Canadian Critical Care Trials Group. A randomized trial of diagnostic techniques for ventilator-associated pneumonia

The Fourth National Institutes of Health Symposium on the Functional Genomics of Critical Injury: Surviving stress from organ systems to molecules

Recent strides in computational biology and high-throughput technologies have generated considerable interest in understanding complex biological systems. The application of these technologies to critical illness and injury offers the potential to define adaptive and maladaptive programs of gene expression induced by infection, shock, trauma, or other inflammatory triggers, and to detect biomarkers and genetic polymorphisms linked to these responses and outcome. A systems biology approach is timely because despite substantial effort, treatment approaches directed at a single mediator or inflammatory pathway have met with little success in altering outcomes of critically ill or injured patients. Highlights from the Fourth National Institute of Health Functional Genomics of Critical Illness and Injury Symposium are described herein, in addition to deliverables for the field identified during panel discussions. Next steps for the community and suggestions for future research are presented.

Blood product transfusion and ventilator-associated pneumonia in trauma patients

BACKGROUND

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in trauma patients, with a high mortality rate. Blood transfusion has been identified as an independent risk factor for VAP in critically ill patients. Prior studies in trauma are limited by retrospective design, lack of multivariable analyses, and scant data on the timing of transfusion. We examined critically the relation between blood product transfusion and VAP in trauma patients.

METHODS

Prospective observational cohort study of 766 trauma patients admitted to the intensive care unit (ICU), who received mechanical ventilation (MV) for >or= 48 h, and who did not have pneumonia on admission. Late-onset VAP was defined as that occurring >or= 72 h after MV. Only transfusions of red blood cell (RBC) concentrate, fresh-frozen plasma (FFP), or platelets before the onset of VAP were considered. Logistic regression analyses controlled for all variables related significantly to VAP by univariate analysis (sex, Injury Severity Score, and ventilator days and ICU length of stay prior to VAP).

RESULTS

A significantly greater proportion of male patients developed VAP. Patients with VAP had a longer duration of MV: The mean number ventilator days prior to VAP was 11.1 +/- 8.0. Transfusion of blood products was an independent risk factor for VAP, and the risk increased with more units transfused. All blood products were associated with a higher risk of VAP (RBC: odds ratio [OR] 4.41; 95% confidence interval [CI] 1.00, 19.54; p = 0.05; FFP: OR 3.34; 95% CI 1.18, 9.43; p = 0.023; platelets: OR 4.19; 95% CI 1.37, 12.83; p = 0.012).

CONCLUSION

Blood product transfusion is an independent risk factor for VAP in trauma, and the odds ratio is significantly higher (3.34-4.41) than in published studies of other types of ICU patients (1.89). To reduce the incidence of VAP, all efforts to reduce the transfusion of blood products to trauma patients should be implemented.

Various randomized designs can be used to evaluate medical tests

OBJECTIVE

To explore designs for evaluating the prognostic and predictive value of medical tests and their effect on patient outcome.

STUDY DESIGN

Theoretical analysis with examples from the medical literature.

RESULTS

For evaluating the prognostic value of a test, one can include the test at baseline in prognostic studies. To evaluate the value of test in predicting treatment outcome, the test results can be used as baseline information in randomized controlled trials of treatment. To compare the prognostic or predictive value of two or more tests, the test result combinations can be used as baseline information. To evaluate the effect on patient outcome, randomized controlled trials of test strategies are an option. Randomization can apply to all tested or be restricted to specific subgroups, such as those with discordant test results, to increase the efficiency of trials.

CONCLUSION

The prognostic and predictive value of medical tests can and should be evaluated, to demonstrate the test's ability to guide clinical decision making and to improve patient outcome. Various randomized designs can be used to evaluate the effects on testing on patient outcome.

Quantitative versus qualitative cultures of respiratory secretions for clinical outcomes in patients with ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is a common infectious disease in intensive care units (ICUs). The best diagnostic approach to resolve this condition remains uncertain.

