Pneumonia and ARDS in patients receiving mechanical ventilation: diagnostic accuracy of chest radiography

Development and validation of prediction scores for the outcome associated with persistent inflammation, immunosuppression, and catabolism syndrome among patients with trauma

Background

Persistent inflammation, immunosuppression, and catabolism syndrome (PICS) has impacted on long-term prognosis of patients with trauma. We aimed to identify patients with trauma at risk of PICS-related complications early in the intensive care unit (ICU) course.

Methods

A single-center retrospective cohort study was conducted. All consecutive patients with trauma who had stayed in the ICU for >7 days were included in the study. We developed the prediction score for the incidence of PICS-related outcomes in the derivation cohort for the initial period and then evaluated in the validation cohort for the subsequent period. Other outcomes were also assessed using the score.

Results

In total, 170 and 133 patients were included in the derivation and validation cohorts, respectively. The prediction score comprised the variables indicating PICS presence, including a maximum value of C-reactive protein >15 mg/dL, minimum value of albumin <2.5 g/dL, and an episode of nosocomial infection for the first 7 days after admission. A score of 1 was assigned to each variable. The area under the receiver operating characteristic curve of the score to predict PICS incidence was 0.74 (95% CI 0.66 to 0.81) and 0.72 (95% CI 0.64 to 0.81) in the derivation and validation cohorts, respectively. The higher score was also significantly associated with a higher Sequential Organ Failure Assessment score at day 14, a longer duration of mechanical ventilation, a longer length of stay in ICU, and experienced multiple episodes of infection. Similar results were obtained in the validation cohort.

Conclusions

Our scoring system could predict the outcomes associated with PICS among patients with trauma. Because the score comprised the parameters measured for the first 7 days during the ICU course, it could contribute to identifying patients at a high risk of unfavorable outcome earlier.

Level of evidence

Multivariate prediction models; level IV.

Diagnostic accuracy of portable chest radiograph in mechanically ventilated patients when compared with autopsy findings

PURPOSE

Evaluate diagnostic accuracy of portable chest radiograph in mechanically ventilated patients taking autopsy findings as the gold standard and the interobserver agreement among intensivists and radiologists.

MATERIALS AND METHODS

Retrospective study of 422 patients over 22 years who died in the ICU, underwent an autopsy, and had at least one portable chest radiograph 72 h prior to death. Two intensivists and two radiologists independently read each chest radiograph. Sensitivity, specificity, positive and negative likelihood ratios were evaluated. Overall performance metrics accuracy between intensivists and radiologists were compared using a generalized estimating equation. Cohen's kappa coefficient was used to evaluate the interobserver agreement with the following values: <0.20:poor, 0.21-0.40:fair, 0.41-0.60:moderate, 0.61-0.80:good, 0.81-1.00:excellent.

RESULTS

Overall sensitivity and specificity for pneumonia was 24% and 91% respectively. Overall sensitivity and specificity for ARDS was 68% and 74% respectively. Sensitivity for pneumonia was higher among radiologists (p < 0,05). Specificity for ADRS was higher among radiologists (p < 0,05). Good interobserver agreement among radiologists and poor correlation between intensivists was found.

CONCLUSIONS

Chest radiographs has a moderate specificity for ARDS and a high specificity for pneumonia, with limited sensitivity in both entities. Interobserver agreement of portable chest radiograph in the mechanically ventilated patients is higher between radiologists than intensivists.

How Can We Distinguish Ventilator-Associated Tracheobronchitis from Pneumonia?

Ventilator-associated tracheobronchitis (VAT) might represent an intermediate process between lower respiratory tract colonization and ventilator-associated pneumonia (VAP), or even a less severe spectrum of VAP. There is an urgent need for new concepts in the arena of ventilator-associated lower respiratory tract infections. Ideally, the gold standard of care is based on prevention rather than treatment of respiratory infection. However, despite numerous and sometimes imaginative efforts to validate the benefit of these measures, most clinicians now accept that currently available measures have failed to eradicate VAP. Stopping the progression from VAT to VAP could improve patient outcomes.

Bedside lung ultrasonography for diagnosis of pneumonia

Objective

The aim of this study was to investigate the accuracy of bedside lung ultrasound (BUS) in the diagnosis of community-acquired pneumonia (CAP) in patients with dyspnoea presenting to the emergency department (ED) and to analyse the characteristic sonographic findings of CAP.

Methods

After a six-hour training program, BUS procedures were performed between October 2011 and February 2012 to prospectively evaluate patients presenting to the ED with dyspnoea. Chest X-ray (CXR) or computerised tomography (CT) were ordered, depending on the presence of consolidation signs on CXR. The outcome was determined by consolidation findings on CXR or CT. BUS results were compared using Chi-squared testing.

Results

Of the 112 enrolled patients with dyspnoea, 40 patients were excluded and 72 were included in the study. Thirty-four patients were BUS positive. Of these, CXR or CT findings agreed with the BUS findings in 27 patients. In 38 cases, BUS was negative, and one patient was diagnosed with pneumonia based on the CT report. The sensitivity, specificity, PPV, NPV, and the positive and negative likelihood ratios for BUS were 96.4%, 84.1%, 79.4%, 97.4%, 6.1 and 0.042, respectively. The diagnostic accuracy of BUS was 89%. The presence of consolidation signs, either shred or hepatisation, were the most frequent sonographic findings in our study.

Conclusions

Acute alveolar consolidation can be diagnosed easily by performing BUS with high degree of accuracy in EDs.

Cardiopulmonary bypass does not induce lung dysfunction after pulmonary thrombarterectomy: role of pulmonary compliance

OBJECTIVES

Pulmonary endarterectomy is a heavy surgical procedure that is performed under cardiopulmonary bypass (CPB) and aimed to cure postembolic pulmonary hypertension. Reperfusion oedema is both the hallmark of successful surgical procedure and the most frequent postoperative complication. Post-CPB lung dysfunction was not mentioned in any report. We undertook a study to determine whether post-CPB lung dysfunction was present in these patients.

