Impact of invasive and noninvasive quantitative culture sampling on outcome of ventilator-associated pneumonia: a pilot study

[Diagnosis of ventilator-associated pneumonia: a prospective comparison of the telescoping plugged catheter with the endotracheal aspirate]

OBJECTIVE

Quantitative culture of endotracheal aspirates (EA) is widely accepted for the diagnosis of ventilator-associated pneumonia (VAP). The aim of the study was to compare the diagnostic accuracy of the EA with the blinded plugged telescoping catheter (PTC) in patients suspected of VAP.

STUDY DESIGN

Prospective non-randomised observational study.

PATIENTS AND METHODS

31 patients suspected of having VAP underwent 46 bronchial samplings. An EA and a blinded PTC were performed successively in each case; the PTC result was taken as the reference standard. The EA and PTC cultures were defined positive if the result of bacterial cultures yielding were > or = 10(5) cfu.mL-1 and > or = 10(3) cfu.mL-1 respectively.

RESULTS

The diagnosis of VAP could be established in 19 cases when PTC was taking as gold test. The overall agreement between the two techniques was 76%. EA had a sensitivity of 89.5%, a specificity of 66.7%, a negative predictive value of 90% and a positive predictive value of 65.4%.

CONCLUSION

EA is a good diagnostic test when a non-invasive test has been chosen. The diagnosis of VAP could be excluded in 90% of cases when the EA cultures yielding were < 10(5) cfu.mL-1. His low specificity could drive in an over treatment of bronchopulmonar bacterial colonization. The accuracy of the EA compares well with that of the TPC for the diagnostic of VAP.

Prevention and management of ventilator-associated pneumonia

Worldwide, the increasing rates of microbial resistance represent a serious public health problem. Therefore, measures to prevent ventilator-associated pneumonia gain increasing importance. Because antimicrobial treatment in the ICU is a major source of microbial resistance, prevention should be understood not only as the sum of preventive measures but also as part of any management strategy. In this year of review, several important contributions have been made to a better understanding of the relative role of preventive measures. This is particularly true of noninvasive ventilation, continuous aspiration of subglottic secretions, and closed endotracheal suctioning. Management strategies for ventilator-assisted pneumonia remain highly controversial. Despite two decades of vigorous research, there is still no evidence that invasive bronchoscopic techniques should form part of a routine approach to suspected ventilator-assisted pneumonia. Moreover, an impact in terms of important outcome variables could not be consistently demonstrated. In the authors' view, the controversy regarding the relative validity of diagnostic tools should end, and the focus should shift to strategies that define low-risk patients with suspected ventilator-assisted pneumonia who can safely be treated by short-term monotherapy. Finally, several contributions have refined the established treatment regimen. Several new drugs for the treatment of ventilator-assisted pneumonia caused by Gram-positive multiresistant pathogens have been evaluated with promising results.

Ventilator-associated pneumonia. Prevention, diagnosis, and therapy

Ventilator-associated pneumonia remains the nosocomial ICU infection of greatest concern. The authors have summarized the clinical trials that have assessed specific strategies to prevent VAP and the current controversies regarding the diagnosis and therapeutic approach to this condition. Improvements in care of patients who are at risk for or who have developed VAP will depend on the judicious application of this information for individual patients.

Pro/con clinical debate: the use of a protected specimen brush in the diagnosis of ventilator associated pneumonia

Although mechanical ventilation is instituted as a life-saving technique, it may lead to complications that can negatively impact on patients' morbidity and/or mortality. Ventilator associated pneumonia (VAP) is one such complication that is a common challenge to intensivists. Although most experts would agree that early 'appropriate' antibiotic use is essential in patients who develop VAP, the best diagnostic test to guide decision-making is far from clear. One diagnostic test that is capable of providing microbiological samples from the lower respiratory tree is invasive bronchoscopy with a protected specimen brush. Such a procedure has long been available to intensivists and is frequently employed in many intensive care units. However, this procedure has associated costs and potential complications, and its utility in VAP has been challenged. In this issue of Critical Care Forum, the two sides of this debate are brought forward with compelling arguments. The authors' arguments should fuel future trials.

Clinical significance of potential pathogenic microorganisms of sputum in patients with pulmonary tuberculosis

BACKGROUND

Bacterial culture of sputum is frequently positive in patients with pulmonary tuberculosis (TB). However, it remains to be clarified whether detection of potential pathogenic microorganisms (PPM) in sputum represents bacterial infection or only colonization of the respiratory tract. In the present study, we investigated the clinical significance of PPM in patients with pulmonary TB.

METHODOLOGY

Sputum culture for PPM was studied in 174 pulmonary TB patients (117 males and 57 females, mean age of 71 years) on the day of admission. Ninety-seven patients (63 males and 34 females, mean age of 67.1 years) also underwent transtracheal aspirates (TTA). Quantitative culture of sputum and TTA was performed to distinguish infection from colonization. The results were evaluated as follows: more than 106 or 105 c.f.u./mL indicated infection in the case of sputum or TTA samples, respectively. We also compared various clinical parameters between patients with PPM and patients with non-potential pathogenic microorganisms (non-PPM).

RESULTS

Potential pathogenic microorganisms were positive in 44% and 24% of sputum and TTA specimens, respectively. However, quantitative culture for PPM showed positive findings in only 11% and 3% of sputum and TTA specimens, respectively. A comparative study of the clinical features revealed that PPM patients had a lower bodyweight and lower serum albumin levels than non-PPM patients. A fatal outcome was also more common in PPM patients than in non-PPM patients. Logistic regression analysis further confirmed that PPM clearly contributed to a fatal outcome in addition to the previously established parameters including age, performance status, haemoglobin, albumin and radiographic disease extent.

