Diagnosis of nosocomial bacterial pneumonia in intubated patients undergoing ventilation: comparison of the usefulness of bronchoalveolar lavage and the protected specimen brush

A systematic review and meta-analysis of prevalence of complications after tracheal stenting in dogs

BACKGROUND

Stenting has become popular to treat tracheal collapse in dogs, but complications might arise and negatively affect treatment outcome.

OBJECTIVES

Determine the overall prevalence of complications of tracheal stenting in dogs.

METHODS

A bibliographic search was performed of publications from 2000 to 2020. Studies were assessed for quality of evidence and measured prevalence of the 8 most commonly reported complications after tracheal stenting in dogs (stent fracture, stent migration, relapsing collapse, granuloma formation, tracheobronchial infections, and early, late, and clinically relevant late cough). Random effects meta-analyses were used to estimate pooled complications prevalence.

RESULTS

Fifteen studies met inclusion criteria. Cough (early: 99%; 95% confidence interval [95% CI]: 95%-100%, late: 75%; 95% CI: 63%-85%, and clinically relevant: 52%; 95% CI: 42%-61%), tracheobronchial infections (24%; 95% CI: 14%-35%), and granulomas (20%; 95% CI: 11%-30%) were common after tracheal stenting. Stent fractures (12%; 95% CI: 5%-20%), relapsing collapse (10%; 95% CI: 5%-15%), and stent migration (5%; 95% CI: 1%-9%) were less frequent. Significant heterogeneity among studies was identified for the estimated prevalence of stent fracture, granulomas, infections, and late cough.

CONCLUSIONS AND CLINICAL IMPORTANCE

Tracheal stenting in dogs is associated with a high risk of coughing and a moderate risk of tracheobronchial infections and granuloma formation. Because most complications will impact a dog's quality of life, owners must be informed that tracheal stenting is a second-line procedure that does not necessarily alleviate the need for medical treatment and frequent follow-up visits. Additional studies are warranted to identify the risk factors of these complications.

Outcomes of Herpes Simplex Virus Pneumonitis in Critically Ill Patients

Critically ill patients, such as those in intensive care units (ICUs), can develop herpes simplex virus (HSV) pneumonitis. Given the high prevalence of acute respiratory distress syndrome (ARDS) and multiple pre-existing conditions among ICU patients with HSV pneumonitis, factors predicting mortality in this patient population require further investigation. In this retrospective study, the bronchoalveolar lavage or sputum samples of ICU patients were cultured or subjected to a polymerase chain reaction for HSV detection. Univariable and multivariable Cox regressions were conducted for mortality outcomes. The length of hospital stay was plotted against mortality on Kaplan–Meier curves. Among the 119 patients with HSV pneumonitis (age: 65.8 ± 14.9 years), the mortality rate was 61.34% (73 deaths). The mortality rate was significantly lower among patients with diabetes mellitus (odds ratio [OR] 0.12, 95% confidence interval [CI]: 0.02–0.49, p = 0.0009) and significantly higher among patients with ARDS (OR: 4.18, 95% CI: 1.05–17.97, p < 0.0001) or high (≥30) Acute Physiology and Chronic Health Evaluation II scores (OR: 1.08, 95% CI: 1.00–1.18, p = 0.02). Not having diabetes mellitus (DM), developing ARDS, and having a high Acute Physiology and Chronic Health Evaluation II (APACHE II) score were independent predictors of mortality among ICU patients with HSV pneumonitis.

Bacterial infection in dogs with aspiration pneumonia at 2 tertiary referral practices

Background

In dogs, antimicrobial drugs are widely prescribed for aspiration pneumonia (AP) despite poor documentation of bacterial infection in AP (b‐AP) using bronchoalveolar lavage fluid (BALF) analysis. Interpretating discordant cytology and culture results is challenging, contributing to lack of a criterion standard, and highlighting differences between veterinary and human medical criteria for b‐AP.

Objectives

Determine how many dogs with AP had BALF collection and differences in diagnosis of b‐AP using veterinary vs human medical criteria. Report findings of noninvasive markers (e.g. fever, band neutrophilia, radiographic severity score) in dogs with and without b‐AP.

Animals

Retrospective cohort study of client‐owned dogs (n = 429) with AP at 2 university veterinary hospitals. Twenty‐four dogs met enrollment criteria.

Methods

Inclusion criteria were radiographic diagnosis of AP, ≥1 risk factor, CBC findings, and BALF cytology and culture results. Veterinary medical b‐AP criteria were cytology findings compatible with sepsis with or without positive culture, or cytology findings not consistent with sepsis and positive culture (≥1.7 × 10³ cfu/mL). Human medical b‐AP criteria required culture with ≥10⁴ cfu/mL or > 7% cells with intracellular bacteria on cytology.

Results

Only 24/429 dogs met all enrollment criteria; 379/429 dogs lacked BALF collection. Diagnosis of b‐AP differed using veterinary (79%) vs human (29%) medical criteria. Fever, band neutrophils and high radiographic scores were noted in dogs with and without b‐AP.

Conclusions and Clinical Importance

Lack of routine BALF collection hampers definitive recognition of bacterial infection in AP. Differences in dogs meeting veterinary vs human medical definitions for b‐AP and usefulness of noninvasive markers warrant further study to improve understanding of the role of bacteria in AP.

Multicentric evaluation of BioFire FilmArray Pneumonia Panel for rapid bacteriological documentation of pneumonia

OBJECTIVES

To evaluate performances of the rapid multiplex PCR assay BioFire FilmArray Pneumonia Panel (FA-PP) for detection of bacterial pathogens and antibiotic resistance genes in sputum, endotracheal aspirate (ETA) and bronchoalveolar lavage (BAL) specimens.

METHODS

This prospective observational study was conducted in 11 French university hospitals (July to December 2018) and assessed performance of FA-PP by comparison with routine conventional methods.

RESULTS

A total of 515 respiratory specimens were studied, including 58 sputa, 217 ETA and 240 BAL. The FA-PP detected at least one pathogen in 384 specimens, yielding an overall positivity rate of 74.6% (384/515). Of them, 353 (68.5%) specimens were positive for typical bacteria while eight atypical bacteria and 42 resistance genes were found. While identifying most bacterial pathogens isolated by culture (374/396, 94.4%), the FA-PP detected 294 additional species in 37.7% (194/515) of specimens. The FA-PP demonstrated positive percentage agreement and negative percentage agreement values of 94.4% (95% CI 91.7%-96.5%) and 96.0% (95% CI 95.5%-96.4%), respectively, when compared with culture. Of FA-PP false-negative results, 67.6% (46/68) corresponded to bacterial species not included in the panel. At the same semi-quantification level (in DNA copies/mL for FA-PP versus in CFU/mL for culture), the concordance rate was 43.4% (142/327) for culture-positive specimens with FA-PP reporting higher semi-quantification of ≥1 log₁₀ in 48.6% (159/327) of cases. Interestingly, 90.1% of detected bacteria with ≥10⁶ DNA copies/mL grew significantly in culture.