METHODS

In a retrospective cohort study with matching on some baseline covariates, we selected 41 patients who had undergone pulmonary endarterectomy and in whom pre-, intra- and postoperative records were complete. The control group was composed of 39 patients operated on from elective cardiac surgery during the same period and matched with a study group for age, gender, body mass index, blood creatinine, diabetes and baseline partial pressure of oxygen/fraction of inspired oxygen ratio. Criteria for post-CPB lung dysfunction were partial pressure of oxygen/fraction of inspired oxygen ratio decrease and bilateral basal oedema. Explanatory variables for post-CPB lung dysfunction were coronary arterial bypass, pleura opening, static pulmonary compliance measured at the time of thorax closed then retracted, fluid infusion, transfusion and vasopressors.

RESULTS

All patients operated on from pulmonary endarterectomy presented radiological oedema reperfusion in surgical unblocking areas. Among them, only 2 had bilateral basal oedema when compared to the 24 patients from the control group (P < 0.001). Partial pressure of oxygen/fraction of inspired oxygen ratio increased in the study group and decreased in the control group (30 ± 109 vs -67 ± 134 mmHg, P < 0.001). Control group patients with high-baseline pulmonary compliance were at risk for post-CPB lung dysfunction.

CONCLUSIONS

Patients operated on from pulmonary endarterectomy were saved from post-CPB lung dysfunction. The latter could be induced by a mechanical phenomenon.

[Nosocomial pneumonia from a radiological perspective]

Due to the high morbidity and mortality, nosocomial pneumonia represents a serious risk in hospitalized patients. The increased risk of infections with multidrug-resistant (MDR) pathogens makes a timely diagnosis and prompt therapy indispensable. A newly occurring or progressive infiltrate in any patient who has been hospitalized for more than 48 h should be viewed with suspicion. In contrast to community acquired pneumonia (CAP), radiography plays a limited role in the diagnosis of hospital-acquired pneumonia (HAP). This is partly due to the technical challenges in imaging of patients who are in a lying position as well as the numerous other possible differential diagnoses. Careful analysis of the various radiological features, such as temporal progression, distribution and appearance can help to narrow down the differential diagnoses. In the absence of a single gold standard, clinical features and appropriate radiological features in addition to cultures obtained from respiratory secretions can help to maximize the diagnostic efficacy and expedite the treatment with appropriate antibiotic therapy.

Diagnostic workup for ARDS patients

Acute respiratory distress syndrome (ARDS) is defined by the association of bilateral infiltrates and hypoxaemia following an initial insult. Although a new definition has been recently proposed (Berlin definition), there are various forms of ARDS with potential differences regarding their management (ventilator settings, prone positioning use, corticosteroids). ARDS can be caused by various aetiologies, and the adequate treatment of the responsible cause is crucial to improve the outcome. It is of paramount importance to characterize the mechanisms causing lung injury to optimize both the aetiological treatment and the symptomatic treatment. If there is no obvious cause of ARDS or if a direct lung injury is suspected, bronchoalveolar lavage (BAL) should be strongly considered to identify microorganisms responsible for pneumonia. Blood samples can also help to identify microorganisms and to evaluate biomarkers of infection. If there is no infectious cause of ARDS or no other apparent aetiology is found, second-line examinations should include markers of immunologic diseases. In selected cases, open lung biopsy remains useful to identify the cause of ARDS when all other examinations remain inconclusive. CT scan is fundamental when there is a suspicion of intra-abdominal sepsis and in some cases of pneumonia. Ultrasonography is important not only in evaluating biventricular function but also in identifying pleural effusions and pneumothorax. The definition of ARDS remains clinical and the main objective of the diagnostic workup should be to be focused on identification of its aetiology, especially a treatable infection.

Infection

Community-Acquired Pneumonia (CAP) is the first leading cause of death due to infection worldwide.Many gram-positive, gram-negative bacteria, funguses and viruses can cause the infectious pulmonary disease, and the severity of pneumonia depends on the balance between the microorganism charge, the body immunity defenses and the quality of the underlying pulmonary tissue. The microorganisms may reach the lower respiratory tract from inhaled air or from infected oropharyngeal secretions. The same organism may produce several different patterns that depend on the balance between the microorganism charge and the body immunity defenses.CAP is classified into three main groups: lobar pneumonia, bronchopneumonia and interstitial pneumonia.Lobar pneumonia is characterized by the filling of alveolar spaces by edema full of white and inflammatory cells. Necrotizing pneumonia consists of a fulminant process associated with focal areas of necrosis that results in abscesses. Bronchopneumonia or lobular pneumonia, is characterized by a peribronchiolar inflammation with thickening of peripheral bronchial wall, the diffusion of inflammation to the centrilobular alveolar spaces and development of nodules.The interstitial pneumonia represents with the destruction and esfoliation of the respiratory ciliated and mucous cells. The interstitial septa, the bronchial and bronchiolar walls become thickened for the inflammation process and lymphocytes interstitial infiltrates.Chest radiography represents an important initial examination in all patients suspected of having pulmonary infection and for monitoring response to therapy.Its role is to identify the pulmonary opacities, their internal characteristics and distribution, pleural effusion and presence of other complications as abscesses and pneumothorax.High spatial CT resolution allows accurate assessment of air space inflammation.The CT findings include nodules, interlobular septal thickening, intralobular reticular opacities, ground-glass opacities, tree-in-bud pattern, lobar-segmental consolidation, lobular consolidation, abscesses, pneumatocele, pleural effusion, pericardial effusion, mediastinal and hilar lymphoadenopaties, airway dilatation and emphysema.

Intensive care unit imaging

Chest radiography serves a crucial role in imaging of the critically ill. It is essential in ensuring the proper positioning of support and monitoring equipment, and in evaluating for potential complications of this equipment. The radiograph is useful in diagnosing and evaluating the progression of atelectasis, aspiration, pulmonary edema, pneumonia, and pleural fluid collections. Computed tomography can be useful when the clinical and radiologic presentations are discrepant, the patient is not responding to therapy, or in further defining the pattern and distribution of a radiographic abnormality.