CONCLUSION

Although sputum PPM represent only colonization of the upper respiratory tract in TB patients, they are associated with a poor prognosis.

Controversies in the diagnosis of ventilator-acquired pneumonia

The appropriate investigation of patients with suspected VAP is controversial. Because it is unlikely that any new diagnostic technique will become available in the near future with better performance characteristics than those currently available, physicians need to tailor their diagnostic approach depending on individual patients and clinical scenarios. The most crucial factor in deciding which diagnostic approach to take is the influence that any test result would have on management. If preliminary screening tests, including Gram stain, are used to determine whether to start antibiotic therapy, invasive diagnostic techniques have an advantage over ETA. Quantitative cultures of respiratory specimens have a higher specificity than qualitative cultures and should be used if there is any possibility that a negative culture result would result in the discontinuation of antibiotic therapy. Physicians are caught between the need to treat VAP promptly with appropriate antibiotics and the undeniable problems of multidrug-resistant bacteria and their association with inappropriate antibiotic use. When clinically possible, a diagnostic strategy should be chosen that maximizes the possibility of limiting broad-spectrum antibiotic use. To give physicians greater comfort in the ability to withhold or discontinue antibiotics safely, further research is needed into the appropriate diagnostic strategies in different clinical settings that make this possible. The studies by Fagon et al and Singh et al are important steps in this direction.

Risk factors for nosocomial pneumonia. Focus on prophylaxis

Despite an increased understanding of the pathogenesis of NP and advances in diagnosis and treatment, the risk, cost, morbidity, and mortality of NP remain unacceptably high. This article has identified strategic areas for primary and secondary prophylaxis that are simple and cost-effective. Realizing that the pathogenesis of NP requires bacterial colonization and the subsequent entry of these bacteria into the lower respiratory tree helps highlight the role of cross-infection and the importance of standard infection control procedures. Similarly the role of sedation and devices as risk factors can be reduced by minimizing the duration and intensity of sedation and length of exposure to invasive devices. Additional low-cost interventions that have been shown to be effective in preventing NP are the positioning of patients in a semirecumbent position and the appropriate use of enteral feeding, antibiotics, and selected medical devices. Prophylaxis of NP and VAP is carried out best by a multidisciplinary management team comprised of physicians (critical care, pulmonary medicine, infectious diseases, and primary care), critical care and infection control nurses, and respiratory therapists, even though this approach may result in decreased professional autonomy and freedom. This group should review the current guidelines, pathways, and standards for short-term and long-term prophylaxis of NP and VAP, then integrate them into and monitor their use for routine patient care. The risk factors and prophylaxis strategies for NP discussed in this article apply primarily to patients in acute care facilities, but also are relevant to alternative health care settings as well as the care of ill patients in ambulatory settings. The routine use of effective team policies for prophylaxis needs to be monitored by the Joint Commission for the Accreditation of Health Care or other agencies. Research to delineate the most effective and feasible strategies for prophylaxis NP has been compromised by insufficient funding and lack of adequate, randomized multicenter studies to enable generalizability of results. Effective strategies for prophylaxis have not been disseminated widely or implemented in hospitals. Successful short-term and long-term strategies for prophylaxis must be evaluated and implemented by a team of physicians, nurses, and respiratory therapists. More than 100 years ago, Sir William Osler warned health care providers, "Remember how much you don't know." The authors would add that clinicians have acquired significant knowledge about risk factors and prophylaxis of NP in the 1980s and 1990s, but prophylaxis as a theory rather than an action. If the tree has not been planted, the time is now.

An emergency department-based randomized trial of nonbronchoscopic bronchoalveolar lavage for early pathogen identification in severe community-acquired pneumonia

STUDY OBJECTIVES

Many patients with community-acquired pneumonia are treated empirically without an aggressive search for causative pathogens, an approach adopted largely because of the costs and difficulties encountered during efforts to identify the causative organisms. Blood and sputum cultures are not sensitive, and the more invasive techniques of bronchoscopy and lung biopsy are generally time consuming and not cost-effective. The technique of nonbronchoscopic bronchoalveolar lavage (BAL) has been shown to accurately diagnose the causes of nosocomial pneumonia. The purpose of this study was to determine whether an emergency department-based BAL protocol would lead to more frequent isolation of pneumonia pathogens and result in more changes to tailored antibiotic therapy in comparison with standard care.

METHODS

We studied all adult patients admitted with a diagnosis of pneumonia who were tracheally intubated and who had obtainable familial consent in the ED of an urban county hospital from March 1998 to October 1999. Exclusions included antibiotic use within the past 5 days, pneumothorax, hemoptysis, or persistent hypoxia using 100% oxygen. Patients were randomized to standard care versus standard care plus BAL. Blood culture specimens were drawn from all patients before the initiation of antibiotics. All other diagnostic tests were ordered at the discretion of treating physicians. BAL fluid, sputum, and blood culture specimens were tracked, and patient antibiotic course was followed to assess any change in regimen.

RESULTS

Twenty-six of 64 patients evaluated for study participation met all eligibility criteria; 14 patients received standard care, and 12 patients received standard care plus BAL. Pneumonia pathogens were identified in 10 (83.3%) of 12 patients in the BAL group and in 4 (28.6%) of 14 patients in the standard care group (P =.007). Comparing BAL versus non-BAL groups, there was no significant difference in the likelihood of overall antibiotic regimen changes (P =.149), but there was a difference with regard to antibiotic changes made in patients with positive culture test results (P =.026). No major complications occurred with BAL catheterizations.

CONCLUSION

ED-based BAL catheterization allows for early identification of pathogens in severe community-acquired pneumonia, which leads to changes in antibiotic therapy.

