B-type natriuretic peptide in the assessment of acute lung injury and cardiogenic pulmonary edema*

Prediction of acute lung injury in severe acute pancreatitis by routine clinical data

AIM

Acute lung injury (ALI) is a common complication of severe acute pancreatitis (SAP) with a high mortality. Early prediction of patients at risk in initial stage can improve the long-term survival.

METHODS

A total of 91 patients with SAP out of 1647 acute pancreatitis patients from January 2015 to December 2020 were considered. A predictive model for SAP-associated ALI was constructed based on the valuable risk factors identified from routine clinical characteristics and plasma biomarkers. The value of the model was evaluated and compared with Lung Injury Prediction Score (LIPS). A nomogram was built to visualize the model.

RESULTS

Diabetes, oxygen supplementation, neutrophil count and D-dimer were found to be associated with ALI in SAP. The predictive model based on these factors had an area under the receiver operating characteristic curve [AUC: 0.88, 95% confidence interval (CI): 0.81-0.95], which was superior to LIPS (AUC: 0.71, 95% CI: 0.60-0.83), also with the higher sensitivity (65%) and specificity (96%) than LIPS (62%, 74%, respectively). Decision curve analysis of the model showed a higher net benefit than LIPS. Visualization by a nomogram facilitated the application of the model.

CONCLUSION

Diabetes, oxygen supplementation, neutrophil count and D-dimer were risk factors for SAP-associated ALI. The combination of these routine clinical data and the model visualization by a nomogram provided a simple and effective way in predicting ALI in the early phase of SAP.

Systemic Markers of Monocyte Activation in Acute Pulmonary Oedema

BACKGROUND

Hydrostatic lung injury followed by pulmonary remodelling variably complicates cardiogenic acute pulmonary oedema (APO). Pulmonary remodelling may be regulated by the balance between distinct phenotypes of pulmonary macrophages; activated/inflammatory (M1), and reparative/anti-inflammatory (M2), derived from circulating monocyte populations. The aim of this study was to identify biomarkers in peripheral blood that are consistent with hydrostatic lung injury and pulmonary remodelling in APO and which follow the variable clinical course.

METHODS

To examine peripheral markers of lung inflammation, resolution and remodelling, 18 patients, admitted to the intensive care unit (ICU) with a clinical diagnosis of APO, were enrolled. Admission, 12- and 24-hour post-admission bloods were assayed for cytokines by ELISA (R&D Systems, Minneapolis, MN, USA) and leukocyte surface markers by flow cytometry.

RESULTS

Admission PaO₂ to FiO₂ ratio was positively correlated with Mon 2 (intermediate) monocyte prevalence, through increasing ratio of CD16⁺ monocytes to CD11b⁺ and CD40⁺ monocytes, and negatively correlated with Mon 1 (classical) monocyte prevalence, through decreasing ratio of CD16⁺ monocytes to CD62L⁺. Secondary cohort analysis compared 10 APO patients with established chronic heart failure (CHF) to eight without CHF. An increase in monocyte chemotactic peptide (MCP)-1, monocyte prevalence, and CD16^-CD62L⁺ monocytes with CHF, all characteristic of monocyte activation to a Mon 1 phenotype, were found in the CHF APO patients.

CONCLUSIONS

Increased systemic monocyte prevalence and expression of cell surface markers suggest a Mon 1 profile in CHF patients during episodes of APO. Future studies should define the role of systemic monocyte prevalence and activation in decompensated CHF.

Systems Biology ARDS Research with a Focus on Metabolomics

Acute respiratory distress syndrome (ARDS) is a clinical syndrome that inflicts a considerably heavy toll in terms of morbidity and mortality. While there are multitudes of conditions that can lead to ARDS, the vast majority of ARDS cases are caused by a relatively small number of diseases, especially sepsis and pneumonia. Currently, there is no clinically agreed upon reliable diagnostic test for ARDS, and the detection or diagnosis of ARDS is based on a constellation of laboratory and radiological tests in the absence of evidence of left ventricular dysfunction, as specified by the Berlin definition of ARDS. Virtually all the ARDS biomarkers to date have been proven to be of very limited clinical utility. Given the heterogeneity of ARDS due to the wide variation in etiology, clinical and molecular manifestations, there is a current scientific consensus agreement that ARDS is not just a single entity but rather a spectrum of conditions that need further study for proper classification, the identification of reliable biomarkers and the adequate institution of therapeutic targets. This scoping review aims to elucidate ARDS omics research, focusing on metabolomics and how metabolomics can boost the study of ARDS biomarkers and help to facilitate the identification of ARDS subpopulations.

A systematic review of diagnostic methods to differentiate acute lung injury/acute respiratory distress syndrome from cardiogenic pulmonary edema

BACKGROUND

Discriminating acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) from cardiogenic pulmonary edema (CPE) is often challenging. This systematic review examines studies using biomarkers or images to distinguish ALI/ARDS from CPE.

METHODS

Three investigators independently identified studies designed to distinguish ALI/ARDS from CPE in adults. Studies were identified from PubMed, and the Cochrane Central Register of Controlled Trials database until July 3, 2017.

RESULTS

Of 475 titles and abstracts screened, 38 full texts were selected for review, and we finally included 24 studies in this systematic review: 21 prospective observational studies, two retrospective observational studies, and one retrospective combined with prospective study. These studies compared various biomarkers to differentiate subjects with ALI/ARDS and in those with CPE, and 13 calculated the area under the receiver operator characteristic curve (AUC). The most commonly studied biomarker (four studies) was brain natriuretic peptide (BNP) and the discriminatory ability ranged from AUC 0.67-0.87 but the timing of measurement varied. Other potential biomarkers or tools have been reported, but only as single studies.

CONCLUSIONS

There were no identified biomarkers or tools with high-quality evidence for differentiating ALI/ARDS from CPE. Combining clinical criteria with validated biomarkers may improve the predictive accuracy.

Acute Lung Injury: A Clinical and Molecular Review

CONTEXT

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are a continuum of lung changes arising from a wide variety of lung injuries, frequently resulting in significant morbidity and frequently in death. Research regarding the molecular pathophysiology of ALI/ARDS is ongoing, with the aim toward developing prognostic molecular biomarkers and molecular-based therapy.

OBJECTIVE

To review the clinical, radiologic, and pathologic features of ALI/ARDS; and the molecular pathophysiology of ALI/ARDS, with consideration of possible predictive/prognostic molecular biomarkers and possible molecular-based therapies.

DATA SOURCES

Examination of the English-language medical literature regarding ALI and ARDS.

CONCLUSIONS

ARDS is primarily a clinicoradiologic diagnosis; however, lung biopsy plays an important diagnostic role in certain cases. A significant amount of progress has been made in the elucidation of ARDS pathophysiology and in predicting patient response, however, currently there is no viable predictive molecular biomarkers for predicting the severity of ARDS, or molecular-based ARDS therapies. The proinflammatory cytokines TNF-α (tumor necrosis factor α), interleukin (IL)-1β, IL-6, IL-8, and IL-18 are among the most promising as biomarkers for predicting morbidity and mortality.

Early Treatment of Severe Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is defined by acute diffuse inflammatory lung injury invoked by a variety of systemic or pulmonary insults. Despite medical progress in management, mortality remains 27% to 45%. Patients with ARDS should be managed with low tidal volume ventilation. Permissive hypercapnea is well tolerated. Conservative fluid strategy can reduce ventilator and hospital days in patients without shock. Prone positioning and neuromuscular blockers reduce mortality in some patients. Early management of ARDS is relevant to emergency medicine. Identifying ARDS patients who should be transferred to an extracorporeal membrane oxygenation center is an important task for emergency providers.

