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

Aportación del laboratorio de microbiología al diagnóstico de la neumonía asociada a la ventilación mecánica

The etiologic diagnosis of ventilator-associated pneumonia (VAP) should be considered as a microbiological emergency due to its impact on morbidity and mortality. Sampling of the lower respiratory tract (LRT) must be performed before starting or modifying antimicrobial therapy. Surveillance cultures in patients without criteria of VAP are not recommended. There is no evidence of any superiority of bronchoscopic over non-bronchoscopic sampling procedures, but quantitative bacterial cultures are essential to allow colonization to be differentiated from true infection of the LRT. Under these conditions, negative cultures practically rule out bacterial infection or, at least, identify patients who will not benefit from antibiotic therapy or who will require a very short course of treatment. Given that identification and antimicrobial susceptibility testing of microorganisms usually takes up to 3 or 4 days, rapid procedures that provide the clinician with useful information are essential. Rapid information, even if partial or less than perfect, is clearly better for the patient than a perfect but delayed report. Gram stain of LRT secretions is an immediate procedure that can guide management and it has a reasonable correlation with culture results. At present, new antibiogram procedures, performed on direct clinical samples, allow presumptive identification and information on susceptibility to commonly used antibiotics in less than 24 hours after sampling. The impact of using this procedure in clinical practice is currently under research.

Both early-onset and late-onset ventilator-associated pneumonia are caused mainly by potentially multiresistant bacteria

OBJECTIVE

To compare the causative pathogens of early-onset and late-onset ventilator-associated pneumonia (VAP) diagnosed by bronchoalveolar lavage quantitative cultures. Most previous reports have been based on endotracheal aspirate cultures and gave uncertain findings.

DESIGN

Prospective evaluation of consecutive patients with clinical suspicion for VAP.

SETTING

Multidisciplinary intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

During a 3-year period 473 patients with clinical suspicion of VAP entered the study. Diagnosis of VAP was confirmed by cultures of bronchoalveolar lavage (> 10(4) cfu/ml) specimens in 408 patients.

INTERVENTIONS

Protected bronchoalveolar lavage samples were taken. Initial antibiotic therapy was modified upon bronchoalveolar lavage culture results.

MEASUREMENTS AND RESULTS

Among 408 patients 191 had early-onset (< 7 days mechanical ventilation) and 217 late-onset (> or = 7 days) VAP. Potentially multiresistant bacteria, mainly Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), were the most commonly isolated pathogens in both types of VAP. No difference was noted in the contribution of potentially multiresistant pathogens (79% vs. 85%), P. aeruginosa (42% vs. 47%), or MRSA (33% vs. 30%) between early-onset and late-onset VAP. Initial antibiotic therapy was modified in 58% of early-onset VAP episodes and in 36% of late-onset VAP episodes. No difference in mortality was found between the two types of VAP.

CONCLUSIONS

Both early-onset and late-onset VAP were mainly caused by potentially multiresistant bacteria, most commonly P. aeruginosa and MRSA. Antimicrobial agents against these pathogens should be prescribed empirically, at least in our institution.

Evaluation of a Clinical Pathway for Ventilator-Associated Pneumonia: Changes in Bacterial Flora and the Adequacy of Empiric Antibiotics over a Three-Year Period

BACKGROUND

Evaluation of causative pathogens is vital for optimizing empiric antibiotic therapy of ventilator-associated pneumonia (VAP). Based on previous data (Ann Surg 1998;227:743-755), empiric antibiotics for our VAP clinical pathway were modified to target early and late occurring pathogens (ampicillin/sulbactam during the first week of hospitalization; cefepime plus vancomycin afterwards). The objectives of this study were to compare organisms causing VAP over a three-year period to previous data, and to determine the adequacy of the empiric antibiotic regimens.

METHODS

A total of 299 critically ill trauma patients with VAP over a three-year period were studied retrospectively. The incidence of pathogens causing VAP in the study period were compared to a previously published study of a two-year period in our intensive care unit (ICU). Sensitivities of Pseudomonas aeruginosa and Acinetobacter baumannii were evaluated over the study period. The adequacy of empiric antibiotic therapy for each episode of VAP was determined. Therapy was considered to be adequate if one or more antibiotics had in vitro activity against the organism causing VAP.

RESULTS

Statistically significant changes in pathogens included increased Staphylococcus aureus (incidence 17% vs. 11%, p = 0.024) and decreased Acinetobacter baumannii (11% vs. 22%, p < 0.001). Susceptibility patterns were statistically unchanged except for increased resistance of P. aeruginosa to extended-spectrum penicillins (p = 0.016). Empiric therapy was adequate in 76% of VAP episodes.