Antibiotic therapy of ventilator-associated pneumonia--a reappraisal of rationale in the era of bacterial resistance

Ventilator-associated pneumonia (VAP) is the most frequent nosocomial infection in intensive care units (ICU). Resistance patterns seen in ICUs suggest that prescribing recommendations should be reappraised to limit practices engendering resistance to large families of antibiotics. Despite concern surrounding the use of antibiotics in the management of VAP, there is limited evidence to assist the clinician in making decisions about the indications for such therapy, the selection of the correct antibiotic(s), the timing of initiation of therapy and its duration. The high amount of antibiotic use, in combination with the low grade colonisation of patients with multi-resistant pathogens at the time of admission, turns the ICU into an environment where antibiotic policy is likely to have an effect on the resistance problem. Opinions are changing as to the validity of invasive techniques in guiding prescribing decisions. Invasive and semi-invasive diagnostic testing increases physician confidence in the diagnosis and management of VAP and helps to limit or discontinue antibiotic treatment.

International Conference for the Development of Consensus on the Diagnosis and Treatment of Ventilator-associated Pneumonia

Ventilator-associated pneumonia (VAP) is an important health problem that still generates great controversy. A consensus conference attended by 12 researchers from Europe and Latin America was held to discuss strategies for the diagnosis and treatment of VAP. Commonly asked questions concerning VAP management were selected for discussion by the participating researchers. Possible answers to the questions were presented to the researchers, who then recorded their preferences anonymously. This was followed by open discussion when the results were known. In general, peers thought that early microbiological examinations are warranted and contribute to improving the use of antibiotherapy. Nevertheless, no consensus was reached regarding choices of antimicrobial agents or the optimal duration of therapy. Piperacillin/tazobactam was the preferred choice for empiric therapy, followed by a cephalosporin with antipseudomonal activity and a carbapenem. All the peers agreed that the pathogens causing VAP and multiresistance patterns in their ICUs were substantially different from those reported in studies in the United States. Pathogens and multiresistance patterns also varied from researcher to researcher inside the group. Consensus was reached on the importance of local epidemiology surveillance programs and on the need for customized empiric antimicrobial choices to respond to local patterns of pathogens and susceptibilities.

Antibacterial treatment of invasive mechanical ventilation-associated pneumonia

Patients admitted to intensive care units (ICU) are at higher risk of acquiring nosocomial infections than patients in other hospital areas. This is the consequence of both a greater severity of illness with its implications (manipulation, invasiveness) and crossed infection from reservoirs inside the ICU. The most frequent nosocomial infection is invasive ventilation-associated pneumonia (VAP) which leads to an important increase in morbidity and mortality. The most important aetiological agents in VAP are bacteria, with a marked predominance of Staphylococcus aureus and Pseudomonas aeruginosa. These aetiologies may be different depending upon the type of ICU (medical, surgical, coronary) or the presence of certain risk factors (duration of mechanical ventilation before onset of pneumonia, previous exposure to antibacterials). Susceptibilities of the aetiological agents to antibacterials may also vary according to the type of ICU and over time. Data from global studies show an increase in multiresistant bacteria but these data may not be applied to a local ICU. The availability of accurate and updated information on the most frequently encountered organisms in each ICU and their susceptibilities is very important in order to provide the most adequate treatment. A controversial issue is the selection of antibacterials. According to the latest evidence the most adequate approach is a prompt administration of empirical treatment. Based on knowledge of bacterial flora in our own ICU, the choice of an adequate therapeutic regimen will decrease both morbidity and mortality. A second issue is monotherapy versus combined therapy. The most common recommendation, with a few exceptions, is to use combined therapy until microbiological results are received. Another controversy is the choice of antibacterials in the combined regimen. The most commonly recommended combination is that of a beta-lactam with an aminoglycoside, except in early-onset pneumonia without risk factors. The use of monotherapy with a cefalosporin without antipseudomonal activity or amoxicillin-clavulanic acid is the recommended regimen. Treatment should be modified based on microbiological results. There are no well documented recommendations on the prophylactic duration of treatment and it must be based on the aetiological agent and the clinical course. In summary treatment of VAP must be prompt, empirical and combined (beta-lactam plus aminoglycoside ). However, the choice of the antibacterial regimen should follow local guidelines of treatment based upon the knowledge of the most frequently isolated bacterial flora and their susceptibilities in different clinical settings.

Diagnostic tests for healthcare epidemiology

Diagnostic tests are important tools for surveillance in healthcare epidemiology. Recent studies regarding the use of diagnostic tests for detecting the following epidemiologically important conditions or pathogens are reviewed: vancomycin-resistant enterococci, Legionella, influenza, ventilator-associated pneumonia, Clostridium difficile, bloodstream infection, and tuberculosis.

Imaging of pneumonia: trends and algorithms

Pneumonia is one of the major infectious diseases responsible for significant morbidity and mortality throughout the world. Imaging plays a crucial role in the detection and management of patients with pneumonia. This review article discusses the different imaging methods used in the diagnosis and management of suspected pulmonary infections. The imaging examination should always begin with conventional radiography. When the results of routine radiography are inconclusive, computed tomography is mandatory. A combination of pattern recognition with knowledge of the clinical setting is the best approach to the pulmonary infectious processes. A specific pattern of involvement can suggest a likely diagnosis in many instances. In acquired immune deficiency syndrome patients, diffuse ground-glass and interstitial infiltrates are most commonly present in Pneumocystis carinii pneumonia whereas in the nonimmunosuppressed patients, a segmental lobar infiltrate is suggestive of a bacterial pneumonia. Round pneumonia is most often encountered in children than adults and is most often caused by Streptococcus pneumoniae. Different combinations of parenchymal and pleural abnormalities may be suggestive for additional diagnoses. When an infectious pulmonary process is suspected, knowledge of the varied radiographic manifestations will narrow the differential diagnosis, helping to direct additional diagnostic measures, and serving as an ideal tool for follow-up examinations.