CONCLUSIONS

FA-PP is a simple and rapid molecular test that could complement routine conventional methods for improvement of diagnosis accuracy of pneumonia.

Ventilator-associated pneumonia in patients with SARS-CoV-2-associated acute respiratory distress syndrome requiring ECMO: a retrospective cohort study

Background

The data on incidence, clinical presentation, and outcomes of ventilator-associated pneumonia (VAP) in patients with severe coronavirus disease 2019 (COVID-19) pneumonia requiring mechanical ventilation (MV) are limited. We performed this retrospective cohort study to assess frequency, clinical characteristics, responsible pathogens, and outcomes of VAP in patients COVID-19 pneumonia requiring MV between March 12th and April 24th, 2020 (all had RT-PCR-confirmed SARS-CoV-2 infection). Patients with COVID-19-associated acute respiratory distress syndrome (ARDS) requiring ECMO were compared with an historical cohort of 45 patients with severe influenza-associated ARDS requiring ECMO admitted to the same ICU during the preceding three winter seasons.

Results

Among 50 consecutive patients with Covid-19-associated ARDS requiring ECMO included [median (IQR) age 48 (42–56) years; 72% male], 43 (86%) developed VAP [median (IQR) MV duration before the first episode, 10 (8–16) days]. VAP-causative pathogens were predominantly Enterobacteriaceae (70%), particularly inducible AmpC-cephalosporinase producers (40%), followed by Pseudomonas aeruginosa (37%). VAP recurred in 34 (79%) patients and 17 (34%) died. Most recurrences were relapses (i.e., infection with the same pathogen), with a high percentage occurring on adequate antimicrobial treatment. Estimated cumulative incidence of VAP, taking into account death and extubation as competing events, was significantly higher in Covid-19 patients than in influenza patients (p = 0.002). Despite a high P. aeruginosa-VAP rate in patients with influenza-associated ARDS (54%), the pulmonary infection recurrence rate was significantly lower than in Covid-19 patients. Overall mortality was similar for the two groups.

Conclusions

Patients with severe Covid-19-associated ARDS requiring ECMO had a very high late-onset VAP rate. Inducible AmpC-cephalosporinase-producing Enterobacteriaceae and Pseudomonas aeruginosa frequently caused VAP, with multiple recurrences and difficulties eradicating the pathogen from the lung.

Detection of microbial genes in a single leukocyte by polymerase chain reaction following laser capture microdissection

Although isolation and identification of bacteria in a clinical specimen constitute essential steps for the diagnosis of bacterial infection, positive results of the bacterial culture are not always attained, despite observing the bacteria by Gram staining. As bacteria phagocytosed by the leukocytes are considered as the causative agents of infectious diseases, this study aims to introduce a new approach for the collection of only bacteria phagocytosed by the neutrophils in an animal model using laser capture microdissection (LCM) followed by the DNA identification using polymerase chain reaction (PCR). We inoculated representative bacteria (Escherichia coli and Staphylococcus aureus) into the abdominal cavities of specific pathogen-free C57BL/6 J mice. After 6 h inoculation, we collected the fluid samples from the peritoneal cavities of mice and demonstrated peritonitis by the increase of neutrophils. Then, we smeared the neutrophils on the membrane slides and collected single-cell phagocytosing bacteria by LCM. The supernatant of the cell lysate was supplied for the PCR reaction to amplify the 16S rRNA gene, and we validated the DNA sequences specific for the inoculated bacteria. In addition, PCR using specific primers for E. coli and S. aureus identified each species of bacteria. Hence, this study suggests that the combination of LCM and PCR could be a novel approach to determine bacteria in infectious diseases. Nevertheless, further investigation is warranted to test various additional bacterial taxa to demonstrate the general applicability of this method to clinical samples.

Ventilator-Associated Pneumonia Patients who Do Not Reduce Bacteria from the Lungs have a Worse Prognosis

The authors determined the significance of serial semi-quantitative bronchoalveolar lavage (BAL) culture results in patients undergoing therapy for ventilator-associated pneumonia. A total of 32 patients underwent at least 2 nonbronchoscopic BAL studies. Fourteen patients had methicillin-resistant Staphylococcus aureus(MRSA). Of these, 11 had more than 100 colony-forming units (cfu) of MRSA/mL of BAL from the follow-up BAL. Eighteen patients had an organism other than MRSA, and 7 of these patients had > 100 cfu of bacteria/mL of BAL from the follow-up BAL. Of the 18 patients with > 100 cfu of bacteria/mL of BAL at follow-up, 14 (79%) died, whereas only 5 of 14 (36%) patients who cleared their bacteria at follow-up died within 28 days. The inability to reduce the bacterial burden from the lower respiratory tract within the first few days of therapy for ventilator-associated pneumonia was associated with increased mortality.

The microbiome at the pulmonary alveolar niche and its role in Mycobacterium tuberculosis infection

Advances in next generation sequencing (NGS) technology have provided the tools to comprehensively and accurately characterize the microbial community in the respiratory tract in health and disease. The presence of commensal and pathogenic bacteria has been found to have important effects on the lung immune system. Until relatively recently, the lung has received less attention compared to other body sites in terms of microbiome characterization, and its study carries special technological difficulties related to obtaining reliable samples as compared to other body niches. Additionally, the complexity of the alveolar immune system, and its interactions with the lung microbiome, are only just beginning to be understood. Amidst this complexity sits Mycobacterium tuberculosis (Mtb), one of humanity's oldest nemeses and a significant public health concern, with millions of individuals infected with Mtb worldwide. The intricate interactions between Mtb, the lung microbiome, and the alveolar immune system are beginning to be understood, and it is increasingly apparent that improved treatment of Mtb will only come through deep understanding of the interplay between these three forces. In this review, we summarize our current understanding of the lung microbiome, alveolar immunity, and the interaction of each with Mtb.

