Pediatric acute lung injury: prospective evaluation of risk factors associated with mortality

Tidal volume and mortality in mechanically ventilated children: a systematic review and meta-analysis of observational studies*

OBJECTIVE

To determine whether tidal volume is associated with mortality in critically ill, mechanically ventilated children.

DATA SOURCES

MEDLINE, EMBASE, and CINAHL databases from inception until July 2013 and bibliographies of included studies without language restrictions.

STUDY SELECTION

Randomized clinical trials and observational studies reporting mortality in mechanically ventilated PICU patients.

DATA EXTRACTION

Two authors independently selected studies and extracted data on study methodology, quality, and patient outcomes. Meta-analyses were performed using the Mantel-Haenszel random-effects model. Heterogeneity was quantified using I. Study quality was assessed using the Newcastle-Ottawa Score for cohort studies.

DATA SYNTHESIS

Out of 142 citations, seven studies met the inclusion criteria, and additional two articles were identified from references of the found articles. One was excluded. These eight studies included 1,756 patients. Mortality rates ranged from 13% to 42%. There was no association between tidal volume and mortality when tidal volume was dichotomized at 7, 8, 10, or 12 mL/kg. Comparing patients ventilated with tidal volume less than 7 mL/kg and greater than 10 mL/kg or greater than 12 mL/kg and tidal volume less than 8 mL/kg and greater than 10 mL/kg or greater than 12 mL/kg also showed no association between tidal volume and mortality. Limiting the analysis to patients with acute lung injury/acute respiratory distress syndrome did not change these results. Heterogeneity was observed in all pooled analyses.

CONCLUSIONS

A relationship between tidal volume and mortality in mechanically ventilated children could not be identified, irrespective of the severity of disease. The significant heterogeneity observed in the pooled analyses necessitates future studies in well-defined patient populations to understand the effects of tidal volume on patient outcome.

Surfactant

Exogenous pulmonary surfactant, widely used in neonatal care, is one of the best-studied treatments in neonatology, and its introduction in the 1990s led to a significant improvement in neonatal outcomes in preterm infants, including a decrease in mortality. This chapter provides an overview of surfactant composition and function in health and disease and summarizes the evidence for its clinical use.

Pulse oximetry vs. PaO2 metrics in mechanically ventilated children: Berlin definition of ARDS and mortality risk

PURPOSE

Requiring PaO2/FiO2 ratio (PF) to define ARDS may bias towards children with cardiovascular dysfunction and hypoxemia. We sought to evaluate (1) the Berlin definition of ARDS in children using PF; (2) the effect of substituting SpO2/FiO2(SF) ratio; (3) differences between patients with and without arterial blood gases; and (4) the ability of SpO2 and PaO2 indices to discriminate ICU mortality.

METHODS

Single center retrospective review (3/2009-4/2013) of mechanically ventilated (MV) children. Initial values for PF, SF, oxygenation index (OI), and oxygen saturation index (OSI) after intubation and average values on day 1 of MV were analyzed against ICU mortality, subgrouped by Berlin severity categories.

RESULTS

Of the 1,833 children included, 129 met Berlin PF ARDS criteria (33 % mortality); 312 met Berlin SF ARDS criteria (22 % mortality). Children with a PaO2 on day 1 of MV had higher mortality and severity of illness, were older, and had more vasoactive-inotropic infusions (p < 0.001). SF could be calculated for 1,201 children (AUC for ICU mortality 0.821), OSI for 1,034 (0.793), PF for 695 (0.706), and OI for 673 (0.739). Average SF on day 1 discriminated mortality better than PF (p = 0.003).

CONCLUSIONS

Berlin PF criteria for ARDS identified less than half of the children with ARDS, favoring those with cardiovascular dysfunction. SF or OSI discriminate ICU mortality as well as PF and OI, double the number of children available for risk stratification, and should be considered for severity of illness scores and included in a pediatric-specific definition of ARDS. Multicenter validation is required.

The Respiratory System

This chapter addresses upper airway physiology for the pediatric intensivist, focusing on functions that affect ventilation, with an emphasis on laryngeal physiology and control in breathing. Effective control of breathing ensures that the airway is protected, maintains volume homeostasis, and provides ventilation. Upper airway structures are effectors for all of these functions that affect the entire airway. Nasal functions include air conditioning and protective reflexes that can be exaggerated and involve circulatory changes. Oral cavity and pharyngeal patency enable airflow and feeding, but during sleep pharyngeal closure can result in apnea. Coordination of breathing with sucking and nutritive swallowing alters during development, while nonnutritive swallowing at all ages limits aspiration. Laryngeal functions in breathing include protection of the subglottic airway, active maintenance of its absolute volume, and control of tidal flow patterns. These are vital functions for normal lung growth in fetal life and during rapid adaptations to breathing challenges from birth through adulthood. Active central control of breathing focuses on the coordination of laryngeal and diaphragmatic activities, which adapts according to the integration of central and peripheral inputs. For the intensivist, knowledge of upper airway physiology can be applied to improve respiratory support. In a second part the mechanical properties of the respiratory system as a critical component of the chain of events that result in translation of the output of the respiratory rhythm generator to ventilation are described. A comprehensive understanding of respiratory mechanics is essential to the delivery of optimized and individualized mechanical ventilation. The basic elements of respiratory mechanics will be described and developmental changes in the airways, lungs, and chest wall that impact on measurement of respiratory mechanics with advancing postnatal age are reviewed. This will be follwowed by two sections, the first on respiratory mechanics in various neonatal pathologies and the second in pediatric pathologies. The latter can be classified in three categories. First, restrictive diseases may be of pulmonary origin, such as chronic interstitial lung diseases or acute lung injury/acute respiratory distress syndrome, which are usually associated with reduced lung compliance. Restrictive diseases may also be due to chest wall abnormalities such as obesity or scoliosis (idiopathic or secondary to neuromuscular diseases), which are associated with a reduction in chest wall compliance. Second, obstructive diseases are represented by asthma and wheezing disorders, cystic fibrosis, long term sequelae of neonatal lung disease and bronchiolitis obliterans following hematopoietic stem cell transplantation. Obstructive diseases are defined by a reduced FEV1/VC ratio. Third, neuromuscular diseases, mainly represented by DMD and SMA, are associated with a decrease in vital capacity linked to respiratory muscle weakness that is better detected by PImax, PEmax and SNIP measurements.

[Acute respiratory distress syndrome complicating an acute chest syndrome: potential benefit of early combination of exchange transfusion and prone positioning]

We report the case of an 8-year-old sickle cell anemia child admitted for acute respiratory failure complicating acute chest syndrome. Because of threatening respiratory failure, tracheal intubation was performed immediately after ICU admission. The patient met the criteria for ARDS with a PaO2/FiO2 ratio of 94mmHg. An exchange transfusion was performed immediately after admission. HbS fraction failed from 69 % to 30 %. Fluid resuscitation with crystalloids and continuous norepinephrine infusion was needed because of arterial hypotension. Due to persistent severe hypoxemia with PaO2/FiO2 ratio below 100, the patient was placed in prone positioning 16hours after admission, for a total duration of 14hours. A second 12-hour session of prone positioning was performed 41h after admission and PaO2/FiO2 ratio reached 300mmHg after. Treatment also included transfusion of two red-cell pack on day 1 and 2 after admission in order to maintain hemoglobin level above 8g/dL, and a daily folic acid supplementation. The control of hyperthermia was achieved by a systematic parenteral administration of paracetamol. Cefotaxime and erythromycine were continued until day 7 despite the negative results of all bacteriological samples. The outcome was favorable from day 3 and the patient met the criteria for extubation on day 5. A first attempt of extubation was performed on day 5, but re-intubation was required because of laryngeal edema. Steroids were given for 48h and the patient was successfully extubated on day 7. She was discharged from the ICU on day 8, and from the hospital on day 12. We discuss the various treatments available for the management of acute chest syndrome and their actual relevance in acute respiratory distress syndrome in the absence of strong evidence-based guidelines in pediatric ARDS.