Flexible bronchoscopy in nosocomial pneumonia

In this article, an overview on the diagnostic performances of bronchoscopic techniques for the diagnosis of nosocomial pneumonia is given with special emphasis on the inherent problems of the methodology of validation applied to different studies. The current evidence about the importance of bronchoscopic techniques for the outcome is reviewed. It is outlined that future prospects of bronchoscopic investigations mainly include the evaluation of its role in the reassessment of the patient with pneumonia not responding to the initial antimicrobial treatment.

Microbial investigation in ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is a serious infectious condition in intensive care unit (ICU) patients, currently related to a high mortality rate. Therefore, this complication of mechanical ventilation requires a prompt diagnosis and adequate antibiotic treatment. The detection of the causative organism is imperative for guiding an appropriate therapy as there is strong evidence of the adverse effect of inadequate empirical treatment on outcome. The major difficulty of the microbial investigation is to obtain the sample from the lower respiratory tract, mainly because of the potential contamination with upper airways flora, which may result in a misinterpretation of the cultures. Microbial investigation in VAP is based on the culture of samples obtained from lower respiratory tract by noninvasive or invasive methods. The most common techniques of sampling are the endotracheal aspirate (ETA), which is considered a noninvasive method, the protected specimen brush (PSB) and the bronchoalveolar lavage (BAL), both being invasive methods of investigation. The latter were designed as an attempt to avoid the colonizing flora of the upper airways. The best of these diagnostic approaches is still controversial. In terms of outcome, there is strong evidence that the impact of both invasive and noninvasive methods seems to be similar. In terms of cost, however, the endotracheal aspirate is less expensive compared to BAL or PSB. On the other hand, invasive methods could be particularly beneficial in patients who are not responding to the initial empirical antibiotic treatment. The rationale for the quantitative culture of the respiratory samples is to differentiate between infection and colonization of lower airways, because the bacterial colonization is a frequent event in mechanically ventilated patients. The thresholds currently employed for the diagnosis of the pneumonia are the following: ETA samples, > or = 10(5)-10(6) colony forming units (cfu).mL(-1); PSB samples, > or =10(3) cfu.mL(-1); and BAL samples, > or =10(4) cfu.mL(-1). Intending to provide a practical approach to the issue, the present manuscript reviews the available noninvasive (blood culture, endotracheal aspirate) and invasive (protected specimen brush, bronchoalveolar lavage, blinded methods and lung biopsy) techniques used for the diagnosis of ventilator-associated pneumonia.

Are quantitative cultures useful in the diagnosis of hospital-acquired pneumonia?

Noninvasive and invasive tests have been developed and studied for their utility in diagnosing and guiding the treatment of hospital-acquired pneumonia, a condition with an inherently high mortality. Early empiric antibiotic treatment has been shown to reduce mortality, so delaying this treatment until test results are available is not justifiable. Furthermore, tailoring therapy based on results of either noninvasive or invasive tests has not been clearly shown to affect morbidity and mortality. This may be related to quantitative limitations of these tests or possibly to a high false-negative rate in patients who receive early antibiotic treatment and may therefore have suppressed bacterial counts. Results of these tests, however, do influence treatment. It is therefore hoped that they may ultimately provide a rational basis for making therapeutic decisions. In the future, outcomes research should be a part of large-scale clinical trials, and noninvasive and invasive tests should be incorporated into the design in an attempt to provide a better understanding of the value of such tests.

Hospital-acquired pneumonia: risk factors, microbiology, and treatment

Pneumonia complicates hospitalization in 0.5 to 2.0% of patients and is associated with considerable morbidity and mortality. Risk factors for hospital-acquired pneumonia (HAP) include mechanical ventilation for > 48 h, residence in an ICU, duration of ICU or hospital stay, severity of underlying illness, and presence of comorbidities. Pseudomonas aeruginosa, Staphylococcus aureus, and Enterobacter are the most common causes of HAP. Nearly half of HAP cases are polymicrobial. In patients receiving mechanical ventilation, P aeruginosa, Acinetobacter, methicillin-resistant S aureus, and other antibiotic-resistant bacteria assume increasing importance. Optimal therapy for HAP should take into account severity of illness, demographics, specific pathogens involved, and risk factors for antimicrobial resistance. When P aeruginosa is implicated, monotherapy, even with broad-spectrum antibiotics, is associated with rapid evolution of resistance and a high rate of clinical failures. For pseudomonal HAP, we advise combination therapy with an antipseudomonal beta-lactam plus an aminoglycoside or a fluoroquinolone (eg, ciprofloxacin).