Imaging of Pulmonary Infections

Pulmonary infection is one of the most frequent causes of morbidity and mortality throughout the world. Many infections occur in individuals with concomitant intrapulmonary or extrathoracic diseases; however, they commonly develop in otherwise healthy people. In the non-immunocompromised population, pneumonia is the most prevalent community-acquired infection and the second most common nosocomial infectious disorder. In immunocompromised patients, in children, and in the elderly, pneumonia, as well as other pulmonary infections, may develop into a life-threatening condition.

Application of fiberoptic bronchscopy in patients with acute exacerbations of chronic obstructive pulmonary disease during sequential weaning of invasive-noninvasive mechanical ventilation

BACKGROUND

Early withdrawal of invasive mechanical ventilation (IMV) followed by noninvasive MV (NIMV) is a new strategy for changing modes of treatment in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) with acute respiratory failure (ARF). Using pulmonary infection control window (PIC window) as the switch point for transferring from invasive to noninvasive MV, the time for early extubation can be more accurately judged, and therapy efficacy can be improved. This study aimed to prospectively investigate the clinical effectiveness of fiberoptic bronchscopy (FOB) in patients with AECOPD during sequential weaning of invasive-noninvasive MV.

METHODS

Since July 2006 to January 2011, 106 AECOPD patients with ARF were treated with comprehensive medication and IMV after hospitalization. Patients were randomly divided into two groups according to whether fiberoptic bronchoscope is used (group A, n=54) or not (group B, n=52) during sequential weaning from invasive to noninvasive MV. In group A, for sputum suction and bronchoalveolar lavage (BAL), a fiberoptic bronchoscope was put into the airway from the outside of an endotracheal tube, which was accompanied with uninterrupted use of a ventilator. After achieving PIC window, patients of both groups changed to NIMV mode, and weaned from ventilation. The following listed indices were used to compare between the groups after treatment: 1) the occurrence time of PIC, the duration of MV, the length of ICU stay, the success rate of weaning from MV for the first time, the rate of reventilation and the occurrence rate of ventilator-associated pneumonia (VAP); 2) the convenience and safety of FOB manipulation. The results were compared using Student's t test and the Chi-square test.

RESULTS

The occurrence time of PIC was (5.01±1.49) d, (5.87±1.87) d in groups A and B, respectively (P<0.05); the duration of MV was (6.98±1.84) d, (8.69±2.41) d in groups A and B, respectively (P<0.01); the length of ICU stay was (9.25±1.84) d, (11.10±2.63) d in groups A and B, respectively (P<0.01); the success rate of weaning for the first time was 96.30%, 76.92% in groups A and B, respectively (P<0.01); the rate of reventilation was 5.56%, 19.23% in groups A and B, respectively (P<0.05); and the occurrence rate of VAP was 3.70%, 23.07% in groups A and B, respectively (P<0.01). Moreover, it was easy and safe to manipulate FOB, and no side effect was observed.

CONCLUSIONS

The application of FOB in patients with AECOPD during sequential weaning of invasive-noninvasive MV is effective in ICU. It can decrease the duration of MV and the length of ICU stay, increase the success rate from weaning MV for the first time, reduce the rate of reventilation and the occurrence rate of VAP. In addition, such a method is convenient and safe in patients of this kind.

Incidence and outcomes of ventilator-associated tracheobronchitis and pneumonia

BACKGROUND

Prolonged intubation with mechanical ventilation carries a risk for ventilator-associated respiratory infections manifest as tracheobronchitis or pneumonia. This study analyzed natural history, incidence, and outcomes of patients developing ventilator-associated tracheobronchitis and pneumonia.

METHODS

We studied 188 mixed intensive care unit (ICU) patients intubated ≥48 hours for the development of tracheobronchitis defined as quantitative endotracheal aspirate ≥10(5) cfu/mL plus at least 2 clinical criteria (fever, leukocytosis, or purulent sputum). Pneumonia was defined as microbiologic criteria for tracheobronchitis and a new and persistent infiltrate on chest radiograph.

RESULTS

Airways of 41 (22%) patients became heavily colonized with a bacterial pathogen(s) at a concentration of ≥10(5) cfu/mL. Tracheobronchitis developed in 21 (11%) study patients, of which 6 (29%) later progressed to pneumonia. Including these 6 patients, 28 (15%) study patients developed pneumonia. Multidrug-resistant pathogens were isolated in 39% of pneumonia patients. Patients with tracheobronchitis and pneumonia had significantly more ventilator days and longer stays in the ICU (P ≤.02).

CONCLUSIONS

Approximately one third of tracheobronchitis patients later developed pneumonia. Patients with tracheobronchitis or pneumonia experienced significantly more ventilator days and longer ICU stays, but had no difference in mortality. Better patient outcomes and reduced health care costs may be achieved by earlier treatment of ventilator-associated respiratory infections, manifest as tracheobronchitis or pneumonia.

Objective surveillance definitions for ventilator-associated pneumonia

OBJECTIVES

The subjectivity and complexity of surveillance definitions for ventilator-associated pneumonia preclude meaningful internal or external benchmarking and therefore hamper quality improvement initiatives for ventilated patients. We explored the feasibility of creating objective surveillance definitions for ventilator-associated pneumonia.

DESIGN

We identified clinical signs suitable for inclusion in objective definitions, proposed candidate definitions incorporating these objective signs, and then applied these definitions to retrospective clinical data to measure their frequencies and associations with adverse outcomes using multivariate regression models for cases and matched controls.

SETTING

Medical and surgical intensive care units in eight U.S. hospitals (four tertiary centers, three community hospitals, and one Veterans Affairs institution).

PATIENTS

Eight thousand seven hundred thirty-five consecutive episodes of mechanical ventilation for adult patients.

INTERVENTIONS

We evaluated 32 different candidate definitions composed of different combinations of the following signs: three thresholds for respiratory deterioration defined by sustained increases in daily minimum positive end-expiratory pressure or FIO2 after either 2 or 3 days of stable or decreasing ventilator settings, abnormal temperature, abnormal white blood cell count, purulent pulmonary secretions defined by neutrophils on Gram stain, and positive cultures for pathogenic organisms.