FiO2 predicts outcome in infants with respiratory syncytial virus-induced acute respiratory distress syndrome

OBJECTIVE

Respiratory syncytial virus (RSV) infection can progress to acute respiratory distress syndrome (ARDS) in infants. ARDS is a life-threatening condition that is characterized by severe hypoxemia, defined as PaO(2)/FiO(2) ratio <300 mmHg. This ratio is used in many trials as the sole oxygenation criterion for ARDS. Recently, however, it has been shown in adults with ARDS that FiO(2), independently of the PaO(2)/FiO(2) ratio predicts mortality. Because epidemiology and outcome of ARDS differ strongly between children and adults, we determined if FiO(2) on admission (baseline FiO(2)) independently predicted the duration of mechanical ventilation (MV) and length of stay (LOS) in the pediatric intensive care unit (PICU) in infants with RSV-induced ARDS.

DESIGN

Retrospective observational study.

SETTING

A 14-bed pediatric intensive care unit.

PATIENTS

One hundred twenty-nine mechanically ventilated infants with RSV-induced ARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Independent predictors for outcome, including baseline FiO(2) and PEEP, were analyzed using the cox regression model. Endpoints were duration of MV and LOS in the PICU. A higher baseline FiO(2) was independently associated with a longer duration of MV (HR 0.12, CI 0.02-0.87, P = 0.036) and increased LOS in the PICU (HR 0.09, CI 0.01-0.57, P = 0.023). Neither baseline PEEP nor PaO(2)/FiO(2) ratio correlated with outcome.

CONCLUSIONS

FiO(2) level independently predicted outcome in infants with RSV-induced ARDS, whereas both PEEP and the PaO(2)/FiO(2) ratio did not. This suggests that FiO(2) should be taken into account in defining disease severity in infants with RSV-induced ARDS.

Ventilator-induced lung injury. Similarity and differences between children and adults

It is well established that mechanical ventilation can injure the lung, producing an entity known as ventilator-induced lung injury (VILI). There are various forms of VILI, including volutrauma (i.e., injury caused by overdistending the lung), atelectrauma (injury due to repeated opening/closing of lung units), and biotrauma (release of mediators that can induce lung injury or aggravate pre-existing injury, potentially leading to multiple organ failure). Experimental data in the pediatric context are in accord with the importance of VILI, and appear to show age-related susceptibility to VILI, although a conclusive link between use of large Vts and mortality has not been demonstrated in this population. The relevance of VILI in the pediatric intensive care unit population is thus unclear. Given the physiological and biological differences in the respiratory systems of infants, children, and adults, it is difficult to directly extrapolate clinical practice from adults to children. This Critical Care Perspective analyzes the relevance of VILI to the pediatric population, and addresses why pediatric patients might be less susceptible than adults to VILI.

Evolving epidemiology and definitions of the acute respiratory distress syndrome and early acute lung injury

This article reviews the evolving definitions and epidemiology of the acute respiratory distress syndrome (ARDS) and highlights current efforts to improve identification of high-risk patients, thus to target prevention and early treatment before progression to ARDS. This information will be important for general practitioners and intensivists interested in improving the care of patients at risk for ARDS, and clinical researchers interested in designing clinical trials targeting the prevention and early treatment of acute lung injury.

Predictive value of plasma biomarkers for mortality and organ failure development in patients with acute respiratory distress syndrome

PURPOSE

To evaluate the predictive value of 6 different biomarkers in the development of multiple-organ failure (MOF) and mortality in a contemporary prospective cohort of acute respiratory distress syndrome (ARDS).

METHODS

Patients with ARDS admitted to a tertiary referral center during an 8-month period were included. Plasma sample collection of 6 different biomarkers on days 1, 3, and 5 after ARDS onset was performed (von Willebrand factor, thrombin-antithrombin III complex, plasminogen activator inhibitor 1, interleukin 8, receptor for advanced glycation end-products, and club cell secretory protein). Main outcomes included hospital mortality and development of MOF. Logistic regression models for MOF and mortality prediction were created including biomarkers levels and clinical predictors.

RESULTS

One hundred patients were included in the study. Do-not-resuscitate status and McCabe score were independently associated with increased mortality. None of the 6 biomarkers measured at the time of ARDS diagnosis predicted hospital mortality. After adjustment for important clinical characteristics, elevated day-1 interleukin 8 levels were associated with the development of MOF.

CONCLUSIONS

Addition of biomarkers did not improve mortality prediction in this cohort of ARDS. Association between elevated interleukin 8 levels and progression of organ failures suggests an important role of exaggerated inflammatory response in the development of MOF.

Development of learning objectives and a validated testing tool for management of pediatric mechanical ventilation*

OBJECTIVES

Graduate medical education is shifting toward an outcome-based paradigm, where physicians are evaluated for competency using well-defined criteria. Our aim was to learning objectives and a testing tool to assess competency in the management of mechanical ventilation for infants, children, and adolescents and to verify that the test was reliable and valid.

DESIGN

Prospective reliability and validity study.

SETTING

Large, university-affiliated academic hospital.

SUBJECTS

Sixty-one total subjects from five different academic centers divided into three groups of varying experience. The groups were second- and third-year pediatric residents (Novice), second- and third-year pediatric critical care fellows (Advanced), and pediatric critical care faculty (Expert).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Ten learning objectives considered important for the management of pediatric mechanical ventilation were developed from expert opinion and current evidence. Based on these objectives, a 35-question multiple choice, knowledge- and case-based test was created. Content validity was achieved by consensus of three experts in pediatric critical care medicine evaluating whether the questions reflected the learning objectives and the responses were consistent with current practice and evidence-based medicine. The test was then administered to the three groups to establish construct validity. The "Novice" group scored a mean of 34.6% (95% CI, 28-41%), the "Advanced" group a mean of 59.4% (95% CI, 53-65%), and the "Expert" group a mean of 74.8% (95% CI, 69-80%), with p less than 0.01 for all comparisons. As determined by Hoyt's analysis, the reliability coefficient was 0.89, reflecting excellent reliability.

CONCLUSIONS

This is the first description of specific learning objectives for management of pediatric mechanical ventilation and the first validated and reliable testing tool for assessing knowledge. This tool could be used by fellowship programs to assess fellow competency and identify knowledge gaps in this area prior to completion of training. Further work must be done to determine the criteria for determination of competency.

Nonrespiratory pediatric logistic organ dysfunction-2 score is a good predictor of mortality in children with acute respiratory failure

OBJECTIVE

Multiple organ dysfunction, not respiratory failure, is the major cause of death in children with acute lung injury or acute respiratory distress syndrome. This study was undertaken to estimate the predictive value of death of the nonrespiratory Pediatric Logistic Organ Dysfunction-2 in children with acute respiratory failure.

DESIGN

Analysis of the database of the recently published Pediatric Logistic Organ Dysfunction-2.

SETTING

Nine multidisciplinary, tertiary-care PICU of university-affiliated hospitals in France and Belgium.

PATIENTS

All consecutive children (excluding neonates) admitted to these PICUs (June 2006 to October 2007) and having acute respiratory failure.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

We prospectively collected data on variables considered for the Pediatric Logistic Organ Dysfunction-2 score during PICU stay up to eight time points: days 1, 2, 5, 8, 12, 16, and 18, plus PICU discharge. For each variable considered in the Pediatric Logistic Organ Dysfunction-2 score, the most abnormal value observed during time points was collected. Outcome was vital status at PICU discharge. We used areas under receiver operating characteristic curve to estimate the discrimination and Hosmer-Lemeshow goodness-of-fit tests to estimate calibration of the Pediatric Logistic Organ Dysfunction-2 and the nonrespiratory Pediatric Logistic Organ Dysfunction-2 scores, with correction for the optimism bias using a bootstrap resampling method. We included 1,572 consecutive patients (median age, 20.6 months; interquartile range, 5.5-80.2; mortality rate, 9.5%). Discrimination of the Pediatric Logistic Organ Dysfunction-2 and the nonrespiratory Pediatric Logistic Organ Dysfunction-2 were excellent (areas under receiver operating characteristic curve = 0.93 and 0.92, respectively) and calibration (chi-square test for goodness-of-fit = 5.8, p = 0.45 and 7.6, p = 0.27, respectively) was good. The four nonrespiratory organ dysfunctions were closely related to the risk of mortality (p< 0.001).