Diagnosis of pneumonia and monitoring of infection eradication

Pneumonia can be classified as community-acquired (CAP) or hospital-acquired (nosocomial). Both are frequent infections that demand a great amount of medical resources. The diagnosis of CAP is based on clinical signs and the presence of a pulmonary infiltrate visible on chest radiograph. For practical purposes, CAP has been classified as typical, with an acute onset in which the most representative microorganism is Streptococccus pneumoniae, and atypical, with a subacute onset (Mycoplasma pneumoniae). Nevertheless, so far no studies have clearly demonstrated the utility of this classification in predicting the aetiology. Guidelines on CAP recommend associating the aetiology of CAP with comorbidity, age and severity. The microbiological diagnosis relies mainly on Gram stain and sputum culture, but this technique has disadvantages such as frequent contamination of the sample with oropharyngeal commensal flora, frequent sterile cultures associated with previous antibiotic treatment, and the fact that approximately 40% of patients are not able to expectorate. Other diagnostic techniques such as blood cultures, serological tests and fibreoptic bronchoscopy must be reserved for patients who are hospitalised, especially if they need admission to an intensive care unit. Compared with CAP, nosocomial pneumonia has major diagnostic problems due to the presence of other diseases able to mimic pneumonia and frequent bacterial colonisation of the lower respiratory tract. Most of the diagnostic techniques produce a high percentage of false-negative and false-positive results. This is especially true for ventilator-associated pneumonia. There is controversy over using a comprehensive aetiological work-up based on bronchoscopic techniques or only on quantitative culture of endotracheal aspiration. By contrast, there is consensus about the importance of the adequacy of empirical antibiotic treatment, since mortality rates are higher in patients who are inadequately treated. Once treatment of pneumonia has begun, it must be maintained for 48 to 72 hours because this is the minimum time to evaluate a clinical response. Antibacterial agents have to be adjusted according to microbiological findings. In nonresponding patients, pneumonia-related complications and the presence of multiresistant micro-organisms or non-covered pathogens must be ruled out.

Impact of BAL in the management of pneumonia with treatment failure: positivity of BAL culture under antibiotic therapy

BACKGROUND

Pneumonia is responsible for 50% of antibiotics prescribed in ICUs. Treatment failure, ie, absence of improvement or clinical deterioration under antibiotic therapy, presents a dilemma to physicians. BAL is an invasive method validated for etiologic diagnosis in pneumonia.

STUDY OBJECTIVE

To evaluate in ICU patients the impact of BAL in the etiologic diagnosis, treatment, and outcome of pneumonia with treatment failure.

DESIGN

Prospective clinical study.

SETTING

Nonsurgical, medical ICU of a university hospital in Brazil.

PATIENTS AND PARTICIPANTS

Sixty-two episodes of pneumonia treated for at least 72 h without clinical improvement in 53 patients hospitalized for diverse clinical emergencies. Mean duration of hospitalization was 14.2 days. Mean duration of previous antibiotic therapy was 11.4 days.

INTERVENTIONS

Bronchoscopy and BAL were performed in each episode. BAL fluid was cultivated for aerobic and anaerobic bacteria; the cutoff considered positive was 10(4) cfu/mL; 10(3) cfu/mL was also analyzed if under treatment. Pneumocystis carinii, fungi, Legionella spp, and Mycobacterium spp were also researched.

MEASUREMENTS AND RESULTS

Fifty-eight of 62 BAL were performed under antibiotics. The results showed positivity in 45 of 62 (72.6%); 42 of the 45 positive episodes (93.3%) had > 10(4) cfu/mL. The three cases with between 10(3) and 10(4) cfu/mL were considered positive and were treated according to BAL cultures. The main agents were Acinetobacter baumannii (37.1%), Pseudomonas aeruginosa (17.7%), and methicillin-resistant Staphylococcus aureus (MRSA; 16.1%); 46.7% of the episodes (21 of 45) were polymicrobial. BAL results directed a change of therapy in 34 episodes (54.8%). Overall mortality was 43.5%. There was no difference in mortality among positives, negatives, and patients who changed therapy guided by BAL culture.

CONCLUSIONS

(1) BAL fluid examination was positive in 45 of 62 episodes (72.6%), with 58 of 62 BAL performed under antibiotics. This suggests that BAL may be a sensitive diagnostic method for treatment failures of clinically diagnosed pneumonias, even if performed under antibiotics; (2) the main pathogens in our study were A baumannii, P aeruginosa, and MRSA, and approximately 45% of infections were polymicrobial; (3) BAL culture results directed a change of therapy in 75.6% of positive episodes (34 of 45) and in 54.8% of all episodes of treatment failure (34 of 62); and (4) there was no difference in mortality among positives, negatives, and patients who changed therapy guided by BAL culture.

Impact of quantitative invasive diagnostic techniques in the management and outcome of mechanically ventilated patients with suspected pneumonia

OBJECTIVE

To assess how data obtained by invasive diagnostic techniques may affect management and outcome of patients with suspected ventilator-associated pneumonia (VAP), in comparison with noninvasive qualitative techniques.

DESIGN

Prospective study.

SETTING

An 18-bed medical and surgical intensive care unit.

PATIENTS

A total of 91 patients suspected of having VAP were randomized into two groups. In group A (n = 45), quantitative cultures obtained by either bronchoscopic or nonbronchoscopic techniques were performed, whereas in group B (n = 43), patients were treated based on clinical judgment and nonquantitative tracheal aspirates cultures. Three patients were excluded because of the absence of follow-up.

RESULTS

In patients with positive cultures, therapeutic changes were made in 20 patients. In four patients (three from group A and one from group B, p = NS), initial empirical antibiotic treatment was modified because the isolated microorganisms were not susceptible (all of them had late-onset pneumonia). The isolated organisms responsible for antibiotic modifications were methicillin-resistant Staphylococcus aureus (three patients) and Pseudomonas aeruginosa (one patient). In three patients, the antimicrobial therapy was considered inappropriate because the isolated microorganisms were multiresistant and treated with only one effective antibiotic. In 13 patients (ten from group A and three from group B, p < .05), treatment was changed to select a narrower spectrum antibiotic. No therapeutic modifications were made in patients with negative cultures based on the results of quantitative cultures. The overall mortality was 22.2% in group A and 20.9% in group B. There were no differences in intensive care unit stay or days of mechanical ventilation (23.67+/-3.15 vs. 22.42+/-3.01 and 19.99+/-2.88 vs. 19.24+/-3.04, respectively).

CONCLUSIONS

In our study population, the routine use of quantitative invasive diagnostic tools is not justified in the setting of ventilated patients clinically suspected of having nosocomial pneumonia.

