Diagnosis of nosocomial pneumonia in mechanically ventilated patients by the blind protected telescoping catheter

Ventilator-Associated Pneumonia: A Review

Ventilator-associated pneumonia is the most frequent intensive care unit (ICU)-related infection in patients requiring mechanical ventilation. In contrast to other ICU-related infections, which have a low mortality rate, the mortality rate for ventilator-associated pneumonia ranges from 20% to 50%. These clinically significant infections prolong duration of mechanical ventilation and ICU length of stay, underscoring the financial burden these infections impose on the health care system. The causes of ventilator-associated pneumonia are varied and differ across different patient populations and different types of ICUs. This varied presentation underscores the need for the intensivist treating the patient with ventilator-associated pneumonia to have a clear knowledge of the ambient microbiologic flora in their ICU. Prevention of this disease process is of paramount importance and requires a multifaceted approach. Once a diagnosis of ventilator-associated pneumonia is suspected, early broad-spectrum antibiotic administration decreases morbidity and mortality and should be based on knowledge of the sensitivities of common infecting organisms in the ICU. De-escalation of therapy, once final culture results are available, is necessary to minimize development of resistant pathogens. Duration of therapy should be based on the patient’s clinical response, and every effort should be made to minimize duration of therapy, thus further minimizing the risk of resistance.

Diagnosis of bacterial ventilator-associated pneumonia in children: reproducibility of blind bronchial sampling

OBJECTIVE

To evaluate the reproducibility of blind bronchial sampling in patients with suspected diagnosis of bacterial ventilator-associated pneumonia.

DESIGN

Prospective study.

SETTING

Pediatric intensive care unit of a tertiary care, multidisciplinary, teaching hospital in Northern India.

PATIENTS

All consecutive patients on mechanical ventilation for >48 hrs were evaluated clinically for ventilator-associated pneumonia.

INTERVENTIONS

Children with clinical ventilator-associated pneumonia were subjected to blind bronchial sampling twice.

MEASUREMENTS AND MAIN RESULTS

Sixty-eight blind bronchial sampling samples from 34 patients were analyzed for polymorphonuclear cells, the presence, type, and number of bacteria. Acinetobacter baumannii was the most common organism grown from distal respiratory secretions. For polymorphonuclear cells, the concordance between two blind bronchial samples was 85.3% and kappa coefficient was 0.65. The concordance for the presence and type of bacteria in Gram staining in two samples was 85.3% and kappa coefficient was 0.68. The intraclass coefficients for bacterial index and predominant species index were 0.82 (95% confidence interval 0.65-0.91) and 0.89 (95% confidence interval 0.78-0.94), respectively. The use of prior antibiotics did not adversely affect the reproducibility of blind bronchial sampling. No major complications were recorded during the procedure.

CONCLUSIONS

Blind bronchial sampling of lower respiratory tract secretions in mechanically ventilated patients generates reproducible results of quantitative and qualitative cultures. We suggest that blind bronchial sampling may provide valuable clue to the bacterial etiology in ventilated child with suspected clinical ventilator-associated pneumonia.

Bilateral versus unilateral bronchoalveolar lavage for the diagnosis of ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) complicates the clinical course of critically injured intubated patients. Bronchoscopic bronchoalveolar lavage (BAL) represents an invasive and accurate means of VAP diagnosis. Unilateral and blinded techniques offer less invasive alternatives to bronchoscopic BAL. This study evaluated clinical criteria as well as unilateral directed versus bilateral BAL for VAP diagnosis.

METHODS

A retrospective chart review of 113 consecutive intubated trauma patients with clinically suspected VAP undergoing unilateral versus bilateral BAL was performed with comparison of positive culture results (>10(4) colony-forming units [CFU]/mL). Culture results were compared with chest radiograph (CXR) infiltrates and white blood cell (WBC) count elevation.

RESULTS

Bilateral BAL was more likely to be positive than unilateral BAL (50.4% vs. 25.5%). In 37.1% of bilateral BALs, there was discordance between the sides of positivity or the bacteria isolated. A CXR infiltrate and WBC count elevation did not predict positive BAL.

CONCLUSIONS

Clinical indicators of VAP are inaccurate, and bilateral bronchoscopic BAL is more likely than unilateral BAL to provide a positive sample in intubated trauma patients. Techniques that do not sample both lungs reliably should be avoided for diagnosis in this patient population.

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.

Diagnosis of ventilator-associated pneumonia in children in resource-limited setting: a comparative study of bronchoscopic and nonbronchoscopic methods

OBJECTIVES

To compare the available methods for the diagnosis of ventilator-associated pneumonia in intubated pediatric patients and to suggest less costly diagnostic method for developing countries.

DESIGN

Prospective study.

SETTING

Pediatric intensive care unit of a tertiary care, multidisciplinary teaching hospital located in northern India.