CONCLUSION

Our study demonstrates that the nonrespiratory Pediatric Logistic Organ Dysfunction-2 score of the entire PICU stay is highly predictive of death in children with acute respiratory failure of whom 94.3% were invasively ventilated. The nonrespiratory Pediatric Logistic Organ Dysfunction-2 score could represent the nonrespiratory organ failure definition tool whose development was recommended in the international expert recommendations on pediatric acute respiratory distress syndrome.

Adjunctive treatments in pediatric acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a devastating process that involves pulmonary inflammation, alveolar damage and hypoxemic respiratory failure. Although advances in management approaches over the past two decades have resulted in significantly improved outcomes, death from pediatric ARDS may still occur in up to 35% of patients. While invasive mechanical ventilation is an essential component of ARDS management, various adjuncts have been utilized as treatment for these patients. However, evidence-based data in infants and children in this area are lacking. In this article, the authors review the available evidence supporting (or not supporting) the use of non-ventilatory adjunctive strategies in the management of pediatric ARDS, including prone positioning, pulmonary vasodilators, β-agonists, steroids and surfactant.

High frequency oscillation and airway pressure release ventilation in pediatric respiratory failure

BACKGROUND

Airway pressure release ventilation (APRV) and high frequency oscillatory ventilation (HFOV) are frequently used in acute lung injury (ALI) refractory to conventional ventilation. Our aim was to describe our experience with APRV and HFOV in refractory pediatric ALI, and to identify factors associated with survival.

METHODS

We analyzed 104 patients with hypoxemia refractory to conventional ventilation transitioned to either APRV or HFOV. Demographics, oxygenation index (OI), and PaO2 /FiO2 (PF ratio) were recorded before transition to either mode of nonconventional ventilation (NCV) and for every 12 hr after transition.

RESULTS

Relative to APRV, patients on HFOV were younger and had more significant lung disease evidenced by higher OI (28.5 [18.6, 36.2] vs. 21.0 [15.5, 30.0], P = 0.008), lower PF ratios (73 [59,94] vs. 99 [76,131], P = 0.002), and more frequent use of inhaled nitric oxide. In univariate analysis, HFOV was associated with more frequent neuromuscular blockade. Forty-one of 104 patients died on NCV (39.4%). Survivors demonstrated improvement in OI 24 hr after transition to NCV, whereas non-survivors did not (12.9 [8.9, 20.9] vs. 28.1 [17.6, 37.1], P < 0.001). After controlling for immunocompromised status, number of vasopressors, and OI before transition, mode of NCV was not associated with mortality.

CONCLUSIONS

In a heterogeneous PICU population with hypoxemia refractory to conventional ventilation transitioned to NCV, improvement in oxygenation at 24 hr was associated with survival. Immunocompromised status, number of vasopressor infusions, and the OI before transition to NCV were independently associated with survival.

Computer-aided diagnosis system for the Acute Respiratory Distress Syndrome from chest radiographs

This paper presents a computer-aided diagnosis (CAD) system for the assessment of Acute Respiratory Distress Syndrome (ARDS) from chest radiographs. Our method consists in automatically extracting intercostal patches from chest radiographs belonging to the test database using a semiautomatic segmentation method of the ribs. Statistical and spectral features are computed from each patch then a method of feature transformation is applied using the Linear Discriminant Analysis (LDA). A training database of 321 patches was classified by an expert in two classes, a class of normal patches and a class of abnormal patches. Patches belonging to the test database are then classified using the SVM classifier. Finally, the rate of abnormal patches is calculated for each quadrant to decide if the chest radiograph presents an ARDS. The method has been evaluated on 90 radiographs where 53 images present ARDS. The results show a sensitivity of 90.6% at a specificity of 86.5%.

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.

Lung inflammation and thymic atrophy after bleomycin are controlled by the prostaglandin D2 receptor DP1

Acute lung injury (ALI) can be accompanied by secondary systemic manifestations. In a model of ALI induced by bleomycin (bleo), we examined the response of D prostanoid receptor 1 (DP1)-deficient mice (DP1(-/-)) to better understand these processes. DP1 deficiency aggravated the toxicity of bleo as indicated by enhanced body weight loss, mortality, and lung inflammation including bronchoalveolar permeability and neutrophilia. Thymic atrophy was also observed after bleo and was strongly exacerbated in DP1(-/-) mice. This resulted from the enhanced depletion of immature T lymphocytes in the thymus of DP1(-/-) mice, a phenomenon usually related to increased glucocorticoid release in blood. Serum corticosterone was more elevated in DP1(-/-) mice after bleo than in wild-type (wt) mice. Thymocytes of DP1(-/-) mice were not more sensitive to dexamethasone in vitro, and systemic delivery of dexamethasone or peritoneal inflammation after LPS induced a similar thymic atrophy in wt and DP1(-/-) mice, indicating that pulmonary DP1 was critical to the control of thymic atrophy after bleo. DP1(-/-) mice showed increased lung and/or blood mediators involved in neutrophil recruitment and/or glucocorticoid production/thymic atrophy (osteopontin, leukemia inhibitory factor, and keratinocyte-derived chemokine) after bleo. Finally, local pulmonary DP1 activation or inhibition in wt mice abrogated or amplified thymic atrophy after bleo, respectively. Altogether, our data reveal that ALI can perturb the systemic T-cell pool by inducing thymic atrophy and that both pathological processes are controlled by the pulmonary DP1 receptor. This new pathway represents a potential therapeutic target in ALI.

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.

Imbalance between pulmonary angiotensin-converting enzyme and angiotensin-converting enzyme 2 activity in acute respiratory distress syndrome

OBJECTIVE

Angiotensin-converting enzyme and its effector peptide angiotensin II have been implicated in the pathogenesis of acute respiratory distress syndrome. Recently, angiotensin-converting enzyme 2 was identified as the counter-regulatory enzyme of angiotensin-converting enzyme that converts angiotensin II into angiotensin-(1-7). The aim of this study was to determine pulmonary angiotensin-converting enzyme and angiotensin-converting enzyme 2 activity in patients with acute respiratory distress syndrome.

DESIGN

Prospective observational pilot study.

SETTING

A PICU of a university hospital.

PATIENTS

Fourteen patients admitted, requiring mechanical ventilation for respiratory syncytial virus lower respiratory tract infection.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Two groups of patients were distinguished at admission: a group fulfilling the criteria for acute respiratory distress syndrome and a non-acute respiratory distress syndrome group. Angiotensin-converting enzyme and angiotensin-converting enzyme 2 activity were measured in bronchoalveolar lavage fluid. Patients with acute respiratory distress syndrome had increased angiotensin-converting enzyme activity and decreased angiotensin-converting enzyme 2 activity (p < 0.001) compared with the control group.

CONCLUSION

It is shown for the first time that in acute respiratory distress syndrome, enhanced angiotensin-converting enzyme activity is paralleled by a reduced angiotensin-converting enzyme 2 activity, similar to that found in an experimental rat model of acute respiratory distress syndrome. The reduced angiotensin-converting enzyme 2 activity may be counteracted by restoring angiotensin-(1-7) level, thereby offering a novel treatment modality for this syndrome.

Automated alerting and recommendations for the management of patients with preexisting hypoxia and potential acute lung injury: a pilot study

BACKGROUND

Acute lung injury (ALI) is associated with high mortality. Low tidal volume (Vt) ventilation has been shown to reduce mortality in ALI patients in the intensive care unit. Anesthesiologists do not routinely provide lung-protective ventilation strategies to patients with ALI in the operating room. The authors hypothesized that an alert, recommending lung-protective ventilation regarding patients with potential ALI, would result in lower Vt administration.