Nosocomial pneumonia: epidemiology, pathogenesis, diagnosis, treatment and prevention

Nosocomial pneumonia is the second most common nosocomial infection and the leading cause of death from hospital-acquired infection. Supine body position in mechanically ventilated patients, and cardiopulmonary resuscitation and continuous sedation are significant risk factors for developing nosocomial pneumonia. During the past 2 years some new therapeutic approaches for nosocomial pneumonia and modifications to established therapies have been described, such as optimal pharmacodynamic evaluations, monotherapy versus combination therapy, computer-assisted management programmes and antibiotic rotations.

Short-course empiric antibiotic therapy for patients with pulmonary infiltrates in the intensive care unit. A proposed solution for indiscriminate antibiotic prescription

Inappropriate antibiotic use for pulmonary infiltrates is common in the intensive care unit (ICU). We sought to devise an approach that would minimize unnecessary antibiotic use, recognizing that a gold standard for the diagnosis of nosocomial pneumonia does not exist. In a randomized trial, clinical pulmonary infection score (CPIS) (Pugin, J., R. Auckenthaler, N. Mili, J. P. Janssens, R. D. Lew, and P. M. Suter. Diagnosis of ventilator-associated pneumonia by bacteriologic analysis of bronchoscopic and nonbronchoscopic "blind" bronchoalveolar lavage fluid. Am. Rev. Respir. Dis. 1991;143: 1121-1129) was used as operational criteria for decision-making regarding antibiotic therapy. Patients with CPIS </= 6 (implying low likelihood of pneumonia) were randomized to receive either standard therapy (choice and duration of antibiotics at the discretion of physicians) or ciprofloxacin monotherapy with reevaluation at 3 d; ciprofloxacin was discontinued if CPIS remained </= 6 at 3 d. Antibiotics were continued beyond 3 d in 90% (38 of 42) of the patients in the standard as therapy compared with 28% (11 of 39) in the experimental therapy group (p = 0.0001). In patients in whom CPIS remained </= 6 at the 3 d evaluation point, antibiotics were still continued in 96% (24 of 25) in the standard therapy group but in 0% (0 of 25) of the patients in the experimental therapy group (p = 0.0001). Mortality and length of ICU stay did not differ despite a shorter duration (p = 0.0001) and lower cost (p = 0.003) of antimicrobial therapy in the experimental as compared with the standard therapy arm. Antimicrobial resistance, or superinfections, or both, developed in 15% (5 of 37) of the patients in the experimental versus 35% (14 of 37) of the patients in the standard therapy group (p = 0.017). Thus, overtreatment with antibiotics is widely prevalent, but unnecessary in most patients with pulmonary infiltrates in the ICU. The operational criteria used, regardless of the precise definition of pneumonia, accurately identified patients with pulmonary infiltrates for whom monotherapy with a short course of antibiotics was appropriate. Such an approach led to significantly lower antimicrobial therapy costs, antimicrobial resistance, and superinfections without adversely affecting the length of stay or mortality.

Noninvasive versus invasive microbial investigation in ventilator-associated pneumonia: evaluation of outcome

Noninvasive and invasive diagnostic techniques have been shown to achieve comparable performances in the evaluation of suspected ventilator-associated pneumonia (VAP). We studied the impact of both approaches on outcome in a prospective, open, and randomized study in three intensive care units (ICUs) of a 1,000-bed tertiary care university hospital. Patients with suspected VAP were randomly assigned to noninvasive (Group 1) versus invasive (Group 2) investigation (tracheobronchial aspirates [TBAS] versus bronchoscopically retrieved protected specimen brush [PSB] and bronchoalveolar lavage [BAL]. Samples were cultured quantitatively, and BAL fluid (BALF) was examined for intracellular organisms (ICO) additionally. Initial empiric antimicrobial treatment was administered following the guidelines of the American Thoracic Society (ATS) and adjusted according to culture results (and ICO counts in Group 2). Outcome variables included length of ICU stay and mechanical ventilation as well as mortality. Overall, 76 patients (39 noninvasive, 37 invasive) were investigated. VAP was microbiologically confirmed in 23 of 39 (59%) and 23 of 37 (62%) (p = 0.78). There were no differences with regard to the frequencies of community-acquired and potentially drug-resistant microorganisms (PDRM). Antimicrobial treatment was changed in seven patients (18%) of Group 1 and 10 patients (27%) of Group 2 because of etiologic findings (including five of 17 with ICO = 2% (p = not significant [NS]). Length of ICU stay and mechanical ventilation were also not significantly different in both groups. Crude 30-d mortality was 31 of 76 (41%), and 18 of 39 (46%) in Group 1 and 14 of 37 (38%) in Group 2 (p = 0.46). Adjusted mortality was 16% versus 11% (p = 0.53), and mortality of microbiologically confirmed pneumonia 10 of 23 (44%) in both groups (p = 1.0). We conclude that the outcome of VAP was not influenced by the techniques used for microbial investigation.

Nosocomial or Healthcare Facility-Related Pneumonia in Adults

Nosocomial or hospital-acquired pneumonia (HAP) is a dynamic disease with multiple etiologic agents and a changing natural history. The emergence and spread of multidrug-resistant bacterial pathogens is a current concern. Because of the parallels between HAP and pneumonia occurring in patients in subacute or chronic care facilities, we suggest the use of a more inclusive term for these patients: healthcare facility-related pneumonia. This article focuses on current controversies in the pathogenesis, diagnosis, management, and prevention of bacterial HAP in adults. We endorse early, appropriate antibiotic therapy based on disease severity and the use of strategies to prevent infection, improve patient outcome, and reduce hospital costs.

