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

[Relationship between PAO2/FIO2 and SATO2/FIO2 with mortality and duration of admission in critically ill children]

OBJECTIVES

The aim of this study is to analyse the relationships and the association between PaO(2)/FiO(2) and SatO(2)/FiO(2with) the duration of admission in Paediatric Intensive Care Units (PICU) and mortality, and to study the relationships between both ratios.

MATERIAL AND METHODS

A retrospective study was conducted on PICU patients in whom a gas analysis was performed in the first twenty-four hours of admission. Demographic, clinical and ventilation variables were collected, and the relationship between PaO(2)/FiO(2) and SatO(2)/FiO(2) with days of admission and mortality was determined. Finally, the best cut-off points of SatO(2)/FiO(2) were determined for PaO(2)/FiO(2) values greater and less than 200.

RESULTS

Of 512 patients admitted during one year, a gas analysis was performed on 358, 65% of those in arterial blood. The median duration of hospitalization was two days and there were 11 patient deaths. There was a low negative correlation between the values of PaO(2)/FiO(2) and SatO(2/)FiO(2) on admission to PICU and with duration of admission, and an inverse association with mortality (P<.01). This association was stronger for the PaO(2)/FiO(2) ratio in patients with heart disease, those undergoing invasive mechanical ventilation, and for arterial blood samples. PaO(2)/FiO(2) and SatO(2)/FiO(2) ratios were significantly correlated with each other. A cut-off of 200 for SatO(2)/FiO(2) had a sensitivity of 97.5% for classifying patients with PaO(2)/FiO(2) values lower or higher than 200.

CONCLUSIONS

PaO(2)/FiO(2) and SatO(2)/FiO(2) index are markers of severity in critically ill patients. In patients who do not have an arterial line, SatO(2)/FiO(2) index can be used for assessment of oxygenation as an indicator of severity in children in critical condition.

The influence of genetic variation in surfactant protein B on severe lung injury in African American children

OBJECTIVE

To determine whether genetic variations in the gene coding for surfactant protein B are associated with lung injury in African American children with community-acquired pneumonia.

DESIGN

A prospective cohort genetic association study of lung injury in children with community-acquired pneumonia.

SETTING

Two major tertiary care children's hospitals.

SUBJECTS

African American children with community-acquired pneumonia (n = 395) either evaluated in the emergency department or admitted to the hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Three hundred ninety-five African American children (14 days to 18 yrs of age) with community-acquired pneumonia were enrolled. Thirty-seven patients required mechanical ventilation and 26 of these were diagnosed with acute lung injury or acute respiratory distress syndrome. Genotyping was performed on seven linkage disequilibrium-tag single nucleotide polymorphisms in the surfactant protein B gene. Univariate analysis demonstrated two linkage disequilibrium-tag single nucleotide polymorphisms, rs1130866 (also known as SP-B + 1580 C/T) and rs3024793, were associated with the need for mechanical ventilation in African American children (p = .016 and p = .030, respectively). Multivariable analysis indicated that both of these single nucleotide polymorphisms are independently associated with need for mechanical ventilation (p = .040 and p = .012, respectively) as was rs7316 when its interaction with age was considered (p = .015). Multivariable analysis examining acute lung injury demonstrated a significant association of rs7316 with acute lung injury (p = .031). Haplotype analysis was also performed. Two haplotypes, GTGCGCG and ATATAAG, were associated with need for mechanical ventilation using either univariate (p = .041 and p = .043, respectively) or multivariable analysis (odds ratios of 2.62, p = .048, and 3.12, p = .033, respectively).

CONCLUSIONS

Genetic variations in the gene coding for surfactant protein B are associated with more severe lung injury as indicated by the association of specific single nucleotide polymorphism genotypes and haplotypes with the need for mechanical ventilation in African American children with community-acquired pneumonia.

Pediatric acute respiratory failure: areas of debate in the pediatric critical care setting

Pediatric intensive care units across the world care for large numbers of mechanically ventilated infants and children on a daily basis, yet management of these patients is far from standardized. This lack of standardization may be a necessity in certain situations given variation between underlying disease processes, pathophysiology, response to therapy and available resources. However, there are many situations in which similar patients are managed differently across pediatric intensive care units simply because there are a shortage of available data to guide the management of these critically ill infants and children. Thus, a large fraction of pediatric critical care involves a combination of institutional preference, individual experience, opinion and extrapolation of adult data.

Surfactant therapy for acute lung injury and acute respiratory distress syndrome

This article examines exogenous lung surfactant replacement therapy and its usefulness in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Surfactant therapy is beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 years with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. This article reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, focusing on its potential advantages in patients with direct pulmonary forms of these syndromes.

Experimental models and emerging hypotheses for acute lung injury

Acute lung injury (ALI) involves the activation of multiple pathways leading to lung injury, resolution, and repair. Exploration of the roles of individual pathways in humans and animal models has led to a greater understanding of the complexity of ALI and the links between ALI and systemic multiorgan failure. However, there is still no integrated understanding of the initiation, the progression, and the repair of ALI. A better understanding is needed of how pathways interact in the human ALI syndrome and how complementary treatments can be used to modify the onset, severity, and outcome of ALI in humans.

Efficacy and safety of lung recruitment in pediatric patients with acute lung injury

OBJECTIVE

To assess the safety and efficacy of a recruitment maneuver, the Open Lung Tool, in pediatric patients with acute lung injury and acute respiratory distress syndrome.

DESIGN

Prospective cohort study using a repeated-measures design.

SETTING

Pediatric intensive care unit at an urban tertiary children's hospital.

PATIENTS

Twenty-one ventilated pediatric patients with acute lung injury.

INTERVENTION

Recruitment maneuver using incremental positive end-expiratory pressure.

MEASUREMENTS AND MAIN RESULTS

The ratio of partial pressure of arterial oxygen over fraction of inspired oxygen (Pao2/Fio2 ratio) increased 53% immediately after the recruitment maneuver. The median Pao2/Fio2 ratio increased from 111 (interquartile range, 73-266) prerecruitment maneuver to 170 (interquartile range, 102-341) immediately postrecruitment maneuver (p < .01). Improvement in Pao2/Fio2 ratio persisted with an increase of 80% over the baseline at 4 hrs and 40% at 12 hrs after the recruitment maneuver. The median Pao2/Fio2 ratio was 200 (interquartile range, 116-257) 4 hrs postrecruitment maneuver (p < .05) and 156 (interquartile range, 127-236) 12 hrs postrecruitment maneuver (p < .01). Compared with prerecruitment maneuver, the partial pressure of arterial carbon dioxide (Paco2) was significantly decreased at 4 hrs postrecruitment maneuver but not immediately after the recruitment maneuver. The median Paco2 was 49 torr (interquartile range, 44-60) prerecruitment maneuver compared with 48 torr (interquartile range, 43-50) immediately postrecruitment maneuver (p = .69), 45 torr (interquartile range, 41-50) at 4 hrs postrecruitment maneuver (p < .01), and 43 torr (interquartile range, 38-51) at 12 hrs postrecruitment maneuver. Recruitment maneuvers were well tolerated except for significant increase in Paco2 in three patients. There were no serious adverse events related to the recruitment maneuver.

CONCLUSIONS

Using the modified open lung tool recruitment maneuver, pediatric patients with acute lung injury may safely achieve improved oxygenation and ventilation with these benefits potentially lasting up to 12 hrs postrecruitment maneuver.