MEASUREMENTS AND MAIN RESULTS

Ventilator-associated pneumonia incidence, attributable ventilator days, hospital days, and hospital mortality. All candidate definitions were significantly associated with increased ventilator days and hospital days, but only definitions requiring objective evidence of respiratory deterioration were significantly associated with increased hospital mortality. Significant odds ratios for hospital mortality ranged from 1.9 (95% confidence interval 1.2-2.9) to 6.1 (95% confidence interval 2.2-17). Requiring additional clinical signs beyond respiratory deterioration alone decreased event rates, had little impact on attributable lengths of stay, and diminished sensitivity and positive predictive values for hospital mortality.

CONCLUSIONS

Objective surveillance definitions that include quantitative evidence of respiratory deterioration after a period of stability strongly predict increased length of stay and hospital mortality. These definitions merit further evaluation of their utility for hospital quality and safety improvement programs.

Rapid and reproducible surveillance for ventilator-associated pneumonia

BACKGROUND

The complexity and subjectivity of ventilator-associated pneumonia (VAP) surveillance limit its value in assessing and comparing quality of care for ventilated patients. A simpler, more quantitative VAP definition may increase utility.

METHODS

We streamlined the Centers for Disease Control and Prevention definition of VAP to increase objectivity and efficiency. Qualitative criteria were replaced with quantitative criteria, and changes in ventilator settings were used to screen patients for worsening oxygenation. We retrospectively compared surveillance time, reproducibility, and outcomes for streamlined versus conventional surveillance among medical and surgical patients on mechanical ventilation in 3 university hospitals.

RESULTS

Application of the streamlined definition was faster (mean 3.5 minutes vs 39.0 minutes per patient) and more objective (interrater reliability κ 0.79 vs 0.45) than the conventional definition. On multivariate analysis, the streamlined definition predicted increases in ventilator days (6.5 days [95% CI, 4.1-10.0] vs 6.4 days [95% CI, 4.7-8.6]), intensive care days (5.6 days [95% CI, 3.2-8.9] vs 6.2 days [95% CI, 4.6-8.2]), and hospital mortality (odds ratio [OR] 0.84 [95% CI, 0.31-2.29] vs OR 0.69 [95% CI, 0.30-1.55]) as effectively as conventional surveillance. The conventional definition was a marginally superior predictor of increased hospital days (5.2 days [95% CI, 3.4-7.6] vs 2.1 days [95% CI, -0.5-5.6]).

CONCLUSIONS

A streamlined version of the VAP definition was faster, more objective, and predicted patients' outcomes almost as effectively as the conventional definition. VAP surveillance using the streamlined method may facilitate more objective and efficient quality assessment for ventilated patients.

Diagnosis of ventilator-associated respiratory infections (VARI): microbiologic clues for tracheobronchitis (VAT) and pneumonia (VAP)

Intubated patients are at risk of bacterial colonization and ventilator-associated respiratory infection (VARI). VARI includes tracheobronchitis (VAT) or pneumonia (VAP). VAT and VAP caused by multidrug-resistant (MDR) pathogens are increasing in the United States and Europe. In patients with risk factors for MDR pathogens, empiric antibiotics are often initiated for 48 to 72 hours pending the availability of pathogen identification and antibiotic sensitivity data. Extensive data indicate that early, appropriate antibiotic therapy improves outcomes for patients with VAP. Recognizing and treating VARI may allow earlier appropriate therapy and improved patient outcomes.

Lung sonography and recruitment in patients with early acute respiratory distress syndrome: a pilot study

INTRODUCTION

Bedside lung sonography is a useful imaging tool to assess lung aeration in critically ill patients. The purpose of this study was to evaluate the role of lung sonography in estimating the nonaerated area changes in the dependent lung regions during a positive end-expiratory pressure (PEEP) trial of patients with early acute respiratory distress syndrome (ARDS).

METHODS

Ten patients (mean ± standard deviation (SD): age 64 ± 7 years, Acute Physiology and Chronic Health Evaluation II (APACHE II) score 21 ± 4) with early ARDS on mechanical ventilation were included in the study. Transthoracic sonography was performed in all patients to depict the nonaerated area in the dependent lung regions at different PEEP settings of 5, 10 and 15 cm H2O. Lung sonographic assessment of the nonaerated lung area and arterial blood gas analysis were performed simultaneously at the end of each period. A control group of five early ARDS patients matched for APACHE II score was also included in the study.

RESULTS

The nonaerated areas in the dependent lung regions were significantly reduced during PEEP increases from 5 to 10 to 15 cm H2O (27 ± 31 cm2 to 20 ± 24 cm2 to 11 ± 12 cm2, respectively; P < 0.01). These changes were associated with a significant increase in arterial oxygen partial pressure (74 ± 15 mmHg to 90 ± 19 mmHg to 102 ± 26 mmHg; P < 0.001, respectively). No significant changes were observed in the nonaerated areas in the dependent lung regions in the control group.

CONCLUSIONS

In this study, we show that transthoracic lung sonography can detect the nonaerated lung area changes during a PEEP trial of patients with early ARDS. Thus, transthoracic lung sonography might be considered as a useful clinical tool in the management of ARDS patients.

Clinical practice guidelines for hospital-acquired pneumonia and ventilator-associated pneumonia in adults

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are important causes of morbidity and mortality, with mortality rates approaching 62%. HAP and VAP are the second most common cause of nosocomial infection overall, but are the most common cause documented in the intensive care unit setting. In addition, HAP and VAP produce the highest mortality associated with nosocomial infection. As a result, evidence-based guidelines were prepared detailing the epidemiology, microbial etiology, risk factors and clinical manifestations of HAP and VAP. Furthermore, an approach based on the available data, expert opinion and current practice for the provision of care within the Canadian health care system was used to determine risk stratification schemas to enable appropriate diagnosis, antimicrobial management and nonantimicrobial management of HAP and VAP. Finally, prevention and risk-reduction strategies to reduce the risk of acquiring these infections were collated. Future initiatives to enhance more rapid diagnosis and to effect better treatment for resistant pathogens are necessary to reduce morbidity and improve survival.

Prevention of VAP: is zero rate possible?