PATIENTS

All consecutive patients on mechanical ventilation for >48 hrs were evaluated clinically for ventilator-associated pneumonia.

INTERVENTIONS

Four diagnostic procedures (tracheal aspiration, blind bronchial sampling, blind bronchoalveolar lavage, and bronchoscopic bronchoalveolar lavage) were performed in the same sequence within 12 hrs of clinical suspicion of ventilator-associated pneumonia. The bacterial density > or =104 colony-forming units/mL in a bronchoscopic bronchoalveolar lavage sample was taken as reference standard.

MEASUREMENTS AND MAIN RESULTS

Thirty patients with 40 episodes of ventilator-associated pneumonia were included in the study. Tracheal aspirate at the cutoff of > or =105 colony-forming units/mL was found to have sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 84%, 77%, 87.5%, 73%, and 80%, respectively. For blind bronchial sampling at > or =104 colony-forming units/mL cutoff, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88%, 82%, 88%, 83%, and 87%, respectively; the most reliable results were obtained with blind bronchoalveolar lavage at the cutoff of > or =103 cfu/mL (sensitivity 96%, specificity 80%, positive predictive value 88%, negative predictive value 92%, and accuracy 90%). The area under the receiver operating characteristic curve of tracheal aspiration, blind bronchial sampling, and blind bronchoalveolar lavage was 0.87 +/- 0.06, 0.89 +/- 0.06, and 0.89 +/- 0.05, respectively. The cost of balloon-tip pressure catheter used for blind bronchoalveolar lavage was INR 1600.00 (US$40) whereas that for blind bronchial sampling was only INR 35.00 (<1 US$).

CONCLUSIONS

Blind bronchoalveolar lavage was the most reliable method followed closely by blind bronchial sampling for the diagnosis of ventilator-associated pneumonia. Considering the difference of the cost in the two procedures, blind bronchial sampling may be the preferred method in the pediatric intensive care unit of a developing country.

[Duration of antibiotic therapy for ventilator-associated pneumonia: comparison of 7 and 10 days. A pilot study]

OBJECTIVE

To compare the efficiency of a 7-day antibiotics regimen with a 10-day regimen for ventilator-associated pneumonia (VAP).

STUDY DESIGN

Prospective randomized study.

PATIENTS AND METHODS

Adults patients ventilated for more than 48 hours in the intensive care unit (ICU) with a clinical diagnosis of VAP documented by positive quantitative cultures of tracheal aspiration were included in this study. All included patients were randomized in two groups. Ten-day group: 10 days antibiotic therapy, and 7-day group: 7 days antibiotic therapy. Primary judgment criteria were 14- and 28-day mortality, the number of days without antibiotics. Secondary judgments criteria were rate of recurrent pulmonary infection, the evolution of the clinical pulmonary infection scores (CPIS), the length of ICU stay and the length of mechanical ventilation.

RESULTS

Thirty patients were included in this study (16 in the 10-day group and 14 in the 7-day group). The demographic and clinical characteristics of the groups assigned to receive antibiotic therapy for 7 or 10 days were generally similar. The 14-day and 28-day mortality rate following VAP onset were 31.2 and 37.5% in the 10-day group and 7.1 and 35.7% in the 7-day group. The difference was not significant. The number of day without antibiotics and without mechanical ventilation turned out: 1.75 and 2.06 days versus 4.14 and 3.43 days in the 10-day group and 7-day group respectively, the recurrent rate of pulmonary infection (12.5% versus 14.3%, p=0.6), the length of stay in the ICU (27.7 days versus 26.0 days, p=0.8) and the evolution of the CPIS were no different in the two groups.

CONCLUSION

In patients with microbiologically confirmed VAP who received appropriate empirical antibiotic therapy, a 7-day antibiotic regimen was as efficient clinically and microbiologically as a 10-day antibiotic regimen with a reduction of antibiotic use.

Diagnostic strategies for nosocomial pneumonia

PURPOSE OF REVIEW

This review describes advances in clinical and microbiological modalities for diagnosis of nosocomial pneumonia and the role of biological markers.

RECENT FINDINGS

Serial assessments with the clinical pulmonary infection score identifies nonsurvivors and allows discontinuation of antibiotics when there is low suspicion of pneumonia. Studies evaluating its clinical utility show mixed results. A meta-analysis revealed that an invasive approach does not affect mortality but reduces costs, antibiotic exposure, and multidrug resistance. In contrast to these findings, a recent trial comparing nonquantitative endotracheal aspirate and quantitative bronchoalveolar lavage cultures showed similar clinical outcomes and antibiotic utilization. The role of quantitative endotracheal aspirate for diagnosis of pneumonia not related to mechanical ventilation was recently evaluated. Procalcitonin and soluble triggering receptor expressed on myeloid cells-1 aid in diagnosis, identify sepsis related to ventilator-associated pneumonia and patients with worst outcomes.