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.

Positive fluid balance is associated with higher mortality and prolonged mechanical ventilation in pediatric patients with acute lung injury

Introduction. We analyzed a database of 320 pediatric patients with acute lung injury (ALI), to test the hypothesis that positive fluid balance is associated with worse clinical outcomes in children with ALI. Methods. This is a post-hoc analysis of previously collected data. Cumulative fluid balance was analyzed in ml per kilogram per day for the first 72 hours after ALI while in the PICU. The primary outcome was mortality; the secondary outcome was ventilator-free days. Results. Positive fluid balance (in increments of 10 mL/kg/24 h) was associated with a significant increase in both mortality and prolonged duration of mechanical ventilation, independent of the presence of multiple organ system failure and the extent of oxygenation defect. These relationships remained unchanged when the subgroup of patients with septic shock (n = 39) were excluded. Conclusions. Persistently positive fluid balance may be deleterious to pediatric patients with ALI. A confirmatory, prospective randomized controlled trial of fluid management in pediatric patients with ALI is warranted.

The utility of clinical predictors of acute lung injury: towards prevention and earlier recognition

Despite significant advances in our understanding of the pathophysiology of acute lung injury, a lung-protective strategy of mechanical ventilation remains the only therapy with a proven survival advantage. Numerous pharmacologic therapies have failed to show benefit in multicenter clinical trials. The paradigm of early, goal-directed therapy of sepsis suggests greater clinical benefit may derive from initiating therapy prior to the onset of respiratory failure that requires mechanical ventilation. Thus, there is heightened interest in more accurate and complete characterization of high-risk patient populations and identification of patients in the early stage of acute lung injury, prior to the need for mechanical ventilation. This article discusses the growing literature on clinical predictors of acute lung injury (including risk factors for specific subgroups) with an emphasis on transfusion-related risk factors and recent research targeting the early identification of high-risk patients and those with early acute lung injury prior to the onset of respiratory failure.

Extracorporeal membrane oxygenation for pediatric respiratory failure: Survival and predictors of mortality

OBJECTIVE

The last multicentered analysis of extracorporeal membrane oxygenation in pediatric acute respiratory failure was completed in 1993. We reviewed recent international data to evaluate survival and predictors of mortality.

DESIGN

Retrospective case series review.

SETTING

The Extracorporeal Life Support Organization Registry, which includes data voluntarily submitted from over 115 centers worldwide, was queried. The work was completed at the Division of Pediatric Critical Care, Department of Pediatrics, Primary Children's Medical Center, University of Utah, Salt Lake City, UT.

SUBJECTS

Patients aged 1 month to 18 yrs supported with extracorporeal membrane oxygenation for acute respiratory failure from 1993 to 2007.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 3,213 children studied. Overall survival remained relatively unchanged over time at 57%. Considerable variability in survival was found based on pulmonary diagnosis, ranging from 83% for status asthmaticus to 39% for pertussis. Comorbidities significantly decreased survival to 33% for those with renal failure (n = 329), 16% with liver failure (n = 51), and 5% with hematopoietic stem cell transplantation (n = 22). The proportion of patients with comorbidities increased from 19% during 1993 to 47% in 2007. Clinical factors associated with mortality included precannulation ventilatory support longer than 2 wks and lower precannulation blood pH.

CONCLUSIONS

Although the survival of pediatric patients with acute respiratory failure treated with extracorporeal membrane oxygenation has not changed, this treatment is currently offered to increasingly medically complex patients. Mechanical ventilation in excess of 2 wks before the initiation of extracorporeal membrane oxygenation is associated with decreased survival.

Daily practice of mechanical ventilation in Italian pediatric intensive care units: a prospective survey

OBJECTIVES

To assess how children requiring endotracheal intubation are mechanically ventilated in Italian pediatric intensive care units (PICUs).

DESIGN

A prospective, national, observational, multicenter, 6-month study.

SETTING

Eighteen medical-surgical PICUs.

PATIENTS

A total of 1943 consecutive children, aged 0-16 yrs, admitted between November 1, 2006 and April 30, 2007.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data on cause of respiratory failure, length of mechanical ventilation (MV), mode of ventilation, use of specific interventions were recorded for all children requiring endotracheal intubation for >24 hrs. Children were stratified for age, type of patient, and cause of respiratory failure. A total of 956 (49.2%) patients required MV via an endotracheal tube; 673 (34.6%) were ventilated for >24 hrs. The median length of MV was 4.5 days for all patients. If postoperative patients were excluded, the median time was 5 days. Bronchiolitis (6.7%), pneumonia (6.7%), and upper airway obstruction (5.3%) were the most frequent causes of acute respiratory failure, and altered mental status (9.2%) was the most frequent reason for MV. The overall mortality was 6.7% with highest rates for heart disease (nonoperative), sepsis, and acute respiratory distress syndrome (26.1%, 22.2%, and 16.7% respectively). Length of stay, associated chronic disease, severity score on admission, and PICU mortality were significantly higher in children who received MV (p < .05) than in children who did not. Controlled MV and pressure support ventilation + synchronized intermittent mandatory ventilation were the most frequently used modes of ventilatory assistance during PICU stay.

CONCLUSIONS

Mechanical ventilation is frequently used in Italian PICUs with almost one child of two requiring endotracheal intubation. Children treated with MV represent a more severe category of patients than children who are breathing spontaneously. Describing the standard care and how MV is performed in children can be useful for future clinical studies.

Acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a common diagnosis among children admitted to pediatric intensive care units. This heterogeneous disorder has numerous pulmonary and non-pulmonary causes and is associated with a significant risk of mortality. Many supportive therapies exist for ARDS. SEARCH: Literature search was performed by using the key words ARDS and related topics on the Pubmed search engine maintained by the National Heart, Lung, Blood Institute. Pediatric randomized controlled trials that have been published in the last 10 years were included. Emphasis was placed on pediatric literature, although sentinel adult studies have been included. Most of the evidence presented is of levels I and II.

RESULTS

Low tidal volume is the only strategy that has consistently improved outcome in ARDS. A tidal volume of ≤ 6 mL/kg predicted body weight should be used. Ventilator induced lung injury may result in systemic effects with multi-system organ failure, and all efforts should be made to minimize this. Positive end-expiratory pressure should be used to judiciously maintain lung recruitment. There is insufficient evidence to routinely use high frequency ventilation, prone positioning, or inhaled nitric oxide. Calfactant therapy is promising and may be considered in children with direct lung injury and ARDS. Current literature does not support routine use of corticosteroids for non-resolving ARDS.

Lung protective strategy and prone ventilation resulting in successful outcome in a patient with ARDS due to H1N1

Acute respiratory distress syndrome (ARDS) is an acute respiratory condition caused by various pulmonary and extrapulmonary conditions including H1N1 virus infection. ARDS has a high mortality worldwide and in India various studies suggest that mortality in children is as high as 73-75%. Different lung protective ventilation strategies have recently been adopted to reduce mortality. The authors report a successful outcome in a 3.5-year-old child with ARDS secondary to H1N1 infection following use of a very low tidal volume (4-6 ml/kg) along with high positive end-expiratory pressure breathing and prone ventilation. As far as we are aware, this is the first case report of a successful outcome in a child with ARDS secondary to H1N1 in India.