METHODS

The authors conducted a randomized controlled trial on anesthesia providers caring for patients with potential ALI. Patients with an average or last collected ratio of partial pressure of arterial oxygen to inspired fraction of oxygen less than 300 were randomized to providers being sent an alert with a recommended Vt of 6 cc/kg predicted body weight or conventional care. Primary outcomes were Vt/kg predicted body weight administered to patients. Secondary outcomes included ventilator parameters, length of postoperative ventilation, and death.

RESULTS

The primary outcome was a clinically significant reduction in mean Vt from 508-458 cc (P = 0.033), with a reduction in Vt when measured in cc/kg predicted body weight from 8 to 7.2 cc/kg predicted body weight (P = 0.040). There were no statistically significant changes in other outcomes or adverse events associated with either arm.

CONCLUSIONS

Automated alerts generated for patients at risk of having ALI resulted in a statistically significant reduction in Vt administered when compared with a control group. Further research is required to determine whether a reduction in Vt results in decreased mortality and/or postoperative duration of mechanical ventilation.

The use of the Berlin definition for acute respiratory distress syndrome during infancy and early childhood: multicenter evaluation and expert consensus

PURPOSE

A new acute respiratory distress syndrome (ARDS) definition has been recently issued: the so-called Berlin definition (BD) has some characteristics that could make it suitable for pediatrics. The European Society for Pediatric Neonatal Intensive Care (ESPNIC) Respiratory Section started a project to evaluate BD validity in early childhood. A secondary aim was reaching a consensus on clinical tools (risk factors list and illustrative radiographs) to help the application of BD.

METHODS

This was an international, multicenter, retrospective study enrolling 221 children [aged greater than 30 days and less than 18 months; median age 6 (range 2-13) months], admitted to seven European pediatric intensive care units (PICU) with acute lung injury (ALI) or ARDS diagnosed with the earlier definition.

RESULTS

Patients were categorized according to the two definitions, as follows: ALI, 36; ARDS, 185 (for the American-European Consensus Conference (AECC) definition); mild, 36; moderate, 97; severe ARDS, 88 (for BD). Mortality (13.9 % for mild ARDS; 11.3 % for moderate ARDS; 25 % for severe ARDS, p = 0.04) and the composite outcome extracorporeal membrane oxygenation (ECMO)/mortality (13.9 % for mild ARDS; 11.3 % for moderate ARDS; 28.4 % for severe ARDS, p < 0.01) were different across the BD classes, whereas they were similar using the previous definition. Mortality [HR 2.7 (95 % CI 1.1-7.1)] and ECMO/mortality [HR 3 (95 % CI 1.1-7.9)] were increased only for the severe ARDS class and remained significant after adjustment for confounding factors. PICU stay was not different across severity classes, irrespective of the definition used. There was significant concordance between raters evaluating radiographs [ICC 0.6 (95 % CI 0.2-0.8)] and risk factors [ICC 0.92 (95 % CI 0.8-0.97)].

CONCLUSIONS

BD validity for children is similar to that already reported in adults and mainly due to the introduction of a "severe ARDS" category. We provided clinical tools to use BD for clinical practice, research, and health services planning in pediatric critical care.

Neurogenic pulmonary edema and acute respiratory distress syndrome in a healthy child with febrile status epilepticus

Neurogenic pulmonary edema is a clinical syndrome that manifests as an acute onset of pulmonary edema in the setting of a central nervous system injury, without cardiac dysfunction. Neurogenic pulmonary edema is rare in children, and the mechanism is still not completely understood.  The clinical pathology overlaps with acute lung injury and acute respiratory distress syndrome. The authors report a case of a 14-month-old previously healthy child who presented with febrile status epilepticus, fulminant neurogenic pulmonary edema, and acute respiratory distress syndrome.  Neurogenic pulmonary edema should be considered in the differential diagnosis for the rapid progression of respiratory failure following an acute neurological injury such as status epilepticus in a child. Prompt respiratory support and treatment of the acute neurological insult can prevent further cerebral hypoxemic injury.

Mechanical ventilation strategies in children with acute lung injury: a survey on stated practice pattern*

OBJECTIVES

The aim of this survey was to determine North American and European pediatric intensivists' knowledge and stated practice in the management of children with acute respiratory distress syndrome with regard to mechanical ventilation settings; blood gas and SO2 targets; and use of adjunctive treatments at sites where actual practice had just been assessed.

DESIGN AND SETTING

A survey using three case scenarios to assess mechanical ventilation strategies used in children with acute respiratory distress syndrome was sent out toward the end of data collection to all centers participating in the Pediatric Acute Lung Injury Mechanical Ventilation study (59 PICUs in 12 countries). For each case scenario, intensivists were asked to report the optimal mechanical ventilation parameters; blood gas and SO2 acceptable targets; and threshold for considering high-frequency oscillatory ventilation, and other adjunctive treatments.

PARTICIPANTS

Fifty-four pediatric intensivists, representing 47 centers from 11 countries.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Many pediatric intensivists reported using a tidal volume of 5-8 mL/kg (88-96%) and none reported using a tidal volume above 10 mL/kg. On average, the upper threshold of positive inspiratory pressure at which intensivists would consider another ventilation mode was 35 cm H2O. Permissive hypercapnia and mild hypoxemia (SO2 as low as 88%) was considered tolerable by many pediatric intensivists. Finally, a large proportion of pediatric intensivists reported they would use adjunctive treatments (nitric oxide, prone position, extracorporeal membrane oxygenation, surfactant, steroids, β-agonists) if the patient's condition worsened.

CONCLUSIONS

Although in theory, many pediatric intensivists agreed with adult recommendations to ventilate with lower tidal volumes and pressure limits, the Pediatric Acute Lung Injury Mechanical Ventilation data revealed that over 25% of pediatric patients with acute lung injury/acute respiratory distress syndrome at many of these practice sites were ventilated with tidal volumes above 10 mL/kg and that high positive inspiratory pressure levels (> 35 mm Hg) were often tolerated.

High-frequency oscillatory ventilation in children with acute respiratory distress syndrome: experience of a pediatric intensive care unit

OBJECTIVE

To describe the effects of high-frequency oscillatory ventilation (HFOV) as a rescue ventilatory support in pediatric patients with acute respiratory distress syndrome (ARDS).

METHODS

Twenty-five children (1 month < age < 17 years) admitted to a university hospital pediatric intensive care unit (ICU) with ARDS and submitted to HFOV for a minimum of 48 hours after failure of conventional mechanical ventilation were assessed.

RESULTS

Twenty eight days after the onset of ARDS, the mortality rate was 52% (13/25). Over the course of 48 hours, the use of HFOV reduced the oxygenation index [38 (31-50) vs. 17 (10-27)] and increased the ratio of partial arterial pressure O2 and fraction of inspired O2 [65 [44-80) vs. 152 (106-213)]. Arterial CO2 partial pressure [54 (45-74) vs. 48 (39-58) mmHg] remained unchanged. The mean airway pressure ranged between 23 and 29 cmH2O. HFOV did not compromise hemodynamics, and a reduction in heart rate was observed (141±32 vs. 119±22 beats/min), whereas mean arterial pressure (66±20 vs. 71±17 mmHg) and inotropic score [44 (17-130) vs. 20 (16-75)] remained stable during this period. No survivors were dependent on oxygen.

CONCLUSION

HFOV improves oxygenation in pediatric patients with ARDS and severe hypoxemia refractory to conventional ventilatory support.

Mechanisms of acute respiratory distress syndrome in children and adults: a review and suggestions for future research

OBJECTIVES

To provide a current overview of the epidemiology and pathophysiology of acute respiratory distress syndrome in adults and children, and to identify research questions that will address the differences between adults and children with acute respiratory distress syndrome.

DATA SOURCES

Narrative literature review and author-generated data.