Structure of type II dehydroquinase from Pseudomonas aeruginosa

Pseudomonas aeruginosa causes opportunistic infections and is resistant to most antibiotics. Ongoing efforts to generate much-needed new antibiotics include targeting enzymes that are vital for P. aeruginosa but are absent in mammals. One such enzyme, type II dehydroquinase (DHQase), catalyzes the interconversion of 3-dehydroquinate and 3-dehydroshikimate, a necessary step in the shikimate pathway. This step is vital for the proper synthesis of phenylalanine, tryptophan, tyrosine and other aromatic metabolites. The recombinant expression, purification and crystal structure of catalytically active DHQase from P. aeruginosa (PaDHQase) are presented. Cubic crystals belonging to space group F23, with unit-cell parameters a=b=c=125.39 Å, were obtained by vapor diffusion in sitting drops and the structure was refined to an R factor of 16% at 1.74 Å resolution. PaDHQase is a prototypical type II DHQase with the classical flavodoxin-like α/β topology.

Abundant DNase I-sensitive bacterial DNA in healthy porcine lungs and its implications for the lung microbiome

Human lungs are constantly exposed to bacteria in the environment, yet the prevailing dogma is that healthy lungs are sterile. DNA sequencing-based studies of pulmonary bacterial diversity challenge this notion. However, DNA-based microbial analysis currently fails to distinguish between DNA from live bacteria and that from bacteria that have been killed by lung immune mechanisms, potentially causing overestimation of bacterial abundance and diversity. We investigated whether bacterial DNA recovered from lungs represents live or dead bacteria in bronchoalveolar lavage (BAL) fluid and lung samples in young healthy pigs. Live bacterial DNA was DNase I resistant and became DNase I sensitive upon human antimicrobial-mediated killing in vitro. We determined live and total bacterial DNA loads in porcine BAL fluid and lung tissue by comparing DNase I-treated versus untreated samples. In contrast to the case for BAL fluid, we were unable to culture bacteria from most lung homogenates. Surprisingly, total bacterial DNA was abundant in both BAL fluid and lung homogenates. In BAL fluid, 63% was DNase I sensitive. In 6 out of 11 lung homogenates, all bacterial DNA was DNase I sensitive, suggesting a predominance of dead bacteria; in the remaining homogenates, 94% was DNase I sensitive, and bacterial diversity determined by 16S rRNA gene sequencing was similar in DNase I-treated and untreated samples. Healthy pig lungs are mostly sterile yet contain abundant DNase I-sensitive DNA from inhaled and aspirated bacteria killed by pulmonary host defense mechanisms. This approach and conceptual framework will improve analysis of the lung microbiome in disease.

Storage of bronchoalveolar lavage fluid and accuracy of microbiologic diagnostics in the ICU: a prospective observational study

INTRODUCTION

Early initiation of appropriate antimicrobial treatment is a cornerstone in managing pneumonia. Because microbiologic processing may not be available around the clock, optimal storage of specimens is essential for accurate microbiologic identification of pathogenetic bacteria. The aim of our study was to determine the accuracy of two commonly used storage approaches for delayed processing of bronchoalveolar lavage in critically ill patients with suspected pneumonia.

METHODS

This study included 132 patients with clinically suspected pneumonia at two medical intensive care units of a tertiary care hospital. Bronchoalveolar lavage samples were obtained and divided into three aliquots: one was used for immediate culture, and two, for delayed culture (DC) after storage for 24 hours at 4°C (DC4) and -80°C (DC-80), respectively.

RESULTS

Of 259 bronchoalveolar lavage samples, 84 (32.4%) were positive after immediate culture with 115 relevant culture counts (≥104 colony-forming units/ml). Reduced (<104 colony-forming units/ml) or no growth of four and 57 of these isolates was observed in DC4 and DC-80, respectively. The difference between mean bias of immediate culture and DC4 (-0.035; limits of agreement, -0.977 to 0.906) and immediate culture and DC-80 (-1.832; limits of agreement, -4.914 to 1.267) was -1.788 ± 1.682 (P < 0.0001). Sensitivity and negative predictive value were 96.5% and 97.8% for DC4 and 50.4% and 75.4% for DC-80, respectively; the differences were statistically significant (P < 0.0001).

CONCLUSIONS

Bronchoalveolar lavage samples can be processed for culture when stored up to 24 hours at 4°C without loss of diagnostic accuracy. Delayed culturing after storage at -80°C may not be reliable, in particular with regard to Gram-negative bacteria.

Clinical Aspects of Upper and Lower Respiratory Tract Infections

Respiratory tract infections are among the most common illnesses leading to medical consultation, and are associated with significant mortality. Community-acquired pneumonia is a common illness and, while Streptococcus pneumoniae continues to be the most frequent causative agent, atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella species are now identified as additional common aetiological agents. Since clinical and roentgenographic features poorly predict the aetiological agent in most cases of community-acquired pneumonia, empirical therapy is generally recommended. Nosocomial pneumonia is the second most common hospital-acquired infection and is associated with significant mortality. Aerobic Gram-negative bacilli and Staphylococcus aureus are the predominant causative pathogens. New techniques to improve the diagnosis of nosocomial pneumonia have been introduced, but their role has not been entirely clarified. Therapy directed toward the most likely pathogens (aerobic Gram-negative species and S. aureus) on an empirical basis is recommended until more specific information is obtained. Acute exacerbations of chronic bronchitis should be treated with antimicrobial therapy directed toward S. pneumoniae, Haemophilus influenzae or Moraxella catarrhalis. Because of the emergence of β-lactamase-producing strains of H. influenzae and M. catarrhalis, the choice of an antimicrobial agent has to be carefully considered. Group A β-haemolytic streptococci are the most common cause of bacterial pharyngitis and penicillin remains the drug of choice. Patients suffering from otitis media and sinusitis are infected with the same organisms as those patients with acute exacerbations of chronic bronchitis and antibacterial choices are therefore similar.

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.

Ventilator-associated pneumonia: current status and future recommendations

OBJECTIVE

Ventilator-associated pneumonia (VAP) is a common hazardous complication in ICU patients. The aim of the current review is to give an update on the current status and future recommendations for VAP prevention.

METHODS

This article gives an updated review of the current literature on VAP. The first part briefly reviews pathogenesis and epidemiology while the second includes an in-depth review of evidence-based practice guidelines (EBPG) and new technologies developed for prevention of VAP.