SUMMARY

The diagnostic modality chosen depends on availability, personnel experience, and the patient's clinical status. Recent guidelines support the use of quantitative cultures in an integrated clinical and microbiological algorithm. The decision to adjust antibiotics involves clinical reassessment and interpretation of culture results. Biological markers have a potential role as screening and prognostic tools.

Ventilator-associated pneumonia: diagnosis, treatment, and prevention

While critically ill patients experience a life-threatening illness, they commonly contract ventilator-associated pneumonia. This nosocomial infection increases morbidity and likely mortality as well as the cost of health care. This article reviews the literature with regard to diagnosis, treatment, and prevention. It provides conclusions that can be implemented in practice as well as an algorithm for the bedside clinician and also focuses on the controversies with regard to diagnostic tools and approaches, treatment plans, and prevention strategies.

Use of quantitative cultures and reduced duration of antibiotic regimens for patients with ventilator-associated pneumonia to decrease resistance in the intensive care unit

Ventilator-associated pneumonia is responsible for approximately half of the infections acquired in the intensive care unit and represents one of the principal reasons for the prescription of antibiotics in this setting. Invasive diagnostic methods, including bronchoalveolar lavage and/or protected specimen bronchial brushing, could improve the identification of patients with true bacterial pneumonia and facilitate decisions of whether to treat. These techniques also permit rapid optimization of the choice of antibiotics in patients with proven bacterial infection, once the results of respiratory tract cultures become available, based on the identity of the specific pathogens and their susceptibility to specific antibiotics, to avoid prolonged use of a broader spectrum of antibiotic therapy than is justified by the available information. Because unnecessary prolongation of antibiotic therapy for patients with true bacterial infection may lead to the selection of multidrug-resistant microorganisms without improving clinical outcome, efforts to reduce the duration of therapy for nosocomial infections are also warranted. An 8-day regimen can probably be standard for patients with ventilator-associated pneumonia. Possible exceptions to this recommendation include immunosuppressed patients, patients who are bacteremic or whose initial antibiotic therapy was not appropriate for the causative microorganism(s), and patients whose infection is with very difficult-to-treat microorganisms and show no improvement in clinical signs of infection.

Quantitative cultures for diagnosing ventilator-associated pneumonia: a critique

The diagnosis of ventilator-associated pneumonia has been clouded by uncertainty, because a reference standard has never been established. The use of invasive procedures to obtain respiratory tract samples for culture, with quantitation of the bacteria isolated, has been the approach most commonly advocated. Quantitation of bacteria from lower respiratory tract specimens can be used to distinguish colonization from infection. We review the invasive procedures (bronchoalveolar lavage, protected specimen brushing, nonbronchoscopic bronchoalveolar lavage, and blinded bronchial sampling), the methods of quantitation used, the types of catheters used, the sample collection methods, and the criteria used as cutoffs for the quantitative cultures. Quantitation of lower respiratory tract samples is inherently unstable from a mathematical perspective, given the variability in the volume of fluid instilled and reaspirated and the magnitude and complexity of the area being sampled. We also briefly review the use of quantitation for bacterial infections other than pneumonia, including urinary tract infection and catheter-related bacteremia. The variability in both the methods and reference criteria in the studies reviewed show that the quantitation approach is neither standardized nor evidence based.

Diagnosis of ventilator-associated pneumonia: focus on nonbronchoscopic techniques (nonbronchoscopic bronchoalveolar lavage, including mini-BAL, blinded protected specimen brush, and blinded bronchial sampling) and endotracheal aspirates

The ideal diagnostic approach for ventilator-associated pneumonia currently is based on invasive procedures to obtain respiratory tract cultures. Given the lack of consensus and relatively poor acceptance of full bronchoscopic bronchoalveolar lavage (BAL) and protected specimen brush (PSB), less invasive procedures have been developed. We review the nonbronchoscopic procedures (nonbronchoscopic bronchoalveolar lavage, including mini-BAL, blinded protected specimen, and blinded bronchial sampling) and endotracheal aspiration. We provide a critique of the methods used, the types of catheters inserted, and the sample collection methods. Most studies were flawed in that antibiotic use before initiation of the procedure was not controlled. The variability of both the methods and the criteria for the gold standard in the numerous investigations show that these procedures are neither standardized nor proven to be accurate and often did not improve management. Pending future studies, use of endotracheal aspirates without the use of quantitation seems to be a reasonable approach for clinicians who are not committed to an invasive procedure.

Blind and bronchoscopic sampling methods in suspected ventilator-associated pneumonia

OBJECTIVE

To compare four sampling methods: blind tracheal aspirate (blind TA), blind protected telescoping catheter (blind PTC), bronchoscopic PTC and bronchoscopic bronchoalveolar lavage (bronchoscopic BAL), for diagnosis of ventilator-associated pneumonia (VAP).