DATA SELECTION

The epidemiology of acute respiratory distress syndrome in adults and children, lung morphogenesis, and postnatal lung growth and development are reviewed. The pathophysiology of acute respiratory distress syndrome is divided into eight categories: alveolar fluid transport, surfactant, innate immunity, apoptosis, coagulation, direct alveolar epithelial injury by bacterial products, ventilator-associated lung injury, and repair.

DATA EXTRACTION AND SYNTHESIS

Epidemiologic data suggest significant differences in the prevalence and mortality of acute respiratory distress syndrome between children and adults. Postnatal lung development continues through attainment of adult height, and there is overlap between the regulation of postnatal lung development and inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms. Therefore, there is a different biological baseline network of gene and protein expression in children as compared with adults.

CONCLUSIONS

There are significant obstacles to performing research on children with acute respiratory distress syndrome. However, epidemiologic, clinical, and animal studies suggest age-dependent differences in the pathophysiology of acute respiratory distress syndrome. In order to reduce the prevalence and improve the outcome of patients with acute respiratory distress syndrome, translational studies of inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms are needed. Understanding the differences in pathophysiologic mechanisms in acute respiratory distress syndrome between children and adults should facilitate identification of novel therapeutic interventions to prevent or modulate lung injury and improve lung repair.

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.

The acute respiratory distress syndrome in 2013

Acute lung injury and the acute respiratory distress syndrome are major causes of morbidity and mortality in critically ill patients. This review focuses on new developments in definitions, epidemiology, clinical and basic research, and promising new directions in treatment. There is new information about the potential contribution of environmental factors, especially exposure to cigarette smoke. Pathologic findings in ARDS have been limited to case reports of open lung biopsies and post-mortem studies but there is some new information from a recent pathology study relative to the frequency of diffuse alveolar damage and the severity of arterial hypoxemia. Further, therapy with lung-protective ventilation and fluid conservative protocol has improved outcomes, but several new trials are in progress to test several promising strategies.

[Sodium dichloroisocyanurate-induced acute lung injury in a child]

Intoxication, by cyanurate and its chlorated derivatives in children, is increasingly reported in the literature due to accidental ingestion compared to accidental inhalation. We report a case in a 5-year-old child who presented with acute lung injury due to accidental inhalation of gas formed after a reaction of sodium dichloroisocyanurate tablets with water. Prevention remains the best way to reduce the risk of children being intoxicated by inhalation of the gas formed after contact of tablets with water.

High-frequency ventilation versus conventional ventilation for treatment of acute lung injury and acute respiratory distress syndrome

BACKGROUND

High frequency oscillation is an alternative to conventional mechanical ventilation that is sometimes used to treat patients with acute respiratory distress syndrome, but effects on oxygenation, mortality and adverse clinical outcomes are uncertain. This review was originally published in 2004 and was updated in 2011.

OBJECTIVES

To determine clinical and physiological effects of high frequency oscillation (HFO) in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) compared to conventional ventilation.

SEARCH METHODS

We electronically searched CENTRAL (Ovid), MEDLINE (Ovid), EMBASE (Ovid), and ISI (from inception to March 2011). The original search was performed in 2002. We manually searched reference lists from included studies and review articles; searched conference proceedings of the American Thoracic Society (1994 to 2010), Society of Critical Care Medicine (1994 to 2010), European Society of Intensive Care Medicine (1994 to 2010), and American College of Chest Physicians (1994 to 2010); contacted clinical experts in the field; and searched for unpublished and ongoing trials in clinicaltrials.gov and controlled-trials.com.

SELECTION CRITERIA

Randomized controlled clinical trials comparing treatment using HFO with conventional mechanical ventilation for children and adults diagnosed with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data on clinical, physiological, and safety outcomes according to a predefined protocol. We contacted investigators of all included studies to clarify methods and obtain additional data. We used random-effects models in the analyses.

MAIN RESULTS

Eight RCTs (n = 419) were included; almost all patients had ARDS. The risk of bias was low in six studies and unclear in two studies. The quality of evidence for hospital and six-month mortality was moderate and low, respectively. The ratio of partial pressure of oxygen to inspired fraction of oxygen at 24, 48, and 72 hours was 16% to 24% higher in patients receiving HFO. There were no significant differences in oxygenation index because mean airway pressure rose by 22% to 33% in patients receiving HFO (P < 0.01).  In patients randomized to HFO, mortality was significantly reduced (RR 0.77, 95% CI 0.61 to 0.98; P = 0.03; 6 trials, 365 patients, 160 deaths) and treatment failure (refractory hypoxaemia, hypercapnoea, hypotension, or barotrauma) was less likely (RR 0.67, 95% CI 0.46 to 0.99; P = 0.04; 5 trials, 337 patients, 73 events). Other risks, including adverse events, were similar. We found substantial between-trial statistical heterogeneity for physiological (I(2) = 21% to 95%) but not clinical (I(2) = 0%) outcomes.  Pooled results were based on few events for most clinical outcomes.

AUTHORS' CONCLUSIONS

The findings of this systematic review suggest that HFO was a promising treatment for ALI and ARDS prior to the uptake of current lung protective ventilation strategies. These findings may not be applicable with current conventional care, pending the results of large multi-centre trials currently underway.

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.

Pediatric Acute Lung Injury Epidemiology and Natural History study: Incidence and outcome of the acute respiratory distress syndrome in children

OBJECTIVES

The incidence and outcome of the acute respiratory distress syndrome in children are not well-known, especially under current ventilatory practices. The goal of this study was to determine the incidence, etiology, and outcome of acute respiratory distress syndrome in the pediatric population in the setting of lung protective ventilation.

DESIGN

A 1-yr, prospective, multicenter, observational study in 12 geographical areas of Spain (serving a population of 3.77 million ≤ 15 yrs of age) covered by 21 pediatric intensive care units.

SUBJECTS

All consecutive pediatric patients receiving invasive mechanical ventilation and meeting American-European Consensus Criteria for acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data on ventilatory management, gas exchange, hemodynamics, and organ dysfunction were collected. A total of 146 mechanically ventilated patients fulfilled the acute respiratory distress syndrome definition, representing a incidence of 3.9/100,000 population ≤ 15 yrs of age/yr. Pneumonia and sepsis were the most common causes of acute respiratory distress syndrome. At the time of meeting acute respiratory distress syndrome criteria, mean PaO2/FIO2 was 99 mm Hg ± 41 mm Hg, mean tidal volume was 7.6 mL/kg ± 1.8 mL/kg predicted body weight, mean plateau pressure was 27 cm H2O ± 6 cm H2O, and mean positive end-expiratory pressure was 8.9 cm ± 2.9 cm H2O. Overall pediatric intensive care unit and hospital mortality were 26% (95% confidence interval 19.6-33.7) and 27.4% (95% confidence interval 20.8-35.1), respectively. At 24 hrs, after the assessment of oxygenation under standard ventilatory settings, 118 (80.8%) patients continued to meet acute respiratory distress syndrome criteria (PaO2/FIO2 104 mm Hg ± 36 mm Hg; pediatric intensive care units mortality 30.5%), whereas 28 patients (19.2%) had a PaO2/FIO2 >200 mm Hg (pediatric intensive care units mortality 7.1%) (p = .014).

CONCLUSIONS

This is the largest study to estimate prospectively the pediatric population-based acute respiratory distress syndrome incidence and the first incidence study performed during the routine application of lung protective ventilation in children. Our findings support a lower acute respiratory distress syndrome incidence and mortality than those reported for adults. PaO2/FIO2 ratios at acute respiratory distress syndrome onset and at 24 hrs after onset were helpful in defining groups at greater risk of dying (clinical trials registered with http://www.clinicaltrials.gov; NCT 01142544).