OBJECTIVES

To evaluate whether quantitative cultures of respiratory secretions are effective in reducing mortality in immunocompetent patients with VAP, compared with qualitative cultures. We also considered changes in antibiotic use, length of ICU stay and mechanical ventilation.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, issue 4), which contains the Acute Respiratory Infections Group's Specialized Register; MEDLINE (1966 to December 2007); EMBASE (1974 to December 2007); and LILACS (1982 to December 2007).

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing respiratory samples processed quantitatively or qualitatively, obtained by invasive or non-invasive methods from immunocompetent patients with VAP, and which analyzed the impact of these methods on antibiotic use and mortality rates.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed and selected trials from the search results, and assessed studies for suitability, methodology and quality. We analyzed data using Review Manager software. We pooled the included studies to yield the risk ratio (RR) for mortality and antibiotic change with 95% confidence intervals (CI).

MAIN RESULTS

Of the 3931 references identified from the electronic databases, five RCTs (1367 patients) met the inclusion criteria. Three studies compared invasive methods using quantitative cultures versus non-invasive methods using qualitative cultures, and were used to answer the main objective of this review. The other two studies compared invasive versus non-invasive methods, both using quantitative cultures. All five studies were combined to compare invasive versus non-invasive interventions for diagnosing VAP. The studies that compared quantitative and qualitative cultures (1240 patients) showed no statistically significant differences in mortality rates (RR = 0.91, 95% CI 0.75 to 1.11). The analysis of all five RCTs showed there was no evidence of mortality reduction in the invasive group versus the non-invasive group (RR = 0.93, 95% CI 0.78 to 1.11). There were no significant differences between the interventions with respect to the number of days on mechanical ventilation, length of ICU stay or antibiotic change.

AUTHORS' CONCLUSIONS

There is no evidence that the use of quantitative cultures of respiratory secretions results in reduced mortality, reduced time in ICU and on mechanical ventilation, or higher rates of antibiotic change when compared to qualitative cultures in patients with VAP. Similar results were observed when invasive strategies were compared with non-invasive strategies.

[Study protocol of the VISEP study. Response of the SepNet study group]

In the commentary by Zander et al. the authors appear concerned about the methods and results of our, at that time, unpublished sepsis trial evaluating hydroxyethyl starch (HES) and insulin therapy. Unfortunately, the authors' concerns are based on false assumptions about the design, conduct and modes of action of the compounds under investigation. For instance, in our study the HES solution was not used for maintenance of daily fluid requirements, so that the assumption of the authors that this colloid was used "exclusively" is wrong. Moreover, the manufacturer of Hemohes, the HES product we used, gives no cut-off value for creatinine, thus the assumption that this cut-off value was "doubled" in our study is also incorrect. Other claims by the authors such as that lactated solutions cause elevated lactate levels, iatrogenic hyperglycemia and increase O(2) consumption are unfounded. There is no randomized controlled trial supporting such a claim - this claim is neither consistent with our study data nor with any credible published sepsis guidelines or with routine practice worldwide. We fully support open scientific debate. Our study methods and results have now been published after a strict peer-reviewing process and this data is now open to critical and constructive reviewing. However, in our opinion this premature action based on wrong assumptions and containing comments by representatives of pharmaceutical companies does not contribute to a serious, unbiased scientific discourse.

Subthreshold quantitative bronchoalveolar lavage: clinical and therapeutic implications

BACKGROUND

Quantitative bronchoalveolar lavage (qBAL) is used for accurate diagnosis of ventilator-associated pneumonia (VAP). The current study aims at defining the incidence, outcomes and therapeutic implications of false-negative (FN) qBAL.

METHODS

Ventilated trauma, surgery, and burn, patients suspected of VAP underwent bronchoscopic qBAL. VAP was defined as qBAL with >10(5) CFU/mL (threshold). To identify FN BALs, blood cultures drawn concomitant with BAL (+/-5 days of BAL) were analyzed. qBAL specimens growing <10(5) CFU/mL (subthreshold) with blood culture identifying the same organism, without any other source, were classified as FN.