RESULTS

VAP remains a frequent and costly complication of critical illness with a pooled relative risk of 9-27% and mortality of 25-50%. Strikingly, VAP adds an estimated cost of more than $40,000 to a typical hospital admission. An important aetiological mechanism of VAP is gross or micro-aspiration of oropharyngeal organisms around the cuff of the endotracheal tube (ETT) into the distal bronchi. Prevention of VAP is preferable. Preventative measures can be divided into two main groups: the implemen- tation of EBPGs and use of device-based technologies. EBPGs have been authored jointly by the American Thoracic Society and the Infectious Diseases Society of America. The Canadian Critical Care Trials group also published VAP Guidelines in 2008. Their recommendations are detailed in this review. The current device-based technologies include drainage of subglottic secretions, silver coated ETTs aiming to influence the internal bio-layer of the ETT, better sealing of the lower airways with ultrathin cuffs and loops for optimal cuff pressure control.

CONCLUSIONS

EBPG consensus includes: elevation of the head of the bed, use of daily "sedation vacations" and decontamination of the oropharynx. Technological solutions should aim to use the most comprehensive combination of subglottic suction of secretions, optimization of ETT cuff pressure and ultrathin cuffs. VAP is a type of hospital-acquired pneumonia that develops more than 48 h after endotracheal intubation. Its incidence is estimated to be 9-27%, with a mortality of 25-50% [Am J Respir Crit Care Med 171:388-416 (2005), Am J Med 85:499-506 (1988), Chest 122:2115-2121 (2002), Intensive Care Med 35:9-29 (2009)]. The most important target in VAP handling is its prevention. The aim of this article is to review the pathogenesis, epidemiology and the different strategies/technologies for prevention of VAP.

Ventilator-Associated Pneumonia

The area of the alveolar epithelium of the lung is approximately 70 m². This area is constantly in contact with the ambient air and is therefore vulnerable to contamination with airborne microbes and particles of respirable size. Due to the configuration of the respiratory tract, airborne particles having diameters in the range of 0.5-2.0 μ can reach and deposit in the terminal part of the tracheobronchial tree - most bacteria are of this size. In reality, very few bacteria cause infections by spreading via the airborne route (e.g., mycobacteria, viruses, and legionella). Most bacteria cause pneumonia by first colonizing the upper respiratory tract and later descending into the tracheobronchial tree.

The use of carbapenems in the treatment of serious infections

Inadequate initial antimicrobial treatment in serious infections leads to increased mortality. Achieving adequate treatment is increasingly difficult because of the increasing prevalence of multidrug-resistant (MDR) pathogens. The carbapenems are potent, broad-spectrum antibiotics that have been shown to be safe and efficacious therapies in the treatment of serious infections. This review is intended to compare the 4 major members of the carbapenem class, which include imipenem, meropenem, ertapenem, and doripenem, with other widely used antimicrobial agents in the intensive care unit (ICU). The carbapenems are potent, broad-spectrum antibiotics that have been shown to be safe and efficacious therapies in the treatment of serious infections. They provide better gram-negative coverage than other beta-lactams and are stable against extended-spectrum beta-lactamases and AmpC beta-lactamases, making them effective in the treatment of many MDR bacteria. The newly approved carbapenem, doripenem, may help preserve the utility of the carbapenem class.

Does de-escalation of antibiotic therapy for ventilator-associated pneumonia affect the likelihood of recurrent pneumonia or mortality in critically ill surgical patients?

BACKGROUND

Ventilator-associated pneumonia (VAP) is a leading cause of mortality in critically ill patients. Although previous studies have shown that de-escalation therapy (DT) of antibiotics may decrease costs and the development of resistant pathogens, minimal data have shown its effect in surgical patients or in any patients with septic shock. We hypothesized that DT for VAP was not associated with an increased rate of recurrent pneumonia (RP) or mortality in a high acuity cohort of critically ill surgical patients.

METHODS

All surgical intensive care unit (SICU) patients from January 2005 to May 2007 with VAP diagnosed by quantitative bronchoalveolar lavage with a positive threshold of 10,000 CFU/mL were identified. Data collected included age, gender, Acute Physiologic and Chronic Health Evaluation Score III (A3), type of bacterial or other pathogen, antibiotics used for initial and final therapy, mortality, RP, and appropriateness of initial therapy (AIT). Patients were designated as receiving AIT, DT, or escalation of antibiotic therapy based on microbiology for their VAP.

RESULTS

One hundred thirty-eight of 1,596 SICU patients developed VAP during the study period (8.7%). For VAP patients, the mean Acute Physiologic and Chronic Health Evaluation III score was 82.7 points with a mean age of 63.8 years. The RP rate was 30% and did not differ between patients receiving DT (27.3%) and those who did not receive DT (35.1%). Overall mortality was 37% (55% predicted by A3 norms) and did not differ between those receiving DT (33.8%) or not (42.1%). The most common pathogens for primary VAP were methicillin-resistant Staphylococcus aureus (14%), Escherichia coli (11%), and Pseudomonas aeruginosa (9%) whereas P. aeruginosa was the most common pathogen in RP. The AIT for all VAP was 93%. De-escalation of therapy occurred in 55% of patients with AIT whereas 8% of VAP patients required escalation of antibiotic therapy. The most commonly used initial antibiotic choice was vancomycin/piperacillin-tazobactam (16%) and the final choice was piperacillin-tazobactam (20%). Logistic regression demonstrated no specific parameter correlated with development of RP. Higher A3 (Odds ratio, 1.03; 95% confidence interval, 1.01-1.05) was associated with mortality whereas lack of RP (odds ratio, 0.31; 95% confidence interval, 0.12-0.80), and AIT reduced mortality (odds ratio, 0.024; 95% confidence interval, 0.007-0.221). Age, gender, individual pathogen, individual antibiotic regimen, and the use of DT had no effect on mortality.

CONCLUSION

De-escalation therapy did not lead to RP or increased mortality in critically ill surgical patients with VAP. De-escalation therapy was also shown to be safe in patients with septic shock. Because of its acknowledged benefits and lack of demonstrable risks, de-escalation therapy should be used whenever possible in critically ill patients with VAP.

Influence of antibiotic therapy on the cytological diagnosis of ventilator-associated pneumonia

OBJECTIVE

To assess the influence of antibiotics on the value of various cytological parameters, and their combinations, in diagnosing ventilator-associated pneumonia (VAP).

DESIGN

Prospective study.

SETTING

The general intensive care unit (17 beds) of the University Hospital Maastricht.

PATIENTS

Three hundred and thirty-five episodes of clinically suspected VAP (defined by the clinical and radiological criteria previously described by Bonten et al.) in 282 patients were studied.

INTERVENTIONS

No additional interventions were conducted.