CONCLUSIONS

The clinical pathway's empiric antibiotic regimen was associated with only modest changes in organisms causing VAP and provided a high rate of adequate empiric coverage.

Bronchoalveolar lavage in diagnosis of ventilator-associated pneumonia in patients with burns

Ventilator-associated pneumonia (VAP) remains a major cause of morbidity and mortality for patients with burns. In nonburn populations, bronchoalveolar lavage (BAL) excludes other pathology such as systemic inflammatory response syndrome. We hypothesized that BAL would decrease our false-positive VAP rate. All ventilated patients with burn injury who were admitted to our institution from July 2000 through June 2003 were included. After June 2001, BAL was used to make the diagnosis of VAP, with > or =10(4) organisms considered a positive result. Fifty patients met criteria for VAP, 21 in the pre-BAL period and 29 in the BAL period. Six patients (21%) in the BAL group had quantitative cultures <10(4) and were not treated. The outcomes for these patients were not different than those treated for VAP. There were no differences in age, TBSA size, antibiotic use, or ventilator days for the pre-BAL or BAL groups, although the pneumonia rate was lower for the BAL time period. The use of BAL eliminated the unnecessary antibiotic treatment of 21% of patients in the BAL time period and was associated with a lower rate of VAP.

Early antibiotic treatment for BAL-confirmed ventilator-associated pneumonia: a role for routine endotracheal aspirate cultures

STUDY OBJECTIVES

To test whether routine quantitative cultures of endotracheal aspirates obtained before the onset of ventilator-associated pneumonia (VAP) could help to predict the causative microorganisms and to select early appropriate antimicrobial therapy before obtaining BAL culture results.

DESIGN

Prospective observational study.

SETTING

French medical ICU.

PATIENTS

A total of 299 patients received mechanical ventilation for at least 48 h.

INTERVENTIONS

Endotracheal aspiration (EA) was performed twice weekly in all mechanically ventilated patients. A diagnosis of VAP was made by BAL culture. Only the EA performed just before the suspicion of VAP (EA-pre) were evaluated. This strategy (ie, the EA-pre-based strategy) was compared with an antibiotic therapy that would have been prescribed if the recommendations of both the American Thoracic Society (ATS) and Trouillet et al (Am J Respir Crit Care Med 1998; 157:531-539) had been applied.

MEASUREMENTS AND RESULTS

VAP was diagnosed (by BAL culture) in 41 of the 75 patients in whom BAL was performed. Among the 41 BAL specimens that were positive for VAP, EA-pre had identified the same microorganisms (with the same antibiotic resistance patterns) in 34 cases (83%). In one case, EA-pre was not available at the time BAL was performed (a case of early-onset VAP), but the empiric antibiotic therapy was adequate. While EA-pre did not give the same results as the BAL culture, the antibiotic therapy based on the results of the EA-pre was adequate in four other cases. Finally, antibiotic therapy was delayed in only two cases. Antibiotic treatment was therefore adequate in 38 of the 40 assessable cases (95%). If the Trouillet-based strategy had been used, the antibiotic treatment would have been adequate in 34 of the 41 cases (83%; p = 0.15 [vs EA-pre strategy]). Based on the ATS classification, the antibiotic treatment would have been adequately prescribed in only 28 of the 41 cases (68%; p = 0.005 [vs EA-pre strategy]).

CONCLUSIONS

Routine EA performed twice a week makes it possible to prescribe adequate antibiotic therapy (while waiting for BAL culture results) in 95% of the patients in whom a VAP is ultimately diagnosed by BAL culture.

Nonresolving Pneumonia

Uncertainty over the expected clinical course of a community-acquired or nosocomial pneumonia is a common reason for pulmonary consultation. Determining which patients with prolonged pneumonia and at what point during therapy they should undergo further evaluation can be challenging. This article reviews "normal" resolution times for the most common pneumonias, risk factors for delayed resolution, and infectious and noninfectious conditions that can cause nonresolving pneumonia. An approach to the evaluation of the patient with this common problem is described.

Invasive approaches to the diagnosis of ventilator-associated pneumonia: a meta-analysis

OBJECTIVE

Ventilator-associated pneumonia remains a major challenge in the intensive care unit. The role for invasive diagnostic methods (e.g., bronchoscopy) remains unclear. We hypothesized that invasive testing would alter antibiotic management in patients with ventilator-associated pneumonia but would not necessarily alter mortality.