RESULTS

Over 39 months, 246 patients underwent 365 qBALs. Ninety-one specimens had no growth and 274 specimens grew 433 organisms--100 at threshold and 333 at subthreshold strength. Sixteen percent of threshold and 11% of subthreshold organisms were associated with bacteremia. Rates of bacteremia were similar across strengths of growth. Bacteremia at all strengths of growth was more common with Staphylococcal species (methicillin sensitive and resistant) and for hospital-acquired gram-negatives. Rates of bacteremia at all strengths of growth were significantly higher after the first week of hospitalization. Bacteremia worsened outcomes in both threshold group (higher mortality, p < 0.05) and subthreshold group (longer lengths of stay, p < 0.05).

CONCLUSIONS

qBAL has 11% FN rate as measured by blood stream invasion. Propensity of blood stream invasion is related to species of organism (Staphylococcal species and hospital-acquired gram-negatives) and duration of hospitalization, but not to strength of growth. Isolation of these organisms in BAL, at any strength, after the first week should prompt strong consideration for antimicrobial therapy.

Increased mortality of ventilated patients with endotracheal Pseudomonas aeruginosa without clinical signs of infection

OBJECTIVE

To investigate the frequency and outcomes of ventilated patients with newly acquired large burdens of Pseudomonas aeruginosa and to test the hypothesis that large quantities of bacteria are associated with adverse patient outcomes.

DESIGN

A prospective, single-center, observational, cohort study.

SETTING

Medical-surgical intensive care units in a tertiary care university hospital.

PATIENTS

All adult patients requiring > or = 48 hrs of mechanical ventilation and identified as having newly acquired P. aeruginosa in their lower respiratory tracts between October 2002 and April 2006.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Daily surveillance cultures of endotracheal aspirates were performed on patients intubated > or = 48 hrs; 69 patients with newly acquired P. aeruginosa were enrolled. Daily P. aeruginosa quantification of endotracheal aspirates was performed; clinical signs of infection were noted. Of 45 patients with high P. aeruginosa burdens (> or = 1,000,000 colony-forming units/mL in endotracheal aspirates; > or = 10,000 colony-forming units/mL in bronchoalveolar-lavage), 17 (37.8%) patients did not meet clinical criteria for ventilator-associated pneumonia and had a statistically significant higher risk of death (adjusted hazard ratio, 37.53; 95% confidence interval, 3.79-371.96; p = 0.002) when compared with the patients who had P. aeruginosa ventilator-associated pneumonia. When excluding the ten patients who had ventilator-associated pneumonia attributed to bacteria other than P. aeruginosa or attributed to multiple bacteria including P. aeruginosa, the risk of death remained statistically significant (adjusted hazard ratio, 23.98; 95% confidence interval: 2.49-230.53; p = 0.006). Furthermore, more patients with high P. aeruginosa burdens secreted the type III secretion facilitator protein, PcrV (p = 0.01).

CONCLUSIONS

A group of patients with large burdens of P. aeruginosa who did not meet clinical criteria for ventilator-associated pneumonia had an increased risk of death when compared with patients who had high P. aeruginosa burdens and met ventilator-associated pneumonia criteria. Patients with high P. aeruginosa burden seemed to possess more virulent strains.

Evidence-based algorithms for diagnosing and treating ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is widely recognized as a serious and common complication associated with high morbidity and high costs. Given the complexity of caring for heterogeneous populations in the intensive care unit (ICU), however, there is still uncertainty regarding how to diagnose and manage VAP.

OBJECTIVE

We recently conducted a national collaborative aimed at reducing health care-associated infections in ICUs of hospitals operated by the Hospital Corporation of America (HCA). As part of this collaborative, we developed algorithms for diagnosing and treating VAP in mechanically ventilated patients. In the current article, we (1) review the current evidence for diagnosing VAP, (2) describe our approach for developing these algorithms, and (3) illustrate the utility of the diagnostic algorithms using clinical teaching cases.

DESIGN

This was a descriptive study, using data from a national collaborative focused on reducing VAP and catheter-related bloodstream infections.

SETTING

The setting of the study was 110 ICUs at 61 HCA hospitals.

INTERVENTION

None.

