Pediatric acute lung injury

Hospital-acquired venous thromboembolism during invasive mechanical ventilation in children: a single-center, retrospective cohort study

BACKGROUND

Invasive mechanical ventilation (IMV) has been independently associated with hospital-acquired venous thromboembolism (HA-VTE) among critically ill children, including extremity deep venous thrombosis and pulmonary embolism.

OBJECTIVES

We aimed to characterize the frequency and timing of HA-VTE following IMV exposure.

METHODS

This was a single-center, retrospective cohort study including children aged <18 years, hospitalized in a pediatric intensive care unit, undergoing mechanical ventilation for >24 hours from October 2020 through April 2022. Encounters with an existing tracheostomy or receiving treatment for HA-VTE prior to endotracheal intubation were excluded. The primary outcomes characterized clinically-relevant HA-VTE, including timing after intubation, location, and the presence of known hypercoagulability risk factors. Secondary outcomes were IMV exposure magnitude, defined by IMV duration and ventilator parameters (ie, volumetric, barometric, and oxygenation indices).

RESULTS

Of 170 consecutive, eligible encounters, 18 (10.6%) experienced HA-VTE at a median of 4 days (IQR, 1.4-6.4) following endotracheal intubation. Those with HA-VTE had an increased frequency of a prior venous thromboembolism (27.8% vs 8.6%, P = .027). No differences in frequency of other HA-VTE risk factors (ie, acute immobility, hematologic malignancy, sepsis, and COVID-19-related illness), presence of a concurrent central venous catheter, or the magnitude of IMV exposure were noted.

CONCLUSION

Children undergoing IMV experience HA-VTE at markedly higher rates than previously estimated in the general pediatric intensive care unit population after endotracheal intubation. While prospective validation is needed, these findings are an important step toward informing the development of risk-stratified thromboprophylaxis trials in critically ill children.

Comparison of the Montreux definition with the Berlin definition for neonatal acute respiratory distress syndrome

To compare the similarities and differences between the Montreux definition and the Berlin definition in terms of the prevalence, mortality, and complications of neonatal acute respiratory distress syndrome (ARDS). We retrospectively analyzed the data of neonates with respiratory failure treated in a neonatal intensive care unit (NICU) between 1 November 2019 and 31 December 2021. In total, 554 infants had neonatal ARDS (524 infants, Montreux definition; 549 infants, Berlin definition). The prevalence (3.1% vs. 3.3%, p = 0.438) and mortality (18.9% vs.18.0%, p = 0.716) of neonatal ARDS did not differ between the definitions. Among the 519 infants meeting both definitions, key clinical outcomes did not differ between the definitions such as ventilation duration, NICU stay, complication rates, and antibiotic use, except for nitric oxide inhalation. The Montreux and Berlin definitions identified an additional 5 and 30 patients, respectively, not captured by the other definition. The rate of inhaled nitric oxide treatment (20.0% vs. 0%, p = 0.013), air leaks (20.0% vs. 0%, p = 0.013), and invasive ventilation duration (110.00 vs.0.00 h, p = 0.002) significantly differed between the above two groups. Sixty-two patients had moderate and severe ARDS according to the Montreux and Berlin definitions, respectively. The rates of adverse outcomes (e.g., mortality, invasive ventilation time) among these patients were similar to the rates among patients with moderate ARDS according to both definitions than among patients with severe ARDS according to both definitions.  Conclusion: The prevalence, mortality, and most complications of neonatal ARDS were similar between the Montreux and Berlin definitions, which mainly differed in terms of the severity of neonatal ARDS. What is Known: • The Montreux definition was first proposed for the diagnosis of neonatal acute respiratory distress syndrome and was established in 2017. To date, the Montreux definition has not been compared with other diagnostic definitions of ARDS. What is New: • The study suggests that perinatal lung disease need not be excluded in the diagnosis of neonatal ARDS, and that the Montreux definition is more applicable to neonates, taking into account their specific physiological characteristics.

Exploring Key Genes and Mechanisms in Respiratory Syncytial Virus-Infected BALB/c Mice via Multi-Organ Expression Profiles

Respiratory syncytial virus (RSV) a leading cause of pediatric and adult morbidity and mortality worldwide. It can cause complications in multiple organs, thus increasing hospital stays and costs. However, RSV-based studies have primarily focused on effects in the lungs and blood, thereby potentially neglecting critical genes and pathways. Hence, studying RSV infection via a novel multi-organ approach is important. In this study, lung, intestine, brain, and spleen tissues from six BALB/c mice (6–8 weeks old; three in control group and three in RSV-infected group) were subjected to RNA sequencing. Differentially expressed genes (DEGs) in each organ were obtained and functional enrichment analysis was performed. We first used CIBERSORT to evaluate the immune-infiltration landscape. Subsequently, common DEGs (co-DEGs) among the four organs were analyzed to identify key genes and pathways. After quantitative reverse transcription-polymerase chain reaction, western blotting, and external validation analysis of key hub genes, their correlation with immune cells and potential functions were explored. We found that the host response to RSV infection varied among the four organs regarding gene expression profiles and immune cell infiltration. Analysis of the 16 co-DEGs indicated enrichment in the platelet and neutrophil degranulation pathways. Importantly, the key gene hemopexin (Hpx) was strongly correlated with the immune cell fraction in the lungs and may participate in the regulation of platelet activation and immune response.

Isoflurane attenuates sepsis-associated lung injury

Acute lung injury is one of major complications associated with sepsis, responsible for morbidity and mortality. Patients who suffer from acute lung injury often require respiratory support under sedations, and it would be important to know the role of sedatives in lung injury. We examined volatile anesthetic isoflurane, which is commonly used in surgical setting, but also used as an alternative sedative in intensive care settings in European countries and Canada. We found that isoflurane exposure attenuated neutrophil recruitment to the lungs in mice suffering from experimental polymicrobial abdominal sepsis. We found that isoflurane attenuated one of major neutrophil chemoattractants LTB4 mediated response via its receptor BLT1 in neutrophils. Furthermore, we have shown that isoflurane directly bound to BLT1 by a competition assay using newly developed labeled BLT1 antagonist, suggesting that isoflurane would be a BLT1 antagonist.

Pharmacological Effects of Marine-Derived Enterococcus faecium EA9 against Acute Lung Injury and Inflammation in Cecal Ligated and Punctured Septic Rats

Microorganisms obtained from the marine environment may represent a potential therapeutic value for multiple diseases. This study explored the possible protective role of marine-derived potential probiotic Enterococcus faecium EA9 (E. faecium) against pulmonary inflammation and oxidative stress using the cecal ligation and puncture (CLP) model of sepsis in Wistar rats. Animals were pretreated with E. faecium for 10 days before either sham or CLP surgeries. Animals were sacrificed 72 hours following the surgical intervention. The histological architecture of lung tissues was evaluated as indicated by the lung injury score. In addition, the extend of pulmonary edema was determined as wet/dry weight ratio. The inflammatory cytokines were estimated in lung tissues, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) using the enzyme-linked-immunosorbent-assay (ELISA) technique. Moreover, markers for lipid peroxidation such as thiobarbituric acid reaction substances (TBARs), and endogenous antioxidants, including reduced glutathione (GSH) were determined in lung tissues. Finally, the enzymatic activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) were assayed in the lungs. Pretreatment with E. faecium markedly attenuated CLP-induced lung injury and pulmonary edema. Markers for inflammation, including TNF-α, IL-6, and IL-1β were augmented in the lung tissues of CLP animals, while E. faecium ameliorated their augmented levels. E. faecium pretreatment also restored the elevated TBARS levels and the prohibited CAT, SOD, and GPx enzymatic activities in CLP animals. GSH levels were corrected by E. faecium in CLP animals. The inflammatory and lipid peroxidation mediators were positively correlated, while antioxidant enzymatic activities were negatively correlated with CLP-induced lung injury and pulmonary edema. Collectively, marine-derived Enterococcus faecium EA9 might be considered as a prospective therapeutic tool for the management of pulmonary dysfunction associated with sepsis.

Recombinant human thrombomodulin for pneumonia-induced severe ARDS complicated by DIC in children: a preliminary study

Purpose

Recombinant human soluble thrombomodulin (rTM) has been used to treat disseminated intravascular coagulation (DIC). Recent studies have shown the efficacy of rTM through its anti-inflammatory effects for treatment of adults with acute respiratory distress syndrome (ARDS). However, the safety and efficacy of rTM in children with severe ARDS complicated by DIC have not been reported. In this preliminary study, we reported the feasibility of using rTM for the treatment of pneumonia-induced severe ARDS complicated by DIC in children.