DESIGN

Meta-analysis of randomized, controlled trials of invasive diagnostic strategies in suspected ventilator-associated pneumonia and a separate pooled analysis of prospective, observational studies of the effect of invasive cultures on antibiotic utilization in ventilator-associated pneumonia.

SETTING

NA.

PATIENTS

Subjects enrolled in the various clinical trials identified.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We identified four randomized, controlled trials that included 628 patients. The overall quality of these studies was moderate (median Jadad score of 5) and there was both clinical and statistical heterogeneity among these trials. Ventilator-associated pneumonia was confirmed bronchoscopically in 44-69% of participants, with Pseudomonas aeruginosa and Staphylococcus aureus being the most frequently isolated pathogens. Most subjects (90.3%) received adequate antibiotics; however, in one trial there was a significant difference between the invasive and noninvasive arms with respect to this factor. Overall, an invasive approach did not alter mortality (odds ratio 0.89, 95% confidence interval 0.56-1.41). Invasive testing, though, affected antibiotic utilization (odds ratio for change in antibiotic management after invasive sampling, 2.85, 95% confidence interval 1.45-5.59). Five prospective observational studies examined invasive testing and included 635 subjects. These reports confirm that invasive sampling leads to modifications in the antibiotic regimen in more than half of patients (pooled estimate for rate of alteration in antibiotic prescription, 50.3%, 95% confidence interval 35.9-64.6%).

CONCLUSIONS

Few trials have systematically examined the impact of diagnostic techniques on outcomes for patients suspected of suffering from ventilator-associated pneumonia. Invasive strategies do not alter mortality. Invasive approaches to ventilator-associated pneumonia affect antibiotic use and prescribing.

Diagnosis of ventilator-associated pneumonia

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

Managing infection in the critical care unit: how can infection control make the ICU safe?

The goal of this article is to use ventilator-associated pneumonia (VAP) as a prototype for nosocomial infections to explore the issues of patient safety and infection control. To do this, we review disease-specific aspects of VAP, develop a brief working definition of patient safety, and then determine how the concepts of infection control fit into the broader context of patient safety.

Healthcare-associated pneumonia in adults: management principles to improve outcomes

Guidelines for Management of HAP were developed jointly by the ATS and IDSA in 2004. These guidelines were designed to improve patient outcomes and to decrease the emergence of MDR pathogens (see Fig. 1).Principles include early initiation of appropriate and adequate antibiotic therapy after cultures of blood and sputum are obtained. Quantitative distal airway sampling by bronchoscopy provides greater diagnostic specificity for VAP: in one randomized study, improved outcomes were noted, compared with clinical diagnosis with qualitative endotracheal aspirates. Higher doses of initial, empiric antibiotics also are recommended. Assessment of the patient's clinical response to empiric antibiotics should be correlated with microbiologic results to streamline, de-escalate, or stop unnecessary anti-biotic treatment. Duration of therapy for uncomplicated HAP should be limited to 7 days followed by close monitoring for relapse after cessation of antibiotics. The authors suggest that prevention strategies target modifiable short- and long-term risk factors. They also advocate the use of a multidisciplinary team that is dedicated to the treatment and prevention of HCAP and the basic principle of the modern Hippocratic Oath: "I will prevent disease whenever I can, for prevention is preferable to cure."

Diagnosis of infection in sepsis: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for the diagnosis of infection in sepsis that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSIONS

Obtaining a precise bacteriological diagnosis before starting antibiotic therapy is, when possible, of paramount importance for the success of therapeutic strategy during sepsis. Two to three blood cultures should be performed, preferably from a peripheral vein, without interval between samples to avoid delaying therapy. A quantitative approach is preferred in most cases when possible, in particular for catheter-related infections and ventilator-associated pneumonia. Diagnosing community-acquired pneumonia is complex, and a diagnostic algorithm is proposed. Appropriate samples are indicated during soft tissue and intraabdominal infections, but cultures obtained through the drains are discouraged.

Ventilator associated pneumonia: comparison between quantitative and qualitative cultures of tracheal aspirates

Introduction

Deferred or inappropriate antibiotic treatment in ventilator-associated pneumonia (VAP) is associated with increased mortality, and clinical and radiological criteria are frequently employed to establish an early diagnosis. Culture results are used to confirm the clinical diagnosis and to adjust or sometimes withdraw antibiotic treatment. Tracheal aspirates have been shown to be useful for these purposes. Nonetheless, little is known about the usefulness of quantitative findings in tracheal secretions for diagnosing VAP.