Comparison of hospital mortality and long-term survival in patients with acute lung injury/ARDS vs cardiogenic pulmonary edema

BACKGROUND

Early differential diagnosis of acute lung injury (ALI) vs cardiogenic pulmonary edema (CPE) is important for selecting the most appropriate therapy, but the prognostic implications of this distinction have not been studied. Accurate prognostic information is essential for providing appropriate informed consent prior to initiation of mechanical ventilation.

METHODS

This is a long-term follow-up study of a previously established population-based cohort of critically ill adult patients with acute pulmonary edema admitted at a tertiary-care center during 2006 to 2009, in which post hoc expert review had established ALI vs CPE diagnosis. Using logistic and Cox regression, hospital mortality and long-term survival were compared in patients with ALI vs patients with CPE.

RESULTS

Of 328 patients (ALI = 155, CPE = 173), 240 patients (73%) died during a median follow-up of 160 days. After adjusting for confounders, patients with ALI were significantly more likely to die in the hospital (OR = 4.2, 95% CI = 2.3-7.8, n = 325, P < .001), but among hospital survivors the risk of death during follow-up was the same in both groups (hazard ratio = 1.13, 95% CI = 0.79-1.62, n = 229, P = .50). Independent predictors of mortality included age and APACHE (Acute Physiology and Chronic Health Evaluation) III score. Results were similar when restricting patients with ALI to the subset with ARDS (Berlin definition). In post hoc analyses, the mortality rate in hospital survivors compared with the general US population was significantly higher during the first 2 years but essentially converged by year five.

CONCLUSIONS

Although hospital mortality is higher in patients with ALI/ARDS compared with patients with CPE, long-term survival is similar in hospital survivors from both groups.

Decision support tool for differential diagnosis of Acute Respiratory Distress Syndrome (ARDS) vs Cardiogenic Pulmonary Edema (CPE): a prospective validation and meta-analysis

Introduction

We recently presented a prediction score providing decision support with the often-challenging early differential diagnosis of acute lung injury (ALI) vs cardiogenic pulmonary edema (CPE). To facilitate clinical adoption, our objective was to prospectively validate its performance in an independent cohort.

Methods

Over 9 months, adult patients consecutively admitted to any intensive care unit of a tertiary-care center developing acute pulmonary edema were identified in real-time using validated electronic surveillance. For eligible patients, predictors were abstracted from medical records within 48 hours of the alert. Post-hoc expert review blinded to the prediction score established gold standard diagnosis.

Results

Of 1,516 patients identified by electronic surveillance, data were abstracted for 249 patients (93% within 48 hours of disease onset), of which expert review (kappa 0.93) classified 72 as ALI, 73 as CPE and excluded 104 as “other”. With an area under the curve (AUC) of 0.81 (95% confidence interval =0.73 to 0.88) the prediction score showed similar discrimination as in prior cohorts (development AUC = 0.81, P = 0.91; retrospective validation AUC = 0.80, P = 0.92). Hosmer-Lemeshow test was significant (P = 0.01), but across eight previously defined score ranges probabilities of ALI vs CPE were the same as in the development cohort (P = 0.60). Results were the same when comparing acute respiratory distress syndrome (ARDS, Berlin definition) vs CPE.

Conclusion

The clinical prediction score reliably differentiates ARDS/ALI vs CPE. Pooled results provide precise estimates of the score’s performance which can be used to screen patient populations or to assess the probability of ALI/ARDS vs CPE in specific patients. The score may thus facilitate early inclusion into research studies and expedite prompt treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0659-x) contains supplementary material, which is available to authorized users.

Role of microtubules in attenuation of PepG-induced vascular endothelial dysfunction by atrial natriuretic peptide

Apart from control of circulating fluid, atrial natriuretic peptide (ANP) exhibits anti-inflammatory effects in the lung. However, molecular mechanisms of ANP anti-inflammatory effects are not well-understood. Peripheral microtubule (MT) dynamics is essential for agonist-induced regulation of vascular endothelial permeability. Here we studied the role of MT-dependent signaling in ANP protective effects against endothelial cell (EC) barrier dysfunction and acute lung injury induced by Staphylococcus aureus-derived peptidoglican-G (PepG). PepG-induced vascular endothelial dysfunction was accompanied by MT destabilization and disruption of MT network. ANP attenuated PepG-induced MT disassembly, NFκB signaling and activity of MT-associated Rho activator GEF-H1 leading to attenuation of EC inflammatory activation reflected by expression of adhesion molecules ICAM1 and VCAM1. ANP-induced EC barrier preservation and MT stabilization were linked to phosphorylation and inactivation of MT-depolymerizing protein stathmin. Expression of stathmin phosphorylation-deficient mutant abolished ANP protective effects against PepG-induced inflammation and EC permeability. In contrast, siRNA-mediated stathmin knockdown prevented PepG-induced peripheral MT disassembly and endothelial barrier dysfunction. ANP protective effects in a murine model of PepG-induced lung injury were associated with increased phosphorylation of stathmin, while exacerbated lung injury in the ANP knockout mice was accompanied by decreased pool of stable MT. Stathmin knockdown in vivo reversed exacerbation of lung injury in the ANP knockout mice. These results show a novel MT-mediated mechanism of endothelial barrier protection by ANP in pulmonary EC and animal model of PepG-induced lung injury via stathmin-dependent control of MT assembly.

Pathophysiology and biomarkers of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is defined as an acute-onset, progressive, hypoxic condition with radiographic bilateral lung infiltration, which develops after several diseases or injuries, and is not derived from hydrostatic pulmonary edema. One specific pathological finding of ARDS is diffuse alveolar damage. In 2012, in an effort to increase diagnostic specificity, a revised definition of ARDS was published in JAMA. However, no new parameters or biomarkers were adopted by the revised definition. Discriminating between ARDS and other similar diseases is critically important; however, only a few biomarkers are currently available for diagnostic purposes. Furthermore, predicting the severity, response to therapy, or outcome of the illness is also important for developing treatment strategies for each patient. However, the PaO₂/FIO₂ ratio is currently the sole clinical parameter used for this purpose. In parallel with progress in understanding the pathophysiology of ARDS, various humoral factors induced by inflammation and molecules derived from activated cells or injured tissues have been shown as potential biomarkers that may be applied in clinical practice. In this review, the current understanding of the basic pathophysiology of ARDS and associated candidate biomarkers will be discussed.

Barrier enhancing signals in pulmonary edema

Increased endothelial permeability and reduction of alveolar liquid clearance capacity are two leading pathogenic mechanisms of pulmonary edema, which is a major complication of acute lung injury, severe pneumonia, and acute respiratory distress syndrome, the pathologies characterized by unacceptably high rates of morbidity and mortality. Besides the success in protective ventilation strategies, no efficient pharmacological approaches exist to treat this devastating condition. Understanding of fundamental mechanisms involved in regulation of endothelial permeability is essential for development of barrier protective therapeutic strategies. Ongoing studies characterized specific barrier protective mechanisms and identified intracellular targets directly involved in regulation of endothelial permeability. Growing evidence suggests that, although each protective agonist triggers a unique pattern of signaling pathways, selected common mechanisms contributing to endothelial barrier protection may be shared by different barrier protective agents. Therefore, understanding of basic barrier protective mechanisms in pulmonary endothelium is essential for selection of optimal treatment of pulmonary edema of different etiology. This article focuses on mechanisms of lung vascular permeability, reviews major intracellular signaling cascades involved in endothelial monolayer barrier preservation and summarizes a current knowledge regarding recently identified compounds which either reduce pulmonary endothelial barrier disruption and hyperpermeability, or reverse preexisting lung vascular barrier compromise induced by pathologic insults.