Methods

Six children (age: median 10 months old) with pneumonia-induced severe ARDS complicated by DIC were enrolled in this preliminary study. rTM (380 U/kg) was administered for a maximum of 6 days, in addition to conventional therapies after diagnosis of severe ARDS complicated by DIC. After administration of rTM, we measured changes in the plasma TM concentration and evaluated the clinical course, status of DIC and ARDS, and other laboratory findings, including levels of cytokines, chemokines, and biomarkers.

Results

In all six children, the plasma concentration of TM increased and DIC scores decreased after administration of rTM. Four of the six children recovered from the severe ARDS complicated by DIC after treatment, and were discharged from the hospital with no complications. In survived children, levels of soluble receptors for advanced glycation end products, interleukin-6, interleukin-8 and monocyte chemotactic protein-1 decreased after administration of rTM compared to those before rTM.

Conclusions

The rTM administration is feasible as an adjunctive therapeutic strategy for children over 2 months with pneumonia-induced severe ARDS complicated by DIC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00540-021-02971-3.

HFOV vs CMV for neonates with moderate-to-severe perinatal onset acute respiratory distress syndrome (NARDS): a propensity score analysis

This study aimed to evaluate whether high-frequency oscillatory ventilation (HFOV) could reduce mortality and the incidence of bronchopulmonary dysplasia (BPD) of perinatal-onset neonatal acute respiratory distress syndrome (NARDS) compared with conventional mechanical ventilation (CMV). Medical records were collected and retrospectively analyzed. Among the 700 neonates with NARDS who needed invasive ventilation, 501 (71.6%) received CMV, while 199 (28.4%) received HFOV. One-to-one propensity score matching (127:127) was used to match the baseline characteristics of patients who received CMV and HFOV. The results showed that birth weight and oxygenation index (OI) were independently associated with mortality in the multivariate logistic regression. No significant differences were observed in mortality or the incidence of BPD between the two groups. The incidence of intraventricular hemorrhage (IVH) and ventilation-free days were significantly lower in the HFOV group than in the CMV group (3.9 vs 11.80%, p=0.02; 15.226 vs 20.967 days, p=0.01). There were no significant differences between the two groups regarding other secondary outcomes.Conclusion: HFOV was associated with a decreased incidence of IVH in infants with NARDS compared with CMV. However, there were significantly more VFDs in the CMV group than in the HFOV group, and HFOV did not appear to be superior to CMV in decreasing the mortality and incidence of BPD in infants with NARDS. What is Known: • The diagnostic criteria of neonatal acute respiratory distress syndrome (Montreux criteria) were established in 2017. • To date, studies comparing high-frequency oscillatory ventilation and conventional mechanical ventilation in the treatment of neonatal acute respiratory distress syndrome are insufficient. What is New: • High-frequency oscillatory ventilation did not appear to be superior to conventional mechanical ventilation in decreasing the mortality and incidence of bronchopulmonary dysplasia in infants with moderate-to-severe perinatal-onset neonatal acute respiratory distress syndrome. • High-frequency oscillatory ventilation was associated with a decreased incidence of intraventricular hemorrhage in infants with moderate-to-severe perinatal-onset acute respiratory distress syndrome compared with conventional mechanical ventilation.

Inhaled Nitric Oxide Use in Pediatric Hypoxemic Respiratory Failure

OBJECTIVES

To characterize contemporary use of inhaled nitric oxide in pediatric acute respiratory failure and to assess relationships between clinical variables and outcomes. We sought to study the relationship of inhaled nitric oxide response to patient characteristics including right ventricular dysfunction and clinician responsiveness to improved oxygenation. We hypothesize that prompt clinician responsiveness to minimize hyperoxia would be associated with improved outcomes.

DESIGN

An observational cohort study.

SETTING

Eight sites of the Collaborative Pediatric Critical Care Research Network.

PATIENTS

One hundred fifty-one patients who received inhaled nitric oxide for a primary respiratory indication.

MEASUREMENTS AND MAIN RESULTS

Clinical data were abstracted from the medical record beginning at inhaled nitric oxide initiation and continuing until the earliest of 28 days, ICU discharge, or death. Ventilator-free days, oxygenation index, and Functional Status Scale were calculated. Echocardiographic reports were abstracted assessing for pulmonary hypertension, right ventricular dysfunction, and other cardiovascular parameters. Clinician responsiveness to improved oxygenation was determined. One hundred thirty patients (86%) who received inhaled nitric oxide had improved oxygenation by 24 hours. PICU mortality was 29.8%, while a new morbidity was identified in 19.8% of survivors. Among patients who had echocardiograms, 27.9% had evidence of pulmonary hypertension, 23.1% had right ventricular systolic dysfunction, and 22.1% had an atrial communication. Moderate or severe right ventricular dysfunction was associated with higher mortality. Clinicians responded to an improvement in oxygenation by decreasing FIO2 to less than 0.6 within 24 hours in 71% of patients. Timely clinician responsiveness to improved oxygenation with inhaled nitric oxide was associated with more ventilator-free days but not less cardiac arrests, mortality, or additional morbidity.

CONCLUSIONS

Clinician responsiveness to improved oxygenation was associated with less ventilator days. Algorithms to standardize ventilator management may improve signal to noise ratios in future trials enabling better assessment of the effect of inhaled nitric oxide on patient outcomes. Additionally, confining studies to more selective patient populations such as those with right ventricular dysfunction may be required.

Evaluation of anticoagulant agents for the treatment of human metapneumovirus infection in mice

Thrombin has been demonstrated to be involved in several viral diseases including human metapneumovirus (hMPV) infections. We previously showed that immediate administration of thrombin inhibitor argatroban post-infection protected mice against hMPV disease. This current work aims at determining whether warfarin and heparin, two other anticoagulants inhibiting thrombin formation and activities, may also be used for treatment against hMPV in vivo. We found that immediate injections of argatroban, warfarin or heparin after virus challenge protected mice against hMPV infection, as evidenced by decreased or no mortality, less weight loss, reduced viral load and attenuated inflammation. However, delayed treatments starting 1 day post-infection with argatroban or warfarin almost did not impact the survival whereas delayed treatment with heparin induced an increased mortality during infection. Moreover, these treatments also did not reduce weight loss, viral replication and inflammation. In agreement with these results, thrombin generation was decreased upon immediate anticoagulant treatments but was unaltered upon delayed treatments. Thus, thrombin generation occurs at the onset of hMPV infection and thrombin inhibition may be only useful for the treatment of this disease when initiated in the early stage. In this case, heparin is not recommended because of its reduced efficacy on mortality in infected mice whereas argatroban and warfarin appear as safe and effective drugs for the treatment of hMPV disease. The antiviral and anti-inflammatory effects of argatroban occur via thrombin-dependent pathways whereas the mechanisms by which warfarin exerts its beneficial effects against hMPV infection were not elucidated and need to be further studied.

Surfactants in Acute Respiratory Distress Syndrome in Infants and Children: Past, Present and Future

There is a lack of definitive data on the effective management of acute respiratory distress syndrome (ARDS) in infants and children. The development and validation of the Berlin definition (BD) for ARDS and the Pediatric Acute Lung Injury Consensus Conference (PALICC) recommendations in children represented a major advance in optimizing research and treatment, mainly due to the introduction of a severe ARDS category. Proposed reasons for the lack of consistent results with surfactants in children and infants compared with neonates include different causes, type of lung damage (direct or indirect), timing and mode of administration as well as the type of surfactant used. Secretory phospholipase A2 plays an important role in inflammation and possible dysfunction of surfactants in ARDS. Bronchoalveolar lavage (BAL) with normal saline and surfactant allows the removal of inhaled material, the recruitment of non-ventilating areas and the maintenance of the surfactant pool size. BAL with diluted surfactant allows rapid absorption of the surfactant at the air/liquid interface, which blocks the progression of pathological lung disease and in turn disrupts the inflammatory cycle. Importantly, it is now recognized that the type of surfactant, the time of administration and the method of administration could all play an important role in the management of ARDS, and there is evidence that surfactant is effective and well tolerated in children and infants with ARDS.

Aerosolized prostacyclins for acute respiratory distress syndrome (ARDS)

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a critical condition that is associated with high mortality and morbidity. Aerosolized prostacyclin has been used to improve oxygenation despite the limited evidence available so far.This review was originally published in 2010 and updated in 2017.

OBJECTIVES

To assess the benefits and harms of aerosolized prostacyclin in adults and children with ARDS.