MEASUREMENTS AND RESULTS

Bronchoalveolar lavage fluid cytology included a total cell count per millilitre, differential cell count and the percentage of infected cells (cells containing phagocytised organisms). Antibiotic therapy from 72 h prior to lavage was recorded. Areas under the curve (AUCs) of receiver operating characteristic curves were calculated for various cytological parameters and their combinations, in patients with and without antibiotic therapy. In 126 episodes (37.6%) in 106 patients, VAP was confirmed. There was no difference in AUCs between patients with and without antibiotic therapy for any parameter studied. The most prominent AUCs were (for patient groups with and without antibiotics combined): total cell count, 0.65; percentage polymorphonuclear neutrophils, 0.71; and percentage infected cells, 0.90. The combination of percentage infected cells with any other cytological parameter did not increase the AUC.

CONCLUSION

Antibiotic therapy did not influence the predictive value of the percentage infected cells in BALF in diagnosing VAP.

Sepsis: rethinking the approach to clinical research

The clinical syndrome of sepsis encompasses a highly heterogeneous group of clinical disorders, varying with respect to the site, bacteriology, and even presence of infection and with the clinical syndrome evolving in the host. Clinical trials of strategies to modulate the host response that mediates sepsis were first initiated 25 years ago. A continuing record of disappointment has characterized subsequent work, and only a single new therapy has been licensed for clinical use. Yet, these commercial disappointments obscure a vibrant body of new knowledge that has clarified the biology of the innate immune response whose deranged expression is responsible for sepsis and that has provided important new insights into the failings of the traditional model of clinical research in sepsis. This review highlights advances in basic biology and underlines insights from clinical research that may point to new and more effective ways of translating an understanding of innate immunity into effective treatments for a leading cause of global morbidity and mortality.

Bacterial Infections

In Osier’s time, bacterial pneumonia was a dreaded event, so important that he borrowed John Bunyan’s characterization of tuberculosis and anointed the pneumococcus, as the prime pathogen, “Captain of the men of death.”1 One hundred years later much has changed, but much remains the same. Pneumonia is now the sixth most common cause of death and the most common lethal infection in the United States. Hospital-acquired pneumonia is now the second most common nosocomial infection.2 It was documented as a complication in 0.6% of patients in a national surveillance study,3 and has been reported in as many as 20% of patients in critical care units.4 Furthermore, it is the leading cause of death among nosocomial infections.5 Leu and colleagues6 were able to associate one third of the mortality in patients with nosocomial pneumonia to the infection itself. The increase in hospital stay, which averaged 7 days, was statistically significant. It has been estimated that nosocomial pneumonia produces costs in excess of $500 million each year in the United States, largely related to the increased length of hospital stay.

A contributive result of open-lung biopsy improves survival in acute respiratory distress syndrome patients

OBJECTIVE

The impact of a contributive result of open-lung biopsy on the outcome of patients with acute respiratory distress syndrome (ARDS) has not been extensively investigated. The aim of this study was therefore to determine the rate of contributive open-lung biopsy and whether it improved the prognosis of ARDS patients.

DESIGN

Prospective study conducted during an 8-yr period.

SETTING

A 14-bed medico-surgical intensive care unit and a 12-bed medical intensive care unit from the same hospital.

PATIENTS

One hundred open-lung biopsies were performed in 100 patients presenting ARDS.

INTERVENTIONS

Open-lung biopsy was performed after > or = 5 days of evolution of ARDS when there was no improvement in the respiratory status despite negative microbiological samples cultures and potential indication for corticosteroid treatment.

MEASUREMENTS AND MAIN RESULTS

Ten patients presented a mechanical complication following open-lung biopsy (two pneumothoraces and eight moderate air leaks). The unique independent factor associated with this complication was the minute ventilation when open-lung biopsy was performed (odds ratio, 1.20; 95% confidence interval, 1.03-1.41; p = .02). Fibrosis was noted in 53 patients but was associated with an infection in 29 of these 53 patients (55%). A contributive result of open-lung biopsy (defined as the addition of a new drug) was noted in 78 patients. Simplified Acute Physiology Score II was the only independent predictive factor of a contributive open-lung biopsy (odds ratio, 0.96; 95% confidence interval, 0.92-0.99; p = .04). Survival was higher in patients with a contributive open-lung biopsy (67%) than in patients in whom open-lung biopsy results did not modify the treatment (14%) (p < .001). The factors predicting survival were a contributive result of open-lung biopsy, female gender, and the Organ System Failures score the day of open-lung biopsy.

CONCLUSIONS

The present study shows that open-lung biopsy provided a contributive result in 78% of ARDS patients with a negative bronchoalveolar lavage. Survival of ARDS patients improved when open-lung biopsy was contributive.

Does invasive diagnosis of nosocomial pneumonia during off-hours delay treatment?

OBJECTIVE

We examined whether invasive lung-specimen collection-to-treatment times for intensive care unit patients with suspected ventilator-associated pneumonia (VAP) differ with to the work shift during which specimens were collected. We compared weekday day shifts and off-hours (from 6:30 p.m. to 8:29 a.m. the next day for night shifts, from Saturday 1:00 p.m. to Monday 8:29 a.m. for weekends, and from 8:30 a.m. to 8:29 a.m. the following morning for public holidays).

DESIGN AND SETTING

Single-center, observational study in the intensive care unit in an academic teaching hospital.

PATIENTS AND PARTICIPANTS

101 patients who developed 152 episodes of bacteriologically confirmed VAP.

MEASUREMENTS AND RESULTS

Of the 152 VAP episodes 66 were diagnosed during off-hours. Neither more bronchoscopy complications nor more inappropriate initial antimicrobial treatments for patients were observed between day and off-hour shifts. Indeed, the overall time from brochoalveolar lavage to antibiotic administration was shorter for off-hours than day-shifts due to shorter specimen collection-to-antibiotic prescription times, but antibiotic prescription-to-administration times were the same.

CONCLUSIONS

An invasive strategy based on bronchoscopy to diagnose VAP was not associated with a longer time to first appropriate antibiotic administration when clinical suspicion of VAP occurs during off-hours.

Herpes simplex virus lung infection in patients undergoing prolonged mechanical ventilation

RATIONALE

It is not known whether the isolation of herpes simplex virus (HSV) from lower respiratory tract samples of nonimmunocompromised ventilated patients corresponds to bronchial contamination from the mouth and/or throat, local tracheobronchial excretion of HSV, or true HSV lung involvement (bronchopneumonitis) with its own morbidity/mortality.

OBJECTIVES

This prospective, single-center, observational study was conducted to define the frequency, risk factors, and relevance of HSV bronchopneumonitis.