Role of B-type natriuretic peptide as a marker of mortality in acute kidney injury patients treated with continuous renal replacement therapy

OBJECTIVES

Acute kidney injury (AKI) treated with continuous renal replacement therapy (CRRT) is associated with poor outcome. Plasma B-type natriuretic peptide (BNP) is a biomarker related to fluid volume overload, and is elevated in AKI patients. The purpose of the study was to assess whether BNP levels at the time of starting CRRT could be used as a predictor of mortality in patients with AKI receiving CRRT.

METHODS

We conducted a prospective observational cohort study enrolling 149 patients with AKI receiving CRRT. The primary outcome was mortality during CRRT.

RESULTS

The median BNP level of 84 (56.3%) patients who expired was significantly higher than that of those who survived (1812.5 vs. 475.0 pg/mL; p = 0.01). Receiver operating characteristic curves demonstrated BNP levels as a predictor of mortality during CRRT with an area under the curve of 0.77 (p = 0.000), and the optimal threshold for BNP was 1054 pg/mL. Patients with BNP levels above 1054 pg/mL had a significantly higher mortality (76.6 vs. 34.7%; p = 0.01).

CONCLUSION

Elevated BNP level is associated with mortality in patients with AKI receiving CRRT.

Serum levels of N-terminal proB-type natriuretic peptide in mechanically ventilated critically ill patients--relation to tidal volume size and development of acute respiratory distress syndrome

Background

Serum levels of N–terminal proB–type natriuretic peptide (NT–proBNP) are elevated in patients acute respiratory distress syndrome (ARDS). Recent studies showed a lower incidence of acute cor pulmonale in ARDS patients ventilated with lower tidal volumes. Consequently, serum levels of NT–proBNP may be lower in these patients.

We investigated the relation between serum levels of NT–proBNP and tidal volumes in critically ill patients without ARDS at the onset of mechanical ventilation.

Methods

Secondary analysis of a randomized controlled trial of lower versus conventional tidal volumes in patients without ARDS. NT–pro BNP were measured in stored serum samples. Serial serum levels of NT–pro BNP were analyzed controlling for acute kidney injury, cumulative fluid balance and presence of brain injury. The primary outcome was the effect of tidal volume size on serum levels of NT–proBNP. Secondary outcome was the association with development of ARDS.

Results

Samples from 150 patients were analyzed. No relation was found between serum levels of NT–pro BNP and tidal volume size. However, NT-proBNP levels were increasing in patients who developed ARDS. In addition, higher levels were observed in patients with acute kidney injury, and in patients with a more positive cumulative fluid balance.

Conclusion

Serum levels of NT–proBNP are independent of tidal volume size, but are increasing in patients who develop ARDS.

Protective effects of recombinant human brain natriuretic peptide against LPS-Induced acute lung injury in dogs

BACKGROUND

Acute lung injury (ALI) is a common component of systemic inflammatory disease without more effective treatments. However, recent studies have demonstrated that the recombinant human brain natriuretic peptide (rhBNP) has anti-inflammatory effects. Therefore, we found that rhBNP could prevent lipopolysaccharide (LPS)-induced acute lung injury in a dog model.

METHODS

Dogs were injected with LPS and subjected to continuous intravenous infusion (CIV) of saline solution or rhBNP. We detected the protective effects of rhBNP by histological examination and determination of serum cytokine levels and lung myeloperoxidase (MPO) activity and malondialdehyde (MDA) activity. Histological examination indicated marked inflammation, edema and hemorrhage in lung tissue taken 12h after rhBNP treatment compared with tissue from dogs which received saline treatment after LPS injection. LPS injection induced cytokine (IL-6 and TNF-α) secretion and lung MPO and MDA activities, which were also attenuated by rhBNP treatment.

RESULTS

Inductions of IL-6 and TNF-α were significantly attenuated in the L-rhBNP and the H-rhBNP groups. The ratios of the L-rhBNP group and H-rhBNP group were lower than that in the lung injury group. Furthermore, MPO and MDA activities were significantly lower in the H-rhBNP group compared to those in the LI group.

CONCLUSION

Our data indicate that rhBNP treatment may exert protective effects and may be associated with adjusting endogenous antioxidant enzymes. Thus, rhBNP may be considered as a therapeutic agent for various clinical conditions involving lung injury by sepsis.

The prevalence and impact of mortality of the acute respiratory distress syndrome on admissions of patients with ischemic stroke in the United States

PURPOSE

To determine the epidemiology of the acute respiratory distress syndrome (ARDS) and impact on in-hospital mortality in admissions of patients with acute ischemic stroke (AIS) in the United States.

METHODS

Retrospective cohort study of admissions with a diagnosis of AIS and ARDS from 1994 to 2008 identified through the Nationwide Inpatient Sample.

RESULTS

During the 15-year study period, we found 55 58 091 admissions of patients with AIS. The prevalence of ARDS in admissions of patients with AIS increased from 3% in 1994 to 4% in 2008 (P < .001). The ARDS was more common among younger men, nonwhites, and associated with history of congestive heart failure, hypertension, chronic obstructive pulmonary disease, renal failure, chronic liver disease, systemic tissue plasminogen activator, craniotomy, angioplasty or stent, sepsis, and multiorgan failures. Mortality due to AIS and ARDS decreased from 8% in 1994 to 6% in 2008 (P < .001) and 55% in 1994 to 45% in 2008 (P < .001), respectively. The ARDS in AIS increased in-hospital mortality (odds ratio, 14; 95% confidence interval, 13.5-14.3). A significantly higher length of stay was seen in admissions of patients with AIS having ARDS.

CONCLUSION

Our analysis demonstrates that ARDS is rare after AIS. Despite an overall significant reduction in mortality after AIS, ARDS carries a higher risk of death in this patient population.

Impact of acute lung injury and acute respiratory distress syndrome after traumatic brain injury in the United States

BACKGROUND

Traumatic brain injury (TBI) is a major cause of disability, morbidity, and mortality. The effect of the acute respiratory distress syndrome and acute lung injury (ARDS/ALI) on in-hospital mortality after TBI remains controversial.

OBJECTIVE

To determine the epidemiology of ARDS/ALI, the prevalence of risk factors, and impact on in-hospital mortality after TBI in the United States.

METHODS

Retrospective cohort study of admissions of adult patients>18 years with a diagnosis of TBI and ARDS/ALI from 1988 to 2008 identified through the Nationwide Inpatient Sample.

RESULTS

During the 20-year study period, the prevalence of ARDS/ALI increased from 2% (95% confidence interval [CI], 2.1%-2.4%) in 1988 to 22% (95% CI, 21%-22%) in 2008 (P<.001). ARDS/ALI was more common in younger age; males; white race; later year of admission; in conjunction with comorbidities such as congestive heart failure, hypertension, chronic obstructive pulmonary disease, chronic renal and liver failure, sepsis, multiorgan dysfunction; and nonrural, medium/large hospitals, located in the Midwest, South, and West continental US location. Mortality after TBI decreased from 13% (95% CI, 12%-14%) in 1988 to 9% (95% CI, 9%-10%) in 2008 (P<.001). ARDS/ALI-related mortality after TBI decreased from 33% (95% CI, 33%-34%) in 1988 to 28% (95% CI, 28%-29%) in 2008 (P<.001). Predictors of in-hospital mortality after TBI were older age, male sex, white race, cancer, chronic kidney disease, hypertension, chronic liver disease, congestive heart failure, ARDS/ALI, and organ dysfunctions.

CONCLUSION

Our analysis demonstrates that ARDS/ALI is common after TBI. Despite an overall reduction of in-hospital mortality, ARDS/ALI carries a higher risk of in-hospital death after TBI.