SEARCH METHODS

In this update, we searched CENTRAL (2017, Issue 4); MEDLINE (OvidSP), Embase (OvidSP), ISI BIOSIS Previews, ISI Web of Science, LILACS, CINAHL (EBSCOhost), and three trials registers. We handsearched the reference lists of the latest reviews, randomized and non-randomized trials, and editorials, and cross-checked them with our search of MEDLINE. We contacted the main authors of included studies to request any missed, unreported or ongoing studies. The search was run from inception to 5 May 2017.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs), irrespective of publication status, date of publication, blinding status, outcomes published or language. We contacted trial investigators and study authors to retrieve relevant and missing data.

DATA COLLECTION AND ANALYSIS

Three authors independently abstracted data and resolved any disagreements by discussion. Our primary outcome measure was all-cause mortality. We planned to perform subgroup and sensitivity analyses to assess the effect of aerosolized prostacyclin in adults and children, and on various clinical and physiological outcomes. We assessed the risk of bias through assessment of methodological trial components and the risk of random error through trial sequential analysis.

MAIN RESULTS

We included two RCTs with 81 participants.One RCT involved 14 critically ill children with ARDS (very low quality of evidence), and one RCT involved 67 critically ill adults (very low quality evidence).Only one RCT (paediatric trial) provided data on mortality and found no difference between intervention and control. However, this trial was eligible for meta-analysis due to a cross-over design.We assessed the benefits and harms of aerosolized prostacyclin. One RCT found no difference in improvement of partial pressure of oxygen in arterial blood/fraction of inspired oxygen (PaO₂/FiO₂) ratio (mean difference (MD) -25.35, 95% confidence interval (CI) -60.48 to 9.78; P = 0.16; 67 participants, very low quality evidence).There were no adverse events such as bleeding or organ dysfunction in any of the included trials. Due to the limited number of RCTs, we were unable to perform the prespecified subgroup and sensitivity analyses or trial sequential analysis.

AUTHORS' CONCLUSIONS

We are unable to tell from our results whether the intervention has an important effect on mortality because the results were too imprecise to rule out a small or no effect. Therefore, no current evidence supports or refutes the routine use of aerosolized prostacyclin for people with ARDS. There is an urgent need for more RCTs.

[Acute respiratory distress syndrome in childhood: Changing definition and news from the Pediatric Consensus Conference]

Acute respiratory distress syndrome (ARDS) is a rapidly progressive hypoxemic respiratory insufficiency induced by alveolar filling mainly caused by alveolocapillary wall disruption, following direct or indirect pulmonary injury. Much less frequent in children than in adults, pediatric intensivists had long applied adult guidelines to their daily practice. In 2015, experts from the Pediatric Acute Lung Injury Consensus Conference (PALICC) published the first international guidelines specifically dedicated to pediatric ARDS. After a short summary of the history of the ARDS definition since its first report in 1967, we describe the main diagnostic and therapeutic guidelines for PALICC.

The effect of inhaled nitric oxide in acute respiratory distress syndrome in children and adults: a Cochrane Systematic Review with trial sequential analysis

Acute respiratory distress syndrome is associated with high mortality and morbidity. Inhaled nitric oxide has been used to improve oxygenation but its role remains controversial. Our primary objective in this systematic review was to examine the effects of inhaled nitric oxide administration on mortality in adults and children with acute respiratory distress syndrome. We included all randomised, controlled trials, irrespective of date of publication, blinding status, outcomes reported or language. Our primary outcome measure was all-cause mortality. We performed several subgroup and sensitivity analyses to assess the effect of inhaled nitric oxide. There was no statistically significant effect of inhaled nitric oxide on longest follow-up mortality (inhaled nitric oxide group 250/654 deaths (38.2%) vs. control group 221/589 deaths (37.5%; relative risk (95% CI) 1.04 (0.9-1.19)). We found a significant improvement in PaO₂ /F_I O₂ ratio at 24 h (mean difference (95% CI) 15.91 (8.25-23.56)), but not at 48 h or 72 h, while four trials indicated improved oxygenation in the inhaled nitric oxide group at 96 h (mean difference (95% CI) 14.51 (3.64-25.38)). There were no statistically significant differences in ventilator-free days, duration of mechanical ventilation, resolution of multi-organ failure, quality of life, length of stay in intensive care unit or hospital, cost-benefit analysis and methaemoglobin and nitrogen dioxide levels. There was an increased risk of renal impairment (risk ratio (95% CI) 1.59 (1.17-2.16)) with inhaled nitric oxide. In conclusion, there is insufficient evidence to support inhaled nitric oxide in any category of critically ill patients with acute respiratory distress syndrome despite a transient improvement in oxygenation, since mortality is not reduced and it may induce renal impairment.

Inhaled nitric oxide for acute respiratory distress syndrome (ARDS) in children and adults

BACKGROUND

Acute hypoxaemic respiratory failure (AHRF) and mostly acute respiratory distress syndrome (ARDS) are critical conditions. AHRF results from several systemic conditions and is associated with high mortality and morbidity in individuals of all ages. Inhaled nitric oxide (INO) has been used to improve oxygenation, but its role remains controversial. This Cochrane review was originally published in 2003, and has been updated in 2010 and 2016.

OBJECTIVES

The primary objective was to examine the effects of administration of inhaled nitric oxide on mortality in adults and children with ARDS. Secondary objectives were to examine secondary outcomes such as pulmonary bleeding events, duration of mechanical ventilation, length of stay, etc. We conducted subgroup and sensitivity analyses, examined the role of bias and applied trial sequential analyses (TSAs) to examine the level of evidence.

SEARCH METHODS

In this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2015 Issue 11); MEDLINE (Ovid SP, to 18 November 2015), EMBASE (Ovid SP, to 18 November 2015), CAB, BIOSIS and the Cumulative Index to Nursing and Allied Health Literature (CINAHL). We handsearched the reference lists of the newest reviews and cross-checked them with our search of MEDLINE. We contacted the main authors of included studies to request any missed, unreported or ongoing studies. The search was run from inception until 18 November 2015.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs), irrespective of publication status, date of publication, blinding status, outcomes published or language. We contacted trial investigators and study authors to retrieve relevant and missing data.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and resolved disagreements by discussion. Our primary outcome measure was all-cause mortality. We performed several subgroup and sensitivity analyses to assess the effects of INO in adults and children and on various clinical and physiological outcomes. We presented pooled estimates of the effects of interventions as risk ratios (RRs) with 95% confidence intervals (CIs). We assessed risk of bias through assessment of trial methodological components and risk of random error through trial sequential analysis.

MAIN RESULTS

Our primary objective was to assess effects of INO on mortality. We found no statistically significant effects of INO on longest follow-up mortality: 250/654 deaths (38.2%) in the INO group compared with 221/589 deaths (37.5%) in the control group (RR 1.04, 95% CI 0.9 to 1.19; I² statistic = 0%; moderate quality of evidence). We found no statistically significant effects of INO on mortality at 28 days: 202/587 deaths (34.4%) in the INO group compared with 166/518 deaths (32.0%) in the control group (RR 1.08, 95% CI 0.92 to 1.27; I² statistic = 0%; moderate quality of evidence). In children, there was no statistically significant effects of INO on mortality: 25/89 deaths (28.1%) in the INO group compared with 34/96 deaths (35.4%) in the control group (RR 0.78, 95% CI 0.51 to 1.18; I² statistic = 22%; moderate quality of evidence).Our secondary objective was to assess the benefits and harms of INO. For partial pressure of oxygen in arterial blood (PaO2)/fraction of inspired oxygen (FiO2), we found significant improvement at 24 hours (mean difference (MD) 15.91, 95% CI 8.25 to 23.56; I² statistic = 25%; 11 trials, 614 participants; moderate quality of evidence). For the oxygenation index, we noted significant improvement at 24 hours (MD -2.31, 95% CI -2.73 to -1.89; I² statistic = 0%; five trials, 368 participants; moderate quality of evidence). For ventilator-free days, the difference was not statistically significant (MD -0.57, 95% CI -1.82 to 0.69; I² statistic = 0%; five trials, 804 participants; high quality of evidence). There was a statistically significant increase in renal failure in the INO groups (RR 1.59, 95% CI 1.17 to 2.16; I² statistic = 0%; high quality of evidence).

AUTHORS' CONCLUSIONS

Evidence is insufficient to support INO in any category of critically ill patients with AHRF. Inhaled nitric oxide results in a transient improvement in oxygenation but does not reduce mortality and may be harmful, as it seems to increase renal impairment.