METHODS

All consecutive nonimmunocompromised patients receiving mechanical ventilation for 5 days or more were evaluated. Bronchoalveolar lavage, oropharyngeal swabs, and bronchial biopsies (presence of macroscopic bronchial lesions) were obtained for all who deteriorated clinically with suspected lung infection. HSV bronchopneumonitis was defined as this deterioration, associated with HSV in bronchoalveolar lavage and HSV-specific nuclear inclusions in cells recovered during lavage or bronchial biopsies.

MEASUREMENTS AND MAIN RESULTS

HSV bronchopneumonitis was diagnosed in 42 (21%) of the 201 patients who deteriorated clinically, with a mean mechanical ventilation duration before diagnosis of 14 +/- 6 days. Risk factors associated with HSV bronchopneumonitis were oral-labial lesions, HSV in the throat, and macroscopic bronchial lesions seen during bronchoscopy. Patients with HSV bronchopneumonitis were comparable to those without at admission, but their courses were more complicated, with longer duration of mechanical ventilation and intensive care unit stays.

CONCLUSIONS

HSV bronchopneumonitis is common in nonimmunocompromised patients with prolonged mechanical ventilation, is associated with HSV reactivation or infection of the mouth and/or throat, and seems to be associated with poorer outcome.

Bronchoalveolar lavage cytological alveolar damage in patients with severe pneumonia

Introduction

Histological examination of lung specimens from patients with pneumonia shows the presence of desquamated pneumocytes and erythrophages. We hypothesized that these modifications should also be present in bronchoalveolar lavage fluid (BAL) from patients with hospital-acquired pneumonia.

Methods

We conducted a prospective study in mechanically ventilated patients with clinical suspicion of pneumonia. Patients were classified as having hospital-acquired pneumonia or not, in accordance with the quantitative microbiological cultures of respiratory tract specimens. A group of severe community-acquired pneumonias requiring mechanical ventilation during the same period was used for comparison. A specimen of BAL (20 ml) was taken for cytological analysis. A semiquantitative analysis of the dominant leukocyte population, the presence of erythrophages/siderophages and desquamated type II pneumocytes was performed.

Results

In patients with confirmed hospital-acquired pneumonia, we found that 13 out of 39 patients (33.3%) had erythrophages/siderophages in BAL, 18 (46.2%) had desquamated pneumocytes and 8 (20.5%) fulfilled both criteria. Among the patients with community-acquired pneumonia, 7 out of 15 (46.7%) had erythrophages/siderophages and 6 (40%) had desquamated pneumocytes on BAL cytology. Only four (26.7%) fulfilled both criteria. No patient without hospital-acquired pneumonia had erythrophages/siderophages and only 3 out of 18 (16.7%) had desquamated pneumocytes on BAL cytology.

Conclusion

Cytological analysis of BAL from patients with pneumonia (either community-acquired or hospital-acquired) shows elements of cytological alveolar damage as hemorrhage and desquamated type II pneumocytes much more frequently than in BAL from patients without pneumonia. These elements had a high specificity for an infectious cause of pulmonary infiltrates but low specificity. These lesions could serve as an adjunct to diagnosis in patients suspected of having ventilator-associated pneumonia.

Inflammatory subtypes in asthma: assessment and identification using induced sputum

OBJECTIVE

The authors sought to investigate the detection of non-eosinophilic asthma using induced sputum. Although this is an important subtype of clinical asthma, its recognition is not standardized.

METHODS

Adult non-smokers with asthma and healthy controls underwent sputum induction and hypertonic saline challenge. Non-eosinophilic asthma was defined as symptomatic asthma with normal sputum eosinophil counts. The normal range for sputum eosinophil count was determined using the 95th percentile from the healthy control group as a cut-off point.

RESULTS

The recognition of non-eosinophilic asthma using eosinophil proportion was in agreement with a definition based on absolute eosinophil count (kappa 0.67). Non-eosinophilic asthma was a stable subtype over both the short term (4 weeks) and longer term (5 years, kappa 0.77). Airway inflammation in asthma could be categorized into four inflammatory subtypes based on sputum eosinophil and neutrophil proportions. These subtypes were neutrophilic asthma, eosinophilic asthma, mixed granulocytic asthma and paucigranulocytic asthma. Subjects with increased neutrophils (neutrophilic asthma and mixed granulocytic asthma) were older and had an increased total cell count and cell viability compared with other subtypes.

CONCLUSION

Induced sputum eosinophil proportion is a good discriminator for eosinophilic asthma, providing a reproducible definition of a homogenous group. The remaining non-eosinophilic subjects are heterogeneous and can be further classified based on the presence of neutrophils. These inflammatory subtypes have important implications for the investigation and characterization of airway inflammation in asthma.

Ventilator associated pneumonia and infection control

Ventilator associated pneumonia (VAP) is the leading cause of morbidity and mortality in intensive care units. The incidence of VAP varies from 7% to 70% in different studies and the mortality rates are 20-75% according to the study population. Aspiration of colonized pathogenic microorganisms on the oropharynx and gastrointestinal tract is the main route for the development of VAP. On the other hand, the major risk factor for VAP is intubation and the duration of mechanical ventilation. Diagnosis remains difficult, and studies showed the importance of early initiation of appropriate antibiotic for prognosis. VAP causes extra length of stay in hospital and intensive care units and increases hospital cost. Consequently, infection control policies are more rational and will save money.

Control and Outcome of a Large Outbreak of Colonization and Infection with Glycopeptide-Intermediate Staphylococcus aureus in an Intensive Care Unit

BACKGROUND

Glycopeptide-intermediate Staphylococcus aureus (GISA) is emerging as a cause of nosocomial infection and outbreaks of infection and colonization in intensive care units (ICUs). We describe an outbreak of GISA colonization/infection and the ensuing control measures in an ICU and investigate outcomes of the affected patients.

METHODS

We describe an outbreak of GISA colonization and infection that affected 21 patients in a medical ICU at a tertiary care teaching hospital, as well as the measures taken to eradicate the GISA strain.

RESULT

Recognition of the outbreak was difficult. Infections, all of which were severe, were diagnosed in 11 of 21 patients. Patient isolation and barrier precautions failed when used alone. Addition of a stringent policy of restricted admissions, twice daily environmental cleaning, and implementation of hand decontamination with a hydroalcoholic solution led to outbreak termination. This was associated with increases in workload, despite a marked decrease in the number of admissions.

CONCLUSION

This first description of a large outbreak of GISA colonization and infection underlines the importance of routine GISA-strain detection when methicillin-resistant S. aureus is isolated. Outbreak control may be difficult to achieve.