The acute respiratory distress syndrome: pathogenesis and treatment

The acute respiratory distress syndrome (ARDS) causes 40% mortality in approximately 200,000 critically ill patients annually in the United States. ARDS is caused by protein-rich pulmonary edema that causes severe hypoxemia and impaired carbon dioxide excretion. The clinical disorders associated with the development of ARDS include sepsis, pneumonia, aspiration of gastric contents, and major trauma. The lung injury is caused primarily by neutrophil-dependent and platelet-dependent damage to the endothelial and epithelial barriers of the lung. Resolution is delayed because of injury to the lung epithelial barrier, which prevents removal of alveolar edema fluid and deprives the lung of adequate quantities of surfactant. Lymphocytes may play a role in resolution of lung injury. Mortality has been markedly reduced with a lung-protective ventilatory strategy. However, there is no effective pharmacologic therapy, although cell-based therapy and other therapies currently being tested in clinical trials may provide novel treatments for ARDS.

The evolution of patient selection criteria and indications for extracorporeal life support in pediatric cardiopulmonary failure: next time, let's not eat the bones

Bill James, baseball statistician and author, tells the story of hungry cavemen sitting about a campfire, waiting for tomatoes to ripen. One has the inspiration to throw an ox on the fire, and the first barbecue ensued and was endured. After eating, the conversation goes something like this. "There were some good parts." "Yeah, but there were some bad parts." And the smart one says, "This time, let's not eat the bones." The evolution of patient selection criteria for the use of extracorporeal support (ECLS) is a bit like those cavemen and their first barbecued ox. Extracorporeal life support technology and application to patient care is the unique result of a long standing history of ambitious attempt, evaluation, debate, collaboration and extension.

Differences in organ dysfunctions between neonates and older children: a prospective, observational, multicenter study

Introduction

The multiple organ dysfunction syndrome (MODS) is a major cause of death for patients admitted to pediatric intensive care units (PICU). The Pediatric Logistic Organ Dysfunction (PELOD) score has been validated in order to describe and quantify the severity of organ dysfunction (OD). There are several physiological differences between neonates and older children. The objective of the study was to determine whether there are differences in incidence of ODs and mortality rate between full-term neonates (age <28 days) and older children.

Methods

In a prospective, observational study, 1806 patients, admitted to seven PICUs between September 1998 and February 2000 were included. The PELOD score, which includes six organ dysfunctions and 12 variables, was recorded daily. For each variable, the most abnormal value was used to define the daily OD. For each OD, the most abnormal value each day and that during the entire stay were used in calculating the daily PELOD and PELOD scores, respectively. The relationships between OD, daily OD, PELOD, daily PELOD and mortality were compared between the two strata (neonates, older children) based on the discrimination power, logistic and multiple regression analyses.

Results

Of the 1806 enrolled patients 171 (9.5%) were neonates. Incidence of MODS and mortality rate were higher among neonates than in older children (14.6% vs. 5.5%, P < 10^-7; 75.4%, vs. 50.9%, P < 10^-4; respectively). Daily PELOD scores were significantly higher in neonates from day 1 to day 4. Daily cardiovascular, respiratory and renal dysfunction scores from day 1 to day 4 as well as the PELOD score for the entire pediatric intensive care unit stay were also significantly higher in neonates. Neurological, cardiovascular, and hepatic dysfunctions were independent predictors of death among neonates while all ODs significantly contributed to the risk of mortality in older children.

Conclusions

Our data demonstrate that incidence of MODS and mortality rate are higher among neonates compared to older children. Neurological, cardiovascular, and hepatic dysfunctions were the only significant contributors to neonatal mortality. Stratification for neonates versus older children might be useful in clinical trials where MODS is considered as an outcome measure.

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.

Acute lung injury in children: therapeutic practice and feasibility of international clinical trials

OBJECTIVES

To describe mechanical ventilation strategies in acute lung injury and to estimate the number of eligible patients for clinical trials on mechanical ventilation management. In contrast to adult medicine, there are few clinical trials to guide mechanical ventilation management in children with acute lung injury.

DESIGN

A cross-sectional study for six 24-hr periods from June to November 2007.

SETTING

Fifty-nine pediatric intensive care units in 12 countries in North America and Europe.

PATIENTS

We identified children meeting acute lung injury criteria and collected detailed information on illness severity, mechanical ventilatory support, and use of adjunctive therapies.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 3823 patients screened, 414 (10.8%) were diagnosed with acute lung injury by their treating physician, but only 165 (4.3%) patients met prestablished inclusion/exclusion criteria to this trial and, therefore, would have been eligible for a clinical trial. Of these, 124 (75.2%) received conventional mechanical ventilation, 27 (16.4%) received high-frequency oscillatory ventilation, and 14 (8.5%) received noninvasive mechanical ventilation. In the conventional mechanical ventilation group, 43.5% were ventilated in a pressure control mode with a mean tidal volume of 8.3 ± 3.3 mL/kg; and there was no clear relationship between positive end-expiratory pressure and Fio2 delivery in the conventional mechanical ventilation group. Use of adjunctive treatments, including nitric oxide, prone positioning, surfactant, hemofiltration, recruitment maneuvers, steroids, bronchodilators, and fluid restriction, was highly variable.

CONCLUSIONS

Our study reveals inconsistent mechanical ventilation practice and use of adjunctive therapies in children with acute lung injury. Pediatric clinical trials assessing mechanical ventilation management are needed to generate evidence to optimize outcomes. We estimate that a large number of centers (∼60) are needed to conduct such trials; it is imperative, therefore, to bring about international collaboration.

Effects of age on the synergistic interactions between lipopolysaccharide and mechanical ventilation in mice

Children have a lower incidence and mortality from acute lung injury (ALI) than adults, and infections are the most common event associated with ALI. To study the effects of age on susceptibility to ALI, we investigated the responses to microbial products combined with mechanical ventilation (MV) in juvenile (21-d-old) and adult (16-wk-old) mice. Juvenile and adult C57BL/6 mice were treated with inhaled Escherichia coli 0111:B4 lipopolysaccharide (LPS) and MV using tidal volume = 15 ml/kg. Comparison groups included mice treated with LPS or MV alone and untreated age-matched control mice. In adult animals treated for 3 hours, LPS plus MV caused synergistic increases in neutrophils (P < 0.01) and IgM in bronchoalveolar lavage fluid (P = 0.03) and IL-1β in whole lung homogenates (P < 0.01) as compared with either modality alone. Although juvenile and adult mice had similar responses to LPS or MV alone, the synergistic interactions between LPS and MV did not occur in juvenile mice. Computational analysis of gene expression array data suggest that the acquisition of synergy with increasing age results, in part, from the loss of antiapoptotic responses and the acquisition of proinflammatory responses to the combination of LPS and MV. These data suggest that the synergistic inflammatory and injury responses to inhaled LPS combined with MV are acquired with age as a result of coordinated changes in gene expression of inflammatory, apoptotic, and TGF-β pathways.

Impact of continuous renal replacement therapy on oxygenation in children with acute lung injury after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Acute lung injury (ALI) continues to carry a high mortality rate in children after allogeneic hematopoietic stem cell transplant (HSCT). Continuous renal replacement therapy (CRRT) is often used for these patients for various indications including renal failure and fluid overload, and may have a beneficial effect on oxygenation and survival. Therefore, we sought to determine the effect of CRRT on oxygenation in mechanically ventilated pediatric allogeneic HSCT patients with ALI, and to document survival to intensive care unit discharge in this at-risk population receiving both mechanical ventilation and CRRT.