Methods

To determine the value of quantification of bacterial colonies in tracheal aspirates for diagnosing VAP, we conducted a prospective follow-up study of 106 intensive care unit patients who were under ventilatory support. In total, the findings from 219 sequential weekly evaluations for VAP were examined. Clinical and radiological parameters were recorded and evaluated by three independent experts; a diagnosis of VAP required the agreement of at least two of the three experts. At the same time, cultures of tracheal aspirates were analyzed qualitatively and quantitatively (10⁵ colony-forming units [cfu]/ml and 10⁶ cfu/ml)

Results

Quantitative cultures of tracheal aspirates (10⁵ cfu/ml and 10⁶ cfu/ml) exhibited increased specificity (48% and 78%, respectively) over qualitative cultures (23%), but decreased sensitivity (26% and 65%, respectively) as compared with the qualitative findings (81%). Quantification did not improve the ability to predict a diagnosis of VAP.

Conclusion

Quantitative cultures of tracheal aspirates in selected critically ill patients have decreased sensitivity when compared with qualitative results, and they should not replace the latter to confirm a clinical diagnosis of VAP or to adjust antimicrobial therapy.

[Difficulties on diagnosis of ventilator associated pneumonia]

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

Efficacy of adequate early antibiotic therapy in ventilator-associated pneumonia: influence of disease severity

OBJECTIVE

To test the hypothesis that the outcome of patients with ventilator-associated pneumonia (VAP) depends on both their baseline severity at VAP onset and the adequacy of empirical antibiotic therapy.

DESIGN AND SETTING

Prospective clinical study in six intensive care units in Paris, France.

PATIENTS

One hundred and forty-two patients with VAP after >/= 48 h of mechanical ventilation.

MEASUREMENTS AND RESULTS

Patients were compared according to whether adequate antibiotics were started when VAP was first suspected (D0). At day 0, the rate of adequate antibiotic therapy was 44.4% and rose to 92% at day 2. Outcomes were recorded at the ICU and hospital discharge. Overall, no significant mortality difference was found with and without adequate early antibiotics. When patients were also classified based on the initial Logistic Organ Dysfunction score (LOD), mortality was significantly higher with inadequate early antibiotic therapy in the groups with LOD </= 4 (ICU mortality: 37% vs 7%, P=0.006; hospital mortality: 44% vs 15%, P=0.01). A multivariate logistic regression confirmed that inadequate antibiotic therapy increased mortality in patients with LOD </= 4 after adjustment on other prognostic factors.

CONCLUSIONS

Inadequate empirical treatment seemed to be associated with a poor prognosis only in patients with LOD </= 4. These results need to be confirmed by further studies before any reappraisal of current guidelines for empirical antibiotic therapy of VAP can be envisaged.

Severity of illness and risk of death associated with pulmonary artery catheter use

OBJECTIVE

To examine the association between the use of the pulmonary artery catheter and mortality rate in critically ill patients with a higher vs. a lower severity of illness.

DESIGN

Observational cohort study.

SETTING

A tertiary care university teaching hospital from March 1988 to March 1998.

PATIENTS

A total of 7,310 critically ill adult patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The main outcome measure was hospital mortality rate, controlled by multivariable logistic regression within four patient groups based on severity of illness. Cutoffs for severity of illness were chosen based on Acute Physiology and Chronic Health Evaluation (APACHE) II score 25th percentiles. Logistic regression analysis demonstrated no increased risk of death associated with exposure to the pulmonary artery catheter in the population as a whole. The associated odds ratio of hospital death for the entire cohort was 1.05 (95% confidence interval, 0.92-1.21). Subgroup analysis of severity of illness revealed the highest risk of death to be associated with the lowest APACHE II score quartile vs. a decreased associated mortality rate with the highest APACHE II score quartile after adjustment with multivariable logistic regression (APACHE II <18: odds ratio, 2.47, 95% confidence interval, 1.27-4.81; APACHE II 18-24: odds ratio, 1.64, 95% confidence interval, 1.24-2.17; APACHE II 25-31: odds ratio, 1.00, 95% confidence interval, 0.80-1.24; APACHE II >31: odds ratio, 0.80, 95% confidence interval, 0.64-1.00).

CONCLUSIONS

The use of the pulmonary artery catheter may decrease mortality rate in the most severely ill while increasing it in a population with a lower severity of illness. These findings underscore the necessity of examining the effect of severity of illness in future randomized controlled trials.

Nosocomial pneumonia in the intensive care unit: controversies and dilemmas

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

Treatment failures in patients with ventilator-associated pneumonia

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

Hospital-acquired pneumonia: diagnostic strategies: lessons from clinical trials

It should be emphasized that, for the management of VAP, like for all infectious diseases, the choice of antimicrobial treatment is much easier when the specific etiologic agents are identified by a reliable diagnostic technique. Before new antibiotics are administered, reliable pulmonary specimens (chosen according to the literature and within the capabilities of the local microbiology laboratory) must be obtained for direct examination and cultures from patients clinically suspected of having developed VAP.

