC and 11 patients with placebo. The rh-APC infusion was associated with higher APC levels in plasma during the infusion period of 4 days (P = 0.001), as well as higher APC levels in NBLF up to day 5 after the start of the infusion (P = 0.028). An infusion of rh-APC was associated with lower levels of thrombin-antithrombin complexes (P = 0.009) and soluble tissue factor (P = 0.011) in NBLF, compared with treatment with placebo. An infusion of rh-APC affected fibrinolysis, as plasminogen activator activity levels in NBLF were higher in the patients treated with rh-APC (P = 0.01), presumably as a result of lower NBLF levels of plasminogen activator inhibitor 1, (P = 0.01). The rh-APC infusion decreased the lung injury score (P = 0.005) and simplified the acute physiology score (P = 0.013) on day 5, when compared with baseline. The rh-APC infusion was not associated with bleeding complications.

CONCLUSION

An infusion of rh-APC in patients with ARDS attenuates pulmonary coagulopathy and injury.

Activated protein C in the treatment of acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) frequently necessitate mechanical ventilation in the intensive care unit. The syndromes have a high mortality rate and there is at present no treatment specifically directed at the underlying pathogenesis. Central in the pathophysiology of ALI/ARDS is alveolocapillary inflammation leading to permeability edema. As a result of the crosstalk between inflammation and coagulation, activation of proinflammatory and procoagulant/antifibrinolytic pathways contributes to disruption of the endothelial barrier. Protein C (PC) plays a central role in maintaining the equilibrium between coagulation and inflammation. Additionally, natural anticoagulants, such as PC, are depleted, both in blood as well as in the lung. Therefore, the PC system is of interest as a therapeutic target in patients with ALI/ARDS.

METHOD

This review is based on a Medline search of relevant basic and clinical studies.

OBJECTIVE

It discusses the potential role of activated PC in modulating the proinflammatory/procoagulant state for enhancing endothelial barrier function in animal models and human ALI/ARDS.

Validation of the Thorax Trauma Severity Score for mortality and its value for the development of acute respiratory distress syndrome

BACKGROUND

The aim of the present study was to evaluate and to validate the Thorax Trauma Severity Score (TTSS) for mortality.

METHODS

By database analysis 712 patients with an injury to the chest admitted to the Universal Medical Center Utrecht between 2000 and 2004 were studied. All patients with a score of ≥1 on the AISthorax were included in the study. The patients' file was evaluated for: TTSS, intensive care unit stay, days on ventilation, thorax trauma-related complications (eg, acute respiratory distress syndrome [ARDS]), total hospital stay, and mortality.

RESULTS

Of the 516 patients included in the study, 140 (27%) developed thorax-related complications. The overall in-hospital mortality rate was 10%. The receiver operating characteristic curve for predicting mortality demonstrated an adequate discrimination by a value of 0.844. The TTSS was statistically significant higher in patients who died of thorax-related complications than in patients who died because of nonthorax-related complications and survivors (P < 0.001, confidence interval [CI] 95%). In patients who developed ARDS the TTSS was significant higher (P = 0.005, CI 95%).

CONCLUSION

This study supports the use of the TTSS for predicting mortality in thoracic injury patients. Furthermore, the TTSS appears capable of predicting ARDS.

Efeito do treinamento físico no pulmão de ratos submetidos à ingestão alcoólica

O alcoolismo crônico provoca alterações nos tecidos pulmonares caracterizadas por edema pulmonar e formação de extenso infiltrado inflamatório. O objetivo deste trabalho foi avaliar o efeito do exercício físico sobre as lesões pulmonares provocadas por ingestão crônica de álcool em ratos Wistar. MATERIAL E MÉTODOS: Trinta e dois ratos Wistar machos (261,1 ± 1,3 gramas) receberam aguardente de cana-de-açúcar diluída (30%, v/v, grupo alcoolizado) ou água potável (grupo controle) durante 120 dias. Após este período, cinco animais de cada grupo foram sacrificados. Os demais animais receberam apenas água potável até o final do experimento e foram divididos em quatro grupos: alcoolizados sedentários (AS), controle sedentários (CS), alcoolizados treinados (AT) e controles treinados (CT). Os animais AT e CT foram submetidos a protocolo de natação, aumentando gradativamente o tempo de exercício até 20 minutos por dia, cinco vezes por semana, durante um período total de cinco semanas. Neste mesmo período, os animais AS e CS foram mantidos em sedentarismo. RESULTADOS: Após o período de ingestão alcoólica, os animais do grupo alcoolizado apresentaram redução de peso (P < 0,05) e aumento da massa relativa do pulmão (P < 0,05). O pulmão do grupo alcoolizado apresentou edema pulmonar e extenso infiltrado inflamatório. Os animais dos grupos CS e CT não apresentaram diferenças morfológicas. Os animais do grupo AT apresentaram aumento do quadro de edema pulmonar e do número de macrófagos pigmentados em relação ao grupo AC (P < 0,05). CONCLUSÃO: O exercício físico pode acentuar o processo inflamatório pulmonar quando aplicado em animais com lesão pulmonar inflamatória provocada pelo consumo crônico de álcool.