The effects of colloids or crystalloids on acute respiratory distress syndrome in swine (<em>Sus scrofa</em>) models with severe sepsis: analysis on extravascular lung water, IL-8, and VCAM-1

Background: Acute respiratory distress syndrome (ARDS) is a fatal complication of severe sepsis. Due to its higher molecular weight, the use of colloids in fluid resuscitation may be associated with fewer cases of ARDS compared to crystalloids. Extravascular lung water (EVLW) elevation and levels of interleukin-8 (IL-8) and vascular cell adhesion molecule-1 (VCAM-1) have been studied as indicators playing a role in the pathogenesis of ARDS. The aim of the study was to determine the effects of colloid or crystalloid on the incidence of ARDS, elevation of EVLW, and levels of IL-8 and VCAM-1, in swine models with severe sepsis.Methods: This was a randomized trial conducted at the Laboratory of Experimental Surgery, School of Veterinary Medicine, IPB, using 22 healthy swine models with a body weight of 8 to 12 kg. Subjects were randomly allocated to receive either colloid or crystalloid fluid resuscitation. After administration of endotoxin, clinical signs of ARDS, EVLW, IL-8, and VCAM-1 were monitored during sepsis, severe sepsis, and one- and three hours after fluid resuscitation. Analysis of data using the Wilcoxon test , Kolmogorov-Smirnov test, Mann-Whitney test, unpaired t test.Results: Mild ARDS was more prevalent in the colloid group, while moderate ARDS was more frequent in the crystalloid group. EVLW elevation was lower in the colloid compared to the crystalloid group. There was no significant difference in IL-8 and VCAM-1 levels between the two groups.Conclusion: The use of colloids in fluid resuscitation does not decrease the probability of ARDS events compared to crystalloids. Compared to crystalloids, colloids are associated with a lower increase in EVLWI, but not with IL-8 or VCAM-1 levels.

Exogenous surfactant and alveolar recruitment in the treatment of the acute respiratory distress syndrome

OBJECTIVE

To investigate the effect of alveolar recruitment combined with surfactant administration on children with acute respiratory distress syndrome (ARDS).

MATERIAL AND METHODS

A prospective, randomized, controlled and sequential study was carried out. Group A (16 children) was treated with both the alveolar recruitment manoeuvres (ARM) and the administration of the surfactant every 8 h for 3 days; group B (15) received the usual treatment only. The alveolar recruitment was carried out by increasing positive end-expiratory pressure 2 by 2 cm H₂ O to improve the transcutaneous oxygen saturation values up to 88% and 90%. Demographic data, gasometric and ventilator parameters, chest radiography and 28-day mortality were evaluated.

RESULTS

There were no significant differences in baseline characteristics between groups. An hour after treatment, significant differences (P < 0.001) were observed in transcutaneous oxygen saturation (SaO₂ ; Group A: 94.1%, Group B: 89.9%), PaO₂ /FiO₂ (212.7 and 126.4) and oxygenation index (OI; 11.4 and 18.5). After 8 h, the differences in SaO₂ (Group A: 94.6%, Group B: 90.3%), PaO₂ /FiO₂ (225.8 and 126.9) and OI (10.8 and 18.4) were also significant (P < 0.001). From the fifth dose of the surfactant, the static compliance (P = 0.0034) and radiological images (P = 0.002) were more greatly improved in group A than in group B. Survival was significantly higher in group A (81.3%) than in group B (26.7%) (P = 0.006).

CONCLUSIONS

The combined treatment of surfactant administration and ARM resulted in a better oxygenation and survival in children with ARDS than when only recruitment was used.

Survival of a child with spinal muscular atrophy and acute respiratory distress syndrome

Spinal muscular atrophy (SMA), a lower motor neuron anterior horn cell disease, causes significant respiratory morbidity and mortality in children. Acute respiratory distress syndrome (ARDS) accounts for 1-4% of all Pediatric Intensive Care Unit (PICU) admissions. Management outcomes for ARDS in patients with SMA have not been described. We present the case of a 5-year-old boy with Type II SMA and ARDS requiring invasive mechanical ventilation. He improved with meticulous management of mechanical ventilation, airway clearance, fluid/nutrition, and sedation/analgesia. He was successfully extubated after 14 days of invasive mechanical ventilation and discharged home after a 20 day hospitalization.

The use of inhaled prostaglandins in patients with ARDS: a systematic review and meta-analysis

OBJECTIVE

This study aimed to determine whether inhaled prostaglandins are associated with improvement in pulmonary physiology or mortality in patients with ARDS and assess adverse effects.

METHODS

The following data sources were used: PubMed, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, reference lists, conference proceedings, and ClinicalTrials.gov. Studies selected included randomized controlled trials and nonrandomized studies. For data extraction, two reviewers independently screened titles and abstracts for eligibility. With regard to data synthesis, 25 studies (two RCTs) published over 21 years (1993-2014) were included. The PROSPERO registration number was CRD42014013180.

RESULTS

One randomized controlled trial showed no difference in the change in mean Pao2 to Fio2 ratio when comparing inhaled alprostadil to placebo: 141.2 (95% CI, 120.8-161.5) to 161.5 (95% CI, 134.6-188.3) vs 163.4 (95% CI, 140.8-186.0) to 186.8 (95% CI, 162.9-210.7), P = .21. Meta-analysis of the remaining studies demonstrated that inhaled prostaglandins were associated with improvement in Pao2 to Fio2 ratio (16 studies; 39.0% higher; 95% CI, 26.7%-51.3%), and Pao2 (eight studies; 21.4% higher; 95% CI, 12.2%-30.6%), and a decrease in pulmonary artery pressure (-4.8 mm Hg; 95% CI, -6.8 mm Hg to -2.8 mm Hg). Risk of bias and heterogeneity were high. Meta-regression found no association with publication year (P = .862), baseline oxygenation (P = .106), and ARDS etiology (P = .816) with the treatment effect. Hypotension occurred in 17.4% of patients in observational studies.

CONCLUSIONS

In ARDS, inhaled prostaglandins improve oxygenation and decrease pulmonary artery pressures and may be associated with harm. Data are limited both in terms of methodologic quality and demonstration of clinical benefit. The use of inhaled prostaglandins in ARDS needs further study.

Lactobacillus rhamnosus GG and Bifidobacterium longum attenuate lung injury and inflammatory response in experimental sepsis

Introduction

Probiotic use to prevent nosocomial gastrointestinal and potentially respiratory tract infections in critical care has shown great promise in recent clinical trials of adult and pediatric patients. Despite well-documented benefits of probiotic use in intestinal disorders, the potential for probiotic treatment to reduce lung injury following infection and shock has not been well explored.

Objective

Evaluate if Lactobacillus rhamnosus GG (LGG) or Bifidobacterium longum (BL) treatment in a weanling mouse model of cecal ligation and puncture (CLP) peritonitis will protect against lung injury.

Methods

3 week-old FVB/N mice were orally gavaged with 200 µl of either LGG, BL or sterile water (vehicle) immediately prior to CLP. Mice were euthanized at 24 h. Lung injury was evaluated via histology and lung neutrophil infiltration was evaluated by myeloperoxidase (MPO) staining. mRNA levels of IL-6, TNF-α, MyD88, TLR-4, TLR-2, NFΚB (p50/p105) and Cox-2 in the lung analyzed via real-time PCR. TNF-α and IL-6 in lung was analyzed via ELISA.

Results

LGG and BL treatment significantly improved lung injury following experimental infection and sepsis and lung neutrophil infiltration was significantly lower than in untreated septic mice. Lung mRNA and protein levels of IL-6 and TNF-α and gene expression of Cox-2 were also significantly reduced in mice receiving LGG or BL treatment. Gene expression of TLR-2, MyD88 and NFΚB (p50/p105) was significantly increased in septic mice compared to shams and decreased in the lung of mice receiving LGG or BL while TLR-4 levels remained unchanged.

Conclusions

Treatment with LGG and BL can reduce lung injury following experimental infection and sepsis and is associated with reduced lung inflammatory cell infiltrate and decreased markers of lung inflammatory response. Probiotic therapy may be a promising intervention to improve clinical lung injury following systemic infection and sepsis.

Epidemiology of pediatric acute respiratory distress syndrome in singapore: risk factors and predictive respiratory indices for mortality

AIM

Acute respiratory distress syndrome (ARDS) represents the most severe form of acute lung injury. The aim of our study is to describe the epidemiology of pediatric ARDS in Singapore and compare the outcomes of ARDS using the following respiratory indices: PaO2/FiO2 ratio (P/F ratio), SpO2/FiO2 ratio (S/F ratio), oxygenation index (OI), and oxygen saturation index (OSI).