Enfoque clínico del paciente con neumonía asociada a ventilación mecánica

Ventilator-associated pneumonia (VAP) is the most frequent infection in the intensive care unit. The importance of this entity lies not only in its high incidence but also in the significant mortality it produces. Therefore, a new episode of VAP should be clinically suspected when new or persistent radiological opacity, purulent respiratory secretions and other signs of sepsis (fever and leukocytosis) are present. In these patients, at the very least, tracheal aspirate samples with quantitative culture and direct staining should be immediately obtained, followed by prompt initiation of empirical broad-spectrum antibiotic therapy. The choice of initial antibiotic therapy should be patient-based, taking into account the risk factors associated especially with VAP caused by Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus, because of the high associated mortality. To evaluate resolution of VAP, we analyze various clinical variables (based mainly on resolution of fever and hypoxemia) and microbiologic information. Once the microorganism responsible for VAP has been isolated, antibiotic therapy can be adapted, based on de-escalation, to reduce the emergence of resistant bacteria. Recent studies suggest that shorter antibiotic regimens reduce the emergence of antibiotic-resistant pathogens, cost and adverse events.

Ventilator-associated pneumonia: Increased bacterial counts in bronchoalveolar lavage by using urea as an endogenous marker of dilution

OBJECTIVE

Invasive diagnostic procedures such as bronchoalveolar lavage (BAL) with quantitative microbiological cultures are currently recommended for the diagnosis of nosocomial pneumonia. Commonly, in clinical practice, a threshold of > or =10 colony forming units/mL is used for therapeutic decisions. The use of these measurements in daily practice assumes that their repeatability is acceptable. However, many variations among the positive results have been noted. One of the most important is dilution of BAL, which may influence the quantitative results by minimizing bacterial counts. Knowledge of the extent of dilution may increase dramatically the value of quantitative cultures. The aim of this study was to determine to what extent specimens are diluted in BAL by measuring urea in BAL and blood. Furthermore, the impact of a potential dilution effect on the diagnosis of ventilator-associated pneumonia was studied.

PATIENTS AND SETTING

A total of 47 patients with ventilator-associated pneumonia in two medical intensive care units at the Vienna General Hospital, a university-affiliated facility.

DESIGN

Prospective study performed between January 2001 and July 2002.

METHODS

BAL fluid was divided immediately into two samples: one for direct microscopic examination of cytocentrifuge preparations for Gram staining to determine percentages of cells containing intracellular bacteria and one for quantitative cultures according to the Cumitech 7A guidelines. Epithelial lining fluid volume was calculated using urea as a marker of dilution and correlated with colony forming units per milliliter.

RESULTS

Nineteen out of 47 patients (40%) revealed significant bacterial growth (> or =10 colony forming units/mL). Eight additional patients (17%) would have reached the cutoff level after correction of the dilution effect, which varied between 1.8- and 130-fold.

CONCLUSIONS

Data suggest a great variation of dilution during BAL procedures, which influences quantitative results. Using urea to determine the dilution quotient could increase the value of bacterial thresholds in the diagnosis and therapeutic decision of ventilator-associated pneumonia.

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.

[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.

Variation of infected cell count in bronchoalveolar lavage and timing of ventilator-associated pneumonia

OBJECTIVES

The aim of this study was to evaluate and compare the accuracy of the percentage of infected cells (%IC) in bronchoalveolar lavage (BAL) for ventilator-associated pneumonia (VAP) diagnosis according to its onset from the initiation of mechanical ventilation.

PATIENTS

One hundred and eight patients admitted to a surgical ICU were retrospectively included (1999-2001). A total of 171 cases of VAP were diagnosed on clinical, biological, chest X-ray and BAL results (threshold >/=10(4 )cfu/ml).

RESULTS

The %IC significantly decreased with the timing of VAP diagnosis: 12.2+/-12.1% for VAP occurring less than 7 days after the initiation of mechanical ventilation, 7.4+/-9.2% for VAP occurring between 7 and 15 days and 4.8+/-6.4% for VAP after 15 days ( p=0.0002), despite the same number of elements and proportion of polymorphonuclear neutrophils in BAL. In addition, a relationship between the %IC and the pathogen responsible for VAP was observed for P. aeruginosa [higher for VAP <7 days than for VAP 7-15 days ( p=0.01) and VAP >15 days ( p=0.006)] and S. aureus [lower for VAP >15 days than VAP 7-15 days ( p=0.04) and VAP <7 days ( p=0.04)]. Furthermore, the %IC in BAL was lower in patients undergoing antimicrobial therapy than in patients without antibiotics ( p=0.04). Three factors were independently associated with the %IC: quantitative culture of BAL (beta=0.42, p<0.0001), ongoing antimicrobial therapy (beta= -0.21, p=0.003) and onset of VAP (beta= -0.17, p=0.01).

CONCLUSIONS

A relationship between the %IC in BAL, duration of ventilation, quantitative culture of BAL and ongoing antimicrobial therapy has been proved in this study. The %IC for VAP diagnosis may not be accurate in patients with ongoing antibiotics and late onset infections (>7 days).

Accuracy of delayed (24 hours) processing of bronchoalveolar lavage for diagnosing bacterial pneumonia

OBJECTIVE

Pneumonia in the intensive care unit is associated with a high mortality rate. Diagnostic accuracy is mandatory to improve prognosis. However, in many hospitals, samples from the respiratory tract cannot be immediately processed bacteriologically around the clock. This may complicate therapeutic choice based on invasive diagnostic procedures. We evaluated the effect of storing bronchoalveolar lavage fluid at 4 degrees C for 24 hrs on direct examination and culturing for diagnosing pneumonia.

DESIGN

Prospective, paired comparison study.

SETTING

Intensive care unit in a university hospital.

PATIENTS

A total of 93 bronchoalveolar lavages were performed on 66 intensive care unit patients who were suspected to have bacterial pneumonia.

INTERVENTION

Each sample was divided into two; one half was processed immediately (H0), and the other was processed after refrigeration at 4 degrees C for 24 hrs (H24).

MEASUREMENTS AND MAIN RESULTS

All negative H0 culture samples (n = 31) were also negative for pathogens in H24 samples. Sixty two bronchoalveolar lavage cultures yielded one or more microorganisms, giving a total of 113 microorganisms in one or both samples. The results of positive cultures at H0 and H24 for the culturing diagnostic threshold of 10 colony forming units/mL agreed well (Kappa coefficient, 0.84); agreement was even better (Kappa coefficient, 0.85) when possible contaminants were excluded. The bias calculated as the mean difference between paired culture results was 0.195 +/- 1.31 (Delta log). When considering the accepted threshold of 10 colony forming units/mL, specificity at H24 compared to H0 was excellent (100%), but sensitivity was slightly lower (80%).