[Particularities of ECMO in acute respiratory distress syndrome in pediatrics]

Les techniques de circulation extracorporelle sont utilisées en pédiatrie dans les syndromes de détresse respiratoire aiguë (SDRA) les plus graves depuis les années 1980. Les données du registre international de l’Extracorporeal Life Support Organization révèlent plus 5 000 enfants placés en extracorporeal membrane oxygenation (ECMO) en 2012 avec une augmentation du nombre de cas annuels depuis l’épidémie de 2009. La survie, de 56 %, est stable alors que le nombre d’enfants avec des comorbidités augmente grâce aux améliorations apportées au matériel. Bien que nous ne disposions pas d’études randomisées, ces résultats encouragent à proposer l’ECMO dans l’arsenal thérapeutique du SDRA de l’enfant. Si les techniques veinoveineuses doivent être privilégiées dans les affections respiratoires, l’ECMO veinoartérielle peut être nécessaire et reste d’une utilisation fréquente chez l’enfant (50 % des cas). En pédiatrie, les particularités techniques sont liées d’une part aux particularités physiologiques de l’enfant et d’autre part aux contraintes dues au matériel proposé selon les différentes catégories d’âge. L’ECMO est une technique de recours lourde qui nécessite une expertise à la fois technique et pédiatrique spécialisée en raison de ce terrain particulier.

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.

A pilot, randomized, controlled clinical trial of lucinactant, a peptide-containing synthetic surfactant, in infants with acute hypoxemic respiratory failure

OBJECTIVE

Inhibition of surfactant function and abnormal surfactant synthesis lead to surfactant dysfunction in children with acute hypoxemic respiratory failure. We evaluated whether intratracheal lucinactant, a synthetic, peptide-containing surfactant, was safe and well-tolerated in infants with acute hypoxemic respiratory failure, and assessed its effects on clinical outcomes.

METHODS AND MAIN RESULTS

Infants ≤ 2 yrs of age with acute hypoxemic respiratory failure were enrolled in a phase II, double-blind, multinational, placebo-controlled randomized trial across 36 pediatric intensive care units. Infants requiring mechanical ventilation with persistent hypoxemia meeting acute lung injury criteria were randomized to receive intratracheal lucinactant (175 mg/kg) or air placebo. One retreatment was allowed 12-24 hrs after initial dosing if hypoxemia persisted. Peri-dosing tolerability of intratracheal lucinactant and adverse experiences were assessed. Mechanical ventilation duration was analyzed using analysis of variance. The Cochran-Mantel-Haenszel test was used for categorical variables.We enrolled 165 infants (84 lucinactant; 81 placebo) with acute hypoxemic respiratory failure. There were no significant differences in baseline subject characteristics, with the exception of a lower positive end-expiratory pressure and higher tidal volume in placebo subjects. The incidence of transient peri-dosing bradycardia and desaturation was significantly higher in the lucinactant treatment group. There were no statistical differences between groups for other adverse events or mortality. Oxygenation improved in infants randomized to receive lucinactant as indicated by fewer second treatments (67% lucinactant vs. 81% placebo, p = .02) and a trend in improvement in partial pressure of oxygen in arterial blood to fraction of inspired oxygen from eligibility to 48 hrs after dose (p = .06). There was no significant reduction in duration of mechanical ventilation with lucinactant (geometric least square means: 4.0 days lucinactant vs. 4.5 days placebo; p = .254). In a subset of infants (n = 22), the duration of mechanical ventilation in children with acute lung injury (partial pressure of oxygen in arterial blood to fraction of inspired oxygen >200) was significantly shorter with lucinactant (least square means: 2.4 days lucinactant vs. 4.3 days placebo; p = .006).

CONCLUSIONS

In mechanically ventilated infants with acute hypoxemic respiratory failure, treatment with intratracheal lucinactant appeared to be generally safe. An improvement in oxygenation and a significantly reduced requirement for retreatment suggests that lucinactant might improve lung function in infants with acute hypoxemic respiratory failure.

The need for and feasibility of a pediatric ventilation trial: reflections on a survey among pediatric intensivists*

OBJECTIVE

To explore what design would be reasonable, acceptable, and feasible for a pediatric trial investigating the effect of low tidal volume ventilation.

DESIGN

A two-round modified Delphi approach among pediatric intensivists with a visible special interest in mechanical ventilation.

SETTINGS

None.

SUBJECTS

Pediatric intensivists.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

In the first questionnaire "experts" classified 64 items as "important," "not so important" or "not important" (June 2010). The second questionnaire included the 29 items having been classified by more than 50% of the experts as being "important" in the first questionnaire that needed to be ranked in order of importance (August 2010). Twenty-nine of 50 (64%) experts responded to the first questionnaire, and 28 of the 29 initial responders (96.6%) to the second questionnaire. Actual expert opinion favored the following: age of study population 0 yrs to 2 yrs, expected duration of ventilation ≥ 48 hrs, and stratification by the severity of hypoxemia (cutoff PaO(2)/FIO(2) < 200). The two study arms should compare the effect of 6 mL/kg vs. 10 mL/kg on mortality. However, these views of the experts face two major issues. First, 10 mL/kg does not represent standard of care. Second, numerous uncertainties render mortality unsuitable as primary measure of outcome including a large sample size (>1500).

CONCLUSIONS

Actual expert opinion favored investigating the effect of 6 mL/kg vs.10 mL/kg on mortality. Such a design suffers from various serious criticisms. Therefore, and in our opinion, a pediatric Acute Respiratory Distress Syndrome Network trial is not realistic.

High-frequency oscillatory ventilation in pediatric acute hypoxemic respiratory failure: disease-specific morbidity survival analysis

Background

Multiple ventilatory strategies for acute hypoxemic respiratory failure (AHRF) in children have been advocated, including high-frequency oscillatory ventilation (HFOV). Despite the frequent deployment of HFOV, randomized controlled trials remain elusive and currently there are no pediatric trials looking at its use. Our longitudinal study analyzed the predictive clinical outcome of HFOV in pediatric AHRF given disease-specific morbidity.

Methods

A retrospective 8-year review on pediatric intensive care unit admissions with AHRF ventilated by HFOV was performed. Primary outcomes included survival, morbidity, length of stay (LOS), and factors associated with survival or mortality.

Results

A total of 102 patients underwent HFOV with a 66 % overall survival rate. Survivors had a greater LOS than nonsurvivors (p = 0.001). Mortality odds ratio (OR) for patients without bronchiolitis was 8.19 (CI = 1.02, 65.43), and without pneumonia it was 3.07 (CI = 1.12, 8.39). A lower oxygenation index (OI) after HFOV commencement and at subsequent time points analyzed predicted survival. After 24 h, mortality was associated with an OI > 35 [OR = 31.11 (CI = 3.25, 297.98)]. Sepsis-related mortality was associated with a higher baseline FiO₂ (0.88 vs. 0.65), higher OI (42 vs. 22), and augmented metabolic acidosis (pH of 7.25 vs. 7.32) evaluated 4 h on HFOV (p < 0.05).

Conclusion

High-frequency oscillatory ventilation may be safely utilized. It has a 66 % overall survival rate in pediatric AHRF of various etiologies. Patients with morbidity limited to the respiratory system and optimized oxygenation indices are most likely to survive on HFOV.

The acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure that is often associated with multiple organ failure. Several clinical disorders can precipitate ARDS, including pneumonia, sepsis, aspiration of gastric contents, and major trauma. Physiologically, ARDS is characterized by increased permeability pulmonary edema, severe arterial hypoxemia, and impaired carbon dioxide excretion. Based on both experimental and clinical studies, progress has been made in understanding the mechanisms responsible for the pathogenesis and the resolution of lung injury, including the contribution of environmental and genetic factors. Improved survival has been achieved with the use of lung-protective ventilation. Future progress will depend on developing novel therapeutics that can facilitate and enhance lung repair.