PROCEDURE

Retrospective analysis of a pediatric allogeneic HSCT cohort admitted to intensive care unit of a single pediatric oncology center from 1994 to 2006 who received CRRT during a course of mechanical ventilation for ALI.

RESULTS

Thirty post-HSCT mechanically ventilated children with ALI who underwent CRRT were included. There was a significant improvement in PaO(2)/FiO(2) with median increase of 31 and 43 in the 24 and 48 hr intervals after initiation of CRRT compared with the 24 hr interval before CRRT (P = 0.0008 and 0.0062, respectively). This improvement in PaO(2)/FiO(2) correlated significantly with reduction of fluid balance achieved after initiation of CRRT (P = 0.0001). There was a trend not reaching statistical significance in improvement in mean airway pressure 48 hr after CRRT in survivors compared to non-survivors.

CONCLUSIONS

CRRT improved oxygenation in mechanically ventilated pediatric allogeneic HSCT patients with ALI.

Cleaved caspase-3 in lung epithelium of children who died with acute respiratory distress syndrome

OBJECTIVE

To investigate the extent of cleaved caspase-3 immunostaining in lung epithelial cells in children with acute respiratory distress syndrome.

DESIGN

Observational study in sixteen children who died with acute respiratory distress syndrome and diffuse alveolar damage.

SETTING

Pediatric intensive care unit.

PATIENTS

Sixteen children with fatal acute respiratory distress syndrome and diffuse alveolar damage.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Double immunohistochemistry for cleaved caspase-3 and (pan)cytokeratin in lung tissues obtained at autopsy. Spectral imaging was used for the quantification of immunohistochemistry colocalization of these markers. We found a wide range in the percentage of alveolar epithelial cell surface area with positive cleaved caspase-3 staining in the lungs of children with acute respiratory distress syndrome (from 1% to almost 20%). The degree of caspase-3 immunostaining in epithelial cells positively correlated with age.

CONCLUSION

There is a high variability in the extent of classic apoptosis in lung epithelial cells in pediatric acute respiratory distress syndrome, potentially in part dependent on age.

Acute lung injury in the child

Acute lung injury(ALI) is an important condition in critically ill children, contributing to overall mortality and morbidity. ALI represents the severe spectrum of lower airways disease in children. It is the pathological culmination of diseases such as pneumonia and sepsis. These conditions elicit a host response, which results in a clinically and radiologically defined pulmonary syndrome, leading to additional physiological burden. Despite ALI being well described in the paediatric age group, its management has been largely based on adult studies. Ventilatory support with low tidal volumes, positive end expiratory pressure(PEEP) and permissive hypercapnoea are the pillars of management - derived from adult studies. For those caring for critically unwell children, this review outlines recent paediatric studies, current therapies in the context of available literature and novel emerging approaches.

The design of future pediatric mechanical ventilation trials for acute lung injury

Pediatric practitioners face unique challenges when attempting to translate or adapt adult-derived evidence regarding ventilation practices for acute lung injury or acute respiratory distress syndrome into pediatric practice. Fortunately or unfortunately, there appears to be selective adoption of adult practices for pediatric mechanical ventilation, many of which pose considerable challenges or uncertainty when translated to pediatrics. These differences, combined with heterogeneous management strategies within pediatric critical care, can complicate clinical practice and make designing robust clinical trials in pediatric acute respiratory failure particularly difficult. These issues surround the lack of explicit ventilator protocols in pediatrics, either computer or paper based; differences in modes of conventional ventilation and perceived marked differences in the approach to high-frequency oscillatory ventilation; challenges with patient recruitment; the shortcomings of the definition of acute lung injury and acute respiratory distress syndrome; the more reliable yet still somewhat unpredictable relationship between lung injury severity and outcome; and the reliance on potentially biased surrogate outcome measures, such as ventilator-free days, for all pediatric trials. The purpose of this review is to highlight these challenges, discuss pertinent work that has begun to address them, and propose potential solutions or future investigations that may help facilitate comprehensive trials on pediatric mechanical ventilation and define clinical practice standards.

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.

Acute lung injury: epidemiology, pathogenesis, and treatment

Acute lung injury (ALI) remains a significant source of morbidity and mortality in the critically ill patient population. Defined by a constellation of clinical criteria (acute onset of bilateral pulmonary infiltrates with hypoxemia without evidence of hydrostatic pulmonary edema), ALI has a high incidence (200,000 per year in the US) and overall mortality remains high. Pathogenesis of ALI is explained by injury to both the vascular endothelium and alveolar epithelium. Recent advances in the understanding of pathophysiology have identified several biologic markers that are associated with worse clinical outcomes. Phase III clinical trials by the NHLBI ARDS Network have resulted in improvement in survival and a reduction in the duration of mechanical ventilation with a lung-protective ventilation strategy and fluid conservative protocol. Potential areas of future treatments include nutritional strategies, statin therapy, and mesenchymal stem cells.

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

BACKGROUND

Acute hypoxaemic respiratory failure (AHRF), defined as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), are critical conditions. AHRF results from a number of systemic conditions and is associated with high mortality and morbidity in all ages. Inhaled nitric oxide (INO) has been used to improve oxygenation but its role remains controversial.

OBJECTIVES

To systematically assess the benefits and harms of INO in critically ill patients with AHRF.

SEARCH STRATEGY

Randomized clinical trials (RCTs) were identified 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 (up to 31st January 2010). We contacted trial authors, authors of previous reviews, and manufacturers in the field.

SELECTION CRITERIA

We included all RCTs, irrespective of blinding or language, that compared INO with no intervention or placebo in children or adults with AHRF.

DATA COLLECTION AND ANALYSIS

Two authors independently abstracted data and resolved any disagreements by discussion. We presented pooled estimates of the intervention effects on dichotomous outcomes as relative risks (RR) with 95% confidence intervals (CI). 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 and the risk of random error through trial sequential analysis.

MAIN 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%) (RR 1.06, 95% CI 0.93 to 1.22; I(2) = 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 partial pressure of oxygen to fraction of inspired oxygen and the oxygenation index (MD 15.91, 95% CI 8.25 to 23.56; I(2) = 25%). However, INO appears to increase the risk of renal impairment among adults (RR 1.59, 95% CI 1.17 to 2.16; I(2) = 0) but not the risk of bleeding or methaemoglobin or nitrogen dioxide formation.

AUTHORS' CONCLUSIONS

INO cannot be recommended for patients with AHRF. INO results in a transient improvement in oxygenation but does not reduce mortality and may be harmful.

Plasma interleukin-8 is not an effective risk stratification tool for adults with vasopressor-dependent septic shock

OBJECTIVE

Plasma interleukin-8 levels of <220 pg/mL have an excellent negative predictive value (94% to 95%) for death at 28 days in children with septic shock and thus may be useful for risk stratification in clinical trial enrollment in this population. Whether plasma interleukin-8 would have similar utility in adults with septic shock is unknown.

DESIGN

Analysis of plasma interleukin-8 levels and prospectively collected clinical data from patients enrolled in two large randomized controlled trials of ventilator strategy for acute lung injury.

SETTING

Intensive care units of university hospitals participating in the National Institutes of Health Acute Respiratory Distress Syndrome Network.