Prevalence of acute lung injury among medical patients in the emergency department

BACKGROUND

Acute lung injury (ALI) affects an estimated 190,000 persons per year in U.S. intensive care units (ICUs), but little is known about its prevalence in the emergency department (ED).

OBJECTIVES

The objective was to describe the prevalence of ALI among mechanically ventilated adult nontrauma patients in the ED. The hypothesis was that the prevalence of ALI in adult ED patients would be low.

METHODS

This was a retrospective cohort study of admitted nontrauma patients presenting to an academic ED. Two trained investigators abstracted data from patient records using a standardized form. The use of mechanical ventilation in the ED was identified in two phases. First, all ED patients were screened for the current procedural terminology (CPT) code for endotracheal intubation (CPT 31500) from January 1, 2003, to December 31, 2006. Second, each patient record was reviewed to verify the use of mechanical ventilation. ALI was defined in accordance with a modified version of the American-European Consensus Conference criteria as: 1) hypoxemia defined as PaO(2) /FiO(2) ratio ≤300 mm Hg on all arterial blood gases (ABGs) in the ED and the first 24 hours of admission, 2) the presence of bilateral infiltrates on chest radiograph, and 3) the absence of left atrial hypertension. Data are presented in absolute numbers and percentages. Interobserver agreement was evaluated using the kappa statistic.

RESULTS

Of the 552 patients who received mechanical ventilation in the ED and were subsequently admitted, a total of 134 (24.3%, 95% confidence interval [CI] = 20.8% to 28.0%) met hypoxemia criteria. Of these, 34 had evidence of left atrial hypertension, 52 did not have chest radiograph findings consistent with ALI, and two did not have a chest radiograph performed; the remaining 46 met ALI criteria. An additional two patients who died in the ED had clinical evidence of ALI. Thus, 48 of 552, or 8.7% (95% CI = 6.6% to 11.3%), met criteria for ALI. The kappa value for determination of ALI was 0.84 (95% CI = 0.54 to 1.0).

CONCLUSIONS

The prevalence of ALI was nearly 9% in adult nontrauma patients receiving mechanical ventilation in the ED. Further study is required to determine which types of patients present to the ED with ALI, the extent to which lung protective ventilation is used, and the need for ED ventilator management algorithms.

Non-cardiogenic pulmonary edema complicating electroconvulsive therapy: short review of the pathophysiology and diagnostic approach

Acute pulmonary edema complicating electroconvulsive therapy is an extremely uncommon event that has rarely been described in the literature. Different theories, including one suggesting a cardiogenic component, have been proposed to explain its genesis. The present report describes a classic presentation of this condition with review of its potential mechanisms and diagnostic approach. After successful completion of a session of electroconvulsive therapy, a 42-year-old woman with major depressive disorder developed acute systemic high blood pressure, shortness of breath, and hemoptysis. A chest radiograph demonstrated diffuse bilateral pulmonary infiltrates. Initially cardiogenic pulmonary edema was presumed, but an extensive diagnostic work-up demonstrated normal systolic and diastolic left ventricular function, and with only supportive measures, a complete clinical and radiographic recovery was achieved within 48 hours. The present case does not support any cardiogenic mechanism in the genesis of this condition.

Copeptin in the assessment of acute lung injury and cardiogenic pulmonary edema

BACKGROUNDS

Copeptin has been studied as an excellent predictor of outcome in a variety of diseases, its value is even superior to that of B-type natriuretic peptide (BNP) in heart failure, but little is known about its characteristics in acute respiratory distress syndrome (ARDS)/acute lung injury (ALI). We sought to assess the diagnostic and prognostic value of copeptin together with N-terminal pro-BNP (NT-proBNP) in patients with ARDS/ALI or cardiogenic pulmonary edema (CPE).

METHODS

Measurement of copeptin and NT-proBNP levels in plasma from 121 consecutive patients with either ARDS/ALI or CPE enrolled in a prospective single center study.

RESULTS

In a derivation cohort of 87 patients with ARDS/ALI and 34 patients with CPE, a copeptin threshold of >40.11 pmol/L provided a specificity of 88.2% and a sensitivity of 60.9% for the diagnosis of ARDS/ALI, a NT-proBNP cut point of <2813 pg/ml had a specificity of 79.4% and sensitivity of 65.5% for it. Multivariate Cox regression analysis showed that copeptin was the strongest predictor for mortality in patients with ARDS/ALI [hazard ratio (HR) = 4.72, P < 0.001] and CPE (HR = 3.52, P = 0.019), the association between increasing copeptin and death was statistically significant in patients with ARDS/ALI (HR = 2.64, P = 0.035) and patients with CPE (HR = 1.62, P = 0.029).

CONCLUSION

Copeptin of >40.11 pmol/L had a high specificity for the diagnosis of ARDS/ALI in patients presenting with ARDS/ALI or CPE. Compared to NT-proBNP, copeptin was a stronger prognostic marker for short-term mortality.

Cardiac biomarkers in the intensive care unit

Cardiac biomarkers (CB) were first developed for assisting the diagnosis of cardiac events, especially acute myocardial infarction. The discoveries of other CB, the better understanding of cardiac disease process and the advancement in detection technology has pushed the applications of CB beyond the 'diagnosis' boundary. Not only the measurements of CB are more sensitive, the applications have now covered staging of cardiac disease, timing of cardiac events and prognostication. Further, CB have made their way to the intensive care setting where their uses are not just confined to cardiac related areas. With the better understanding of the CB properties, CB can now help detecting various acute processes such as pulmonary embolism, sepsis-related myocardial depression, acute heart failure, renal failure and acute lung injury. This article discusses the properties and the uses of common CB, with special reference to the intensive care setting. The potential utility of "multimarkers" approach and microRNA as the future CB are also briefly discussed.

[Cardiac biomarkers in the critically ill]

Cardiac biomarkers in intensive care medicine are an excellent complement to existing clinical and diagnostic information in specific diseases. Due to their lack of specificity, the diagnostic properties of common cardiac biomarkers, such as natriuretic peptides and cardiac troponins, remain ambiguous, while their prognostic value has already been proven. In addition, there are several promising new biomarkers that might contribute to a "multimarker strategy" in the critically ill patient in the future, but further evaluation is still required.

Decision support tool for early differential diagnosis of acute lung injury and cardiogenic pulmonary edema in medical critically ill patients

BACKGROUND

At the onset of acute hypoxic respiratory failure, critically ill patients with acute lung injury (ALI) may be difficult to distinguish from those with cardiogenic pulmonary edema (CPE). No single clinical parameter provides satisfying prediction. We hypothesized that a combination of those will facilitate early differential diagnosis.

METHODS

In a population-based retrospective development cohort, validated electronic surveillance identified critically ill adult patients with acute pulmonary edema. Recursive partitioning and logistic regression were used to develop a decision support tool based on routine clinical information to differentiate ALI from CPE. Performance of the score was validated in an independent cohort of referral patients. Blinded post hoc expert review served as gold standard.

RESULTS

Of 332 patients in a development cohort, expert reviewers (κ, 0.86) classified 156 as having ALI and 176 as having CPE. The validation cohort had 161 patients (ALI = 113, CPE = 48). The score was based on risk factors for ALI and CPE, age, alcohol abuse, chemotherapy, and peripheral oxygen saturation/Fio(2) ratio. It demonstrated good discrimination (area under curve [AUC] = 0.81; 95% CI, 0.77-0.86) and calibration (Hosmer-Lemeshow [HL] P = .16). Similar performance was obtained in the validation cohort (AUC = 0.80; 95% CI, 0.72-0.88; HL P = .13).

CONCLUSIONS

A simple decision support tool accurately classifies acute pulmonary edema, reserving advanced testing for a subset of patients in whom satisfying prediction cannot be made. This novel tool may facilitate early inclusion of patients with ALI and CPE into research studies as well as improve and rationalize clinical management and resource use.