Infection prevention measures, specifically targeting ventilator-associated pneumonia (VAP), have been purposed as quality-of-care indicators for patients in intensive care units. The authors discuss some of the recent evidence of the prevention of nosocomial infections, with a particular emphasis on VAP. Moreover, there are several pitfalls in considering VAP rates as a safety indicator. Because of these limitations, the authors recommend the use of specific process measures, designed to reduce VAP, as the basis for interinstitutional benchmarking.

The diagnostic dilemma of ventilator-associated pneumonia in critically ill children

OBJECTIVE

A review of the existing literature on ventilator-associated pneumonia in children with emphasis on problems in diagnosis.

DATA SOURCES

A systematic literature review from 1947 to 2010 using Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Science using key words "ventilator associated pneumonia" and "children." Where pediatric data were lacking, appropriate adult studies were reviewed and similarly referenced.

STUDY SELECTION

Two hundred sixty-two pediatric articles were reviewed and data from 48 studies selected. Data from 61 adult articles were also included in this review.

DATA EXTRACTION AND SYNTHESIS

Ventilator-associated pneumonia is the second most common nosocomial infection and the most common reason for antibiotic use in the pediatric intensive care unit. Attributable mortality is uncertain but ventilator-associated pneumonia is associated with significant morbidity and cost. Diagnosis is problematic in that clinical, radiologic, and microbiologic criteria lack sensitivity and specificity relative to autopsy histopathology and culture. Qualitative tracheal aspirate cultures are commonly used in diagnosis but lack specificity. Quantitative tracheal aspirate cultures have sensitivity (31-69%) and specificity (55-100%) comparable to bronchoalveolar lavage (11-90% and 43-100%, respectively) but concordance for the same bacterial species when compared with autopsy lung culture was better for bronchoalveolar lavage (52-90% vs. 50-76% for quantitative tracheal aspirate). Staphylococcus aureus and Pseudomonas species are the most common organisms, but microbiologic flora change over time and with antibiotic use. Initial antibiotics should offer broad-spectrum coverage but should be narrowed as clinical response and cultures dictate.

CONCLUSIONS

Ventilator-associated pneumonia is an important nosocomial infection in the pediatric intensive care unit. Conclusions regarding epidemiology, treatment, and outcomes are greatly hampered by the inadequacies of current diagnostic methods. We recommend a more rigorous approach to diagnosis by using the Centers for Disease Control and Prevention algorithm. Given that ventilator-associated pneumonia is the most common reason for antibiotic use in the pediatric intensive care unit, more systematic studies are sorely needed.

Bildgebende Verfahren: Röntgen, Ultraschall, CT, Nuklearmedizin

In der Intensivmedizin findet die radiologische Diagnostik überwiegend am Krankenbett statt (»bedside radiology«). Etwa 90 % der radiologischen Untersuchungen in der Intensiv- und Notfallmedizin stellen projektionsradiographische Röntgenaufnahmen des Thorax, des Abdomens und des Skelettsystems dar. In zunehmendem Maße werden neben den klassischen Aufnahmen auch die Schnittbildverfahren eingesetzt. Hier kommt der Ultraschalldiagnostik eine führende Rolle zu, gefolgt von der Computertomographie (CT).

[Agreement between lung ultrasonography and chest radiography in the intensive care unit]

OBJECTIVE

Because the chest radiograph currently remains the routine choice of imaging for the examination of the chest in the intensive care unit, we compared lung ultrasonography with chest radiography.

STUDY DESIGN

Observational prospective study.

METHODS

An ultrasound examination and chest radiography were simultaneously ordered in 50 patients whose clinical exam justified a lung exploration. Each exam was interpreted independently by an intensivist. The abnormalities found were classified into interstitial syndrome, alveolar consolidation, and pleural effusion. An agreement analysis was performed between the results of the two techniques. The delay between the order and interpretation of both investigations, and the degree of interobserver agreement were also collected.

RESULTS

The kappa agreement between lung ultrasonography and chest radiography was 0.42. In total, 329 total abnormalities were detected, 156 abnormalities were found by both techniques, 31 by radiography alone, and 142 by ultrasonography alone. The interobserver agreement was 0.86. Ultrasonography was performed with a shorter delay (14.8 ± 6.9 min vs 44.2 ± 21.4 min).

CONCLUSION

There was only moderate agreement between lung ultrasonography and chest radiography for the diagnosis of interstitial syndrome, alveolar consolidation and pleural effusion in intensive care unit. This result is mainly explained by the higher number of ultrasound abnormalities. With the ability to provide fast diagnosis, good reproducibility and high feasibility, ultrasound scan could represent an alternative exam for chest exploration in intensive care unit.

Ventilator-associated tracheobronchitis: the impact of targeted antibiotic therapy on patient outcomes

Nosocomial lower respiratory tract infections are a common cause of morbidity and mortality in ICU patients receiving mechanical ventilation. Many studies have investigated the management and prevention of ventilator-associated pneumonia (VAP), but few have focused on the role of ventilator-associated tracheobronchitis (VAT). The pathogenesis of lower respiratory tract infections often begins with tracheal colonization that may progress to VAT, and in selected patients to VAP. Since there is no well-established definition of VAT, discrimination between VAT and VAP can be challenging. VAT is a localized disease with clinical signs (fever, leukocytosis, and purulent sputum), microbiologic information (Gram stain with bacteria and leukocytes, with either a positive semiquantitative or a quantitative sputum culture), and the absence of a new infiltrate on chest radiograph. Monitoring endotracheal aspirates has been used to identify and quantify pathogens colonizing the lower airway, to diagnose VAT or VAP, and to initiate early, targeted antibiotic therapy. Recent data suggest that VAT appears to be an important risk factor for VAP and that targeted antibiotic therapy for VAT may be a new paradigm for VAP prevention and better patient outcomes.

ICU imaging

Chest radiography serves a crucial role in imaging of the critically ill. Its uses include diagnosis and monitoring of commonly encountered pulmonary parenchymal and pleural space abnormalities. It is also important in evaluating monitoring and support devices and associated complications. CT, another useful imaging modality in select patients, can better characterize pulmonary parenchymal and pleural space disease.