METHODS

We examined medical records of patients admitted to the Children's Intensive Care Unit in KK Women's and Children's Hospital from 2009 to 2012. Those who fulfilled criteria for the American-European Consensus Conference definition for ARDS were identified. Demographic, clinical, and radiographic information were extracted and analyzed.

RESULTS

We identified 70 patients with ARDS. Median age (interquartile range) was 6.2 (1.4, 10.4) years. The most common risk factor was pneumonia [50 (71%)]. Overall mortality was 44 (63%) patients. Thirty-two (56%) patients had an underlying chronic comorbidity; 18 (46%) were hematology-oncology conditions. Fifty-six (80%) patients had multiorgan dysfunction. Adjunct therapies used in our patients included inhaled nitric oxide [5 (7%)], prone position [22 (31%)], steroids [26 (37%)], and neuromuscular blockade [26 (37%)]. A high OI and low PF ratio after 24 h of diagnosis of ARDS were associated with mortality. From day 3 onward, all four respiratory indices appropriately differentiated survivors from non-survivors. Severity based on the S/F ratio and OSI demonstrated association with decreased ventilator free days and ICU free days.

CONCLUSION

Risk factors for mortality included having an underlying comorbidity, multiorgan dysfunction, a low PF ratio, and high OI at 24 h of ARDS. Abnormal SpO2-based measurements were reliable markers of poor outcomes in pediatric ARDS.

Kidney-lung cross-talk and acute kidney injury

There is a growing appreciation for the role that acute kidney injury (AKI) plays in the propagation of critical illness. In children, AKI is not only an independent predictor of morbidity and mortality, but is also associated with especially negative outcomes when concurrent with acute lung injury (ALI). Experimental data provide evidence that kidney-lung crosstalk occurs and can be bidirectionally deleterious, although details of the precise molecular mechanisms involved in the AKI-ALI interaction remain incomplete. Clinically, ALI, and the subsequent clinical interventions used to stabilize gas exchange, carry consequences for the homeostasis of kidney function. Meanwhile, AKI negatively affects lung physiology significantly by altering the homeostasis of fluid balance, acid-base balance, and vascular tone. Experimental AKI research supports an "endocrine" role for the kidney, triggering a cascade of extra-renal inflammatory responses affecting lung homeostasis. In this review, we will discuss the pathophysiology of kidney-lung crosstalk, the multiple pathways by which AKI affects kidney-lung homeostasis, and discuss how these phenomena may be unique in critically ill children. Understanding how AKI may affect a "balance of communication" that exists between the kidneys and the lungs is requisite when managing critically ill children, in whom imbalance is the norm.

Acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is commonly associated with severe sepsis. While the criteria for diagnosis have evolved since the first description in 1967, the characteristics of hypoxemia, tachypnea, rapidly progressing acute respiratory failure, and poor lung compliance continue. Scoring systems have been developed in an effort to quantify the severity of lung injury, with the most recent being the Berlin Definition. This system attempts to define acute lung injury (ALI) and ARDS with more precision in terms of timing of disease onset, severity of disease, and chest radiograph findings. The number of reported cases of ALI/ARDS per year is lower in pediatric patients vs. adults; however, mortality rates continue to be high. Sepsis-related ARDS has a generally higher disease severity and poorer recovery period from lung injury with an increased mortality rate. ARDS results from an initial insult (direct and/or indirect) which triggers a series of cell-mediated responses leading to damage to the capillary endothelium, alveolar epithelium, and impaired fluid removal from the alveolar space. There is, however, gradual resolution of hypoxemia, lung function, and radiographic abnormalities in survivors of ARDS. Management of ARDS is mainly supportive with specific mechanical ventilation strategies and goal-directed therapies. Prevention of ventilator-induced lung injury (VILI) has been demonstrated to have a positive impact on outcomes in patients with ARDS.

Mobilization of endothelial progenitor cells from bone marrow is impaired in a piglet model of acute respiratory distress syndrome

OBJECTIVES

To characterize the endothelial progenitor cell mobilization in the models of moderate and severe lung injury, we hypothesized that there were differences in endothelial progenitor cell levels and mobilizing cytokines between moderate and severe lung injury.

DESIGN

Prospective, randomized, and controlled experimental study.

SETTING

University research laboratory center.

SUBJECTS

Fifteen healthy piglets.

INTERVENTIONS

Piglets were randomly allocated to control, moderate lung injury (acute lung injury), and severe lung injury (acute respiratory distress syndrome) groups. Lung injury was established by intravenous infusion of oleic acid. Animals were mechanically ventilated for 24-48 hours, and then animals were weaned from ventilation and cared for until day 7.

MEASUREMENTS AND MAIN RESULTS

Endothelial progenitor cells were quantified by flow cytometry. After 24 hours, the number of endothelial progenitor cells in peripheral blood increased in the acute lung injury group but was not altered in the acute respiratory distress syndrome group compared to the control group. The number of CD34KDR, KDRCD133, and CD34KDRCD133 cells was higher in the acute lung injury group than in the acute respiratory distress syndrome group. In bone marrow, the number of CD34KDR and KDRCD133 cells was greater in acute respiratory distress syndrome animals but not altered in acute lung injury animals at 24 hours. Furthermore, plasma stromal cell-derived factor-1 and vascular endothelial growth factor concentrations were higher in acute lung injury than in acute respiratory distress syndrome at 24 hours. Matrix metalloproteinase-9 and soluble kit ligand levels in bone marrow were reduced in acute respiratory distress syndrome compared with acute lung injury. Lung CD34, KDR, and lung stromal cell-derived factor-1 messenger RNA expression were higher in the acute lung injury group than in the acute respiratory distress syndrome group. Furthermore, the expression of CD34, KDR, and CD133 messenger RNA in lung tissue was correlated with stromal cell-derived factor-1 in the lung.

CONCLUSIONS

There was a rapid release of endothelial progenitor cells from bone marrow into circulation in moderate acute lung injury, and endothelial progenitor cell mobilization was impaired in acute respiratory distress syndrome.

Acute respiratory distress syndrome in children: physiology and management

PURPOSE OF REVIEW

The present review seeks to review the pathophysiologic processes that underlie the development of acute respiratory distress syndrome (ARDS) in children. The review intends to provide the physiologic foundation for the treatment strategies that are associated with the most optimal outcome.

RECENT FINDINGS

In infants and children, ARDS remains a significant cause of morbidity and mortality. Although any infant or child can develop ARDS, children who have experienced trauma, pneumonia, aspiration, or immune compromise are at increased risk. Data indicate that adoption of an open-lung ventilation strategy, characterized by sufficient positive end-expiratory pressure to avoid atelectasis, a tidal volume that is limited to less than 5-7  cc/kg per breath and a plateau pressure of 30  cm of water or less provides the greatest likelihood of survival and minimizes lung injury. The relative benefits of strategies such as high frequency oscillatory ventilation, surfactant replacement therapy and inhaled nitric oxide are considered.

SUMMARY

ARDS remains a cause of significant mortality and morbidity in children. By employing sound physiologic principles, clinical outcomes can be optimized.

Treatment with oseltamivir and prone positioning for a 9-year-old boy with ARDS caused by pandemic H1N1 2009 influenza

Here we report the case of a 9-year-old boy with acute respiratory distress syndrome (ARDS) caused by novel H1N1 swine-origin influenza virus A. A diagnosis of ARDS caused by a novel influenza A (H1N1) virus was made on the basis of chest X-ray and computed tomography together with low oxygenation index (OI) and the detection of novel influenza A (H1N1) virus from tracheal secretion samples. Oseltamivir phosphate and prone positioning were effective in the treatment of ARDS in this case. These findings suggest that anti-viral drugs and prone positioning can play an important role in the improvement of ARDS caused by novel H1N1 swine-origin influenza virus A.

Acute respiratory failure

Acute respiratory failure is common in critically ill children, who are at increased risk of respiratory embarrassment because of the developmental variations in the respiratory system. Although multiple etiologies exist, pneumonia and bronchiolitis are most common. Respiratory system monitoring has evolved, with the clinical examination remaining paramount. Invasive tests are commonly replaced with noninvasive monitors. Children with ALI/ARDS have better overall outcomes than adults, although data regarding specific therapies are still lacking. Most children will have some degree of long-term physiologic respiratory compromise after recovery from ALI/ARDS. The physiologic basis for respiratory failure and its therapeutic options are reviewed here.

High-frequency oscillatory ventilation in children: a 10-year experience

OBJECTIVES

The aim of the study was to describe the experience with high-frequency oscillatory ventilation (HFOV) in a Portuguese Pediatric Critical Care Unit, and to evaluate whether HFOV allowed improvement in oxygenation and ventilation.