Invasive and noninvasive strategies for management of suspected ventilator-associated pneumonia. A randomized trial

BACKGROUND

Optimal management of patients who are clinically suspected of having ventilator-associated pneumonia remains open to debate.

OBJECTIVE

To evaluate the effect on clinical outcome and antibiotic use of two strategies to diagnose ventilator-associated pneumonia and select initial treatment for this condition.

DESIGN

Multicenter, randomized, uncontrolled trial.

SETTING

31 intensive care units in France.

PATIENTS

413 patients suspected of having ventilator-associated pneumonia.

INTERVENTION

The invasive management strategy was based on direct examination of bronchoscopic protected specimen brush samples or bronchoalveolar lavage samples and their quantitative cultures. The noninvasive ("clinical") management strategy was based on clinical criteria, isolation of microorganisms by nonquantitative analysis of endotracheal aspirates, and clinical practice guidelines.

MEASUREMENTS

Death from any cause, quantification of organ failure, and antibiotic use at 14 and 28 days.

RESULTS

Compared with patients who received clinical management, patients who received invasive management had reduced mortality at day 14 (16.2% and 25.8%; difference, -9.6 percentage points [95% CI, -17.4 to -1.8 percentage points]; P = 0.022), decreased mean Sepsis-related Organ Failure Assessment scores at day 3 (6.1+/-4.0 and 7.0+/-4.3; P = 0.033) and day 7 (4.9+/-4.0 and 5.8+/-4.4; P = 0.043), and decreased antibiotic use (mean number of antibiotic-free days, 5.0+/-5.1 and 2.2+/-3.5; P < 0.001). At 28 days, the invasive management group had significantly more antibiotic-free days (11.5+/-9.0 compared with 7.5+/-7.6; P < 0.001), and only multivariate analysis showed a significant difference in mortality (hazard ratio, 1.54 [CI, 1.10 to 2.16]; P = 0.01).

CONCLUSIONS

Compared with a noninvasive management strategy, an invasive management strategy was significantly associated with fewer deaths at 14 days, earlier attenuation of organ dysfunction, and less antibiotic use in patients suspected of having ventilator-associated pneumonia.

Diagnostic testing for ventilator-associated pneumonia

This article discusses the interpretation of the diagnostic tests in the management of ventilated patients with suspicion of pneumonia. The specific steps for diagnostic evaluation are identified. An accurate interpretation of the significance of the bacterial burden requires previous evaluation of the sample quality, knowledge of administration of new antibiotics within the prior 48 hours, and evaluation of presence of comorbidities. Finally, the article presents a review of the current debate of impact on outcome.

Controversies on diagnosis and prevention of ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is the most frequent infection among intensive care patients. There is a great deal of controversy about the methods for diagnosis and prevention of this infection. VAP is usually diagnosed on a combination of clinical, microbiological, and radiographic criteria. Although these criteria have a high sensitivity, specificity is low, resulting in unnecessary antibiotic use in many patients. Bronchoscopic techniques, suh as protected specimen brush and bronchoalveolar lavage, in combination with quantitative culture techniques, do have a higher specificity. However, whether implementation of these techniques influences patient care, and to what costs, remains to be determined. Prevention of VAP relies on basic infection control practices. Many specific strategies interfering with colonization routes have been studied. So far, only the use of topical nonabsorbable antibiotics, either of the whole digestive tract or the oropharynx only, consistently reduced the incidence of VAP. However, the effects on patient survival were disappointing and the possibility of selection of antibiotic-resistant bacteria limit the widespread use of these strategies.

Laboratory diagnosis of respiratory infections

The laboratory diagnosis of infections of the respiratory tract is not an exact science, with many clinicians electing to empirically select antimicrobial therapy without the benefit of laboratory testing. With trained laboratory personnel and the proper selection of tests, accurate laboratory diagnosis is available. Progress is occurring most rapidly with molecular methods, such as polymerase chain reaction (PCR) testing. As molecular approaches are technically simplified and become less expensive, advances in the laboratory diagnosis of most respiratory tract infections caused by fastidious pathogens will occur. The diagnosis of non-fastidious bacteria, that require in-vitro antimicrobial testing, will continue to require conventional culture methods. New bronchoscopic methods, quantitative evaluation of cultures, and recognition of intracellular bacteria in stained smears do improve the usefulness of conventional culture and stain in the diagnosis of pneumonia.

The clinical utility of invasive diagnostic techniques in the setting of ventilator-associated pneumonia. Canadian Critical Care Trials Group

OBJECTIVE

To evaluate the clinical utility of bronchoscopy with protected brush catheter (PBC) and BAL for patients with ventilator-associated pneumonia (VAP).

DESIGN

Prospective cohort study.

SETTING

Ten tertiary care ICUs in Canada.

PATIENTS

Ninety-two mechanically ventilated patients with a clinical suspicion of VAP who underwent bronchoscopy were compared with 49 patients with a clinical suspicion of pneumonia who did not.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We compared antibiotic use, duration of mechanical ventilation, ICU stay, and mortality. In addition, for patients who received bronchoscopy, we administered a questionnaire (before and after bronchoscopy) to evaluate the effect of PBC or BAL on (1) physician perception of the probability of VAP, (2) physician confidence in the diagnosis of VAP, and (3) changes to antibiotic management. After bronchoscopy results became available, from the physician's perspective, the diagnosis of VAP was deemed much less likely (p < 0.001), confidence in the diagnosis increased (p = 0.03), and level of comfort with the management plan increased (p = 0.02). Following the results of invasive diagnostic tests, in the group that underwent bronchoscopy, patients were receiving fewer antibiotics (31/92 vs 9/49, p = 0.05) and more patients had treatment with all their antibiotics discontinued (18/92 vs 3/49, p = 0.04) compared with the group that did not undergo bronchoscopy. Duration of mechanical ventilation and ICU stay were similar between the two groups, but mortality was lower in the group that underwent bronchoscopy with PBC or BAL (18.5% vs 34.7%, p = 0.03).