Isolated blunt chest injury leads to transient activation of circulating neutrophils

Introduction

The acute respiratory distress syndrome (ARDS) is a severe and frequently seen complication in multi-trauma patients. ARDS is caused by an excessive innate immune response with a clear role for neutrophils. As ARDS is more frequently seen in trauma patients with chest injury, we investigated the influence of chest injury on the systemic neutrophil response and the development of ARDS.

Materials and methods

Thirteen patients with isolated blunt chest injury [abbreviated injury score (AIS) 2–5] were included. To avoid systemic inflammation caused by tissue damage outside the thorax, injuries to other regions than the chest did not exceed an AIS of 2. At 3, 9 and 24 h after injury, the expression of circulating activating molecules on neutrophils and levels of circulating interleukine (IL)-6 were determined. Blood samples from eight healthy volunteers were used as control.

Results

Blunt chest injury resulted in the activation of circulating neutrophils, as characterized by a decreased expression of l-selectin (CD62L), CXCR2 (CD182b) and C5aR (CD88) compared to control (p < 0.05). Expression of l-selectin, CXCR2 and C5aR was partially restored at 24 h after injury. In addition, the mean expression of FcγRIII (CD16) dropped (p < 0.001), indicating the recruitment of young neutrophils into the circulation. IL-6 levels increased to a maximum mean concentration of 86 ± 31 pg/ml at 24 h postinjury. None of the patients developed ARDS.

Conclusion

Blunt chest trauma caused a systemic inflammatory reaction with transient activation of neutrophils and mobilization of young neutrophils into the circulation. Isolated chest injury, however, was not abundant enough to cause ARDS, so a second hit appears crucial.

The influence of infection sites on development and mortality of ARDS

OBJECTIVE

Infection is the most frequent cause of acute respiratory distress syndrome (ARDS). However, little is known about the influence of infection sites on ARDS. This study aimed to assess the associations of infection sites with ARDS development and mortality in critically ill infected patients.

DESIGN

Prospective observational study.

SETTING

Adult intensive care units (ICUs) of an academic medical center.

PATIENTS

Study population included 1,973 consecutive patients admitted to ICUs with bacteremia, pneumonia or sepsis. During follow-up, 549 patients developed ARDS and 212 of them died within 60 days.

MAIN RESULTS

The distribution of infection sites in ARDS patients was: lung (77.2%), abdomen (19.3%), skin/soft tissues (6.0%), urinary tract (4.7%), unknown (2.6%), and multiple sites (17.7%). On multivariate analysis, lung was the only infection site associated with increased ARDS risk [adjusted odds ratio (OR) 3.49]. Urinary tract (adjusted OR 0.43), skin/soft tissue (adjusted OR 0.64), and unknown-site infections (adjusted OR 0.38) were associated with decreased risk. No association was found between individual infection site and ARDS mortality. However, unknown-site [adjusted hazard ratio (HR) 3.08] and multiple-site infections (adjusted HR 1.63) were associated with increased ARDS mortality. When grouping patients into pulmonary, nonpulmonary, and combined infections, nonpulmonary infection was associated with decreased ARDS risk (adjusted OR 0.28) and combined infections was associated with increased ARDS mortality (adjusted HR 1.69), compared with pulmonary infection.

CONCLUSIONS

In critically ill infected patients, pulmonary infection is associated with higher risk of ARDS development than are infections at other sites. Pulmonary versus nonpulmonary infection significantly affects ARDS development but not mortality.

Acute respiratory failure in the patient with cancer: diagnostic and management strategies

Acute respiratory failure (ARF) remains the major reason for admission to the intensive care unit (ICU) in patients with cancer and is often associated with high mortality, especially in those who require mechanical ventilation. The diagnosis and management of ARF in patients who have cancer pose unique challenges to the intensivist. This article reviews the most common causes of ARF in patients with cancer and discusses recent advances in the diagnostic and management approaches of these disorders. Timely diagnosis and treatment of reversible causes of respiratory failure, including earlier use of noninvasive ventilation and judicious ventilator and fluid management in patients with acute lung injury, are essential to achieve an optimal outcome. Close collaboration between oncologists and intensivists helps ensure that clear goals, including direction of treatment and quality of life, are established for every patient with cancer who requires mechanical ventilation for ARF.

Sildenafil attenuates pulmonary arterial pressure but does not improve oxygenation during ARDS

Objective

Pulmonary hypertension is a characteristic feature of acute respiratory distress syndrome (ARDS) and contributes to mortality. Administration of sildenafil in ambulatory patients with pulmonary hypertension improves oxygenation and ameliorates pulmonary hypertension. Our aim was to determine whether sildenafil is beneficial for patients with ARDS.