Community-acquired and nosocomial pneumonia

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

Concordância entre o aspirado traqueal e o lavado broncoalveolar no diagnóstico das pneumonias associadas à ventilação mecânica

INTRODUÇÃO: Os exames de cultura e o exame bacterioscópico pelo método de coloração de Gram (GRAM) do aspirado traqueal ainda são objeto de controvérsias com relação ao diagnóstico etiológico na pneumonia associada à ventilação mecânica (PAV). OBJETIVO: Avaliar a concordância entre os resultados do GRAM e da cultura quantitativa do aspirado traqueal e do lavado broncoalveolar nos pacientes com PAV. MÉTODO: Foram estudados de modo prospectivo os pacientes internados no período de outubro de 2001 a agosto de 2002, que estavam há mais de 48hs sob ventilação mecânica, e que apresentavam suspeita clínica de PAV. No momento da suspeita clínica foi realizado o aspirado traqueal seguido do lavado broncoalveolar. O diagnóstico de PAV foi confirmado com a suspeita clínica associada à cultura quantitativa do lavado broncoalveolar 10(4)ufc/ml. RESULTADOS: Dos 119 pacientes sob ventilação mecânica, 32 (26,8%) tiveram suspeita clínica de PAV, com confirmação diagnóstica em 25 (78%) deles. A comparação entre o GRAM do aspirado traqueal e a cultura do lavado broncoalveolar mostrou uma moderada concordância (coeficiente de Kappa de 0,56). Houve concordância entre a cultura quantitativa do aspirado traqueal e do lavado broncoalveolar em 22/25 (88%) e discordância em 3/25 (12%) casos (coeficiente de Kappa de 0,71). A sensibilidade e a especificidade do aspirado traqueal para o diagnóstico de PAV com o ponto de corte 10 6 ufc/ml foram de 71% e 72%, respectivamente. CONCLUSÃO: A combinação do GRAM com a cultura quantitativa do aspirado traqueal pode contribuir para a avaliação diagnóstica da PAV.

Quantitative tracheal lavage versus bronchoscopic protected specimen brush for the diagnosis of nosocomial pneumonia in mechanically ventilated patients

BACKGROUND

No gold standard method exists for the diagnosis of ventilator-associated pneumonia despite the availability of multiple techniques.

METHODS

A prospective, crossover study was performed on mechanically ventilated patients meeting with suspected pneumonia. Eighteen paired samples were obtained on 15 patients, comparing the results of quantitative tracheal lavage (QTL) to bronchoscopic protected brush specimen (PSB) by quantitative culture and gram stain examination.

RESULTS

The sensitivity, specificity, positive and negative predictive values, and accuracy are affected by the growth density threshold selected, and whether the same organisms are expected by both methods. There is a significant relationship between QTL and PSB (P = 0.0048; R = 0.632), gram stain and PSB (P <0.001; R = 0.791), and gram stain and QTL (P = 0.0125; R = 0.575), by Spearman rank order correlation.

CONCLUSIONS

QTL may have a role for diagnosing and directing treatment of ventilator-associated pneumonia, allowing reservation of bronchoscopic PSB for secondary, high risk and refractory cases.

Granulocyte-Colony Stimulating Factor (G-CSF) as an adjunct to antibiotics in the treatment of pneumonia in adults

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) is a naturally-occurring cytokine that has been shown to increase neutrophil function and number. Exogenous administration of recombinant G-CSF (filgrastim, pegfilgrastim or lenograstim) has found extensive use in the treatment of febrile neutropaenia, but its role in the treatment of infection in non-neutropaenic hosts is less well defined.

OBJECTIVES

We explored the role of G-CSF as an adjunct to antibiotics in the treatment of pneumonia in non-neutropaenic adults.

SEARCH STRATEGY

We searched the following electronic databases in 2003 and updated the search in 2004: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1, 2004); MEDLINE (January 1966 to March Week 1, 2004); EMBASE (1998 to December 2003); online databases of clinical trials; and reference lists of articles. We also contacted study authors, manufacturers and distributors of G-CSF.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) which included hospitalised adult patients with either community acquired pneumonia or hospital-acquired pneumonia.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. The primary outcome measure was 28 day mortality. Secondary outcome measures included other markers of mortality as well as markers of adverse events, including organ dysfunction. An assessment of methodological quality was made for each study.