PATIENTS

One hundred ninety-two adult patients with vasopressor-dependent septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma interleukin-8 levels > or =220 pg/mL were significantly associated with death at 28 days in this cohort (odds ratio, 2.92; 95% confidence interval, 1.42 to 5.99; p = .001). However, in contrast to the findings in pediatric septic shock, a plasma interleukin-8 cutoff <220 pg/mL had a negative predictive value for death of only 74% (95% confidence interval, 66% to 81%) in adults with septic shock. Receiver operating characteristic analysis found an area under the curve of 0.59 for plasma interleukin-8, indicating that plasma interleukin-8 is a poor predictor of mortality in this group. In adults aged <40 yrs, a plasma interleukin-8 cutoff <220 pg/mL had a negative predictive value of 92%.

CONCLUSIONS

In contrast to similar pediatric patients, plasma interleukin-8 levels are not an effective risk stratification tool in older adults with septic shock. Future studies of biomarkers for risk stratification in critically ill subjects will need to be replicated in multiple different populations before being applied in screening for clinical trials.

Incidence, management and mortality of acute hypoxemic respiratory failure and acute respiratory distress syndrome from a prospective study of Chinese paediatric intensive care network

AIM

To investigate the incidence, clinical management, mortality and its risk factors, major outcome and costs of acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) in a Chinese network of 26 paediatric intensive care unit (PICU).

METHODS

In a consecutive 12-month period, AHRF and ARDS were identified and followed up for 90 days or until death or discharge.

RESULTS

From a total of 11 521 critically ill patients, 461 AHRF were identified in which 306 developed ARDS (66.4%), resulting in incidences of 4% and 2.7%, respectively, with pneumonia (75.1%) and sepsis (14.7%) as main underlying diseases and 83% were 5 years and 1 month-old. In-hospital mortality of AHRF was 41.6% (44.8% for ARDS), accounted for 15.5% of all PICU deaths. For those of pneumonia or sepsis with AHRF and ARDS, mortality and its relative risk were significantly higher than those without. Relatively lower tidal volume and total fluid balance, adequate upper limit of PaCO(2) in the early PICU days, and family affordability, tended to result in better outcome.

CONCLUSION

In this prospective study, AHRF had high possibilities to develop ARDS and death risk, as impacted by ventilation settings and fluid intake in the early treatment, as well as socioeconomic factors, which should be considered for implementation of standard of care in respiratory therapy.

Critically ill infants and children with influenza A (H1N1) in pediatric intensive care units in Argentina

Objective

To determine the epidemiological features, course, and outcomes of critically ill pediatric patients with Influenza A (H1N1) virus.

Design

Prospective cohort of children in pediatric intensive care units (PICUs) due to Influenza A (H1N1) virus infection.

Setting

Seventeen medical-surgical PICUs in tertiary care hospital in Argentina.

Patients

All consecutive patients admitted to the PICUs with influenza A (H1N1) viral infection from 15 June to 31 July 2009.

Measurements and main results

Of 437 patients with acute lower respiratory infection in PICUs, 147 (34%) were diagnosed with influenza A (H1N1) related to critical illness. The median age of these patients was 10 months (IQR 3–59). Invasive mechanical ventilation was used in 117 (84%) on admission. The rate of acute respiratory distress syndrome (ARDS) was 80% (118 of 147 patients). Initial non-invasive ventilation failed in 19 of 22 attempts (86%). Mortality at 28 days was 39% (n = 57). Chronic complex conditions (CCCs), acute renal dysfunction (ARD) and ratio PaO₂/FiO₂ at day 3 on MV were independently associated with a higher risk of mortality. The odds ratio (OR) for CCCs was 3.06, (CI 95% 1.36–6.84); OR for ARD, 3.38, (CI 95% 1.45–10.33); OR for PaO₂/FiO₂, 4 (CI 95% 1.57–9.59). The administration of oseltamivir within 24 h after admission had a protective effect: OR 0.2 (CI 95% 0.07–0.54).

Conclusions

In children with ARDS, H1N1 as an etiologic agent confers high mortality, and the presence of CCCs in such patients increases the risk of death.

Defining acute lung disease in children with the oxygenation saturation index

OBJECTIVE

To evaluate whether a formula could be derived using oxygen saturation (Spo2) to replace Pao2 that would allow identification of children with acute lung injury and acute respiratory distress syndrome. Definitions of acute lung injury and acute respiratory distress syndrome require arterial blood gases to determine the Pao2/Fio2 ratio of 300 (acute lung injury) and 200 (acute respiratory distress syndrome).

DESIGN

Post hoc data analysis of measurements abstracted from two prospective databases of randomized controlled trials.

SETTING

Academic pediatric intensive care units.

PATIENTS

A total of 255 children enrolled in two large prospective trials of therapeutic intervention for acute lung disease: calfactant and prone positioning.

INTERVENTIONS

Data were abstracted including Pao2, Paco2, pH, Fio2, and mean airway pressure. Repeated-measures analyses, using linear mixed-effects models, were used to build separate prediction equations for the Spo2/Fio2 ratio, oxygenation index [(Fio2 x Mean Airway Pressure)/Pao2], and oxygen saturation index [(Fio2 x Mean Airway Pressure)/Spo2 ]. A generalization of R was used to measure goodness-of-fit. Generalized estimating equations with a logit link were used to calculate the sensitivity and specificity for the cutoffs of Pao2/Fio2 ratio of 200 and 300 and equivalent values of Spo2/Fio2 ratio, oxygenation index, and oxygen saturation index.

MEASUREMENTS AND MAIN RESULTS

An Spo2/Fio2 ratio of 253 and 212 would equal criteria for acute lung injury and acute respiratory distress syndrome, respectively. An oxygenation index of 5.3 would equal acute lung injury criteria, and an oxygenation index of 8.1 would qualify for acute respiratory distress syndrome. An oxygen saturation index, which includes the mean airway pressure and the noninvasive measure of oxygenation, of 6.5 would be equivalent to the acute lung injury criteria, and an oxygen saturation index of 7.8 would equal acute respiratory distress syndrome criteria.

CONCLUSIONS

Noninvasive methods of assessing oxygenation may be utilized with reasonable sensitivity and specificity to define acute lung injury and acute respiratory distress syndrome, and, with prospective validation, have the potential to increase the number of children enrolled into clinical trials.

Early elevations in B-type natriuretic peptide levels are associated with poor clinical outcomes in pediatric acute lung injury

OBJECTIVES

To determine B-type natriuretic peptide (BNP) levels in infants and children with acute lung injury (ALI), and to investigate associations between BNP levels and clinical outcome.

DESIGN

Prospective observational study.

SUBJECTS

After informed consent, plasma was collected from 48 pediatric patients on day 1 of ALI.

METHODOLOGY

Plasma BNP levels were measured by immunoassay on day 1 of ALI in 48 pediatric patients. Associations between BNP levels and outcome were determined.

RESULTS

The mean PaO(2)/FiO(2) at the onset of ALI was 155 (+/-74) and BNP values ranged from 5 to 2,060 pg/ml with a mean of 109 (+/-311). BNP levels were inversely correlated with ventilator-free days (Spearman rho -0.30, P = 0.04), and positively correlated with exhaled tidal volume (Spearman rho 0.44, P = 0.02). BNP levels were higher in patients receiving inotropic support (n = 12) than patients not receiving inotropic support (n = 33, P = 0.02). BNP levels were correlated with PRISM III scores (Spearman rho 0.55, P < 0.001) and PELOD scores (Spearman rho 0.4, P = 0.006). Mortality for the cohort was 15%. BNP levels were higher in non-survivors (n = 7) than survivors (n = 41, P = 0.055).