Antimicrobial treatment for ventilator-associated tracheobronchitis: a randomized, controlled, multicenter study

Introduction

Ventilator-associated tracheobronchitis (VAT) is associated with increased duration of mechanical ventilation. We hypothesized that, in patients with VAT, antibiotic treatment would be associated with reduced duration of mechanical ventilation.

Methods

We conducted a prospective, randomized, controlled, unblinded, multicenter study. Patients were randomly assigned (1:1) to receive or not receive intravenous antibiotics for 8 days. Patients with ventilator-associated pneumonia (VAP) prior to VAT and those with severe immunosuppression were not eligible. The trial was stopped early because a planned interim analysis found a significant difference in intensive care unit (ICU) mortality.

Results

Fifty-eight patients were randomly assigned. Patient characteristics were similar in the antibiotic (n = 22) and no antibiotic (n = 36) groups. Pseudomonas aeruginosa was identified in 32% of VAT episodes. Although no difference was found in mechanical ventilation duration and length of ICU stay, mechanical ventilation-free days were significantly higher (median [interquartile range], 12 [8 to 24] versus 2 [0 to 6] days, P < 0.001) in the antibiotic group than in the no antibiotic group. In addition, subsequent VAP (13% versus 47%, P = 0.011, odds ratio [OR] 0.17, 95% confidence interval [CI] 0.04 to 0.70) and ICU mortality (18% versus 47%, P = 0.047, OR 0.24, 95% CI 0.07 to 0.88) rates were significantly lower in the antibiotic group than in the no antibiotic group. Similar results were found after exclusion of patients with do-not-resuscitate orders and those randomly assigned to the no antibiotic group but who received antibiotics for infections other than VAT or subsequent VAP.

Conclusion

In patients with VAT, antimicrobial treatment is associated with a greater number of days free of mechanical ventilation and lower rates of VAP and ICU mortality. However, antibiotic treatment has no significant impact on total duration of mechanical ventilation.

Trial registration

ClinicalTrials.gov, number NCT00122057.

Guidelines for evaluation of new fever in critically ill adult patients: 2008 update from the American College of Critical Care Medicine and the Infectious Diseases Society of America

OBJECTIVE

To update the practice parameters for the evaluation of adult patients who develop a new fever in the intensive care unit, for the purpose of guiding clinical practice.

PARTICIPANTS

A task force of 11 experts in the disciplines related to critical care medicine and infectious diseases was convened from the membership of the Society of Critical Care Medicine and the Infectious Diseases Society of America. Specialties represented included critical care medicine, surgery, internal medicine, infectious diseases, neurology, and laboratory medicine/microbiology.

EVIDENCE

The task force members provided personal experience and determined the published literature (MEDLINE articles, textbooks, etc.) from which consensus was obtained. Published literature was reviewed and classified into one of four categories, according to study design and scientific value.

CONSENSUS PROCESS

The task force met twice in person, several times by teleconference, and held multiple e-mail discussions during a 2-yr period to identify the pertinent literature and arrive at consensus recommendations. Consideration was given to the relationship between the weight of scientific evidence and the strength of the recommendation. Draft documents were composed and debated by the task force until consensus was reached by nominal group process.

CONCLUSIONS

The panel concluded that, because fever can have many infectious and noninfectious etiologies, a new fever in a patient in the intensive care unit should trigger a careful clinical assessment rather than automatic orders for laboratory and radiologic tests. A cost-conscious approach to obtaining cultures and imaging studies should be undertaken if indicated after a clinical evaluation. The goal of such an approach is to determine, in a directed manner, whether infection is present so that additional testing can be avoided and therapeutic decisions can be made.

Intensive-care unit lung infections: The role of imaging with special emphasis on multi-detector row computed tomography

Nosocomial pneumonia is the most frequent hospital-acquired infection. In mechanically ventilated patients admitted to an intensive-care unit as many as 7-41% may develop pneumonia. The role of imaging is to identify the presence, location and extent of pulmonary infection and the presence of complications. However, the poor resolution of bedside plain film frequently limits the value of radiography as an accurate diagnostic tool. To date, multi-detector row computed tomography with its excellent contrast resolution is the most sensitive modality for evaluating lung parenchyma infections.

Ventilator-Associated Pneumonia in Children

The purpose of this report is to review the current knowledge base related to the epidemiology, microbiology, diagnosis, and morbidity and mortality of ventilator-associated pneumonia and to review strategies to reduce the risk of acquiring this condition. Published guidelines are based largely on data from adult populations, and implications for the pediatric population must be extrapolated to a great extent. Some interventions, including elevation of the head of the bed for most patients and deep vein thrombosis prophylaxis in older pediatric patients, seem reasonable based on available literature. The use of daily sedation holidays must be weighed against the risk of inadvertent extubation. The routine use of stress ulcer prophylaxis in the pediatric population cannot be supported by the current literature.

Impact of clinical guidelines in the management of severe hospital-acquired pneumonia

STUDY OBJECTIVES

To asses the impact of locally developed antimicrobial treatment guidelines in the initial empiric treatment of ICU patients with severe hospital-acquired pneumonia (HAP).

DESIGN

Observational cohort study with pre-guideline and post-guideline data collection.

PATIENTS

A total of 48 pre-guideline patients with 56 episodes of severe HAP defined by the National Nosocomial Infections Surveillance (NNIS) compared with 58 guideline-treated (GUIDE) patients with 61 episodes of severe HAP.

RESULTS

The two groups were similar in terms of mean (+/- SD) age (NNIS group, 67.7 +/- 9.6 years; GUIDE group, 68.0 +/- 11.5 years) and simplified acute physiology score (NNIS group, 12.9 +/- 3.9; GUIDE group, 12.6 +/- 3.1) at the HAP diagnosis, and the proportion of the most frequent isolates (ie, Pseudomonas and methicillin-resistant Staphylococcus aureus). There was wide variation in initial antibiotic use in NNIS-treated patients, with cefotaxime, ceftazidime, and piperacillin being the most common agents compared with all of the GUIDE patients who received an imipenem-cilastin-based regimen. Vancomycin use was similar in both groups. The GUIDE patients had a higher percentage of adequately treated patients (81% vs 46%, respectively; p < 0.01) with a lower mortality rate at 14 days (8% vs 23%, respectively; p = 0.03). A lower mortality rate was also noted at the end of 30 days and the end of hospitalization but was not statistically significant. Appropriate imipenem use (as defined by the guidelines) occurred in 74% of the cases, and there was no increase in the number of imipenem-resistant organisms isolated during the course of the study.