Design

Prospective, open-label, multicenter, interventional cohort study.

Setting

Medical-surgical ICU of two university hospitals.

Patients

Ten consecutive patients meeting the NAECC criteria for ARDS.

Interventions

A single dose of 50 mg sildenafil citrate administered via a nasogastric tube.

Main results

Administration of sildenafil in patients with ARDS decreased mean pulmonary arterial pressure from 25 to 22 mmHg (P = 0.022) and pulmonary artery occlusion pressure from 16 to 13 mmHg (P = 0.049). Systemic mean arterial pressures were markedly decreased from 81 to 75 mmHg (P = 0.005). Sildenafil did not improve pulmonary arterial oxygen tension, but resulted in a further increase in the shunt fraction.

Conclusion

Although sildenafil reduced pulmonary arterial pressures during ARDS, the increased shunt fraction and decreased arterial oxygenation render it unsuitable for the treatment of patients with ARDS.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-010-1754-3) contains supplementary material, which is available to authorized users.

Methyl-beta-cyclodextrin restores the structure and function of pulmonary surfactant films impaired by cholesterol

Pulmonary surfactant, a defined mixture of lipids and proteins, imparts very low surface tension to the lung-air interface by forming an incompressible film. In acute respiratory distress syndrome and other respiratory conditions, this function is impaired by a number of factors, among which is an increase of cholesterol in surfactant. The current study shows in vitro that cholesterol can be extracted from surfactant and function subsequently restored to dysfunctional surfactant films in a dose-dependent manner by methyl-beta-cyclodextrin (MbetaCD). Bovine lipid extract surfactant was supplemented with cholesterol to serve as a model of dysfunctional surfactant. Likewise, when cholesterol in a complex with MbetaCD ("water-soluble cholesterol") was added in aqueous solution, surfactant films were rendered dysfunctional. Atomic force microscopy showed recovery of function by MbetaCD is accompanied by the re-establishment of the native film structure of a lipid monolayer with scattered areas of lipid bilayer stacks, whereas dysfunctional films lacked bilayers. The current study expands upon a recent perspective of surfactant inactivation in disease and suggests a potential treatment.

Diagnosing acute lung injury in the critically ill: a national survey among critical care physicians

BACKGROUND

Incidence reports on acute lung injury (ALI) vary widely. An insight into the diagnostic preferences of critical care physicians when diagnosing ALI may improve identification of the ALI patient population.

METHODS

Critical care physicians in the Netherlands were surveyed using vignettes involving hypothetical patients and a questionnaire. The vignettes varied in seven diagnostic determinants based on the North American European Consensus Conference and the lung injury score. Preferences were analyzed using a mixed-effects logistic regression model and presented as an odds ratio (OR) with a 95% confidence interval.

RESULTS

From 243 surveys sent to 30 hospitals, 101 were returned (42%). ORs were as follows: chest X-ray consistent with ALI: OR 1.7 (1.3-2.3), high positive end-expiratory pressure (PEEP) (15 cmH(2)O): OR 5.0 (3.9-6.6), low pulmonary artery occlusion pressures (PAOP) (<18 mmHg): OR 4.7 (3.6-6.1), low compliance (30 ml/cmH(2)O): OR 0.7 (0.5-0.9), low PaO(2)/FiO(2) (<250 mmHg): OR 9.2 (6.9-12.3), absence of heart failure: OR 1.2 (0.9-1.5), presence of a risk factor for ALI (sepsis): OR 1.0 (0.8-1.3). The questionnaire revealed that critical care physicians with an anesthesiology background differed from physicians with an internal medicine background with regard to hemodynamic variables when considering an ALI diagnosis (P<0.05).

CONCLUSIONS

Dutch critical care physicians consider the PEEP level, but not the presence of a risk factor for ALI, as an important factor to diagnose ALI. Background specialty of critical care physicians influences diagnostic preferences and may account for variance in the reported incidence of ALI.

Effects of levosimendan and dobutamine on experimental acute lung injury in rats

The effects of levosimendan on acute lung injury induced by peritonitis and abdominal hypertension in the early stages of sepsis in rats were investigated. Twenty-four adult male Wistar rats were randomized into: (1) sham, (2) subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture, then treated by dobutamine, (3) subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture, then treated by levosimendan, and (4) controls subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture with no treatment. In the control and levosimendan groups, cecal ligation and puncture resulted in moderate IL-1beta immunolabelling in lung tissue; marked IL-1beta immunolabelling was demonstrated in the dobutamine group. TNF-alpha immunolabelling was negative in both the sham and levosimendan groups, but moderate and weak immunoreactivities were observed in the dobutamine and control groups, respectively. There were almost no TUNEL positive cells in the sham, but they were prominent in the control. TUNEL positive cells were significantly less in the levosimendan treated lungs when compared to control and dobutamine groups. Immunoreactivity of eNOS was stronger in the dobutamine group when compared with the levosimendan group. In addition, iNOS immunoreactivity was strongly detected in the control group; this immunoreactivity was less in the levosimendan group than the dobutamine group. In this experimental sepsis model, treatment with levosimendan had a marked effect on attenuating or decreasing apoptosis and inflammation in the lung.