CONCLUSIONS

BNP levels are elevated in children with ALI/ARDS early in the disease course, and increased levels are associated with worse clinical outcome.

Elevated PAI-1 is associated with poor clinical outcomes in pediatric patients with acute lung injury

Purpose

Deposition of fibrin in the alveolar space is a hallmark of acute lung injury (ALI). Plasminogen activator inhibitor-1 (PAI-1) is an antifibrinolytic agent that is activated during inflammation. Increased plasma and pulmonary edema fluid levels of PAI-1 are associated with increased mortality in adults with ALI. This relationship has not been examined in children. The objective of this study was to test whether increased plasma PAI-1 levels are associated with worse clinical outcomes in pediatric patients with ALI.

Design/methods

We measured plasma PAI-1 levels on the first day of ALI among 94 pediatric patients enrolled in two separate prospective, multicenter investigations and followed them for clinical outcomes. All patients met American European Consensus Conference criteria for ALI.

Results

A total of 94 patients were included. The median age was 3.2 years (range 16 days–18 years), the PaO₂/F_iO₂ was 141 ± 72 (mean ± SD), and overall mortality was 14/94 (15%). PAI-1 levels were significantly higher in nonsurvivors compared to survivors (P < 0.01). The adjusted odds of mortality doubled for every log increase in the level of plasma PAI-1 after adjustment for age and severity of illness.

Conclusions

Higher PAI-1 levels are associated with increased mortality and fewer ventilator-free days among pediatric patients with ALI. These findings suggest that impaired fibrinolysis may play a role in the pathogenesis of ALI in pediatric patients and suggest that PAI-1 may serve as a useful biomarker of prognosis in patients with ALI.

Acute respiratory distress syndrome in pediatric intensive care unit

OBJECTIVE

To report causes, clinical feature and outcome of children with Acute Respiratory Distress Syndrome (ARDS).

METHODS

The case records of children admitted with ARDS from June 2003 to June 2006 were retrospectively reviewed and the data collected was analyzed.

RESULTS

A total of 17 children were diagnosed as ARDS during study period giving an incidence of 22.7/1,000 admissions. The mean (SD) age was 74.5 (56.32) mo [range 6-144 mo]. Primary lung pathology contributed to a (53%) cases of ARDS while the rest (47%) had non pulmonary causes. There was not any significant different in mortality between these two groups. Similarly when infections and non infections conditions were considered separately there was no difference in survival. All children were ventilated using Pressure Controlled Ventilation. The mean (SD) duration of ventilation was 5.0 days [range 1-10 days]. The maximum PEEP (SD) used during the course of ventilation was 10 (3.37) cm H2O [range 7-18], while the maximum PIP (SD) used was 31 (3.75) cm H2O (range 25-36). The overall mortality was 70%; highest in children less than 2 years of age. Majority of the children had shock as the most common comorbid factor and had a high mortality (73.3%).

CONCLUSION

The high incidence and mortality of ARDS and the presence of a large proportion of potentially preventable accidents and poisoning cases in the study group underline the need for health education measures addressing preventive strategies among the rural population.

Risk parameters of fulminant acute respiratory distress syndrome and avian influenza (H5N1) infection in Vietnamese children

A clinical picture of patients with acute respiratory distress syndrome (ARDS) induced by highly pathogenic avian influenza A (H5N1) has been reported. We reviewed 37 sets of clinical data for pediatric patients with ARDS at the National Hospital of Pediatrics (Hanoi, Vietnam); 12 patients with H5N1-positive and 25 with H5N1-negative ARDS were enrolled. The H5N1-negative patients had a clinical picture and mortality rate similar to that for the pediatric ARDS patients. However, the H5N1-positive patients had ARDS with normal ventilation capacity at the time of hospital admission, then rapidly proceeded to severe respiratory failure. The survival probability and days until final outcome in groups of H5N1-positive (n=12) vs. H5N1-negative (n=25) patients were 17% versus 52% and 12.3+/-5.7 days (median, 11 days) versus 21.5+/-13.8 days (median, 22 days), respectively. Our observations clarified the clinical picture of H5N1-induced fulminant ARDS and also confirmed that relatively older age (approximately 6 years of age), high fever at onset, and leukopenia and/or thrombocytopenia at the time of hospital admission are risk parameters for H5N1-induced fulminant ARDS.

Effect of tidal volume in children with acute hypoxemic respiratory failure

OBJECTIVES

To determine if tidal volume (VT) between 6 and 10 ml/kg body weight using pressure control ventilation affects outcome for children with acute hypoxemic respiratory failure (AHRF) or acute lung injury (ALI). To validate lung injury severity markers such as oxygenation index (OI), PaO2/FiO2 (PF) ratio, and lung injury score (LIS).

DESIGN

Retrospective, January 2000-July 2007.

SETTING

Tertiary care, 20-bed PICU.

PATIENTS

Three hundred and ninety-eight endotracheally intubated and mechanically ventilated children with PF ratio <300. Outcomes were mortality and 28-day ventilator free days.

MEASUREMENTS AND MAIN RESULTS

Three hundred and ninety-eight children met study criteria, with 20% mortality. 192 children had ALI. Using >90% pressure control ventilation, 85% of patients achieved VT less than 10 ml/kg. Median VT was not significantly different between survivors and non-survivors during the first 3 days of mechanical ventilation. After controlling for diagnostic category, age, delta P (PIP-PEEP), PEEP, and severity of lung disease, VT was not associated with mortality (P > 0.1), but higher VT at baseline and on day 1 of mechanical ventilation was associated with more ventilator free days (P < 0.05). This was particularly seen in patients with better respiratory system compliance [Crs > 0.5 ml/cmH2O/kg, OR = 0.70 (0.52, 0.95)]. OI, PF ratio, and LIS were all associated with mortality (P < 0.05).

CONCLUSIONS

When ventilating children using lung protective strategies with pressure control ventilation, observed VT is between 6 and 10 ml/kg and is not associated with increased mortality. Moreover, higher VT within this range is associated with more ventilator free days, particularly for patients with less severe disease.

Incidence and outcomes of pediatric acute lung injury

OBJECTIVE

This population-based, prospective, cohort study was designed to determine the population incidence and outcomes of pediatric acute lung injury.

METHODS

Between 1999 and 2000, 1 year of screening was performed at all hospitals admitting critically ill children in King County, Washington. County residents 0.5 to 15 years of age who required invasive (through endotracheal tube or tracheostomy) or noninvasive (through full face mask) mechanical ventilation, regardless of the duration of mechanical ventilation, were screened. From this population, children meeting North American-European Consensus Conference acute lung injury criteria were eligible for enrollment. Postoperative patients who received mechanical ventilation for <24 hours were excluded. Data collected included the presence of predefined cardiac conditions, demographic and physiological data, duration of mechanical ventilation, and deaths. US Census population figures were used to estimate incidence. Associations between outcomes and subgroups identified a priori were assessed.

RESULTS

Thirty-nine children met the criteria for acute lung injury, resulting in a calculated incidence of 12.8 cases per 100000 person-years. Severe sepsis (with pneumonia as the infection focus) was the most common risk factor. The median 24-hour Pediatric Risk of Mortality III score was 9.0, and the mean +/- SD was 11.7 +/- 7.5. The hospital mortality rate was 18%, lower than that reported previously for pediatric acute lung injury. There were no statistically significant associations between age, gender, or risk factors and outcomes.