METHODS

This was a retrospective observational cohort study of children ventilated by HFOV between January, 2002 and December, 2011. The following parameters were recorded: demographic and clinical data, and blood gases and ventilatory parameters during the first 48 hours of HFOV.

RESULTS

80 children were included, with a median age of 1.5 months (min: one week; max: 36 months). Pneumonia (n=50; 62.5%) and bronchiolitis (n=18; 22.5%) were the main diagnoses. Approximately 40% (n=32) of the patients developed acute respiratory distress syndrome (ARDS). Conventional mechanical ventilation was used in 68 (85%) of patients prior to HFOV. All patients who started HFOV had hypoxemia, and 56 (70%) also presented persistent hypercapnia. Two hours after starting HFOV, a significant improvement in SatO2/FiO2 ratio (128±0.63 vs. 163±0.72; p<0.001) that was sustained up to 24 hours of HFOV and a decrease in FiO2 were observed. Since the beginning of HFOV, the mean PCO2 significantly decreased (87±33 vs. 66±25; p<0.001), and the pH significantly improved (7.21±0.17 vs. 7.32±0.15; p<0.001). Overall survival was 83.8%.

CONCLUSIONS

HFOV enabled an improvement in hypercapnia and oxygenation. It is a safe option for the treatment of ARDS and severe small airway diseases.

Fluid balance in critically ill children with acute lung injury

OBJECTIVES

In the Fluid and Catheter Treatment Trial (NCT00281268), adults with acute lung injury randomized to a conservative vs. liberal fluid management protocol had increased days alive and free of mechanical ventilator support (ventilator-free days). Recruiting sufficient children with acute lung injury into a pediatric trial is challenging. A Bayesian statistical approach relies on the adult trial for the a priori effect estimate, requiring fewer patients. Preparing for a Bayesian pediatric trial mirroring the Fluid and Catheter Treatment Trial, we aimed to: 1) identify an inverse association between fluid balance and ventilator-free days; and 2) determine if fluid balance over time is more similar to adults in the Fluid and Catheter Treatment Trial liberal or conservative arms.

DESIGN

Multicentered retrospective cohort study.

SETTING

Five pediatric intensive care units.

PATIENTS

Mechanically ventilated children (age≥1 month to <18 yrs) with acute lung injury admitted in 2007-2010.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Fluid intake, output, and net fluid balance were collected on days 1-7 in 168 children with acute lung injury (median age 3 yrs, median PaO2/FIO2 138) and weight-adjusted (mL/kg). Using multivariable linear regression to adjust for age, gender, race, admission day illness severity, PaO2/FIO2, and vasopressor use, increasing cumulative fluid balance (mL/kg) on day 3 was associated with fewer ventilator-free days (p=.02). Adjusted for weight, daily fluid balance on days 1-3 and cumulative fluid balance on days 1-7 were higher in these children compared to adults in the Fluid and Catheter Treatment Trial conservative arm (p<.001, each day) and was similar to adults in the liberal arm.

CONCLUSIONS

Increasing fluid balance on day 3 in children with acute lung injury at these centers is independently associated with fewer ventilator-free days. Our findings and the similarity of fluid balance patterns in our cohort to adults in the Fluid and Catheter Treatment Trial liberal arm demonstrate the need to determine whether a conservative fluid management strategy improves clinical outcomes in children with acute lung injury and support a Bayesian trial mirroring the Fluid and Catheter Treatment Trial.

Respiratory Impairment after Early Red Cell Transfusion in Pediatric Patients with ALI/ARDS

Introduction. In the first 48 hours of ventilating patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), a multipronged approach including packed red blood cell (PRBC) transfusion is undertaken to maintain oxygen delivery. Hypothesis. We hypothesized children with ALI/ARDS transfused within 48 hours of initiating mechanical ventilation would have worse outcome. The course of 34 transfused patients was retrospectively compared to 45 nontransfused control patients admitted to the PICU at Helen DeVos Children's Hospital between January 1st 2008 and December 31st 2009. Results. Mean hemoglobin (Hb) prior to transfusion was 8.2 g/dl compared to 10.1 g/dl in control. P/F ratio decreased from 135.4 ± 7.5 to 116.5 ± 8.8 in transfused but increased from 148.0 ± 8.0 to 190.4 ± 17.8 (P < 0.001) in control. OI increased in the transfused from 11.7 ± 0.9 to 18.7 ± 1.6 but not in control. Ventilator days in the transfused were 15.6 ± 1.7 versus 9.5 ± 0.6 days in control (P < 0.001). There was a trend towards higher rates of MODS in transfused patients; 29.4% versus 17.7%, odds ratio 1.92, 95% CI; 0.6–5.6 Fisher exact P < 0.282. Conclusion. This study suggests that early transfusions of patients with ALI/ARDS were associated with increased ventilatory needs.

Corticosteroids in respiratory diseases in children

We review recent advances in the use of corticosteroids (CS) in pediatric lung disease. CS are frequently used, systemically or by inhalation. Their mechanisms of action in pulmonary diseases are ill defined. CS exert direct inhibitory effects on many inflammatory cells through genomic mechanisms. There is a time lag before clinical response, and the washout of effects is also prolonged. Prompt relief in some conditions, such as croup, may be related to airway mucosal vasoconstriction through a nongenomic mechanism. CS have proven beneficial roles in the treatment of asthma, croup, allergic bronchopulmonary aspergillosis, and subglottic hemangioma. In some conditions, such as bronchiolitis, cystic fibrosis, and bronchopulmonary dysplasia, their use is controversial and is not recommended routinely. In other conditions, such as tuberculosis, interstitial lung disease, acute lung aspiration, and acute respiratory distress syndrome, CS are often used empirically despite the lack of clear evidence of their benefit. New drug regimens, including the more flexible use of inhaled corticosteroids and long-acting β-agonists in asthma, the lack of efficacy of oral corticosteroids in preschool children with acute wheeze, the severe complications of systemic dexamethasone used to prevent bronchopulmonary dysplasia and thus more restricted use, and the beneficial effect of pulse high-dose intravenous methylprednisolone in patients with allergic bronchopulmonary aspergillosis or cystic fibrosis are among the major recent developments. There is concern about adverse effects, especially growth and adrenal suppression, induced by systemic CS in children. These have been reduced, but not eliminated, with the use of the inhaled route. The benefits must be weighed against the potential detrimental effects.

Biomarkers for oxidative stress in acute lung injury induced in rabbits submitted to different strategies of mechanical ventilation

Oxidative damage has been said to play an important role in pulmonary injury, which is associated with the development and progression of acute respiratory distress syndrome (ARDS). We aimed to identify biomarkers to determine the oxidative stress in an animal model of acute lung injury (ALI) using two different strategies of mechanical ventilation. Rabbits were ventilated using either conventional mechanical ventilation (CMV) or high-frequency oscillatory ventilation (HFOV). Lung injury was induced by tracheal saline infusion (30 ml/kg, 38°C). In addition, five healthy rabbits were studied for oxidative stress. Isolated lymphocytes from peripheral blood and lung tissue samples were analyzed by alkaline single cell gel electrophoresis (comet assay) to determine DNA damage. Total antioxidant performance (TAP) assay was applied to measure overall antioxidant performance in plasma and lung tissue. HFOV rabbits had similar results to healthy animals, showing significantly higher antioxidant performance and lower DNA damage compared with CMV in lung tissue and plasma. Total antioxidant performance showed a significant positive correlation (r = 0.58; P = 0.0006) in plasma and lung tissue. In addition, comet assay presented a significant positive correlation (r = 0.66; P = 0.007) between cells recovered from target tissue and peripheral blood. Moreover, antioxidant performance was significantly and negatively correlated with DNA damage (r = -0.50; P = 0.002) in lung tissue. This study indicates that both TAP and comet assay identify increased oxidative stress in CMV rabbits compared with HFOV. Antioxidant performance analyzed by TAP and oxidative DNA damage by comet assay, both in plasma, reflects oxidative stress in the target tissue, which warrants further studies in humans.