Opposite effects of ANP receptors in attenuation of LPS-induced endothelial permeability and lung injury

Atrial natriuretic peptide (ANP) has been recently identified as a modulator of acute lung injury (ALI) induced by pro-inflammatory agonists. While previous studies tested effects of exogenous ANP administration, the role of endogenous ANP in the course of ALI remains unexplored. This study examined regulation of ANP and its receptors NPR-A, NPR-B and NPR-C by LPS and involvement of ANP receptors in the modulation of LPS-induced lung injury. Primary cultures of human pulmonary endothelial cells (EC) were used in the in vitro tests. Expression of ANP and its receptors was determined by quantitative RT-PCR analysis. Agonist-induced cytoskeletal remodeling was evaluated by immunofluorescence staining, and EC barrier function was characterized by measurements of transendothelial electrical resistance. In the murine model of ALI, LPS-induced lung injury was assessed by measurements of protein concentration and cell count in bronchoalveolar lavage fluid (BAL). LPS stimulation significantly increased mRNA expression levels of ANP and NPR-A in pulmonary EC. Pharmacological inhibition of NPR-A augmented LPS-induced EC permeability and blocked barrier protective effects of exogenous ANP on LPS-induced intercellular gap formation. In contrast, pharmacological inhibition of ANP clearance receptor NPR-C significantly attenuated LPS-induced barrier disruptive effects. Administration of NPR-A inhibitor in vivo exacerbated LPS-induced lung injury, whereas inhibition of NPR-C suppressed LPS-induced increases in BAL cell count and protein content. These results demonstrate for the first time opposite effects of NPR-A and NPR-C in the modulation of ALI and suggest a compensatory protective mechanism of endogenous ANP in the maintenance of lung vascular permeability in ALI.

Cardiac biomarkers in the critically ill

Cardiac biomarkers have well-established roles in acute coronary syndrome and congestive heart failure. In many instances, the detection of cardiac biomarkers may aid in the diagnosis and risk assessment of critically ill patients. Despite increasing interest in the use of cardiac biomarkers in noncardiac critical illness, no clear consensus exists on how and in which settings markers should be measured. This article briefly describes what constitutes an ideal biomarker and focuses on those that have been most well studied in critical illness, specifically troponin, the natriuretic peptides, and heart-type fatty acid-binding protein.

Diagnostic utility of C-reactive protein combined with brain natriuretic peptide in acute pulmonary edema: a cross sectional study

INTRODUCTION

Discriminating acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) from cardiogenic pulmonary edema (CPE) using the plasma level of brain natriuretic peptide (BNP) alone remains controversial. The aim of this study was to determine the diagnostic utility of combination measurements of BNP and C-reactive protein (CRP) in critically ill patients with pulmonary edema.

METHODS

This was a cross-sectional study. BNP and CRP data from 147 patients who presented to the emergency department due to acute respiratory failure with bilateral pulmonary infiltrates were analyzed.

RESULTS

There were 53 patients with ALI/ARDS, 71 with CPE, and 23 with mixed edema. Median BNP and CRP levels were 202 (interquartile range 95-439) pg/mL and 119 (62-165) mg/L in ALI/ARDS, and 691 (416-1,194) pg/mL (p < 0.001) and 8 (2-42) mg/L (p < 0.001) in CPE. BNP or CRP alone offered good discriminatory performance (C-statistics 0.831 and 0.887), but the combination offered greater one [C-statistics 0.931 (p < 0.001 versus BNP) (p = 0.030 versus CRP)]. In multiple logistic-regression, BNP and CRP were independent predictors for the diagnosis after adjusting for other variables.

CONCLUSIONS

Measurement of CRP is useful as well as that of BNP for distinguishing ALI/ARDS from CPE. Furthermore, a combination of BNP and CRP can provide higher accuracy for the diagnosis.

Clinical significance of elevated B-type natriuretic peptide in patients with acute lung injury with or without right ventricular dilatation: an observational cohort study

Background

The primary objective of this study was to examine levels of B-type natriuretic peptide (BNP) in mechanically ventilated patients with acute lung injury and to test whether the level of BNP would be higher in patients with right ventricular dilatation and would predict mortality.

Methods

This was a prospective, observational cohort study of 42 patients conducted in the intensive care unit of a tertiary care university hospital. BNP was measured and transthoracic echocardiography was performed within 48 hours of the onset of acute lung injury. The left ventricular systolic and diastolic function, right ventricular systolic function, and cardiac output were assessed. BNP was compared in patients with and without right ventricular dilatation, as well as in survivors versus nonsurvivors.

Results

BNP was elevated in mechanically ventilated patients with acute lung injury (median 420 pg/ml; 25-75% interquartile range 156-728 pg/ml). There was no difference between patients with and without right ventricular dilatation (420 pg/ml, 119-858 pg/ml vs. 387 pg/ml, 156-725 pg/ml; p = 0.96). There was no difference in BNP levels between the patients who died and those who survived at 30 days (420 pg/ml, 120-728 pg/ml vs. 385 pg/ml, 159-1070 pg/ml; p = 0.71).

Conclusions

In patients with acute lung injury the level of BNP is increased, but there is no difference in the BNP level between patients with and without right ventricular dilatation. Furthermore, BNP level is not predictive of mortality in this population.

B-type Natriuretic Peptide: Diagnostic and Therapeutic Applications in Infants and Children

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Peptides of the natriuretic system produced through recombinant DNA technology are now available for clinical use including both atrial natriuretic peptide (ANP) and brain-type natriuretic peptide (BNP). Assays of BNP are available and may be used for both diagnostic and prognostic purposes in various clinical scenarios. The basic physiology of the natriuretic peptide system is presented, applications of BNP monitoring as a diagnostic tool are reviewed, and reports regarding the use of recombinant BNP in the pediatric population are discussed.

Atrial natriuretic peptide attenuates LPS-induced lung vascular leak: role of PAK1

Increased levels of atrial natriuretic peptide (ANP) in the models of sepsis, pulmonary edema, and acute respiratory distress syndrome (ARDS) suggest its potential role in the modulation of acute lung injury. We have recently described ANP-protective effects against thrombin-induced barrier dysfunction in pulmonary endothelial cells (EC). The current study examined involvement of the Rac effector p21-activated kinase (PAK1) in ANP-protective effects in the model of lung vascular permeability induced by bacterial wall LPS. C57BL/6J mice or ANP knockout mice (Nppa(-/-)) were treated with LPS (0.63 mg/kg intratracheal) with or without ANP (2 μg/kg iv). Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count, Evans blue extravasation, and lung histology. Endothelial barrier properties were assessed by morphological analysis and measurements of transendothelial electrical resistance. ANP treatment stimulated Rac-dependent PAK1 phosphorylation, attenuated endothelial permeability caused by LPS, TNF-α, and IL-6, decreased LPS-induced cell and protein accumulation in bronchoalveolar lavage fluid, and suppressed Evans blue extravasation in the murine model of acute lung injury. More severe LPS-induced lung injury and vascular leak were observed in ANP knockout mice. In rescue experiments, ANP injection significantly reduced lung injury in Nppa(-/-) mice caused by LPS. Molecular inhibition of PAK1 suppressed the protective effects of ANP treatment against LPS-induced lung injury and endothelial barrier dysfunction. This study shows that the protective effects of ANP against LPS-induced vascular leak are mediated at least in part by PAK1-dependent signaling leading to EC barrier enhancement. Our data suggest a direct role for ANP in endothelial barrier regulation via modulation of small GTPase signaling.

The interpretation of brain natriuretic peptide in critical care patients; will it ever be useful?