CONCLUSIONS

We present the first population-based estimate of pediatric acute lung injury incidence in the United States. Population incidence and mortality rates are lower than those for adult acute lung injury. Low mortality rates in pediatric acute lung injury may necessitate clinical trial outcome measures other than death.

Characteristics of children intubated and mechanically ventilated in 16 PICUs

BACKGROUND

When designing multicenter clinical trials, it is important to understand the characteristics of children who have received ventilation in PICUs.

METHODS

This study involved the secondary analysis of an existing data set of all children intubated and mechanically ventilated from 16 US PICUs who were initially screened for a multicenter clinical trial on pediatric acute lung injury (ALI).

RESULTS

A total of 12,213 children between 2 weeks and 18 years of age who were intubated and mechanically ventilated were included, representing 30% of PICU admissions (center range, 20 to 64%). Of the children who received ventilation, 22% had cyanotic congenital heart disease; 26% had respiratory failure but not bilateral pulmonary infiltrates on chest radiograph; 8% had chronic respiratory disease; 7% had upper airway obstruction; and 5% had reactive airway disease. At least 1,457 patients (15%) with respiratory failure lacked an arterial line. Of these patients, 97% had a positive end-expiratory pressure <or= 8 cm H(2)O, and 80% were supported on an Fio(2) of <or= 0.40. Moreover, 104 of 904 patients (12%) with pulse oximetric saturation (Spo(2)) and Fio(2) measurements available would have met the oxygenation criteria for ALI according to Spo(2)/Fio(2) ratio criteria.

CONCLUSIONS

At least 30% of children in a cross-section of US PICUs are endotracheally intubated, and 25% of those with respiratory failure do not fulfill the radiographic criteria for ALI. Although few patients without an indwelling arterial line require more than modest ventilator support, many may still meet the oxygenation criteria for ALI. These findings will facilitate sample size calculations and help to determine feasibility for future trials on pediatric mechanical ventilation.

Blood product transfusions and clinical outcomes in pediatric patients with acute lung injury

OBJECTIVE

There are data suggesting that blood product transfusions increase the risk of developing acute lung injury (ALI) in adults, and may be associated with increased mortality in adults with ALI. A possible association between transfusions and adverse outcomes of pediatric patients with ALI has not been studied previously. We tested the hypothesis that blood product transfusions to pediatric patients with ALI within the first 72 hours of the diagnosis would be associated with increased mortality and prolonged mechanical ventilation.

DESIGN

An epidemiologic database of pediatric ALI prospectively gathered from July 1996 to May 2000 was analyzed.

SETTING

Children were enrolled from both a tertiary referral hospital and a major community children's hospital.

PATIENTS

Three hundred fifteen patients who met the 1994 American European Consensus Committee definition of ALI between the ages of 36 weeks corrected gestational age and 18 years.

MAIN OUTCOME MEASURE

Mortality in the pediatric intensive care unit.

RESULTS

Multivariate analyses indicated that the transfusion of fresh-frozen plasma (FFP) was associated with increased mortality, independent of the severity of hypoxemia (Pao2/Fio2), presence of multiple organ system failure or disseminated intravascular coagulation (odds ratio = 1.08, 95% confidence interval = 1.00-1.17, p = 0.04). FFP transfusion was analyzed as a continuous variable, so that for each milliliter of FFP transfused per kilogram patient body weight per day, the odds of death increased by 1.08. There was a trend toward an association of the transfusion of FFP with a fewer number of days of unassisted ventilation (regression coefficient = -0.21, 95% confidence interval = -0.42-0.01, p = 0.06).

CONCLUSIONS

The transfusion of FFP is associated with an increased risk of mortality in children with ALI. The association between FFP and mortality in children with ALI should be investigated further.

Identification of early acute lung injury at initial evaluation in an acute care setting prior to the onset of respiratory failure

BACKGROUND

Despite being a focus of intensive investigation, acute lung injury (ALI) remains a major cause of morbidity and mortality. However, the current consensus definition impedes identification of patients with ALI before they require mechanical ventilation. To establish a definition of early ALI (EALI), we carried out a prospective cohort study to identify clinical predictors of progression to ALI.

METHODS

Potential cases of EALI were identified by daily screening of chest radiographs (CXRs) for all adult emergency department and new medicine service admissions at Stanford University Hospital.

RESULTS

Of 1,935 screened patients with abnormal CXRs, we enrolled 100 patients admitted with bilateral opacities present < 7 days and not due exclusively to left atrial hypertension. A total of 33 of these 100 patients progressed to ALI requiring mechanical ventilation during their hospitalization. Progression to ALI was associated with immunosuppression, the modified Rapid Emergency Medicine Score, airspace opacities beyond the bases, systemic inflammatory response syndrome, and the initial oxygen requirement (> 2 L/min). On multivariate analysis, only an initial oxygen requirement > 2 L/min predicted progression to ALI (odds ratio, 8.1; 95% confidence interval, 2.7 to 24.5). A clinical diagnosis of EALI, defined by hospital admission with bilateral opacities on CXR not exclusively due to left atrial hypertension and an initial oxygen requirement of > 2 L/min, was 73% sensitive and 79% specific for progression to ALI.

CONCLUSIONS

A new clinical definition of EALI may have value in identifying patients with ALI early in their disease course.

The pediatric multiple organ dysfunction syndrome

OBJECTIVES

To review the epidemiology of pediatric multiple organ dysfunction syndrome (MODS) and summarize current concepts regarding the pathophysiology of shock, organ dysfunction, and nosocomial infections in this population.

DATA SOURCE

A MEDLINE-based literature search using the keywords MODS and child, without any restriction to the idiom.

MAIN RESULTS

Critically ill children may frequently develop multisystemic manifestations during the course of severe infections, multiple trauma, surgery for congenital heart defects, or transplantations. Descriptive scores to estimate the severity of pediatric MODS have been validated. Young age and chronic health conditions have also been recognized as important contributors to the development of MODS. Unbalanced inflammatory processes and activation of coagulation may lead to the development of capillary leak and acute respiratory distress syndrome. Neuroendocrine and metabolic responses may result in insufficient adaptive immune response and the development of nosocomial infections, which may further threaten host homeostasis.

CONCLUSIONS

Over the last 20 yrs, there has been an increasing knowledge on the epidemiology of pediatric MODS and on the physiologic mechanisms involved in the genesis of organ dysfunction. Nevertheless, further studies are needed to more clearly evaluate what is the long-term outcome of pediatric MODS.

How is mechanical ventilation employed in a pediatric intensive care unit in Brazil?

OBJECTIVE

To investigate the relationship between mechanical ventilation and mortality and the practice of mechanical ventilation applied in children admitted to a high-complexity pediatric intensive care unit in the city of São Paulo, Brazil.

DESIGN

Prospective cohort study of all consecutive patients admitted to a Brazilian high-complexity PICU who were placed on mechanical ventilation for 24 hours or more, between October 1(st), 2005 and March 31(st), 2006.