CONCLUSIONS

These guidelines represent a successful implementation of a "deescalation" approach, because the recommended empiric therapy with broad-spectrum antibiotics was switched to therapy with narrower spectrum agents after 3 days. Based on our experience, this approach improves the adequacy of antibiotic treatment, with improvement in short-term survival and without increasing the emergence of resistant organisms.

Increased risk of bloodstream and urinary infections in intensive care unit (ICU) patients compared with patients fitting ICU admission criteria treated in regular wards

Critically ill patients, eligible for admission into intensive care units (ICUs), are often hospitalized in other wards due to a lack of ICU beds. Differences in morbidity between patients managed in ICUs and elsewhere are unknown, specifically the morbidity related to hospital-acquired infection. Patients fitting ICU admission criteria were identified by screening five entire hospitals on four separate days. Hospital infections within a 30-day follow-up period were compared in ICU patients and in patients on other wards using Kaplan-Meier curves. Residual differences in the patients' case mix between ICUs and other wards were adjusted for utilizing multivariate Cox models. Of 13415 patients screened, 668 were critically ill. The overall infection rates (per 100 patient-days) were 1.2 for bloodstream infection (BSI) and 1.9 for urinary tract infection (UTI). The adjusted hazard ratios in ICU patients compared with patients on regular wards were 3.1 (P<0.001) for BSI and 2.5 (P<0.001) for UTI. This increased risk persisted even after adjusting for the disparity in the number of cultures sent from ICUs compared with ordinary wards. No interdepartmental differences were found in the rates of pneumonia, surgical wound infections and other infections. Minimizing the differences between characteristics of patients hospitalized in ICUs and in other wards, and controlling for the higher frequency of cultures sent from ICUs did not eliminate the increased risk of BSI and UTI associated with admission into ICUs.

Respiratory nosocomial infections in the medical intensive care unit

Intensive care unit (ICU)-acquired lower respiratory tract infections include acute tracheobronchitis and hospital-acquired and ventilator-associated pneumonia (VAP). Nosocomial pneumonia is the second most common hospital-acquired infection and the leading cause of death in hospital-acquired infections. The mortality rate in VAP ranges from 24% to 76% in several studies. ICU ventilated patients with VAP have a 2- to 10-fold higher risk of death than patients without it. Early oropharyngeal colonization is pivotal in the etiopathogenesis of VAP. The knowledge of risk factors for VAP is important in developing effective preventive programs. Once the physician decides to treat a suspected episode of ICU-acquired pneumonia, some issues should be kept on mind: first, the adequacy of the initial empiric antibiotic therapy; second, the modification of initial inadequate therapy according to microbiological results; third, the benefit of combination therapy; and finally, the duration of the antimicrobial treatment. Additionally, a protocolized work-up to identify the causes of non-response to treatment is mandatory. All these issues are discussed in depth in this article.

Diagnosis of ventilator-associated pneumonia

The diagnosis of ventilator pneumonia remains a controversial area. Use of standard clinical criteria has been found to be inadequate. Use of a clinical pulmonary infection score (CPIS) has improved the diagnostic utility of clinical criteria. For the intubated patient, there is ready access to the lower respiratory tract. Samples include endotracheal aspirates, bronchoalveolar lavage and protected brush specimen. The latter two can be obtained blindly or via a bronchoscope. The culture results are more meaningful if reported in a semi-quantitative model. There is increasing evidence that culture results predict mortality and can be used to direct duration and type of therapy.

Diagnosis of pneumonia with an electronic nose: correlation of vapor signature with chest computed tomography scan findings

OBJECTIVES/HYPOTHESIS

The electronic nose is a sensor of volatile molecules that is useful in the analysis of expired gases. The device is well suited to testing the breath of patients receiving mechanical ventilation and is a potential diagnostic adjunct that can aid in the detection of patients with ventilator-associated pneumonia.

STUDY DESIGN

A prospective study.

METHODS

We performed a prospective study of patients receiving mechanical ventilation in a surgical intensive care unit who underwent chest computed tomography (CT) scanning. A single attending radiologist reviewed the chest CT scans, and imaging features were recorded on a standardized form. Within 48 hours of chest CT scan, five sets of exhaled gas were sampled from the expiratory limb of the ventilator circuit. The gases were assayed with a commercially available electronic nose. Both linear and nonlinear analyses were performed to identify correlations between imaging features and the assayed gas signatures.

RESULTS

Twenty-five patients were identified, 13 of whom were diagnosed with pneumonia by CT scan. Support vector machine analysis was performed in two separate analyses. In the first analysis, in which a training set was identical to a prediction set, the accuracy of prediction results was greater than 91.6%. In the second analysis, in which the training set and the prediction set were different, the accuracy of prediction results was at least 80%, with higher accuracy depending on the specific parameters and models being used.

CONCLUSION

The electronic nose is a new technology that continues to show promise as a potential diagnostic adjunct in the diagnosis of pneumonia and other infectious diseases.

[Difficulties on diagnosis of ventilator associated pneumonia]

Ventilator associated pneumonia is associated with high morbidity and mortality. It is important a correct diagnosis in way to guide the antibiotic therapy in the most appropriate way. However, its diagnosis is difficult, because clinical and radiologic features are not specific and approaches to standard diagnosis, that allow its confirmation, are very invasive or not very frequent. Protected techniques and quantitative cultures have been trying to outline the problem of the contamination of the samples obtained by routine methods and to allow the distinction between colonization and infection. The author makes a revision on the different methods of diagnosis of this clinical entity.