The measurement of B-type natriuretic peptide (BNP) is recommended for the diagnosis of decompensated heart failure, the prognosis of chronic heart failure is worse if BNP is increased and studies suggest that BNP is useful to guide therapy. A study by Di Somma and colleagues adds to the body of evidence showing that patients with a marked decrease in BNP concentrations during their hospital admission are less likely to be readmitted with a further adverse cardiac event than patients in whom BNP fails to decrease. However, the wider interpretation of BNP concentrations in critically ill patients with other conditions remains uncertain.

High circulating N-terminal pro-B-type natriuretic peptide is associated with greater systolic cardiac dysfunction and nonresponsiveness to fluids in septic vs nonseptic critically ill patients

PURPOSE

It is still unclear whether circulating levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) reflect cardiac filling and function in the critically ill patient, particularly during sepsis and a proinflammatory response that may induce NT-proBNP release from the heart.

MATERIALS AND METHODS

We prospectively evaluated the value of NT-proBNP as a marker of cardiac loading, function, and response to fluid loading in 18 septic and 68 nonseptic, critically ill patients in the intensive care unit of a university medical center. Transpulmonary thermal dilution and pressure measurements were done, and plasma NT-proBNP was determined before and after colloid fluid loading.

RESULTS

Compared with nonseptic patients, NT-proBNP plasma levels were higher and systolic cardiac function indices were lower in patients with sepsis than those without sepsis. N-terminal pro-B-type natriuretic peptide best related, from all hemodynamic parameters before and after fluid loading, to systolic cardiac function (rather than diastolic filling) variables, independently of confounders such as renal dysfunction (judged from serum creatinine). In addition, a high NT-proBNP (>3467 pg/mL) predicted absence of fluid responsiveness in sepsis only.

CONCLUSIONS

Our data suggest that an increased circulating NT-proBNP plasma level is an independent marker of greater systolic cardiac dysfunction, irrespective of filling status, and is a better predictor of fluid nonresponsiveness in septic vs nonseptic, critically ill patients.

Use of B-type natriuretic peptide in critically ill patients

B-type natriuretic peptide (BNP) is increasingly used in emergency departments to assess the cause of acute dyspnea and in cardiology to follow treatments and predict outcome. It is increasingly used in the intensive care unit in situations such as respiratory failure (acute pulmonary edema, exacerbation of chronic obstructive pulmonary disease and difficult weaning from ventilator) or when pulmonary embolism is suspected. BNP has also been used to assess alteration of myocardial function in sepsis. Plasma BNP is very high in septic-shock patients (>1000 pg/ml), which is suggested to relate to both myocardial stretch and to an alteration in one of the BNP clearance pathways. Whether BNP at admission or at discharge may predict outcome requires further investigation.

Cardiovascular biomarkers in the ICU

PURPOSE OF REVIEW

Natriuretic peptides are markers of heart failure and/or cardiac dysfunction that provide useful diagnostic and prognostic information in patients with dyspnea and/or respiratory failure in the emergency department. Cardiac troponins (cTn) have markedly simplified the diagnosis of myocardial infarction. In critically ill patients, conditions like coexisting organ dysfunction multiorgan involvement or altered synthesis/clearance may confound interpretation of designated biomarkers, including natriuretic peptides and cTn. This review focuses on recently published articles relating to the use of natriuretic peptides and cTn in critically ill patients.

RECENT FINDINGS

One new study addresses diagnostic utility of B-type natriuretic peptide to distinguish low-pressure pulmonary edema (acute lung injury/acute respiratory distress syndrome) from high-pressure (cardiogenic) pulmonary edema. Other studies highlight the prognostic value of natriuretic peptides either in unselected and general noncardiac ICU patients and reveal an important reason for elevated B-type natriuretic peptide levels in septic shock.Interesting data focusing on diagnostic and prognostic ability of systematic cTn screening measurements in ICU patients became available.

SUMMARY

Recent studies confirm the excellent prognostic value of natriuretic peptide measurements in ICU patients. Diagnostic properties of natriuretic peptide in ICU patients still remain ambiguous and require further evaluation. Systematic screening with cTn reveals more myocardial infarctions and provides important prognostic information.

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.

What is the value of B-type natriuretic peptide testing for diagnosis, prognosis or monitoring of critically ill adult patients in intensive care?

BACKGROUND

B-natriuretic peptide (BNP) and aminoterminal proBNP (NT-proBNP) are clinically useful for the diagnosis of decompensated heart failure and for prognosis in heart failure and acute coronary syndromes. Clinical use of these biomarkers in critically ill patients being treated in intensive care is not well established.

METHODS

This is a narrative review of evidence identified searching MEDLINE with the strategy [(BNP OR NT-proBNP) AND (critical illness AND intensive care)]. Seven primary reports and two narrative reviews were retrieved. For completeness, literature from each of the following searches was reviewed: [(BNP OR NT-proBNP) AND (critical illness)] and [(BNP OR NT-proBNP) AND (intensive care)].

RESULTS

Primary literature used BNP and NT-proBNP for diagnosis, prognosis and monitoring. For diagnosis of acute lung injury in unselected intensive care patients and for diagnosis of heart failure in trauma patients, the biomarkers had low sensitivity and are of modest use. BNP and NT-proBNP were found to have a significant ability to prognosticate adverse outcomes in critically ill patients. A single paper examined the use of BNP as a non-invasive replacement for pulmonary capillary wedge pressure, finding little value. The impact of renal insufficiency on the markers was noted as a confounder in most studies. In the secondary searches, some preliminary data suggested a possible role for the natriuretic peptides in exclusion of a cardiac cause for certain conditions among intensive care unit (ICU) patients. However, the general findings were that the performance of BNP and NT-proBNP is unimpressive among ICU patients.

CONCLUSIONS

Currently, utilization of BNP and NT-proBNP does not appear to provide much useful information or have a substantial role in the care of critically ill patients in intensive care.

Plasma from stored packed red blood cells and MHC class I antibodies causes acute lung injury in a 2-event in vivo rat model

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion death. We hypothesize that TRALI requires 2 events: (1) the clinical condition of the patient and (2) the infusion of antibodies against MHC class I antigens or the plasma from stored blood. A 2-event rat model was developed with saline (NS) or endotoxin (LPS) as the first event and the infusion of plasma from packed red blood cells (PRBCs) or antibodies (OX18 and OX27) against MHC class I antigens as the second event. ALI was determined by Evans blue dye leak from the plasma to the bronchoalveolar lavage fluid (BALF), protein and CINC-1 concentrations in the BALF, and the lung histology. NS-treated rats did not evidence ALI with any second events, and LPS did not cause ALI. LPS-treated animals demonstrated ALI in response to plasma from stored PRBCs, both prestorage leukoreduced and unmodified, and to OX18 and OX27, all in a concentration-dependent fashion. ALI was neutrophil (PMN) dependent, and OX18/OX27 localized to the PMN surface in vivo and primed the oxidase of rat PMNs. We conclude that TRALI is the result of 2 events with the second events consisting of the plasma from stored blood and antibodies that prime PMNs.

The use of B-type natriuretic peptides in the intensive care unit

B-type natriuretic peptide levels are quantitative markers of cardiac stress and heart failure that summarize the extent of systolic and diastolic left ventricular dysfunction, valvular dysfunction, and right ventricular dysfunction. Initial observational pilot studies have addressed 7 potential indications in the intensive care unit: identification of cardiac dysfunction, diagnosis of hypoxic respiratory failure, risk stratification in severe sepsis and septic shock, evaluation of patients with shock, estimation of invasive measurements, weaning from mechanical ventilation, as well as perioperative and postoperative risk prediction. Although additional studies are required to better define the clinical utility of B-type natriuretic peptide values in the intensive care unit, current data suggest that the diagnosis of hypoxic respiratory failure and timing of extubation seem to be the most promising indications.