High-frequency oscillatory ventilation attenuates oxidative lung injury in a rabbit model of acute lung injury

Mechanical ventilation (MV) can induce lung oxidative stress, which plays an important role in pulmonary injury. This study compared protective conventional mechanical ventilation (CMV) and high-frequency oscillatory ventilation (HFOV) for oxygenation, oxidative stress, inflammatory and histopathological lung injury in a rabbit model of acute lung injury (ALI). Rabbits ( n = 30) were ventilated at FiO2 1.0. Lung injury was induced by tracheal saline infusion (30 mL/kg, 38°C). Animals were randomly assigned to: (a) sham control (CG: tidal volume [ VT] 6 mL/kg, positive end expiratory pressure [PEEP] 5 cmH2O, respiratory rate [RR] 40 ipm); (b) ALI + CMV (CMVG: VT 6 mL/kg, PEEP 10 cmH2O, RR 40 ipm); or (c) ALI + HFOV (HFG: mean airway pressure [Paw] 14 cmH2O, RR 10 Hz) groups. Lung oxidative stress was assessed by total antioxidant performance assay, inflammatory response by the number of polymorphonuclear leukocytes/bronchoalveolar lavage fluid/lung and pulmonary histological damage was quantified by a score. Ventilatory and hemodynamic parameters were recorded every 30 min. Both ALI groups showed worse oxygenation after lung injury induction. After four hours of ventilation, HFG showed better oxygenation (partial pressure of oxygen [PaO2] – CG: 465.9 ± 30.5 = HFG: 399.1 ± 98.2 > CMVG: 232.7 ± 104 mmHg, P < 0.05) and inflammatory responses (CMVG: 4.27 ± 1.50 > HFG: 0.33 ± 0.20 = CG: 0.16 ± 0.15; polymorphonuclear cells/bronchoalveolar lavage fluid/lung, P < 0.05), less histopathological injury score (CMVG: 5 [1–16] > HFG: 1 [0–5] > CG: 0 [0–3]; P < 0.05), and lower lung oxidative stress than CMVG (CG: 59.4 ± 4.52 = HFG: 69.0 ± 4.99 > CMVG: 47.6 ± 2.58% protection/g protein, P < 0.05). This study showed that HFOV had an important protective role in ALI. It improved oxygenation, reduced inflammatory process and histopathological damage, and attenuated oxidative lung injury compared with protective CMV under these experimental conditions considering the study limitations.

Early elevation of matrix metalloproteinase-8 and -9 in pediatric ARDS is associated with an increased risk of prolonged mechanical ventilation

Background

Matrix metalloproteinases (MMP) -8 and -9 may play key roles in the modulation of neutrophilic lung inflammation seen in pediatric Acute Respiratory Distress Syndrome (ARDS). We aimed to perform a comprehensive analysis of MMP-8 and MMP-9 activity in tracheal aspirates of pediatric ARDS patients compared with non-ARDS controls, testing whether increased MMP-8 and -9 activities were associated with clinical outcomes.

Methods

Tracheal aspirates were collected from 33 pediatric ARDS patients and 21 non-ARDS controls at 48 hours of intubation, and serially for those who remained intubated greater than five days. MMPs, tissue inhibitor of metalloproteinases (TIMPs), human neutrophil elastase (HNE) and myeloperoxidase (MPO) activity were measured by ELISA, and correlated with clinical indicators of disease severity such as PRISM (Pediatric Risk of Mortality) scores, oxygen index (OI), multi-organ system failure (MOSF) and clinical outcome measures including length of intubation, ventilator-free days (VFDs) and mortality in the Pediatric Intensive Care Unit (PICU).

Results

Active MMP-9 was elevated early in pediatric ARDS subjects compared to non-ARDS controls. Higher MMP-8 and active MMP-9 levels at 48 hours correlated with a longer course of mechanical ventilation (r = 0.41, p = 0.018 and r = 0.75, p<0.001; respectively) and fewer number of VFDs (r = −0.43, p = 0.013 and r = −0.76, p<0.001; respectively), independent of age, gender and severity of illness. Patients with the highest number of ventilator days had the highest levels of active MMP-9. MMP-9 and to a lesser extent MMP-8 activities in tracheal aspirates from ARDS subjects were sensitive to blockade by small molecule inhibitors.

Conclusions

Higher MMP-8 and active MMP-9 levels at 48 hours of disease onset are associated with a longer duration of mechanical ventilation and fewer ventilator-free days among pediatric patients with ARDS. Together, these results identify early biomarkers predictive of disease course and potential therapeutic targets for this life threatening disease.

High-frequency oscillatory ventilation associated with inhaled nitric oxide compared to pressure-controlled assist/control ventilation and inhaled nitric oxide in children: Randomized, non-blinded, crossover study

PURPOSE

To compare the acute oxygenation effects of high-frequency oscillatory ventilation (HFOV) plus inhaled nitric oxide (iNO) with pressure-controlled assist/control ventilation (PCACV) plus iNO in acute hypoxemic respiratory failure (AHRF) children.

METHODS

Children with AHRF, aged between 1 month and 14 years under PCACV with PEEP ≥ 10 cmH(2) O were randomly assigned to PCACV (PCVG, n = 14) or HFOV (HFVG, n = 14) in a crossover design. Oxygenation indexes and hemodynamic variables were recorded at enrollment (Tind), 1 hr after PCACV start (T0) and then every 4 hr (T4h, etc.).

RESULTS

PO(2)/FiO(2) significantly increased after 4 hr compared to enrollment in both groups [(PCVG-Tind: 111.95 ± 37 < T4h: 143.88 ± 47.5 mmHg, P < 0.05; HFVG-Tind: 123.76 ± 33 < T4h: 194.61 ± 62.42 mmHg, P < 0.05)] without any statistical differences between groups. At T8h, PO(2)/FiO(2) was greater for HFVG compared with PCVG (HFVG: 227.9 ± 80.7 > PCVG: 171.21 ± 52.9 mmHg, P < 0.05). FiO(2) could be significantly reduced after 4 hr for HFVG (HFVG-T4h: 0.53 ± 0.09 < Tind: 0.64 ± 0.2; P < 0.05) but only after 8 hr for PCVG. Comparing groups at T8h, it was observed that FiO(2) decrease was greater for HFVG (HFVG: 0.47 ± 0.06 < PCVG: 0.58 ± 0.1; P < 0.05).

CONCLUSION

Both ventilatory techniques with iNO improve oxygenation. HFOV causes earlier FiO(2) reduction and increased PO(2)/FiO(2) ratio compared to PCACV at 8 hr. However, at the end of the protocol, there was no significant difference and no clinical improvement derived from the application of both ventilatory strategies with iNO. It is not possible to say what would have happened if a different conventional ventilatory mode and a fully protective ventilatory strategy had been used, given the fact that our study is non-blind, and that a limited number of patients were included in each group.

The pharmacology of acute lung injury in sepsis

Acute lung injury (ALI) secondary to sepsis is one of the leading causes of death in sepsis. As such, many pharmacologic and nonpharmacologic strategies have been employed to attenuate its course. Very few of these strategies have proven beneficial. In this paper, we discuss the epidemiology and pathophysiology of ALI, commonly employed pharmacologic and nonpharmacologic treatments, and innovative therapeutic modalities that will likely be the focus of future trials.

Inhaled nitric oxide for acute respiratory distress syndrome and acute lung injury in adults and children: a systematic review with meta-analysis and trial sequential analysis

BACKGROUND

Acute hypoxemic respiratory failure, defined as acute lung injury and acute respiratory distress syndrome, are critical conditions associated with frequent mortality and morbidity in all ages. Inhaled nitric oxide (iNO) has been used to improve oxygenation, but its role remains controversial. We performed a systematic review with meta-analysis and trial sequential analysis of randomized clinical trials (RCTs). We searched CENTRAL, Medline, Embase, International Web of Science, LILACS, the Chinese Biomedical Literature Database, and CINHAL (up to January 31, 2010). Additionally, we hand-searched reference lists, contacted authors and experts, and searched registers of ongoing trials. Two reviewers independently selected all parallel group RCTs comparing iNO with placebo or no intervention and extracted data related to study methods, interventions, outcomes, bias risk, and adverse events. All trials, irrespective of blinding or language status were included. Retrieved trials were evaluated with Cochrane methodology. Disagreements were resolved by discussion. Our primary outcome measure was all-cause mortality. We performed subgroup and sensitivity analyses to assess the effect of iNO in adults and children and on various clinical and physiological outcomes. We assessed the risk of bias through assessment of trial methodological components. We assessed the risk of random error by applying trial sequential analysis.

RESULTS

We included 14 RCTs with a total of 1303 participants; 10 of these trials had a high risk of bias. iNO showed no statistically significant effect on overall mortality (40.2%versus 38.6%) (relative risks [RR] 1.06, 95% confidence interval [CI] 0.93 to 1.22; I² = 0) and in several subgroup and sensitivity analyses, indicating robust results. Limited data demonstrated a statistically insignificant effect of iNO on duration of ventilation, ventilator-free days, and length of stay in the intensive care unit and hospital. We found a statistically significant but transient improvement in oxygenation in the first 24 hours, expressed as the ratio of Po₂ to fraction of inspired oxygen (mean difference [MD] 15.91, 95% CI 8.25 to 23.56; I² = 25%). However, iNO appears to increase the risk of renal impairment among adults (RR 1.59, 95% CI 1.17 to 2.16; I² = 0) but not the risk of bleeding or methemoglobin or nitrogen dioxide formation.