MAIN RESULTS

Six studies with a total of 1984 people were identified. G-CSF use appeared to be safe with no increase in the incidence of total serious adverse events (pooled odds ratio (OR) 0.91; 95% confidence interval (CI): 0.73 to 1.14) or organ dysfunction. However, the use of G-CSF was not associated with improved 28 day mortality (pooled OR 0.86; 95% CI: 0.56 to 1.31).

REVIEWERS' CONCLUSIONS

There is no current evidence supporting the routine use of G-CSF in the treatment of pneumonia. Studies in which G-CSF is administered prophylactically or earlier in therapy may be of interest.

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.

Decision analysis of antibiotic and diagnostic strategies in ventilator-associated pneumonia

The optimal strategy for ventilator-associated pneumonia remains controversial. To clarify the tradeoffs involved, we performed a decision analysis. Strategies evaluated included antibiotic therapy with and without diagnostic testing. Tests that were explored included endotracheal aspirates, bronchoscopy with protected brush or bronchoalveolar lavage, and nonbronchoscopic mini-bronchoalveolar lavage (mini-BAL). Outcomes included dollar cost, antibiotic use, survival, cost-effectiveness, antibiotic use per survivor, and the outcome perspective of financial cost-antibiotic use per survivor. Initial coverage with three antibiotics was better than expectant management or one or two antibiotic approaches, leading to both improved survival (54% vs. 66%) and decreased cost (US dollars 55447 vs. US dollars 41483 per survivor). Testing with mini-BAL did not improve survival but did decrease costs (US dollars 41483 vs. US dollars 39967) and antibiotic use (63 vs. 39 antibiotic days per survivor). From the perspective of minimizing cost, minimizing antibiotic use, and maximizing survival, the best strategy was three antibiotics with mini-BAL.

Amoeba-resisting bacteria and ventilator-associated pneumonia

To evaluate the role of amoeba-associated bacteria as agents of ventilator-associated pneumonia (VAP), we tested the water from an intensive care unit (ICU) every week for 6 months for such bacteria isolates; serum samples and bronchoalveolar lavage samples (BAL) were also obtained from 30 ICU patients. BAL samples were examined for amoeba-associated bacteria DNA by suicide-polymerase chain reaction, and serum samples were tested against ICU amoeba-associated bacteria. A total of 310 amoeba-associated bacteria from10 species were isolated. Twelve of 30 serum samples seroconverted to one amoeba-associated bacterium isolated in the ICU, mainly Legionella anisa and Bosea massiliensis, the most common isolates from water (p=0.021). Amoeba-associated bacteria DNA was detected in BAL samples from two patients whose samples later seroconverted. Seroconversion was significantly associated with VAP and systemic inflammatory response syndrome, especially in patients for whom no etiologic agent was found by usual microbiologic investigations. Amoeba-associated bacteria might be a cause of VAP in ICUs, especially when microbiologic investigations are negative.

[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.

The closed tracheal suction catheter: 24 hour or 48 hour change?

Closed suction catheters (CSC) for removal of bronchial secretions in intubated patients have been used in intensive care units (ICU) for many years. Manufacturers still recommend daily changes of the catheter in order to reduce the incidence of ventilator associated pneumonia (VAP). There is, however, a lack of clinical evidence to support this recommendation. The objective of this study was therefore to compare the incidence of VAP in patients who receive either 24 hourly or 48 hourly changes of the CSC. Eligible patients were randomised to one of the two groups to receive either a 24 hourly change (n = 53) or a 48 hourly change (n = 48) of the CSC. Sputum specimens were sent second daily for quantitative culture. Chest x-rays (CXR) and white blood cell counts were attended daily. A VAP was diagnosed according to previously established criteria. A second set of modified criteria were also used to conduct a further analysis of the results. Of the 158 patients randomised, 101 completed the study. These patients had a mean age of 65 years and a mean APACHE II score of 28.2 in the first 24 hours of the study. The average duration in the trial was 10 days. The two groups were comparable in terms of demographic features. There were no reported cases of VAP in either group using the criteria originally selected in the study design. Using a modified criteria to diagnose VAP there were 10 (19%) patients with VAP in the 24 hour group and 13 (27%) in the 48 hour group. The incidence of VAP between the two groups was not statistically different (p = 0.35). To conclude, there was no difference in the incidence of VAP between the two groups studied. Based on previous studies conducted by Quirke and Kollef and the experience of our study we have changed our clinical practice to a 48 hour change of the CSC. We would, however, suggest further study or a meta-analysis of the available literature before a recommendation is made.