MEASUREMENTS AND RESULTS

We assembled an interdisciplinary team that included infectious disease specialists, intensivists, hospitalists, statisticians, critical care nurses, and pharmacists. After reviewing published studies and the Centers for Disease Control and Prevention VAP guidelines, the team iteratively discussed the evidence, achieved consensus, and ultimately developed these practical algorithms. The diagnostic algorithms address infant, pediatric, immunocompromised, and adult ICU patients.

CONCLUSIONS

We present practical algorithms for diagnosing and managing VAP in mechanically ventilated patients. These algorithms may provide evidence-based real-time guidance to clinicians seeking a standardized approach to diagnosing and managing this challenging problem.

Previous cultures are not clinically useful for guiding empiric antibiotics in suspected ventilator-associated pneumonia: secondary analysis from a randomized trial

PURPOSE

To examine the predictive validity of prior cultures at predicting the microorganism isolated at the time of suspicion of ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

We performed a retrospective analysis of a randomized controlled trial of different diagnostic and antibiotic strategies. In a subset of patients with pre-enrollment cultures, we examined agreement between cultures 1 to 3 days before suspicion of VAP and enrollment cultures performed on the day of suspicion of VAP and potential antibiotic error rates (estimated using the equation 1 - crude agreement).

RESULTS

Two hundred eighty-one (39%) of 739 patients had pre-enrollment culture. One hundred thirty (46%) of 281 yielded a pathogenic microorganism. In patients with positive pre-enrollment cultures, crude agreement was 0.63 (95% confidence interval, 0.55-0.71) for organism, 0.84 (0.77-0.89) for Gram class, and 0.61 (0.52-0.69) for species with sensitivity. Potential antibiotic error rates ranged from 16% (11%-33%) to 39% (31%-48%). Better agreement (P = .033) occurred in isolates from patients receiving new antibiotics during the surveillance period (0.78 [0.64-0.87]) compared to those not on antibiotics (0.58 [0.45-0.69]), or on no new antibiotics (0.50 [0.32-0.68]).

CONCLUSIONS

There is poor agreement between prior cultures and cultures performed at time of suspicion of VAP. Prior cultures should not be used to narrow the spectrum of empiric antibiotics.

Comprehensive evidence-based clinical practice guidelines for ventilator-associated pneumonia: diagnosis and treatment

BACKGROUND

Ventilator-associated pneumonia (VAP) is an important cause of morbidity and mortality in ventilated critically ill patients. Despite a large amount of research evidence, the optimal diagnostic and treatment strategies for VAP remain controversial.

PURPOSE

The aim of this study was to develop evidence-based clinical practice guidelines for the diagnosis and treatment of VAP. Data sources include Medline, EMBASE, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Database of Systematic Reviews and Register of Controlled Trials.

STUDY SELECTION

The authors systematically searched for all relevant randomized controlled trials and systematic reviews on the diagnosis and treatment of VAP in mechanically ventilated adults that were published from 1980 to October 1, 2006.

DATA EXTRACTION

Independently and in duplicate, the panel critically appraised each published trial. The effect size, confidence intervals, and homogeneity of the results were scored using predefined definitions. The full guideline development panel arrived at a consensus for scores on safety, feasibility, and economic issues.

LEVELS OF EVIDENCE

Based on the scores for each topic, the following statements of recommendation were used: recommend, consider, do not recommend, and no recommendation because of insufficient or conflicting evidence.

DATA SYNTHESIS

For the diagnosis of VAP in immunocompetent patients, we recommend that endotracheal aspirates with nonquantitative cultures be used as the initial diagnostic strategy. When there is a suspicion of VAP, we recommend empiric antimicrobial therapy (in contrast to delayed or culture directed therapy) and appropriate single agent antimicrobial therapy for each potential pathogen as empiric therapy for VAP. Choice of antibiotics should be based on patient factors and local resistance patterns. We recommend that an antibiotic discontinuation strategy be used in patients who are treated of suspected VAP. For patients who receive adequate initial antibiotic therapy, we recommend 8 days of antibiotic therapy. We do not recommend nebulized endotracheal tobramycin or intratracheal instillation of tobramycin for the treatment of VAP.