DESIGN

Prospective multicentre study.

SETTING

Five intensive care units in France.

PATIENTS

Sixty-three patients with mechanical ventilation for more than 48 h, no recent antibiotic change (<72 h) and suspected nosocomial pneumonia.

INTERVENTIONS

All patients underwent the four sampling methods. Direct examination and quantitative cultures of the four specimens were performed.

MEASUREMENTS AND RESULTS

Visible secretions expelled from the catheter were present 40 times (63%) for blind PTC and 45 times (71%) for bronchoscopic PTC. After exclusion of 11 uncertain cases, 34 VAP were diagnosed. Direct examination of PTC (either blind or bronchoscopic) did not differ from direct examination of bronchoscopic BAL in predicting VAP diagnosis and in guiding initial antibiotic treatment correctly. Compared to that of bronchoscopic BAL (0.98), the area under receiver operating characteristics (ROC) curve was smaller for blind TA (0.78, p=0.002), blind PTC (0.83, p=0.009) and bronchoscopic PTC (0.85, p=0.01). When samples with visible secretions expelled from the catheter were considered, blind and bronchoscopic PTC had areas under ROC curve close to that of bronchoscopic BAL (0.90, p=0.22 and 0.91, p=0.27, respectively).

CONCLUSIONS

Blind PTC appears to be a good alternative to bronchoscopic sampling for VAP diagnosis, provided that the sample contains visible secretions expelled from the catheter.

Diagnosis of ventilator-associated pneumonia: agreement between quantitative cultures of endotracheal aspiration and plugged telescoping catheter

OBJECTIVE

To evaluate the diagnostic agreement between quantitative cultures of samples obtained with endotracheal aspiration (ETA) and plugged telescoping catheter (PTC).

DESIGN

Prospective study.

SETTING

Medical ICU.

PATIENTS

Hundred thirty-eight episodes of suspected ventilator-associated pneumonia studied in 100 consecutive patients.

INTERVENTIONS

For each suspected episode of ventilator-associated pneumonia, ETA and PTC were performed consecutively. The agreement between microbiological results obtained from the two techniques was evaluated (kappa statistic test). Pneumonia was diagnosed on a positive culture result of telescoping catheter with the threshold set at 10(3) cfu/ml or more. The cut-off points evaluated for ETA ranged from 10(2 )to 10(6) cfu/ml.

RESULTS

Micro-organisms retrieved by aspiration and telescoping catheter were similar and bacterial counts obtained by the two procedures were well correlated ( r = 0.71 p < 0.001). There was good agreement between positive and negative ETA and PTC specimens (kappa: 0.78) with a diagnostic threshold for ETA of 10(4) cfu/ml. The sensitivity and specificity of ETA for the diagnosis of PTC-confirmed pneumonia were 92% and 85%, respectively. Kappa decreased to 0.48 when the diagnostic threshold was increased to 10(6) cfu/ml.

CONCLUSIONS

Quantitative cultures of ETA and PTC tallied for both micro-organisms and counts. The simpler ETA appears adequate for determining the presence of pathogenic organisms in significant concentration in the lower respiratory tract.

A rational approach to the evaluation and treatment of the infected patient in the intensive care unit

Critically ill patients are at increased risk of acquiring nosocomial infections. A thorough clinical evaluation and the selection of appropriate diagnostic techniques are important elements in the evaluation of these patients. Nonetheless, this selection process can be difficult because of the wide spectrum of disease that is seen in the ICU and the lack of standardized studies that have evaluated the different diagnostic methods that are available. Many different antimicrobials are available for the treatment of ICU-acquired infections. Most antimicrobial regimens have not been evaluated in large-scale, prospective, randomized trials. Until this information is available, the clinician must make an effort to be familiar with the different clinical and epidemiologic variables that can be used to stratify patients at the moment of selecting antimicrobial therapy. The information provided in this article, used in association with good clinical judgment, will help the critical care physician provide optimal initial management of the infected patient in the ICU.

[Diagnostic value of quantitative cultures of endotracheal aspirate in ventilator-associated pneumonia: a multicenter study]

OBJECTIVE

To study the validity of quantitative cultures of tracheal aspirate (TA) in comparison with the plugged telescoping catheter (PTC) for the diagnosis of mechanical ventilator-associated pneumonia.

METHOD

Prospective multicenter study enrolling patients undergoing mechanical ventilation for longer than 72 hours. TA samples were collected from patients with suspected ventilator-associated pneumonia, followed by PTC sampling. Quantitative cultures were performed on all samples. Patients were classified according to the presence or not of pneumonia, based on clinical and radiologic criteria, clinical course and autopsy findings. The cutoff points were > or = 103 colony-forming units (cfu)/mL for PTC cultures; the TA cutoffs analyzed were > or = 105 and > or = 106 cfu/mL.