Acute respiratory distress syndrome 40 years later: time to revisit its definition

OBJECTIVE

Acute respiratory distress syndrome is a common disorder associated with significant mortality and morbidity. The aim of this article is to critically evaluate the definition of acute respiratory distress syndrome and examine the impact the definition has on clinical practice and research.

DATA SOURCES

Articles from a MEDLINE search (1950 to August 2007) using the Medical Subject Heading respiratory distress syndrome, adult, diagnosis, limited to the English language and human subjects, their relevant bibliographies, and personal collections, were reviewed.

DATA SYNTHESIS

The definition of acute respiratory distress syndrome is important to researchers, clinicians, and administrators alike. It has evolved significantly over the last 40 years, culminating in the American-European Consensus Conference definition, which was published in 1994. Although the American-European Consensus Conference definition is widely used, it has some important limitations that may impact on the conduct of clinical research, on resource allocation, and ultimately on the bedside management of such patients. These limitations stem partially from the fact that as defined, acute respiratory distress syndrome is a heterogeneous entity and also involve the reliability and validity of the criteria used in the definition. This article critically evaluates the American-European Consensus Conference definition and its limitations. Importantly, it highlights how these limitations may contribute to clinical trials that have failed to detect a potential true treatment effect. Finally, recommendations are made that could be considered in future definition modifications with an emphasis on the significance of accurately identifying the target population in future trials and subsequently in clinical care.

CONCLUSION

How acute respiratory distress syndrome is defined has a significant impact on the results of randomized, controlled trials and epidemiologic studies. Changes to the current American-European Consensus Conference definition are likely to have an important role in advancing the understanding and management of acute respiratory distress syndrome.

The accuracy of natriuretic peptides (brain natriuretic peptide and N-terminal pro-brain natriuretic) in the differentiation between transfusion-related acute lung injury and transfusion-related circulatory overload in the critically ill

BACKGROUND

The diagnostic workup of transfusion-related acute lung injury (TRALI) requires an exclusion of transfusion-associated circulatory overload (TACO). Brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic (NT-pro-BNP) accurately diagnosed TACO in preliminary studies that did not include patients with TRALI.

STUDY DESIGN AND METHODS

In this prospective cohort study, two critical care experts blinded to serum levels of BNP and NT-pro-BNP determined the diagnosis of TRALI, TACO, and possible TRALI based on the consensus conference definitions. The accuracy of BNP and NT-pro-BNP was assessed based on the area under the receiver operating curve (AUC).

RESULTS

Of 115 patients who developed acute pulmonary edema after transfusion, 34 were identified with TRALI, 31 with possible TRALI, and 50 with TACO. Median BNP was 375 pg per mL (interquartile range [IQR], 123 to 781 pg/mL) in TRALI, 446 pg per mL (IQR, 128 to 743 pg/mL) in possible TRALI, and 559 pg per mL (IQR, 288 to 1348 pg/mL) in TACO patients (p = 0.038). The NT-pro-BNP levels among patients with TRALI, possible TRALI, and TACO differed significantly with a median value of 1559 pg per mL (IQR, 629 to 5114 pg/mL), 2349 pg/mL (IQR, 919 to 4610 pg/mL), and 5197 pg/mL (IQR, 1695 to 15,714 pg/mL; p = 0.004), respectively. The accuracy of BNP and NT-pro-BNP to diagnose TACO was moderate with an AUC of 0.63 (95% confidence interval [CI], 0.51-0.74) and 0.70 (95% CI, 0.59 to 0.80).

CONCLUSIONS

Natriuretic peptides are of limited diagnostic value in a differential diagnosis of pulmonary edema after transfusion in the critically ill patients.

Pulmonary transfusion reactions

BACKGROUND

In recent years, pulmonary transfusion reactions have gained increasing importance as serious adverse transfusion events.

METHODS

Review of the literature.

RESULTS

Pulmonary transfusion reactions are not extremely rare and, according to hemovigilance data, important causes of transfusion-induced major morbidity and death. They can be classified as primary with predominant pulmonary injury and secondary as part of another transfusion reaction. Primary reactions include transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO) and transfusion-associated dyspnea (TAD). Secondary pulmonary reactions are often observed in the wake of hemolytic transfusion reactions, hypotensive/anaphylactic reactions, and transfusion-transmitted bacterial infections.

CONCLUSION

Knowledge and careful management of cases of pulmonary transfusion reactions are essential for correct reporting to blood services and hemovigilance systems. Careful differentiation between TRALI and TACO is important for taking adequate preventive measures.

Plasma B-type natriuretic peptide monitoring to evaluate cardiovascular function prior to organ procurement in patients with brain death

BACKGROUND

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Assays of plasma concentrations of B-type natriuretic peptide (BNP) may have a diagnostic role in evaluating myocardial function. We present our experience with BNP monitoring to assess myocardial function after the proclamation of brain death in potential organ donors.

METHODS

After the proclamation of brain death and prior to organ donation, a plasma BNP or aminoterminal pro-BNP level was obtained. Additional information from the donor included shortening fraction (SF) or ejection fraction, central venous pressure (CVP) reading, and renal function including blood urea nitrogen and creatinine. When available, data from the pulmonary artery (PA) catheter including pulmonary capillary wedge pressure (PCWP) and cardiac index were also collected.

RESULTS

The cohort for the study included eight patients (age range: 6 months to 21 years). The diagnosis of brain death by clinical or radiological examination had been completed in all patients and the patients were scheduled for organ procurement. Myocardial contractility as assessed by echocardiogram using SF was within normal limits. The CVP varied from 7 to 12 mmHg (9 +/- 2) and the PCWP was 10-11 mmHg in the two patients who had PA catheters in place. No patient was receiving inotropic medications. In five of the six patients, the BNP value was above the upper limit of normal (100 pg x ml(-1)). In two patients, an NT-pro-BNP value was obtained and found to be higher than the upper limits of normal (450 pg x ml(-1)). All eight patients were acceptable cardiac donors and the transplanted hearts functioned without difficulty in the recipients.

CONCLUSIONS

Assays of plasma BNP concentrations have been shown to be helpful in differentiating myocardial dysfunction from primary lung disease in both the adult and pediatric population. However, our data demonstrate that mechanisms other than myocardial performance may regulate BNP levels in patients with severe central nervous system injury who progress to brain death. Our preliminary data suggest that these assays appear to be of limited value in assessing myocardial performance in this population.

Prognostic value of plasma N-terminal probrain natriuretic peptide levels in the acute respiratory distress syndrome

OBJECTIVE

Patients with acute respiratory distress syndrome suffer from profound cardiac and pulmonary derangement, including right ventricular strain and noncardiogenic pulmonary edema, which may potentially alter concentrations of cardiac natriuretic peptides. We sought to determine whether N-terminal probrain natriuretic peptide (NT-proBNP) levels are elevated in acute respiratory distress syndrome and whether they can serve as a marker of prognosis in this setting.

DESIGN

Prospective study.

SETTING

Tertiary-care academic medical center.