CONCLUSION

We present evidence-based recommendations for the diagnosis and treatment of VAP. Implementation of these recommendations into clinical practice may lessen the morbidity and mortality of patients who develop VAP.

Utility of Gram stain in the clinical management of suspected ventilator-associated pneumonia. Secondary analysis of a multicenter randomized trial

PURPOSE

Gram stains of endotracheal aspirates (EA) and bronchoalveolar lavages (BAL) may guide empiric antibiotic therapy in critically ill patients with suspected ventilator-associated pneumonia (VAP). Previous studies differ regarding the ability of the Gram stain to predict final culture results. The aim of the present study was to evaluate the relationship between EA or BAL Gram stains and final culture results in intensive care unit patients with a suspected VAP.

MATERIAL AND METHODS

We retrospectively analyzed data from the Canadian multicenter VAP study to correlate EA or BAL Gram stain and final culture results. We categorized Gram stains as Gram positive (GP) and Gram negative (GN) if any GP or GN organisms respectively were seen on staining. Cultures were considered "positive" if they yielded pathogenic organisms on final results.

RESULTS

Seven hundred forty patients were enrolled in the study; 35 did not have a Gram stain done leaving 350 BALs and 355 EAs from 705 patients. Pooling BAL and EA results, we found the overall agreement between Gram stain class and pathogenic bacteria culture results to be poor (kappa = 0.36; 95% CI, 0.31-0.40). Among specimens with Gram stains showing no organisms, 99 (30%) of 331 grew pathogenic organisms. Among specimens with Gram stains showing no GN organisms, 113 (25%) of 452 grew pathogenic GN organisms. Among specimens with Gram stains showing no GP organisms, 45 (11%) of 428 grew pathogenic GP organisms.

CONCLUSIONS

Gram stains performed for clinically suspected VAP poorly predict the final culture result and thus have a limited role in guiding initial empiric antibiotic therapy in such patients.

Determinants of outcome in patients with a clinical suspicion of ventilator-associated pneumonia

INTRODUCTION

In the absence of a reference standard, a probabilistic approach to the diagnosis of ventilator-associated pneumonia (VAP) has been proposed; and clinician judgment augmented by microbiological tests is used to guide therapy for patients having a clinical suspicion of VAP (CSVAP). However, the correlation of both clinician judgment at the time of CSVAP and the probability of VAP with clinical outcomes is unknown. In a cohort of patients with CSVAP, we sought to determine the correlation of clinician judgment and the probability of VAP with clinical outcomes. In addition, we studied the impact of the clinical and microbiological components of CSVAP on the processes of care and outcomes.

METHODS

We performed a retrospective analysis of data from a multicenter, randomized trial in 740 patients with CSVAP. Prospective clinician judgment of VAP probability at the time of CSVAP and retrospective adjudication of VAP were compared with clinical outcomes. The following determinants of CSVAP on outcomes were studied: time of CSVAP, index culture results, and the presence of bacteremia.

RESULTS

Neither clinician index of suspicion for VAP nor retrospective adjudication of VAP correlated with clinical outcomes. For CSVAP, occurrence >7 days after start of mechanical ventilation and negative index cultures were associated with worse outcomes. Bacteremia was associated with the development of increased organ dysfunction.

CONCLUSION

In patients with CSVAP, clinician judgment as to the probability of VAP does not correlate with processes of care and outcomes; and its use to group patients into those with and without VAP is of limited clinical utility.

The value of pretest probability and modified clinical pulmonary infection score to diagnose ventilator-associated pneumonia

PURPOSE

The aim of the study was to assess the utility of pretest probability and modified clinical pulmonary infection score CPIS in the diagnosis of late-onset ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

In 740 adults enrolled in a multicenter randomized trial, intensivists prospectively rated the pretest probability of VAP as low, moderate, or high based on their clinical judgment. The modified CPIS was calculated without considering culture results. Ventilator-associated pneumonia diagnosis was determined by 2 adjudicators using standardized definitions. We analyzed the relationship between pretest likelihood, CPIS, and VAP diagnosis.