RESULTS

Of the 120 patients studied, 84 had diagnoses of pneumonia and 36 did not (controls). The sensitivity values for TA > or = 106, TA > or = 105, and PTC, respectively, were 54% (95% confidence interval [CI], 42%-64%), 71% (95% CI, 60%-81%), and 68% (95% CI, 57%-78%). The specificity values were 75% (95% CI, 58%-88%), 58% (95% CI, 41%-74%), and 75% (95% CI, 58%-88%), respectively. Staphylococcus aureus was the microorganism most frequently isolated in both TA and PTC samples, followed in frequency by Pseudomomonas aeruginosa in TA samples and Haemophilus influenzae in PTC samples. No significant differences were found between the sensitivity of TA > or = 105 and that of PTC, nor between the specificities of TA > or = 106 and PTC.

CONCLUSIONS

No differences in the specificities of PTC and TA were found when a TA cutoff of > or = 106 cfu/ml was used. Moreover, at a cutoff of > or = 105 the sensitivity of TA was not statistically different from that of PTC. Quantitative cultures of TA can be considered acceptable for the diagnosis of ventilator-associated pneumonia.

Fluconazole improves survival in septic shock: a randomized double-blind prospective study

OBJECTIVE

To demonstrate whether fluconazole reduces multiple organ failure and mortality in early septic shock (<24 hrs).

DESIGN

A prospective randomized double-blind study.

SETTING

A medical and surgical adult intensive care unit in a tertiary referral center.

PATIENTS

Values were obtained from 71 general adult intensive care unit patients.

INTERVENTIONS

During a 2.5-yr period, December 1998-June 2001, 71 patients with septic shock attributed to either nosocomial pneumonia (n = 37) or intra-abdominal sepsis (n = 34) were admitted to our intensive care unit and met the criteria of early septic shock and were entered into this study. All patients were randomized by our clinical pharmacist to receive daily either 200 mg of fluconazole in isotonic saline (fluconazole group = 32) or isotonic saline alone (placebo group = 39) intravenously during the course of their septic shock.

MEASUREMENTS AND MAIN RESULTS

All patients were closely monitored with pulmonary artery catheters and parameters to calculate daily organ dysfunction and Acute Physiology and Chronic Health Evaluation II scores. There was a highly significant increase in 30-day survival in the fluconazole-treated patients compared with the placebo patients (78% vs. 46%). However, fluconazole was found to be more effective in patients with septic shock attributed to intra-abdominal sepsis than to nosocomial pneumonia. Increased survival in the intra-abdominal sepsis clinical category was mirrored by a significantly lower number of organ failures in the treated group compared with the placebo group whereas the number of organ failures in the fluconazole group attributed to nosocomial pneumonia were not significantly increased compared with the control group. The septic shock state was considered in all cases to be attributed to bacterial and not to disseminated yeast infection with the exception of one patient in the control group who was admitted with candidemia. The mechanisms by which fluconazole exerts its protective effect against septic shock in patients is far from clear. However, fluconazole has been shown to enhance bactericidal activity of neutrophils and also to inhibit transmigration and adhesion of neutrophils in capillaries of distant organs.

CONCLUSIONS

The development of organ failure and mortality in septic shock was significantly reduced by fluconazole given intravenously. The mechanism of action of fluconazole in reducing multiple organ dysfunction in this group of patients may be attributed to the ability of fluconazole to increase recruitment, improve bactericidal activity of neutrophils, and to contain microorganisms locally.

Ventilator-associated pneumonia

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

Non-bronchoscopic bronchoalveolar lavage in the microbiological diagnosis of pneumonia in mechanically ventilated patients

A prospective study comparing standardized non-bronchoscopic bronchoalveolar lavage (sNB-BAL) and non-specific endotracheal aspirate (NsETA) in the microbiological diagnosis of pneumonia in mechanically ventilated patients is described. One hundred episodes in 82 mechanically ventilated patients with or without radiological and clinical diagnostic criteria of pneumonia were studied. NsETA and sNB-BAL was performed on the day of study. Fifty-one patients had pneumonia (21 ventilator-associated, 12 hospital-acquired, 18 community-acquired) and 49 had no pneumonia as defined by widely accepted clinico-radiological criteria. The sNB-BAL was found to be significantly more specific (0. 73) compared to NsETA (0.35) for the microbiological diagnosis of pneumonia. Colonization rates with NsETA were significantly higher compared to sNB-BAL (P value <0.0001). No patient had complications attributable to the sNB-BAL procedure. We conlude that sNB-BAL is a safe, effective, sensitive, specific and inexpensive procedure for the serial evaluation of pneumonia in mechanically ventilated patients.

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.