CONCLUSION

Delayed processing of bronchoalveolar lavage sampling is an acceptable alternative when immediate culturing cannot be performed because it enables antibiotic administration.

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.

Nosocomial pneumonia in the intensive care unit: controversies and dilemmas

Nosocomial pneumonia (NP), and its most serious form, ventilator-associated pneumonia (VAP), is a major cause of morbidity and mortality in the ICU. Numerous controversies exist, from diagnostic criteria to prevention and treatment, including the issues of attributable mortality of VAP, differences in the approach to early and late VAP, and the best diagnostic methods. Initial, accurate therapy is one of the most important factors determining outcome in VAP. Antibiotic monotherapy versus combination therapy is not clearly defined, as clinicians struggle with the dual risk of inadequate therapy negatively affecting outcome and overtreatment promoting antibiotic resistance. The role of airway and gastrointestinal colonization and innovative preventive strategies such as noninvasive ventilation, antibiotic rotation, and aerosolized antibiotics are discussed. No uniform standards exist for the approach to VAP. The authors highlight the major controversies and dilemmas in the clinical approach to VAP, with recommendations for the bedside management of these patients.

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.

Clinical pulmonary infection score for ventilator-associated pneumonia: accuracy and inter-observer variability

OBJECTIVE

Although quantitative microbiological cultures of samples obtained by bronchoscopy are considered the most specific tool for diagnosing ventilator-associated pneumonia, this labor-intensive invasive technique is not widely used. The Clinical Pulmonary Infection Score (CPIS), a diagnostic algorithm that relies on easily available clinical, radiographic, and microbiological criteria, could be an attractive alternative for diagnosing ventilator-associated pneumonia. Initially, the CPIS scoring system was validated upon 40 quantitative cultures of bronchoalveolar lavage fluid from 28 patients, and only few other studies have evaluated this scoring system since then. Therefore, little is known about the accuracy of this score.

DESIGN

We compared the scores of a slightly adjusted CPIS with results from quantitative cultures of bronchoalveolar lavage fluid in 99 consecutive patients with suspicion of ventilator-associated pneumonia, using growth of > or =10(4) cfu/ml in bronchoalveolar lavage fluid as a cut-off for diagnosing ventilator-associated pneumonia. In addition, the CPIS were calculated for 52 patients by two different intensivists to determine the inter-observer variability.

RESULTS

Ventilator-associated pneumonia was diagnosed in 69 (69.6%) patients. When using a CPIS >5 as diagnostic cutoff, the sensitivity of the score was 83% and its specificity was 17%. The area under the Receiver Operating Characteristic curve was 0.55. The level of agreement for prospectively measured Clinical Pulmonary Infection Score (< or =6 and >6) was poor (kappa =0.16).

CONCLUSIONS

When compared to quantitative cultures of bronchoalveolar lavage fluid, the CPIS has a low sensitivity and specificity for diagnosing ventilator-associated pneumonia with considerable inter-observer variability.

Airway colonisation in long-term mechanically ventilated patients

OBJECTIVE

To evaluate the impact of continuous subglottic suctioning and semi-recumbent body position on bacterial colonisation of the lower respiratory tract.

DESIGN

A randomised controlled trial.

SETTING

The ten-bed medical ICU of a French university hospital.

PATIENTS

Critically ill patients expected to require mechanical ventilation for more than 5 days.

INTERVENTIONS

Patients were randomly assigned to receive either continuous suctioning of subglottic secretions and semi-recumbent body position or to receive standard care and supine position.

MEASUREMENTS AND RESULTS

Oropharyngeal and tracheal secretions were sampled daily and quantitatively cultured. All included patients were followed up from day 1 (intubation) to day 10, extubation or death. Ninety-seven samples of oropharynx and trachea were analysed (40 for the suctioning group and 57 for the control group). The median bacterial counts in trachea were 6.6 Log10 CFU/ml (interquartile range, IQR, 4.4-8.3) in patients who received continuous suctioning and 5.1 Log10 CFU/ml (IQR 3.6-5.5) in control patients. Most of the patients were colonised in the trachea after 1 day of mechanical ventilation (75% in the suctioning group, 80% in the control group). No significant difference was found in the daily bacterial counts in the oropharynx and in the trachea between the two groups of patients.

CONCLUSION

Tracheal colonisation in long-term mechanically ventilated ICU patients was not modified by the use of continuous subglottic suctioning and semi-recumbent body position.

Correlation of Bronchoalveolar Lavage with Radiographic Evidence of Pneumonia in Thermally Injured Children

The diagnosis of pneumonia in the critically ill patient is very difficult because the usual signs and symptoms are unreliable in the intensive care setting. Bronchoalveolar lavage (BAL) is a diagnostic tool with a reported sensitivity of 70%. The purpose of this study was to determine the efficacy and specificity of BAL in severely burned pediatric patients. An analysis was performed in which BAL cultures were compared and correlated to chest radiographs. Patient characteristics, such as age, sex, burn size, depth of burn, and the presence of inhalation injury were evaluated. Over a period of 18 months, 58 thermally injured children were identified who underwent 101 BALs. The mean age was 6.5 +/- 5 years, mean TBSA was 39 +/- 27%, and inhalation injury was diagnosed in 20 patients (35%). Of 101 BALs, 48 were positive, and of the 101 chest radiographs, 20 demonstrated signs of pneumonia. Ten of those were associated with a positive BAL and 10 with a negative BAL. Thus, the positive predictive value of BAL was 21%, whereas the negative predictive value was 81%. Interestingly 80% of patients with tracheobronchitis from inhalation injury demonstrated a positive BAL. We conclude that in pediatric burn patients BAL correlates poorly with radiographic signs of pneumonia.

Diagnosis of ventilator-associated pneumonia

PURPOSE OF REVIEW

This review examines the various techniques used to diagnose ventilator-associated pneumonia. The ideal diagnostic test not only helps the clinician to recognize whether pneumonia is present, but also to influence clinical outcome.

RECENT FINDINGS

Several studies have suggested that the clinical pulmonary infection score can be used to detect the onset of ventilator associated pneumonia. Serial clinical pulmonary infection scores have also been useful in helping to decide when to stop therapy. Semiquantitative culture methods have been used for nonbronchoscopic and bronchoscopic samples. Adequate initial empiric therapy for those organisms identified in these samples has been associated with improved survival. This supports the use of these culture techniques to diagnose patients with ventilator-associated pneumonia.

SUMMARY

Diagnostic testing for ventilator-associated pneumonia can identify those patients at risk for a poor clinical outcome.