CONCLUSIONS

Invasive diagnostic testing may increase physician confidence in the diagnosis and management of VAP and allows for greater ability to limit or discontinue antibiotic treatment. Whether performing PBC or BAL affects clinically important outcomes requires further study.

Nosocomial pneumonia in the ICU--year 2000 and beyond

Diagnostic and treatment strategies in ICU patients with ventilator-associated pneumonia (VAP) remain controversial, largely because of the paucity of well-controlled comparison trials using clinically important end points. Recent studies indicating that early appropriate antibiotic therapy significantly lowers mortality underscore the urgent need for well-designed comparative trials. When quantitatively cultured, bronchial specimens obtained by noninvasive techniques may provide clinically useful information and avoid the higher costs and risks of invasive bronchoscopic diagnostic techniques. Previous antibiotic use before onset of nosocomial pneumonia raises the likelihood of infection with highly virulent organisms, such as Pseudomonas aeruginosa and Acinetobacter sp. Thus, the empiric antibiotic regimen should be active against these Gram-negative pathogens as well as other common Gram-negative and Gram-positive causative organisms. Promising preventive modalities for nosocomial VAP include use of a semirecumbent position, endotracheal tubes that allow continuous aspiration of secretions, and heat and moisture exchangers. Rotating their standard empiric antibiotic regimens and restricting the use of third-generation cephalosporins as empiric therapy may help hospitals reduce the incidence of nosocomial pneumonia caused by resistant Gram-negative pathogens.

Future of flexible bronchoscopy

Despite some potential "threats" (Table 3), the future of bronchoscopy is likely full with ever expanding applications in clinical medicine and research (Tables 1 and 2). The role of bronchoscopy in lung cancer continues to expand and the usefulness of newer techniques needs to be established. The role of FB is also ever expanding in the immuno compromised host and critically ill patients. Future studies, however, should concentrate on patient outcome, especially survival and performance status. Therapeutic bronchoscopy has been extended to many areas and the emphasis of future research will likely continue to be at the molecular level rather than on studies of better instruments for retrieval purposes. The most exciting developments are likely to be in the field of gene therapy, which has made remarkable progress in the past decade. Gene therapy can be a powerful technology, but several hurdles must be overcome to make gene therapy a reality for treating human disease in the future. As the cost of technology continues to challenge health care delivery systems, a major challenge for the future of bronchoscopy is to evaluate new technologies and applications based on their impact on patient outcome, survival, and management of cost.

The diagnosis and treatment challenges in nosocomial pneumonia

Pneumonia is the second most common type of nosocomial infection and is most prevalent in patients who are mechanically ventilated. Nosocomial pneumonia (NP) is the leading contributor to mortality in patients, accounting for approximately 50% of deaths in patients with hospital-acquired infections. Several factors place patients at risk for developing NP, including prolonged length of hospital stay and local epidemiology. Gram-positive pathogens such as Streptococcus pneumoniae and, more recently, Staphylococcus aureus, as well as atypical organisms such as Legionella spp are increasingly associated with NP. Emerging antimicrobial resistance among these organisms confounds treatment interventions. Lack of local definitive information and patient comorbidities further complicate the physician's treatment decisions. The role of invasive pulmonary diagnostic techniques remains problematic and controversial. Studies, however, have shown that early initiation of appropriate empiric therapy is essential to improving patient outcome and reducing mortality. This article will review therapeutic options and appropriate antimicrobial agents for use in the treatment of nosocomial pneumonia in the era of emerging drug resistances.

Epidemiology of ventilator-acquired pneumonia based on protected bronchoscopic sampling

We performed a prospective observational cohort study of the epidemiology and etiology of nosocomial pneumonia in 358 medical ICU patients in two university-affiliated hospitals. Protected bronchoscopic techniques (protected specimen brush and bronchoalveolar lavage) were used for diagnosis to minimize misclassification. Risk factors for ventilator-associated pneumonia were identified using multiple logistic regression analysis. Twenty-eight cases of pneumonia occurred in 358 patients for a cumulative incidence of 7.8% and incidence rates of 12.5 cases per 1, 000 patient days and 20.5 cases per 1,000 ventilator days. Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Hemophilus species made up 65% of isolates from the lower respiratory tract, whereas only 12.5% of isolates were enteric gram-negative bacilli. Daily surveillance cultures of the nares, oropharynx, trachea, and stomach demonstrated that tracheal colonization preceded ventilator-associated pneumonia in 93.5%, whereas gastric colonization preceded tracheal colonization for only four of 31 (13%) eventual pathogens. By multiple logistic regression, independent risk factors for ventilator- associated pneumonia were admission serum albumin <= 2.2 g/dl (odds ratio [OR] 5.9; 95% confidence interval [CI] 2.0-17.6; p = 0.0013), maximum positive end-expiratory pressure >= 7.5 cm H2O (OR, 4.6; 95% CI, 1.4 to 15.1; p = 0.012), absence of antibiotic therapy (OR, 6.7; 95% CI, 1.8 to 25.3; p = 0.0054), colonization of the upper respiratory tract by respiratory gram-negative bacilli (OR, 3.4; 95% CI, 1.1 to 10.1; p = 0.028), pack-years of smoking (OR, 2.3 for 50 pack-years; 95% CI, 1. 2 to 4.2; p = 0.012), and duration of mechanical ventilation (OR, 3. 4 for 14 d; 95% CI, 1.5 to 7.8; p = 0.0044). Several of these risk factors for ventilator-associated pneumonia appear amenable to intervention.