CONCLUSION

iNO cannot be recommended for patients with acute hypoxemic respiratory failure. iNO results in a transient improvement in oxygenation but does not reduce mortality and may be harmful.

A quasi-equilibrium theory of protein adsorption

A model is developed to describe the adsorption and desorption of proteins to and from a surface film under quasi-equilibrium conditions. Starting from Fick's first law of diffusion, an equation for the flux of molecules to a surface is derived assuming a gradient in the chemical potential from the bulk to the surface and a potential barrier due to an existing surface film. Protein molecules are modeled as components with varying surface areas to depict the different orientations of molecules with respect to the film. For concentrated solutions, formation of multilayer protein films is described by allowing components with small minimum surface areas. The thermodynamic analysis is based on Butler's equation for the chemical potentials of the components of a Gibbs surface layer and a first-order model for the nonideality of the surface layer enthalpy and entropy. The model assumes reversible adsorption, consistent with globular proteins that show little denaturation or flexible-chain proteins that reversibly denature at the interface. The model predicts the behavior of five different experiments measuring film properties of the serum protein albumin in quasi-equilibrium and equilibrium conditions at over 2 orders of magnitude in concentration using a single set of parameters. This provides a new framework for analyzing interactions and adsorption of protein films. The key new features of this model are an extension of the classical Smoluchowski analysis to calculate the adsorption and desorption rate, a model of multilayers with decreased molecular areas to allow effective densities greater than a close-packed monolayer, and a concentration-dependent layer thickness.

Sudden Death from Pulmonary Causes

This chapter seeks to survey many of the common pathological entities identified in the lungs at autopsy and the potential role of pulmonary disease in formulating an opinion regarding the cause of death. Appreciation of pulmonary pathology in the medicolegal context is important as it frequently contributes to the immediate or underlying mechanisms of death. The primacy of the lungs in breathing and their coordinated function with the cardiovascular system means that ­pulmonary failure can rapidly compromise tissue oxygenation and body chemistry, leading to an alteration in blood pH, hypoxic damage to downstream tissues and ultimately multiorgan failure and death. Moreover, given that the lungs have direct contact with the environment through inhalation and receive approximately 50% of the cardiac output with each beat of the heart, they may be adversely affected by hazardous agents from the outside world or other pathologic processes not primarily located in the lungs. The range of topics discussed herein is limited by design to deaths due to disease and largely foregoes discussion of more forensically relevant issues relating to toxicology or trauma. Furthermore, the content and format of this chapter is not intended to be encyclopedic, but rather attempts to highlight selected issues regarding pulmonary disease of potential relevance to surgical or forensic pathologists who perform medicolegal postmortem examinations.

Management of acute lung injury/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are disorders of pulmonary inflammation characterized by hypoxemia and respiratory failure. Children have varying incidence of ALI/ARDS from 2.2 to 16 per 100,000 pediatric population associated with high morbidity, mortality, and financial burden. The diagnostic criteria include: acute onset, severe arterial hypoxemia resistant to oxygen therapy alone (PaO₂/FIO₂ ratio ≤ 200 for ARDS and ≤ 300 for ALI), diffuse pulmonary inflammation (bilateral infiltrates on chest radiograph) and No evidence of left atrial hypertension. Management includes ventilatory therapy including lower tidal volume, relatively high PEEP and supportive care. Guidelines for diagnosis, ventilator management, rescue therapies and supportive care are being discussed in the protocol.

High tidal volume ventilation is not deleterious in infant rats exposed to severe hemorrhage

BACKGROUND

Both high tidal volume (V(T)) ventilation and hemorrhage induce acute lung injury in adult rodents. It is not known whether injurious ventilation augments lung injury in infant rats exposed to severe hemorrhage.

METHODS

Two-week-old rats were allocated for ventilation with VT 7 mL/kg and positive end-expiratory pressure (PEEP) 5 cm H₂O (low V(T)) or V(T) 21 mL/kg and PEEP 1 (high V(T)) for 4 hours. Additional rats were subjected to volume-controlled hemorrhage and delayed saline resuscitation, followed by low V(T) or high V(T) ventilation for 4 hours. Nonventilated control groups were also included. Airway resistance and the coefficient of tissue elastance were derived from respiratory input impedance measurements using the low-frequency forced oscillation technique. Pressure-volume curves were obtained at baseline and at the end of the study. Interleukin-6, macrophage inflammatory protein-2, and tumor necrosis factor alpha were determined in bronchoalveolar lavage fluid (BALF) and serum.

RESULTS

In both healthy and hemorrhage-exposed animals, high V(T) resulted in reduced elastance (better lung compliance) and increased transcutaneous oxygen saturation. Interleukin-6 in BALF was greater in ventilated animals when compared with nonventilated controls, but not different among ventilated groups. No significant differences were found for all other inflammatory mediators, total protein concentration in BALF, and histology.

CONCLUSION

High V(T) ventilation with low PEEP improves respiratory system mechanics without causing additional damage to healthy and hemorrhage-exposed infant rats after 4 hours of ventilation. This study highlights the tolerance to high V(T) ventilation in infant rats and underscores the need for age-specific animal models.

Aerosolized prostacyclin for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS)

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are critical conditions that are associated with high mortality and morbidity. Aerosolized prostacyclin has been used to improve oxygenation despite the limited evidence available so far.

OBJECTIVES

To systematically assess the benefits and harms of aerosolized prostacyclin in critically ill patients with ALI and ARDS.

SEARCH STRATEGY

We identified randomized clinical trials (RCTs) from electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 1); MEDLINE; EMBASE; Science Citation Index Expanded; International Web of Science; CINAHL; LILACS; and the Chinese Biomedical Literature Database (to 31st January 2010). We contacted trial authors and manufacturers in the field.

SELECTION CRITERIA

We included all RCTs, irrespective of blinding or language, that compared aerosolized prostacyclin with no intervention or placebo in either children or adults with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

Two authors independently abstracted data and resolved any disagreements by discussion. We presented pooled estimates of the intervention effects as relative risks (RR) with 95% confidence intervals (CI) for dichotomous outcomes. Our primary outcome measure was all cause mortality. We planned to perform subgroup and sensitivity analyses to assess the effect of aerosolized prostacyclin in adults and children, and on various clinical and physiological outcomes. We assessed the risk of bias through assessment of methodological trial components and the risk of random error through trial sequential analysis.

MAIN RESULTS

We included one paediatric RCT with low risk of bias and involving a total of 14 critically ill children with ALI or ARDS. Aersosolized prostacyclin over less than 24 hours did not reduce overall mortality at 28 days (RR 1.50, 95% CI 0.17 to 12.94) compared with aerosolized saline (a total of three deaths). The authors did not encounter any adverse events such as bleeding or organ dysfunction. We were unable to perform the prespecified subgroups and sensitivity analyses or trial sequential analysis due to the limited number of RCTs. We were also not able to assess the safety and efficacy of aerosolized prostacyclin for ALI and ARDS. We found two ongoing trials, one involving adults and the other paediatric participants. The adult trial has been finalized but the data are not yet available.

AUTHORS' CONCLUSIONS

There is no current evidence to support or refute the routine use of aerosolized prostacyclin for patients with ALI and ARDS. There is an urgent need for more randomized clinical trials.

Inhibition of epithelial sodium channels by respiratory syncytial virus in vitro and in vivo

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and children worldwide. Infection of mice with RSV decreased sodium (Na(+)) dependent alveolar fluid clearance (AFC), resulting in increased lung water content and hypoxemia. RSV infection resulted in higher levels of pyrimidines and purines in the alveolar space. Intratracheal administration of UTP or UDP also decreased AFC. The effects of RSV on AFC and oxygen saturation of Balb/c mice were reversed by intraalveolar administration of antagonists of P2Y nucleotide receptors, enzymes that enhance the breakdown of pyrimidines and systemic or intranasal administration of inhibitors of the de novo pathway of pyrimidine synthesis. RSV infection of H441 or mouse tracheal epithelial cells decreased the amiloride-sensitive Na(+) currents and pretreatment of H441 cells with A77 prevented this effect. These findings indicate that the harmful effects of RSV on lung epithelia are mediated at least in part via the production of UTP and its paracrine action on ENaC.