PATIENTS

One hundred seventy-seven acute respiratory distress syndrome subjects enrolled in a prospective intensive care unit cohort.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

NT-proBNP was measured from blood taken within 48 hrs of acute respiratory distress syndrome onset. Patients were followed for the primary outcome of 60-day mortality and secondary outcomes of organ dysfunction and ventilator-free days. Seventy patients died (40%). Median NT-proBNP level was 3181 ng/L (interquartile range 723-9246 ng/L). NT-proBNP levels were significantly higher among nonsurvivors (p < .0001). Receiver operating curve analysis revealed an optimal NT-proBNP cut-point of 6813 ng/L for predicting death. Patients with levels above the cut-point had significantly higher odds of mortality on multivariable analysis (odds ratio 2.36, 95% confidence interval 1.11-4.99, p = .02) than those with levels below the cut-point. Kaplan-Meier survival analysis showed that this difference emerged early and was sustained (p < .0001). Patients with elevated NT-proBNP also had higher organ dysfunction scores (p < .0001) and fewer ventilator free days (p = .03) than those with lower NT-proBNP levels.

CONCLUSIONS

NT-proBNP levels are elevated among acute respiratory distress syndrome patients and parallel the severity of the syndrome and likelihood for morbidity and mortality. This demonstrates the potential utility of this biomarker for prognosis in this disease.

Diagnostic utility of B-type natriuretic peptide in critically ill patients with pulmonary edema: a prospective cohort study

Introduction

Distinguishing pulmonary edema due to acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS) from hydrostatic or cardiogenic edema is challenging in critically ill patients. B-type natriuretic peptide (BNP) can effectively identify congestive heart failure in the emergency room setting but, despite increasing use, its diagnostic utility has not been validated in the intensive care unit (ICU).

Methods

We performed a prospective, blinded cohort study in the medical and surgical ICUs at the University of Chicago Hospitals. Patients were eligible if they were admitted to the ICU with respiratory distress, bilateral pulmonary edema and a central venous catheter suggesting either high-pressure (cardiogenic) or low-pressure (ALI/ARDS) pulmonary edema. BNP levels were measured within 48 hours of ICU admission and development of pulmonary edema and onward up to three consecutive days. All levels were drawn simultaneously with the measurement of right atrial or pulmonary artery wedge pressure. The etiology of pulmonary edema – cardiogenic or ALI/ARDS – was determined by three intensivists blinded to BNP levels.

Results

We enrolled a total of 54 patients (33 with ALI/ARDS and 21 with cardiogenic edema). BNP levels were lower in patients with ALI/ARDS than in those with cardiogenic edema (496 ± 439 versus 747 ± 476 pg/ml, P = 0.05). At an accepted cutoff of 100 pg/ml, specificity for the diagnosis of ALI/ARDS was high (95.2%) but sensitivity was poor (27.3%). Cutoffs at higher BNP levels improved sensitivity at considerable cost to specificity. Invasive measures of filling pressures correlated poorly with initial BNP levels and subsequent day BNP values fluctuated unpredictably and without correlation with hemodynamic changes and net fluid balance.

Conclusion

BNP levels drawn within 48 hours of admission to the ICU do not reliably distinguish ALI/ARDS from cardiogenic edema, do not correlate with invasive hemodynamic measurements, and do not track predictably with changes in volume status on consecutive daily measurements.

B-type natriuretic peptide monitoring in the Pediatric ICU population

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Assays of these peptides are now available and may be used for both diagnostic and prognostic purposes. Despite its primary use in adults, it may have a diagnostic role in the Pediatric ICU as well. The basic physiology of the natriuretic system is discussed and the potential applications of B-type natriuretic peptide (BNP) monitoring as a diagnostic tool in various clinical scenarios in infants and children in the Pediatric ICU setting is reviewed.

Serum B-type natriuretic peptide: a marker of fluid resuscitation after injury?

BACKGROUND

Excessive volume resuscitation after injury is associated with severe complications. B-type natriuretic peptide (BNP) is secreted from myocardium under increased wall stretch and is used in medical intensive care units (ICUs) as a noninvasive method to detect heart failure. However, the use of BNP as a marker of fluid overload during resuscitation from injury has not been previously described.

METHODS

Serum BNP levels were prospectively followed in 134 trauma ICU patients. Levels were obtained at admission and at 12, 24, and 48 hours. Repeated measures analysis of variance was used to test for differences in BNP levels over time. Post hoc pairwise comparisons were made with Bonferroni correction when the omnibus test indicated significance. Chest films were obtained at 24 hours and scored for the presence of pulmonary edema by a radiologist blinded to BNP measurements (n = 45). Twenty-four hour BNP levels for patients with or without radiographic evidence of pulmonary edema were compared using nonparametric analysis (Mann-Whitney U).

RESULTS

Admission BNP levels were low and increased with fluid resuscitation over time in all patients (p = 0.002) as well as in a subgroup of patients <60 years of age (p = 0.003). At 24 hours, 25 patients had no pulmonary edema evident on chest X-ray, whereas 20 were scored indicating that pulmonary edema was present. Patients with evidence of pulmonary edema had higher mean BNP levels at 24 hours (110 +/- 31 pg/mL) than did patients without edema (47.0 +/- 10.8 pg/mL) (p = 0.04).

CONCLUSIONS

Serum BNP levels increase with resuscitation after injury and levels are higher in patients who develop pulmonary edema. These findings suggest that BNP might be a marker of excessive volume resuscitation after injury.

Toward the prevention of acute lung injury: Protocol-guided limitation of large tidal volume ventilation and inappropriate transfusion*

OBJECTIVE

We evaluated the effect of two quality improvement interventions (low tidal volume ventilation and restrictive transfusion) on the development of acute lung injury in mechanically ventilated patients.

DESIGN

Observational cohort study.

SETTING

Three intensive care units in a tertiary academic center.

PATIENTS

We included patients who were mechanically ventilated for > or =48 hrs excluding those who refused research authorization or had preexisting acute lung injury or pneumonectomy.

INTERVENTIONS

Multifaceted interdisciplinary intervention consisting of Web-based teaching, respiratory therapy protocol, and decision support within computerized order entry.

MEASUREMENTS AND MAIN RESULTS

Of 375 patients who met the inclusion and exclusion criteria, 212 were ventilated before and 163 after the interventions. Baseline characteristics were similar between the two groups except for a lower frequency of sepsis (27% vs. 17%, p = .030), trend toward lower median glucose level (140 mg/dL, interquartile range 118-168 vs. 132 mg/dL, interquartile range 113-156, p = .096), and lower frequency of pneumonia (27% vs. 20%, p = .130) during the second period. We observed a large decrease in tidal volume (10.6-7.7 mL/kg predicted body weight, p < .001), in peak airway pressure (31-25 cm H2O, p < .001), and in the percentage of transfused patients (63% to 38%, p < .001) after the intervention. The frequency of acute lung injury decreased from 28% to 10% (p < .001). The duration of mechanical ventilation decreased from a median of 5 (interquartile range 4-9) to 4 (interquartile range 4-8) days (p = .030). When adjusted for baseline characteristics in a multivariate logistic regression analysis, protocol intervention was associated with a reduction in the frequency of new acute lung injury (odds ratio 0.21, 95% confidence interval 0.10-0.40).

CONCLUSIONS

Interdisciplinary intervention effectively decreased large tidal volumes and unnecessary transfusion in mechanically ventilated patients and was associated with a decreased frequency of new acute lung injury.

Epidemiology and Outcomes of Acute Lung Injury

Acute lung injury (ALI) and its presentation with more severe hypoxemia, the ARDS, is a challenging entity for clinical investigation because, like many critical illness syndromes, it lacks an accepted diagnostic test and relies on a constellation of clinical findings for diagnosis. Despite these barriers, there have been important advances in the clinical and population epidemiology of ALI. This article will review recent studies of the incidence, diagnosis, etiologic and prognostic factors, relevant disease subsets, mortality, and long-term outcomes of ALI. A detailed understanding of the epidemiology and outcomes of ALI is essential for future research on mechanisms of both the acute presentation and long-term sequelae, for designing studies to identify genetic risk factors for developing ALI, and to develop strategies to treat or prevent the morbidity encountered by survivors.