Regional aeration and perfusion distribution in a sheep model of endotoxemic acute lung injury characterized by functional computed tomography imaging

OBJECTIVES

Sepsis-related lung injury is the most common and morbid form of acute lung injury. The objective of this study was to develop an ovine model of septic acute lung injury and characterize its pathophysiology regarding its recruitability and changes in regional aeration and perfusion distributions at injury and during injury evolution.

DESIGN

Experimental animal study.

SETTING

University hospital research laboratory.

SUBJECTS

Adult sheep.

INTERVENTIONS

Twenty-one anesthetized and mechanically ventilated sheep received intravenous Escherichia coli endotoxin infusion until severe hypoxemia was obtained. Inspiratory- and expiratory-gated computed tomography images of the entire lung were acquired in six subjects at baseline, during endotoxin infusion, and at injury. Perfusion images were obtained at apex and base locations at baseline and injury. Computed tomography images were analyzed for total, air, and tissue lung volumes and axial and vertical aeration and perfusion gradients. Lung recruitability was studied in a subgroup of subjects after injury.

MEASUREMENTS AND MAIN RESULTS

Computed tomography imaging showed a patchy, progressive decrease in air volume as injury evolved, partially replaced by an increase in tissue volume. Perfusion showed a nondependent-to-dependent gradient at baseline that remained relatively unchanged with injury. Perfusion to poorly aerated lung regions was unchanged or increased after injury. Aeration and perfusion distributions at baseline were primarily dorsal or dependent. After injury, the heterogeneity of perfusion and aeration increased and the effect of gravity decreased. Recruitment maneuvers and changes in positive end-expiratory pressure resulted in no improvement in aeration or oxygenation.

CONCLUSIONS

The severe hypoxemia, moderate volume loss, and perfusion patterns are consistent with an injury model in which hypoxemia is exacerbated by endotoxin-mediated failure of hypoxic pulmonary vasoconstriction.

The angiopoietin-Tie2 system as a therapeutic target in sepsis and acute lung injury

BACKGROUND

Sepsis and acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are life-threatening syndromes characterised by inflammation and increased vascular permeability. Amongst other factors, the angiopoietin-tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (Tie2) system is involved.

OBJECTIVE

To explore whether the angiopoietin-Tie2 system provides suitable targets for the treatment of sepsis and ALI/ARDS.

METHODS

Original experimental and patient studies on angiopoietins and sepsis/endotoxemia, inflammation, lung injury, hyperpermeability, apoptosis, organ functions and vital outcomes were reviewed.

RESULTS/CONCLUSION

The angiopoietin-Tie2 system controls the responsiveness of the endothelium to inflammatory, hyperpermeability, apoptosis and vasoreactive stimuli. Angiopoietin-2 provokes inflammation and vascular hyperpermeability, while angiopoietin-1 has a protective effect. Targeted angiopoietin-2 inhibition with RNA aptamers or blocking antibodies is a potential anti-inflammatory and anti-vascular hyperpermeability strategy in the treatment of sepsis and ALI/ARDS.

Clinical Aspects of Acute Lung Insufficiency (ALI/TRALI)

SUMMARY: Acute respiratory distress syndrome (ARDS) is a common clinical disorder caused by a variety of direct and indirect injuries to the lung, characterized by alveolar epithelial and endothelial injury resulting in damage to the pulmonary alveolar-capillary barrier. The cardinal clinical feature of ARDS, refractory arterial hypoxemia, is the result of protein-rich alveolar edema with impaired surfactant function, due to vascular leakage and vascular dysfunction with consequently impaired matching of ventilation to perfusion. Since its first description in 1967, considerable knowledge concerning the pathogenesis of ARDS has been obtained, however, a plethora of questions remain. Better understanding of the pathophysiology of ARDS has lead to the development of novel therapies, pharmacological strategies, and advances in mechanical ventilation. However, lung-protective ventilation is the only confirmed option in ARDS management improving survival, and few other therapies have translated into improved oxygenation or reduced ventilation time. But despite improvement in our understanding of the therapy and supportive care for patients with ARDS, mortality remains high. It is the purpose of this article to provide an overview of the definition, clinical features, and pathogenesis of ARDS, and to present and discuss therapeutic options currently available in order to effectively treat this severe disorder.