Ventilator-associated pneumonia or not? Contemporary diagnosis

Ventilator-associated pneumonia (VAP) is pneumonia in patients who have been on mechanical ventilation for > or =48 hours. VAP is most accurately diagnosed by quantitative culture and microscopy examination of lower respiratory tract secretions, which are best obtained by bronchoscopically directed techniques such as the protected specimen brush and bronchoalveolar lavage. These techniques have acceptable repeatability, and interpretation of results is unaffected by antibiotics administered concurrently for infection at extrapulmonary sites as long as antimicrobial therapy has not been changed for <72 hours before bronchoscopy.

Pulmonary Infections in Ventilated Patients: Diagnostic and Therapeutic Options

The diagnosis of pulmonary infections in the ventilated patient has threatened the foundations of medicine. Although the lifesaving techniques of endotracheal intubation (developed for the treatment of diphtheria) and artificial ventilation (developed for the management of poliomyelitis) contribute greatly to medical care, they have resulted in the production of the "progress"-related infection of ventilator-associated pneumonia (VAP). Modern ventilator therapy is a substantial technologic advance from earlier days and, as technology inherently does, has removed some of the human element, the main foundation of Oslerian medical practice. The time-honored clinical diagnosis based on physical examination by an experienced physician has been seriously compromised in the approach to VAP.

Incidence of gastroesophageal reflux and aspiration in mechanically ventilated patients using small-bore nasogastric tubes

BACKGROUND

Use of a large-bore nasogastric tube (NGT) and patient position are considered key factors in promoting gastroesophageal reflux (GER) and pulmonary aspiration in critically ill patients. The objective of this study was to determine the incidence of GER and pulmonary aspiration of gastric contents in mechanically ventilated (MV) patients using small-bore NGTs.

METHODS

We studied 30 patients on mechanical ventilation for acute respiratory failure who tolerated enteral nutrition through a small-bore NGT. Patients were randomly assigned to a group with (n = 16) or without (n = 14) a small-bore NGT and were maintained in a semirecumbent position during the study. GER and aspiration of gastric contents were assessed by a radioisotopic technique. Scans were done 24 hours after technetium-99m administration (n = 30). In 9 patients a dynamic scintigraphy was performed immediately after colloid administration, and samples of blood and tracheal and oropharyngeal secretions were obtained basally, 30 minutes, and 24 hours after technetium administration and analyzed for radioactivity using a gamma counter.

RESULTS

Both groups were similar in age, underlying diagnosis, number of days of mechanical ventilation at the day of study, and mortality. There were no GER reaching the oropharynx and aspiration of gastric contents in both groups.

CONCLUSIONS

GER and aspiration of gastric contents were not detected in MV patients using small-bore NGTs and may be a simple measure to prevent ventilator-associated pneumonia.

Protected specimen brush or bronchoalveolar lavage to diagnose bacterial nosocomial pneumonia in ventilated adults: a meta-analysis

OBJECTIVE

We conducted a meta-analysis by using summary receiver operating characteristic curves to compare the diagnostic value for bacterial nosocomial pneumonia of the following: a) quantitative culture (colony-forming units per milliliter or CFU/mL) of respiratory secretions collected with a bronchoscopic protected specimen brush (PSB); b) quantitative culture of a bronchoscopic bronchoalveolar lavage (BAL); and c) the percentage of infected cells (IC) in BAL.

DATA SOURCES

All studies published in the English or the French language, through January 1, 1995, on the evaluation of PSB or BAL for the diagnosis of pneumonia were considered for analysis. The relevant literature was identified through computer and reference searching and by experts in the field.

STUDY SELECTION

A study was included if at least two of three independent readers regarded its purpose as the evaluation of CFU-PSB, CFU-BAL, or IC-BAL for the diagnosis in human beings of bacterial nosocomial pneumonia in ventilated adults and if the study was prospective and published in a peer-reviewed journal.

DATA EXTRACTION

Three readers reviewed all published articles and decided whether to include each study; consensus was defined as agreement by at least two readers. The authors of each original article included in the meta-analysis were asked to complete a questionnaire in which they were asked to check and to correct the data extracted by one of the independent readers.

DATA SYNTHESIS

Summary receiver operating characteristic curves were used to compare the efficacy of three diagnostic tests. Eighteen studies on CFU-PSB (795 patients) were included, as well as 11 studies on CFU-BAL (435 patients) and 11 on IC-BAL (766 patients). The accuracy of these tests was not different. However, it seems that administration of previous antibiotics markedly decreased accuracy of CFU-PSB (p = .0002) but not the accuracy of CFU-BAL and that of IC-BAL.

CONCLUSION

Both PSB and BAL are reliable to diagnose bacterial nosocomial pneumonia. Because CFU-BAL and IC-BAL seemed more resistant to the effects of antibiotics, we recommend BAL rather than PSB if the patient is already receiving antibiotics.

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.