Therapy of ventilator-associated pneumonia. A patient-based approach based on the ten rules of "The Tarragona Strategy"

Therapy of ventilator-associated pneumonia should be a patient-based approach focusing on some key features are listed here: early initial therapy should be based on broad-spectrum antibiotics. Empirical treatment may be targeted after direct staining and should be modified according to good-quality quantitative microbiological findings, but should never be withdrawn in presence of negative direct staining or delayed until microbiological results are available. Courses of therapy should be given at high doses according to pharmacodynamic and tissue penetration properties. Prolonging antibiotic treatment does not prevent recurrences. Methicillin-sensitive Staphylococcus aureus should be expected in comatose patients. Methicillin-resistant Staphylococcus aureus should not be expected in patients without previous antibiotic coverage. Pseudomonas aeruginosa should be covered with combination therapy. Antifungal therapy, even when Candida spp is isolated in significant concentrations, is not recommended for intubated nonneutropenic patients. Vancomycin, given at the standard doses and route of administration for the treatment of VAP caused by Gram-positive pathogens, is associated with poor outcomes. The choice of initial antibiotic should be based on the patient's previous antibiotic exposure and comorbidities, and local antibiotic susceptibility patterns, which should be updated regularly.

Outcome of postoperative pneumonia in the Eole study

OBJECTIVES

Prognosis factors of ventilator-associated pneumonia (VAP) have been largely investigated, while the data concerning postoperative pneumonia (POP) are scarce. The aim of this multicenter, prospective study was to evaluate the predictive factors of mortality due to POP and the impact of initial antibiotic therapy on outcome.

METHODS

Two hundred centers were included. Diagnosis of POP was assessed on clinical and laboratory criteria, chest X-ray changes and microbiological criteria, when possible. Outcomes of the patients were noted. An independent committee made a retrospective assessment of appropriateness of antimicrobial therapy.

RESULTS

The overall mortality among the 556 cases of POP was 23% (126 patients). Five parameters were independently associated with mortality: American Society of Anesthesiology (ASA) grade 3 or more ( p<0.001), age 64 years or more ( p<0.01), time to onset of pneumonia more than 3 days ( p<0.01), mottling ( p<0.05) and hypotension ( p<0.05). Among the 322 microbiologically confirmed cases of pneumonia, 92 received inappropriate antibiotic (AB) therapy (29%). No difference in mortality was observed between the patients receiving inappropriate and appropriate AB therapy (22.8 vs 16.9%). In this subgroup, three parameters remained independently associated with mortality: ASA grade 3 or higher ( p<0.001), time to onset of pneumonia more than 3 days ( p<0.05) and hypotension ( p<0.05). Inappropriate initial AB did not modify the model ( p=0.22).

CONCLUSIONS

Five independent predictive factors for mortality of POP were identified. Despite a trend toward decreased mortality with appropriate initial antimicrobial therapy, no difference was observed between the groups. Polymicrobial pneumonia or non-fermenting Gram-negative bacilli appeared to be a risk factor for inappropriate AB.

Nosocomial pneumonia: the importance of a de-escalating strategy for antibiotic treatment of pneumonia in the ICU

Nosocomial pneumonia is the second most frequent nosocomial infection and represents the leading cause of death from infections that are acquired in the hospital. In the last decade, a large body of data has accumulated that points to the substantial impact of inadequate antibiotic treatment as a major risk factor for infection-attributed mortality in ventilator-associated pneumonia (VAP) patients. In most instances, high-risk pathogens (eg, highly resistant Gram-negative bacilli, such as Pseudomonas aeruginosa and Acinetobacter spp, as well as methicillin-resistant staphylococci) are the predominant microorganisms causing excess mortality. Among various risk factors for mortality from VAP, which include the severity of the underlying disease and the degree of functional physiologic impairment caused by the pulmonary infectious process, only inappropriate antibiotic therapy is directly amenable to modification by clinicians. Secondary modifications of an initially failing antibiotic regimen do not substantially improve the outcome for these critically ill patients. Therefore, the best approach for reducing infection-related mortality seems to be the initial institution of an adequate and broad-spectrum antibiotic regimen in severely ill patients, which should be modified in a de-escalating strategy when the results from microbiologic testing become available. To circumvent the inherent danger of the emergence of resistance in ICU patients, additional measures have to be implemented and tested in clinical trials to reduce antibiotic consumption, shorten the duration of antibiotic treatment, and reduce the selection pressure on the ICU flora. This latter goal could be met by new antibiotic strategies including scheduled changes of recommended empiric antibiotic regimens at fixed intervals on a rotating basis.