RESULTS

Of the 241 patients admitted, 86 (35.7%) received mechanical ventilation for 24 hours or more. Of these, 49 met inclusion criteria and were thus eligible to participate in the study. Of the 49 patients studied, 45 had chronic functional status. The median age of participants was 32 months and the median length of mechanical ventilation use was 6.5 days. The major indication for mechanical ventilation was acute respiratory failure, usually associated with severe sepsis / septic shock. Pressure ventilation modes were the standard ones. An overall 10.37% incidence of Acute Respiratory Distress Syndrome was found, in addition to tidal volumes > 8 ml/kg, as well as normo- or hypocapnia. A total of 17 children died. Risk factors for mortality within 28 days of admission were initial inspiratory pressure, pH, PaO2/FiO2 ratio, oxygenation index and also oxygenation index at 48 hours of mechanical ventilation. Initial inspiratory pressure was also a predictor of mechanical ventilation for periods longer than 7 days.

CONCLUSION

Of the admitted children, 35.7% received mechanical ventilation for 24 h or more. Pressure ventilation modes were standard. Of the children studied, 91% had chronic functional status. There was a high incidence of Acute Respiratory Distress Syndrome, but a lung-protective strategy was not fully implemented. Inspiratory pressure at the beginning of mechanical ventilation was a predictor of mortality within 28 days and of a longer course of mechanical ventilation.

The epidemiology of acute respiratory distress syndrome in pediatric intensive care units in China

OBJECTIVE

To assess the incidence of, predisposing factors for, and the rates and relative risks of mortality from acute respiratory distress syndrome (ARDS) in pediatric patients.

DESIGN

A prospective study in 12 consecutive months from 2004 to 2005 in 25 pediatric intensive care units (PICUs).

PATIENTS AND SETTING

ARDS was diagnosed according to the 1994 American-European Consensus Conference definitions, applied to all severely ill admissions between 1 month and 14 years of age. The PICUs were in major municipalities and provincial cities, and half were university affiliated.

MEASUREMENTS AND RESULTS

From a total of 12,018 admissions, 7,269 were severely ill. One hundred and five (1.44%) patients developed ARDS and 64 (61.0%) died, which accounts for 13.2%, of the total ICU death (n = 485, 6.7%) or a nine times relative risk of dying. The median age at onset of ARDS was 24 months and 40% were less than 12 month old. Median time from PICU admission to the onset of ARDS was 16 h, and in 63% <24 h. Pneumonia (55.2%) and sepsis (22.9%) were the major predisposing factors for ARDS. These were respectively 14 and 5 times as high a death rate as those of the severely ill patients without ARDS.

CONCLUSIONS

ARDS has a high mortality in these Chinese PICUs, especially in those with pneumonia and sepsis, and adequate management including lung protective ventilation strategy is required.

Pharmacotherapy in pediatric critical illness: a prospective observational study

BACKGROUND AND OBJECTIVES

Pharmacotherapy is an under-evaluated element of critical care medicine. In order to better understand pharmacotherapy in pediatric critical illness, we evaluated a cohort of emergency admissions to a university-affiliated pediatric intensive care unit (PICU).

METHODS

A prospective, observational study was performed. Eligible patients were admitted to this medical-surgical ICU for at least 24 hours. The primary outcomes were the number of drug orders written, the number of different medications ordered, and the number of drug administrations. Multiple regression analyses were used to identify factors independently associated with each primary outcome.

RESULTS

We studied 100 patients with a median age of 40 months (interquartile range [IQR] 9-82), who were admitted for a total of 851 ICU days. These patients received 4419 drug orders and 11 911 intermittent dose-administrations of 241 different medications. Each patient received a median of 29.5 (IQR 16.5-48.5) drug orders, 14 (IQR 9-18.5) different medications, and 58 (IQR 28-129) drug administrations while in the ICU. The most frequent orders were for morphine 457 (10.6%), furosemide (frusemide) 337 (7.8%), potassium 237 (5.5%), lorazepam 226 (5.2%), and albuterol (salbutamol) 158 (3.7%). The duration of PICU stay and severity of illness were independently associated with all primary outcomes.

CONCLUSIONS

Pharmacotherapy is an active component in the practice of pediatric critical care medicine. We demonstrated that increasing numbers of ordered medications, drug orders, and drug administrations were associated with increasing duration of ICU therapies and the length of ICU stay. These data underscore the potential importance of improved safety and efficacy of medicines used to treat critically ill children.

Predictors of outcome for children requiring respiratory extra-corporeal life support: implications for inclusion and exclusion criteria

OBJECTIVES

A range of children receive extra-corporeal life support (ECLS) for respiratory failure, but there is little published data on this group. Our aims were: (1) to analyse predictors of outcome and (2) comment on inclusion and exclusion criteria.

DESIGN

Retrospective review.

SETTING

Tertiary ECLS centre.

PATIENTS

A total of 124 children categorised as 'paediatric respiratory ECLS' from July 1992 to December 2005.

RESULTS

Fifty-three percent of children had one or more co-morbid conditions; the median age was 10.1 (IQR 3-34) months; the median ECLS duration was 9 (IQR 5-17) days; survival to discharge was 62% and at 1 year was 59%. Although survival varied according to primary reason for ECLS (range 36-100%), after adjustment for this, the presence of a co-morbid condition was unrelated to mortality (OR = 1.49, 95% CI 0.65, 3.42, P = 0.34) Predictors of mortality were increased pre-ECLS oxygenation index (OR = 1.09, 95% CI 1.00, 1.18, P = 0.05) and shock (OR 2.53, 95% CI 1.21, 5.28, P = 0.01). The relationship between mortality and end organ dysfunction (OR 2.12, 95% CI 0.89, 5.02, P = 0.09) and greater number of pre-ECLS ventilator days (OR 1.10, 95% CI 0.99, 1.22, P = 0.08) was less conclusive.

CONCLUSIONS

Pre-existing co-morbid conditions may predispose children to develop severe respiratory failure but with careful case selection, do not appear to reduce the chance of survival. Severity of pulmonary dysfunction determined by OI and shock were key predictors of outcome and should remain important determinants of referral for ECLS.

Comparison of the pulse oximetric saturation/fraction of inspired oxygen ratio and the PaO2/fraction of inspired oxygen ratio in children

BACKGROUND

Although diagnostic criteria for acute lung injury (ALI) and ARDS are clear, invasive arterial sampling is required for computation of Pao(2)/fraction of inspired oxygen (Fio(2)) [PF] ratios. The pulse oximetric saturation (Spo(2))/Fio(2) (SF) ratio may be a reliable noninvasive alternative to the PF ratio for identifying children with lung injury.

METHODS

We electronically queried blood gas measurements from two tertiary care pediatric ICUs (PICUs). Included in the analysis were corresponding measurements of Spo(2), Pao(2), and Fio(2) charted within 15 min of each other when Spo(2) values were between 80% and 97%. Computed PF and SF ratios were compared to identify threshold values for SF ratios that correspond to PF criteria for ALI (< or = 300) and ARDS (< or = 200). Data from one PICU were used for derivation and validated with measurements from the second PICU.

RESULTS

From the 1,298 observations in the derivation data set, SF ratio could be predicted by the regression equation SF = 76 + 0.62 x PF (p < 0.0001, R(2) = 0.61). SF ratios of 263 and 201 corresponded to PF ratios of 300 and 200, respectively. The ALI SF cutoff of 263 had 93% sensitivity and 43% specificity, and the ARDS cutoff of 201 had 84% sensitivity and 78% specificity. Applying these values to the 1,845 observations in the validation data set yielded a sensitivity of 86% and specificity of 47% for ALI and a sensitivity of 68% and specificity of 84% for ARDS.

CONCLUSION

SF ratio is a reliable noninvasive marker for PF ratio to identify children with ALI or ARDS.