Respiratory infectious complications in the intensive care unit

Ventilator-associated pneumonia is the most common infectious respiratory complication in intensive care unit patients, particularly those needing mechanical ventilation. Ventilator-associated pneumonia represents a challenging problem in terms of diagnosis, treatment, and prevention. Nosocomial sinusitis is another respiratory infection, not uncommon in mechanically ventilated patients. This type of infection has to be suspected in nasally intubated patients and may be a hidden focus of fever and sepsis.

Invasive diagnostic techniques for pneumonia: protected specimen brush, bronchoalveolar lavage, and lung biopsy methods

We suggest the following strategy for managing patients with pneumonia. For nonventilated patients with either CAP or HAP, empiric antibiotic treatment should be started according to approved guidelines, and if the clinical evolution of the patient is not adequate, fiberoptic bronchoscopy including PSB and BAL could be considered, with modification of the antibiotic treatment accordingly. In ventilated patients with either CAP or HAP, respiratory secretion sampling using noninvasive techniques should be conducted upon clinical suspicion of VAP and before starting a new antibiotic treatment. Antibiotic therapy according to approved guidelines should be started as soon as possible and maintained during the first 48 hours if the patient's evolution is satisfactory and condition has stabilized. Then, initial antibiotic treatment should be adjusted according to cultures. If there is a clear diagnostic alternative to VAP and cultures are negative, this is the only case in which antibiotic treatment could be withdrawn. If the patient's clinical evolution is inadequate (persistence of fever, leukocytosis, increasing infiltrates, and respiratory failure), fiberoptic bronchoscopy with PSB and BAL and modification of the initial antibiotic regimen should be sought. Open lung biopsy may be indicated in patients with diffuse pulmonary infiltrates in whom a diagnosis has not been achieved by other methods, including bronchoscopy. Transbronchial lung biopsy should not be viewed as a diagnostic technique for pneumonia except in immunosuppressed patients with diffuse alveolar infiltrates.

[Diagnostic characteristics of acquired pneumonia in patients under mechanical respiration]

Ventilator-associated pneumonias (VAP) are the most frequent nosocomial lung infections. Histological diagnosis is the standard for reference. A diagnosis of VAP can be considered in presence of fever or hypothermia, hyperleucocytosis or leucopenia, worsening of blood gases, and new radiological infiltrate. Their diagnostical value is dependent on the number of included manifestations. A clinical pulmonary infection score (CPIS) has been produced and compared with histological data. Bacteriological data are essential for an adapted antibiotherapy. The blind non-protected specimen brush is inexpensive and reliable at levels of 10(4) and 10(6) CFU.mL-1, the sensitivity and specificity reach 60%. The double-protected catheter is a sensitive and specific test at the level of 10(3) CFU.mL-1. At present its accuracy has only been compared with bronchial brushing. The culture of a 20 mL mini-broncho-alveolar lavage (same material) is specific (50%) but not sensitive enough (< 70%) at the level of 10(3) CFU.mL-1. The culture of the protected telescopic brush is the most expensive test. It does not carry a risk of contamination, but does not detect a significant amount of VAP even at a level below 10(3) CFU.mL-1. Due to its high specificity it is used as the reference test in numerous studies. The endoscopic broncho-alveolar lavage provides a rapid diagnosis. Although not protected, it carries a low risk of false positives. It also allows the diagnosis of non-bacterial or atypical bacterial lung infections. The diagnosis can also be obtained with lung biopsy which however carries a risk in case of mechanical ventilation, whatever the technique. Except for the protected double catheter, a direct examination has been advocated, for the differentiation between infection and colonization and the improvement of the performances of the simple culture of the broncho-alveolar lavage (search for intra-cellular bacteria).

Nosocomial pneumonia in the critical care unit

Nosocomial pneumonia poses a major threat to the recovery of patients receiving mechanical ventilation. In addition, nosocomial pneumonia is often difficult to diagnose. This article examines the extent of the threat and some of the difficulties facing the critical care physician when diagnosing nosocomial pneumonia.

Ventilator-associated pneumonia: clinical significance and implications for nursing

Pneumonia is the second most common nosocomial infection in the United States and the leading cause of death from nosocomial infections. Intubation and mechanical ventilation greatly increase the risk of bacterial pneumonia. Ventilator-associated pneumonia (VAP) occurs in a patient treated with mechanical ventilation, and it is neither present nor developing at the time of intubation; it is a serious problem--with significant morbidity and mortality rates. Aspiration of bacteria from the oropharynx, leakage of contaminated secretions around the endotracheal tube, patient position, and cross-contamination from respiratory equipment and health care providers are important factors in the development of VAP. Nurses caring for patients treated with mechanical ventilation must recognize risk factors and include strategies for reducing these factors as part of their nursing care. This article summarizes the literature related to VAP: its incidence, associated factors, diagnosis, and current therapies, with an emphasis on nursing implications in the care of these patients.