Quantitative culture of endotracheal aspirates in the diagnosis of ventilator-associated pneumonia in patients with treatment failure

STUDY OBJECTIVE

To study the correlation of bacteriology between quantitative cultures of protected specimen brush (PSB), BAL, and quantitative endotracheal aspirate (QEA) in ventilator-associated pneumonia (VAP) patients with treatment failure.

DESIGN

Prospective observational clinical study.

SETTING

A 15-bed medical ICU of tertiary medical center.

PATIENTS

Forty-eight patients receiving mechanical ventilation with clinical suspected VAP who had been treated with antibiotics for at least 72 h without improvement.

INTERVENTION

QEA, PSB, and BAL were performed with patients receiving antibiotics. The diagnostic thresholds for QEA, PSB, and BAL were 10(5), 10(3), and 10(4) cfu/mL, respectively.

MEASUREMENTS AND RESULTS

Microbial culture findings were positive in 24 BAL samples (50%), in 23 PSB samples (48%), and in 28 QEA samples (58%). The correlations between of QEA vs PSB and QEA vs BAL were significant (rho = 0.567 and rho = 0.620, p < 0.01, respectively). The most commonly isolated microorganisms were Acinetobacter baumannii (27%), Staphylococcus aureus (24%), Stenotrophomonas maltophilia (15%), and Pseudomonas aeruginosa (10%). Using the predetermined criteria, bacterial pneumonia was diagnosed in 28 of 48 suspected VAP episodes based on PSB and/or BAL results. The diagnostic efficiency of QEA at threshold of 10(5) cfu/mL had a sensitivity of 92.8% and a specificity of 80%.

CONCLUSIONS

QEA correlated with PSB and BAL in patients with suspected VAP who responded poorly to the existent antibiotic treatment. QEA missed only two cases of bacterial pneumonia diagnosed by invasive PSB and/or BAL with acceptable sensitivity and specificity. More importantly, QEA is noninvasive and easily repeatable. Early use of QEA is helpful to clinical physicians in decision making with regard to antibiotics use.

Aerobic Gram-negative Bacillary Pneumonia

Gram-negative bacilli (GNB) are a common cause of severe hospital-acquired pneumonia. Due to changes in the health care environment and selective antimicrobial pressure, these bacteria also are becoming a more common cause of pneumonia in venues outside of the traditional hospital setting and are increasingly resistant to antimicrobial agents. Risk factors for acquisition of GNB allow the clinician to efficiently identify patients who are likely to have pneumonia due to these pathogens. Available diagnostic techniques have a limited capacity to accurately detect GNB pulmonary infection. Yet, a pathogen specific diagnosis and knowledge of local resistance patterns are quintessential elements in formulating an effective treatment plan. This article reviews the epidemiologic characteristics, pathogenesis, and current management issues of GNB pneumonia.

Nosocomial and ventilator-associated pneumonias: developing country perspective

Nosocomial pneumonias are recognized as an important cause of morbidity and mortality in industrialized nations. Emerging data show that they play a similar role in the developing world. A host of extrinsic and intrinsic factors predispose individuals to the development of pneumonias, and a modification of some of these factors provides a low cost solution to prevention of pneumonias. The ideal modality for microbiologic diagnosis of pneumonia remains to be determined. Recent data suggest that there is no difference in outcome when noninvasive techniques are compared with invasive techniques. Antimicrobial resistance is a rapidly increasing problem globally, and combating this with appropriate antibiotic policies, close surveillance, and physician education is essential.

The pulmonary physician in critical care * 4: Nosocomial pneumonia

Much progress has been made in the understanding of nosocomial pneumonia but important issues in diagnosis and treatment remain unresolved. The controversy over diagnostic tools should be closed. Instead, every effort should be made to increase our ability to make valid clinical predictions about the presence of ventilator associated pneumonia and to establish criteria to guide restricting empirical antimicrobial treatment without causing patient harm. More emphasis must be put on local infection control measures such as routine surveillance of pathogens, definition of controlled policies of antimicrobial treatment, and effective implementation of strategies of prevention.

Ventilator-associated pneumonia

Ventilator-associated pneumonia is the most serious infectious complication in critically ill patients, associated with increased length of intensive care unit treatment and high mortality rates. Investigations focused on outcome variables have improved the database to estimate diagnostic and therapeutic management strategies. This knowledge has diminished the importance of the discussion on how to diagnose the pneumonia. This review summarizes recent data on epidemiology and mortality, risk factors and prevention, diagnosis, microbiology and antimicrobial treatment of ventilator-associated pneumonia.

[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.