Radiology in the intensive care unit (Part I)

The increasing complexity of the intensive care patient combined with the recent advances in imaging technology has generated a new perspective on intensive care radiology. The purpose of this 2-part review article is to describe the contribution of radiology to the management of these critically ill patients. The first article will discuss the impact of picture archiving and communication system (PACS) on critical care management and utility of the portable chest radiograph in the detection and evaluation of pulmonary disease with correlation to computed tomography (CT). The second article describes in more detail the increasing role of CT in diagnosis and therapeutic procedures. In particular, the implementation of CT pulmonary angiography in the evaluation of pulmonary emboli and the introduction of the new multislice detector CT scanners that allow even the most dyspneic patient to be evaluated. Pleural complications in the intensive care unit and image-guided intervention will also be discussed.

Causes and predictors of nonresponse to treatment of intensive care unit–acquired pneumonia*

OBJECTIVE

To prospectively evaluate the predictive factors for the nonresponse to empirical antibiotic treatment and mortality in patients with intensive care unit-acquired pneumonia.

DESIGN

A 1-yr prospective cohort of patients with suspicion of intensive care unit-acquired pneumonia.

SETTING

Five medical and surgical intensive care units of Hospital Clinic in Barcelona.

PATIENTS

A total of 71 patients with intensive care unit-acquired pneumonia were studied. The definition of nonresponse included at least one of the following: failure to improve the Pao2/Fio2 ratio or need of intubation because of pneumonia, persistence of fever or hypothermia and purulent respiratory secretions, worsening of pulmonary infiltrates, or occurrence of septic shock or multiple organ dysfunction not present at onset of pneumonia.

INTERVENTIONS

Clinical assessment, including severity scores, blood and quantitative cultures of respiratory secretions, and cytokine measurements in serum and bronchoalveolar lavage at onset of pneumonia and 72 hrs after antimicrobial treatment.

MEASUREMENTS AND RESULTS

A total of 44 patients (62%) fulfilled criteria of nonresponse, and at least one cause of nonresponse could be determined in 28 cases (64%): inappropriate treatment in ten (23%), superinfection in six (14%), concomitant foci of infection in 12 (27%), and noninfectious causes in seven cases (16%). The remaining 16 patients with no definite cause of nonresponse presented with septic shock, multiple organ dysfunction, or acute respiratory distress syndrome. Increased levels of interleukin-6 at onset of pneumonia (odds ratio, 9.7; p =.014) was an independent predictor of nonresponse to treatment. Likewise, increased level of interleukin-6 at follow-up (odds ratio, 27; p =.001) was the only independent predictor for hospital mortality.

CONCLUSION

Increased systemic inflammatory response was the main predictor of nonresponse to treatment and mortality.

Treatment failures in patients with ventilator-associated pneumonia

Treatment failures in patients with VAP are a complex issue and form a major challenge for clinicians. The following key elements inherent to a rational approach to treatment failures have been elucidated: (1) the presence of treatment failure must be thoroughly defined and assessed; (2) the many causes behind treatment failures must be realized, particularly the possibility of pneumonia-related and extrapulmonary reasons; (3) the recognition of different patterns of treatment failures as a useful framework for decisions about modalities and intensity of diagnostic reassessment; and (4) the establishment of a protocol for the search of pulmonary and extrapulmonary sites of infection and noninfectious causes of nonresponse. Only such a rational approach precludes the adverse effects of blind empiricism, which always implies a dangerous and costly overtreatment. Many issues related to treatment failures remain unsettled, and efforts will have to be made in the future to improve current clinical attitudes to treatment failures in VAP.

Community-acquired and nosocomial pneumonia

Pneumonia is one of the leading causes of morbidity, hospitalization, and mortality in both industrialized and developing countries. In particular, pulmonary infections acquired in the community, and pneumonias arising in the hospital setting, represent a major medical and economic problem and thus a continuous challenge to health care. For the radiologist, it is important to understand that community-acquired pneumonia (CAP) and nosocomial pneumonia (NP) share a number of characteristics, but should, in many respects be regarded as separate entities. CAP and NP arise in different populations, host different spectra of causative pathogens, and pose different challenges to both the clinician and the radiologist. CAP is generally seen in outpatients, is most frequently caused by Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, and Chlamydia, and its radiologic diagnosis is relatively straightforward. NP, in contrast, develops in the hospital setting, is commonly caused by gram-negative bacteria, and may generate substantial problems for the radiologist. Overall, both for CAP and NP, imaging is an integral component of the diagnosis, important for classification and differential diagnosis, and helpful for follow-up.

Ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation (MV). In contrast to infections of more frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1 to 4%, the mortality rate for VAP ranges from 24 to 50% and can reach 76% in some specific settings or when lung infection is caused by high-risk pathogens. The predominant organisms responsible for infection are Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae, but etiologic agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, and prior antimicrobial therapy. Because appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. Our personal bias is that using bronchoscopic techniques to obtain protected brush and bronchoalveolar lavage specimens from the affected area in the lung permits physicians to devise a therapeutic strategy that is superior to one based only on clinical evaluation. When fiberoptic bronchoscopy is not available to physicians treating patients clinically suspected of having VAP, we recommend using either a simplified nonbronchoscopic diagnostic procedure or following a strategy in which decisions regarding antibiotic therapy are based on a clinical score constructed from seven variables. Selection of the initial antimicrobial therapy should be based on predominant flora responsible for VAP at each institution, clinical setting, information provided by direct examination of pulmonary secretions, and intrinsic antibacterial activities of antimicrobial agents and their pharmacokinetic characteristics. Further trials will be needed to clarify the optimal duration of treatment and the circumstances in which monotherapy can be safely used.

Acute respiratory distress syndrome: imaging of the injured lung

In patients with the acute respiratory distress syndrome (ARDS), there is non-specific but widespread exudation of oedema and inflammatory fluid into the lungs. The clinical corollary (dyspnoea, refractory hypoxia, reduced pulmonary compliance and diffuse pulmonary infiltrates) is catastrophic and generally associated with a poor outcome. Imaging is integral to the care of these critically ill patients on the intensive care unit. In the present review, the radiological changes on plain radiography and computed tomography (CT) in patients with ARDS are discussed. Particular attention is directed at the appearances on CT: the relationships between CT features, histopathological changes and the inevitable alterations in pulmonary physiology are explored.