Nosocomial pneumonia. Diagnosis and prevention

Ventilator-associated pneumonia (VAP) is an important complication in patients with respiratory failure who undergo endotracheal intubation and mechanical ventilation. VAP cannot be accurately diagnosed by clinical or radiographic criteria or culture of endotracheal aspirates; however, it can be accurately diagnosed by histopathologic examination of lung tissue, rapid cavitation of a pulmonary infiltrate, culture of empyema fluid, percutaneous lung needle aspiration, simultaneous recovery of the same microorganism from cultures of respiratory secretions, and blood and quantitative culture of lower respiratory tract secretions obtained by bronchoscopy. VAP can be prevented by proper decontamination and use of ventilatory support equipment, practice of proper nursing techniques during care of the mechanically ventilated patient, and use of face mask ventilation in selected patients.

Usefulness of airway visualization in the diagnosis of nosocomial pneumonia in ventilated patients

Clinical diagnosis of nosocomial pneumonia in ventilated patients remains a challenge in the ICU as none of the clinical biological and radiologic parameters can predict its diagnosis. To our knowledge, however, the accuracy of direct visualization of the bronchial tree has never been investigated.

PURPOSE

To evaluate the interest of airway visualization and to select independent parameters that predict nosocomial pneumonia in ventilated patients.

SETTING

A ten-bed medical-surgical ICU.

METHODS

All consecutive patients suspected of having nosocomial pneumonia who underwent bronchoscopy with protected specimen brush, culture examination of BAL, and direct examination of BAL were studied. Clinical and biological data and airways findings were recorded prospectively. Patients were classified as having pneumonia or not according to the results of distal bacteriologic samples, follow-up, and histologic study. Respective accuracies of each variable were calculated using univariate analysis and stepwise logistic regression.

RESULTS

Ninety-one patients with suspected nosocomial pneumonia were studied. Patients were randomly assigned to a construction group (n = 46) and a validation group (n = 45). Using multivariate analysis, 3 factors were associated with pneumonia (a decrease in PaO2/fraction of inspired oxygen ratio > or = 50 mm Hg, odds ratio [OR] = 9.97, p = 0.026; the presence of distal purulent secretions, OR = 7.46, p = 0.044; the persistence of distal secretions surging from distal bronchi during exhalation, OR = 12.25, p = 0.013). These three factors remained associated with pneumonia in the validation group. Interobserver repeatability of the bronchoscopic parameters was good. Having 2 or more of these 3 independent factors was able to predict pneumonia with a 94% sensitivity and a 89% specificity in the construction group and with a 78% sensitivity and a 89% specificity in the validation group.

CONCLUSION

We conclude that direct visualization of the bronchial tree can immediately and accurately predict nosocomial pneumonia in ventilated patients before obtaining definite results of protected samples.

Value of intracellular bacteria detection in the diagnosis of ventilator associated pneumonia

BACKGROUND

Markers of ventilator associated pneumonia are of interest for confirming the diagnosis and for guiding the initial management of this frequent complication of mechanical ventilation. The detection of intracellular organisms in the polymorphonuclear leucocytes (PMNLs) and/or macrophages of bronchoalveolar lavage (BAL) fluid has been suggested as a specific test for the early indication of an infectious pulmonary process.

METHODS

The diagnostic value of detecting intracellular organisms in two types of BAL fluid--protected (P-BAL) and conventional (C-BAL)--in 25 patients who died in one unit was prospectively studied. Immediately after death both P-BAL and C-BAL were performed bilaterally. Through a minithoracotomy on both sides of the chest bilateral bronchoscopically guided open lung biopsy samples were obtained from the same area, and an average of eight open lung blind biopsy samples (not bronchoscopically guided) were taken from each lung for histological examination. BAL fluid was examined for quantitative cultures (threshold 10(4) cfu/ml) and for the presence of intracellular organisms and extracellular organisms, and differential cell counts were also performed.

RESULTS

Using the histopathology of the bronchoscopically guided open lung biopsies as the gold standard, detection of intracellular organisms in P-BAL (> or = 5%) and C-BAL (> or = 5%) fluids yielded 75% and 57% positive predictive values, and 83% negative predictive values, respectively. Prior treatment with antibiotics decreased the positive and negative predictive values of intracellular organism detection for both types of BAL fluid. The presence of intracellular organisms was correlated with the quantitative cultures of P-BAL and C-BAL samples. Quantitative cultures from P-BAL fluid were less sensitive (22% versus 45%) and more specific (100% versus 55%) than those from C-BAL samples. The percentage of extracellular organisms and the differential cell count in P-BAL and C-BAL samples could not discriminate between the presence or absence of pneumonia.

CONCLUSIONS

The presence of > or = 5% intracellular organisms infecting PMNLs or macrophages in P-BAL or C-BAL fluids is a specific marker of ventilator associated pneumonia.