RESULTS

Among the 739 patients analyzed, 14.5%, 39.6%, and 45.9% had low, moderate, and high pretest probability of VAP. Patients with high pretest probability had a lower PaO2/FiO2 ratio and a larger volume of secretions. High or moderate vs low pretest probability had high sensitivity (0.88; 95% confidence interval [CI], 0.87-0.89) and positive predictive value (0.87; 95% CI, 0.86-0.88) but low specificity (0.27; 95% CI, 0.21-0.35) and negative predictive value (0.29; 95% C,: 0.22-0.37) for the diagnosis of VAP. Therefore, 71% of patients who had a low pretest probability were actually infected (1 - negative predictive value). The area under the receiver operating characteristic curve for the modified CPIS was not significant (0.47; 95% CI, 0.42-0.53), meaning that no score threshold was clinically useful.

CONCLUSIONS

Pretest probability and a modified CPIS, which excludes culture results, are of limited utility in the diagnosis of late-onset VAP.

Ventilator-associated pneumonia caused by multidrug-resistant organisms or Pseudomonas aeruginosa: prevalence, incidence, risk factors, and outcomes

PURPOSE

The aim of this study was to clarify the prevalence and incidence of, risk factors for, and outcomes from suspected ventilator-associated pneumonia (VAP) associated with the isolation of either Pseudomonas or multidrug-resistant (MDR) bacteria ("high risk" pathogens) from respiratory secretions.

MATERIALS AND METHODS

Data were collected as part of a large, multicentered trial of diagnostic and therapeutic strategies for patients (n = 739) with suspected VAP.

RESULTS

At enrollment, 6.4% of patients had Pseudomonas species, and 5.1% of patients had at least 1 MDR organism isolated from respiratory secretions. Over the study period, the incidence of Pseudomonas and MDR organisms was 13.4% and 9.2%, respectively. Independent risk factors for the presence of these pathogens at enrollment were duration of hospital stay >or=48 hours before intensive care unit (ICU) admission (odds ratio, 2.37 [95% CI, 1.40-4.02]; P = .001] and prolonged duration of ICU stay before enrollment (odds ratio, 1.50 [95% CI, 1.17-1.93]; P = .002] per week. Fewer patients whose specimens grew either Pseudomonas or MDR organisms received appropriate empirical antibiotic therapy compared to those without these pathogens (68.5% vs 93.9%, P < .001). The isolation of high risk pathogens from respiratory secretions was associated with higher 28-day (relative risk, 1.59 [95% CI, 1.07-2.37]; P = .04] and hospital mortality (relative risk, 1.48 [95% CI, 1.05-2.07]; P = .05), and longer median duration of mechanical ventilation (12.6 vs 8.7 days, P = .05), ICU length of stay (16.2 vs 12.0 days, P = .05), and hospital length of stay (55.0 vs 41.8 days, P = .05).

CONCLUSIONS

In this patient population, the incidence of high-risk organisms newly acquired during an ICU stay is low. However, the presence of high risk pathogens is associated with worse clinical outcomes.

The safety of targeted antibiotic therapy for ventilator-associated pneumonia: a multicenter observational study

PURPOSE

The aim of this study was to determine the safety of targeted antibiotic therapy (TT) in ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

This was a secondary analysis from a multicenter trial of 740 patients with suspected VAP randomized to bronchoscopy or endotracheal aspirate cultures; all received empirical broad-spectrum antibiotics. Patients were grouped by whether they received TT, defined as tailoring or discontinuing antibiotics in response to enrolment culture results.

RESULTS

For patients with a positive culture (n = 412), baseline demographics, clinical progression of infection and multiple organ dysfunction scores (MODS), and mortality were similar for those on TT (n = 320) or those who did not receive TT (NoTT) (n = 92). The TT group had more days alive and off broad-spectrum antibiotics (14.5 vs 13.2, P = .04). In patients with a negative culture (n = 327), those on TT (n = 230) had similar baseline demographics, less frequent final adjudicated diagnosis of VAP (63.0% vs 76.3%, P = .02), and less severe clinical progression of infection and MODS compared with NoTT (n = 97). The TT group had more days alive and off broad-spectrum antibiotics (15.9 vs 13.1, P < .001), lower delta MODS (2.0 vs 3.0, P = .01), fewer mechanical ventilation days (9.8 vs 14.7, P = .03), and similar mortality compared to NoTT.