Mitogen-activated protein kinase phosphatase 2, MKP-2, regulates early inflammation in acute lung injury

Acute lung injury (ALI) is mediated by an early proinflammatory response resulting from either a direct or indirect insult to the lung mediating neutrophil infiltration and consequent disruption of the alveolar capillary membrane ultimately leading to refractory hypoxemia. The mitogen-activated protein kinase (MAPK) pathways are a key component of the molecular response activated by those insults triggering the proinflammatory response in ALI. The MAPK pathways are counterbalanced by a set of dual-specific phosphatases (DUSP) that deactivate the kinases by removing phosphate groups from tyrosine or threonine residues. We have previously shown that one DUSP, MKP-2, regulates the MAPK pathway in a model of sepsis-induced inflammation; however, the role of MKP-2 in modulating the inflammatory response in ALI has not been previously investigated. We utilized both MKP-2-null (MKP-2(-/-)) mice and MKP-2 knockdown in a murine macrophage cell line to elucidate the role of MKP-2 in regulating inflammation during ALI. Our data demonstrated attenuated proinflammatory cytokine production as well as decreased neutrophil infiltration in the lungs of MKP-2(-/-) mice following direct, intratracheal LPS. Importantly, when challenged with a viable pathogen, this decrease in neutrophil infiltration did not impact the ability of MKP-2(-/-) mice to clear either gram-positive or gram-negative bacteria. Furthermore, MKP-2 knockdown led to an attenuated proinflammatory response and was associated with an increase in phosphorylation of ERK and induction of a related DUSP, MKP-1. These data suggest that altering MKP-2 activity may have therapeutic potential to reduce lung inflammation in ALI without impacting pathogen clearance.

Prolonged extracorporeal membrane oxygenation for children with respiratory failure

OBJECTIVE

Extracorporeal membrane oxygenation is used to support children with respiratory failure. When extracorporeal membrane oxygenation duration is prolonged, decisions regarding ongoing support are difficult as a result of limited prognostic data.

DESIGN

Retrospective case series.

SETTING

Multi-institutional data reported to the Extracorporeal Life Support Organization Registry.

PATIENTS

Patients aged 1 month to 18 yrs supported with extracorporeal membrane oxygenation for respiratory failure from 1993 to 2007 who received support for ≥ 21 days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 3213 children supported with extracorporeal membrane oxygenation during the study period, 389 (12%) were supported ≥ 21 days. Median patient age was 9.1 months (interquartile range, 2.5-41.7 months). Median weight was 6.7 kg (interquartile range, 3.5-15.8 kg). Survival for this group was 38%, significantly lower than survival reported for children supported ≤ 14 days (61%, p < .001). Among children supported with extracorporeal membrane oxygenation for ≥ 21 days, no differences were found between survivors and nonsurvivors with regard to acute pulmonary diagnosis, pre-extracorporeal membrane oxygenation comorbidities, pre-extracorporeal membrane oxygenation adjunctive therapies, or pre-extracorporeal membrane oxygenation blood gas parameters. Only peak inspiratory pressure was significantly different in survivors. Complications occurring on extracorporeal membrane oxygenation were more common among nonsurvivors. The use of inotropic infusion (odds ratio 1.64; 95% confidence interval 1.07-2.52), acidosis (pH <7.2) during extracorporeal membrane oxygenation (odds ratio 2.62; 95% confidence interval 1.51-4.55), and male gender (odds ratio 1.95; 95% confidence interval 1.21-3.15) were independently associated with increased odds of death.

CONCLUSION

Survival declines with duration of extracorporeal membrane oxygenation. Male gender and inadequate cardiorespiratory status during extracorporeal membrane oxygenation increased the risk of death. Prolonged support with extracorporeal membrane oxygenation appears reasonable unless multiorgan failure develops.

Clinical review: Early treatment of acute lung injury--paradigm shift toward prevention and treatment prior to respiratory failure

Acute lung injury (ALI) remains a major cause of morbidity and mortality in critically ill patients. Despite improved understanding of the pathogenesis of ALI, supportive care with a lung protective strategy of mechanical ventilation remains the only treatment with a proven survival advantage. Most clinical trials in ALI have targeted mechanically ventilated patients. Past trials of pharmacologic agents may have failed to demonstrate efficacy in part due to the resultant delay in initiation of therapy until several days after the onset of lung injury. Improved early identification of at-risk patients provides new opportunities for risk factor modification to prevent the development of ALI and novel patient groups to target for early treatment of ALI before progression to the need for mechanical ventilation. This review will discuss current strategies that target prevention of ALI and some of the most promising pharmacologic agents for early treatment of ALI prior to the onset of respiratory failure that requires mechanical ventilation.

Bioinformatics insights into acute lung injury/acute respiratory distress syndrome

Bioinformatics is the application of omics science, information technology, mathematics and statistics in the field of biomarker detection. Clinical bioinformatics can be applied for identification and validation of new biomarkers to improve current methods of monitoring disease activity and identify new therapeutic targets. Acute lung injurt (ALI)/Acute respiratory distress syndrome (ARDS) affects a large number of patients with a poor prognosis. The present review mainly focused on the progress in understanding disease heterogeneity through the use of evolving biological, genomic, and genetic approaches and the role of clinical bioinformatics in the pathogenesis and treatment of ALI/ARDS. The remarkable advances in clinical bioinformatics can be a new way for understanding disease pathogenesis, diagnosis and treatment.

Comparison of SpO2 to PaO2 based markers of lung disease severity for children with acute lung injury

OBJECTIVE

Given pulse oximetry is increasingly substituting for arterial blood gas monitoring, noninvasive surrogate markers for lung disease severity are needed to stratify pediatric risk. We sought to validate prospectively the comparability of SpO2/Fio2 to PaO2/Fio2 and oxygen saturation index to oxygenation index in children. We also sought to derive a noninvasive lung injury score.

DESIGN

Prospective, multicentered observational study in six pediatric intensive care units.

PATIENTS

One hundred thirty-seven mechanically ventilated children with SpO2 80% to 97% and an indwelling arterial catheter.

INTERVENTIONS

Simultaneous blood gas, pulse oximetry, and ventilator settings were collected. Derivation and validation data sets were generated, and linear mixed modeling was used to derive predictive equations. Model performance and fit were evaluated using the validation data set.

MEASUREMENTS AND MAIN RESULTS

One thousand one hundred ninety blood gas, SpO2, and ventilator settings from 137 patients were included. Oxygen saturation index had a strong linear association with oxygenation index in both derivation and validation data sets, given by the equation oxygen saturation index = 2.76 1 0.547*oxygenation index (derivation). 1/SpO2/Fio2 had a strong linear association with 1/PaO2/Fio2 in both derivation and validation data sets given by the equation 1/SpO2/Fio2 = 0.00232 1 0.443/PaO2/Fio2 (derivation). SpO2/Fio2 criteria for acute respiratory distress syndrome and acute lung injury were 221 (95% confidence interval 215-226) and 264 (95% confidence interval 259-269). Multivariate models demonstrated that oxygenation index, serum pH, and Paco(2) were associated with oxygen saturation index (p < .05); and 1/PaO2/Fio2, mean airway pressure, serum pH, and Paco2 were associated with 1/SpO2/Fio2 (p < .05). There was strong concordance between the derived noninvasive lung injury score and the original pediatric modification of lung injury score with a mean difference of 20.0361 α0.264 sd.

CONCLUSIONS

Lung injury severity markers, which use SpO2, are adequate surrogate markers for those that use PaO2 in children with respiratory failure for SpO2 between 80% and 97%. They should be used in clinical practice to characterize risk, to increase enrollment in clinical trials, and to determine disease prevalence.

Fluid overload is associated with impaired oxygenation and morbidity in critically ill children

RATIONALE

Fluid overload is common in the critically ill and is thought to contribute to oxygenation failure and mortality. Since increasing disease severity often requires more fluid for resuscitation, it is unclear whether fluid overload is a causative factor in morbidity or is simply an indicator of disease severity.

OBJECTIVE

Investigate the association between fluid overload and oxygenation while controlling for severity of illness by daily Pediatric Logistic Organ Dysfunction scores.

DESIGN AND SETTING

Retrospective chart review, tertiary children's hospital.

PATIENTS AND METHODS

The oxygenation index, fluid overload percent, and daily Pediatric Logistic Organ Dysfunction scores were obtained in a retrospective chart review of 80 patients (mean age 58.7 ± 73.0 months) with respiratory failure. Univariate and multivariate approaches were used to assess the independent relation between fluid overload percent and duration of stay and ventilation.

INTERVENTIONS

None.

MAIN RESULTS

Higher peak fluid overload percent predicted higher peak oxygenation index, independent of age, gender, and Pediatric Logistic Organ Dysfunction (p = .009). Fluid overload percent ≥15% on any given day was also independently associated with that day's oxygenation index, controlled for age, gender, and Pediatric Logistic Organ Dysfunction (p < .05). Peak fluid overload percent and severe fluid overload percent (≥15%) were both independently associated with longer duration of ventilation (p = .004, p = .01), and pediatric intensive care unit (p = .008, p = .01) and hospital length of stay (p = .02, p = .04), controlled for age, gender, Pediatric Logistic Organ Dysfunction, and in the case of ventilation, respiratory admission.

CONCLUSION

This is the first study to report that positive fluid balance adversely affected the pediatric intensive care unit course in children who did not receive renal replacement therapy. While timely administration of fluids is lifesaving, positive fluid balance after hemodynamic stabilization may impact organ function and negatively influence important outcomes in critically ill patients.

The use of high frequency oscillatory ventilation in a pediatric oncology intensive care unit

BACKGROUND

High frequency oscillatory ventilation (HFOV) has been successfully used in the management of acute respiratory distress syndrome (ARDS) in children. The aim of our study is to determine its effectiveness in pediatric patients with cancer or post hematopoietic stem cell transplantation (HSCT) diagnosed with ARDS.

PROCEDURE

A retrospective case review, in a pediatric intensive care unit (PICU) in a tertiary-care oncology center in Amman, Jordan. Patients included were children with cancer and/or receiving allogeneic HSCT who were diagnosed with ARDS and placed on HFOV from January 2007 to February 2009.

RESULTS

Data from 12 pediatric oncology patients on HFOV were analyzed for demographics, oncological diagnosis, PRISM III scores, ventilator settings before switching to HFOV and 24 hours after switching, complications, and outcomes. Alveolar-arterial oxygen (A-a) gradient and oxygen index (OI) were calculated, and pressure of arterial CO(2) (PaCO(2) ) was measured before and 24 hours after switching. Endpoints were successful extubation and discharge, or death while intubated. After 24 hours on HFOV, the A-a gradient decreased significantly in all patients (from a median of 564-267 torr; P=0.001). OI decreased in all but two patients who died (median 17); PaCO(2) decrease was not significant. Five patients died (two of them post-HSCT) and the 7 (58%) survivors were weaned from HFOV (median, 9 days) and discharged.

CONCLUSIONS

HFOV improves gas exchange and is useful in managing critically ill children with cancer and post-HSCT patients who develop ARDS.

Epidemiological features and risk factor analysis of children with acute lung injury

BACKGROUND

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) represents a devastating complication observed in critical care medicine. The purpose of this study is to investigate the epidemiological aspects of ALI/ARDS in pediatric intensive care unit (PICU) and risk factors of mortality.

METHODS

Patients with ALI/ARDS in PICU of Beijing Children's Hospital, a tertiary medical center from November 1, 2005 to October 31, 2006 were included in this prospective study. We identified the risk factors for underlying diseases and mortality during a 3-month followup using multivariate logistic regression analysis.

RESULTS

In 562 critically ill patients admitted to PICU of Beijing Children's Hospital, there were 15 ALI-non ARDS patients and 29 ARDS patients, resulting in an incidence of 7.8% (44/562). The mortality rate of ARDS was 24.1% (7/29) and that of ALI/ARDS was 18.2% (8/44). At a 3-month follow-up, 12 patients died after being discharged from PICU and the total mortality rate was 45.5% (20/44). ALI/ARDS patients with pulmonary disease had better outcomes than those with extra-pulmonary involvements (P<0.05). Discharge against medical advice, low PaO(2)/FiO(2) during hospital stay and high PaCO2 on PICU admission were risk factors of mortality.

CONCLUSIONS

ARDS has a high mortality rate in PICU, especially in those with extra-pulmonary diseases. In addition to aggressive medical management of comorbidity, lung protection and avoidance of discharge against medical advice will decrease the mortality.

The association between the end tidal alveolar dead space fraction and mortality in pediatric acute hypoxemic respiratory failure

OBJECTIVE

To investigate the relationship of markers of oxygenation, PaO2/FIO2 ratio, SpO2/FIO2 ratio, oxygenation index, oxygen saturation index, and dead space (end tidal alveolar dead space fraction) with mortality in children with acute hypoxemic respiratory failure.

DESIGN

Retrospective.

SETTING

Single-center tertiary care pediatric intensive care unit.

PATIENTS

Ninety-five mechanically ventilated children with a PaO2/FIO2 ratio <300 within 24 hrs of the initiation of mechanical ventilation.

INTERVENTIONS

None.

MAIN RESULTS

The end tidal alveolar dead space fraction, PaO2/FIO2 ratio, SpO2/FIO2 ratio, oxygenation index, and oxygen saturation index were all associated with mortality (p < .02). There was a small correlation between the end tidal alveolar dead space fraction and decreasing PaO2/FIO2 (r2 = .21) and SpO2/FIO2 ratios (r2 = .22), and increasing oxygenation index (r2= .25) and oxygen saturation index (r2 = .24). In multivariate logistic regression modeling, the end tidal alveolar dead space fraction was independently associated with mortality (p < .02). Oxygenation index, oxygen saturation index, and the end tidal alveolar dead space fraction were all acceptable discriminators of mortality with receiver operating characteristic plot area under the curves ≥ 0.7.

CONCLUSIONS

In pediatric acute hypoxemic respiratory failure, easily obtainable pulmonary specific markers of disease severity (SpO2/FIO2 ratio, oxygen saturation index, and the end tidal alveolar dead space fraction) may be useful for the early identification of children at high risk of death. Furthermore, the end tidal alveolar dead space fraction should be considered for risk stratification of children with acute hypoxemic respiratory failure, given that it was independently associated with mortality.

U.S. attitudes and perceived practice for noninvasive ventilation in pediatric acute respiratory failure

OBJECTIVE

Few pediatric studies exist regarding the use of noninvasive positive-pressure ventilation for acute respiratory failure; however, those that do suggest a role. This study seeks to describe attitudes and perceived practices of pediatric intensivists regarding the use of noninvasive positive-pressure ventilation in children with acute respiratory failure.

DESIGN

Electronic survey.

SETTING

Medical institutions.

PARTICIPANTS

Of the 932 physicians approached, 353 (38%) responded to the survey. Respondents included U.S. physicians practicing pediatric critical care (90%), pediatric anesthesia critical care (4%), pediatric pulmonary critical care (4%), and other disciplines (2%).

INTERVENTIONS

Survey.

MEASUREMENTS AND MAIN RESULTS

The survey contained questions regarding 1) practitioner demographics, 2) patient characteristics, and 3) clinical cases designed to assess noninvasive positive-pressure ventilation use in certain patient scenarios. Noninvasive positive-pressure ventilation was used by 99% of the respondents, with 60% using noninvasive positive-pressure ventilation as initial support >10% of the time. Respondents reported use of noninvasive positive-pressure ventilation for acute respiratory failure in lower airway disease (70%), asthma (51%), acute lung injury/acute respiratory distress syndrome (43%), and upper airway obstruction (31%). In clinical scenarios, respondents reported that the factors associated with nonuse of noninvasive positive-pressure ventilation as initial support were disease process (31%), oxygenation (19%), ventilation severity (15%), expectation that the patient was likely to worsen (12%), and age or inability to cooperate (11%).

CONCLUSIONS

Noninvasive positive-pressure ventilation is widely used and most frequently utilized in patients with acute lower airway disease. Factors such as severe defects in oxygenation and ventilation, disease progression, and patient tolerability decreased the likelihood of use. These findings may help direct further studies of noninvasive positive-pressure ventilation in children with acute respiratory failure.