CONCLUSIONS

Targeted therapy is associated with less antibiotic use and no evidence of harm in the management of patients with VAP.

Correlates of clinical failure in ventilator-associated pneumonia: insights from a large, randomized trial

PURPOSE

Our objective was to determine clinical variables measured at baseline and day 3 that may relate to failure of resolution of ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

In patients with confirmed VAP derived from a large, randomized controlled trial comparing different modalities for the diagnosis and treatment of VAP, we identified risk factors associated with clinical failure. Clinical failure was prospectively defined in this trial as death, persistence of clinical and radiographic features of infection throughout the study period requiring additional antibiotics, superinfection, or relapsing infection. We examined the relationship between VAP resolution and clinical characteristics measured both at study enrollment and at day 3. We used logistic regression to identify independent factors associated with clinical failure and conducted a sensitivity analysis focusing only on patients who met the definition for clinical failure but who nonetheless survived until day 28.

RESULTS

Of 563 subjects with VAP, 179 (31.8%) were classified as clinical failures. Death was the most common reason for clinical failure. At baseline, clinical failure patients were older, more severely ill, had been on mechanical ventilation for a longer period, and had higher Clinical Pulmonary Infection Score values and lower Pao2/Fio2 ratios. By day 3, patients defined as clinical failures remained more severely ill and continued to have worse oxygenation. In multivariate analysis, 4 factors were independently associated with clinical failure: older age, duration of ventilation before enrollment, presence of neurologic disease at admission, and failure of the Pao2/Fio2 ratio to improve by day 3. Repeating this multivariable model in only surviving patients suggested that persistence of fever was the only variable associated with clinical failure.

CONCLUSIONS

Clinical characteristics correlate with eventual outcomes in VAP. Failure of the Pao2/Fio2 ratio and fever to improve are independently associated with clinical failure. We suggest that clinicians follow these measures and consider integrating them in their decisions as to when to reevaluate persons with VAP who are not improving.

Diagnosis of ventilator-associated pneumonia: is there a gold standard and a simple approach?

PURPOSE OF REVIEW

Diagnosis of ventilator-associated pneumonia remains controversial. Different approaches are advocated, but none has yet demonstrated superiority. Diagnosis based on clinical data and aetiological diagnosis of ventilator-associated pneumonia episodes are two concepts that should be combined in an integrative evaluation for ventilator-associated pneumonia. Recent findings in diagnosis are reviewed here.

RECENT FINDINGS

Studies of various diagnostic strategies have been conducted to evaluate whether they influence outcome. Strategies include use of biomarkers (e.g. C-reactive protein and procalcitonin) and use of clinical scores to render the diagnostic process more objective. The appropriateness of the available aetiological diagnostic techniques and their reliability in the absence of a 'gold standard' for diagnosis were also recently addressed. It remains controversial whether type of culture (quantitative or nonquantitative) or sampling method (invasive or noninvasive) influences aetiological diagnosis or outcomes in ventilator-associated pneumonia. It is unlikely that any single approach is the optimal diagnostic assessment whenever ventilator-associated pneumonia is suspected.

SUMMARY

Microbiological data should always be used in association with clinical data when assessing patients with suspected ventilator-associated pneumonia. Integration of these data might be the most simple and effective strategy for diagnosing ventilator-associated pneumonia.

Pneumonia caused by methicillin-resistant Staphylococcus aureus

A recent increase in staphylococcal infections caused by methicillin-resistant Staphylococcus aureus (MRSA), combined with frequent, prolonged ventilatory support of an aging, often chronically ill population, has resulted in a large increase in cases of MRSA pneumonia in the health care setting. In addition, community-acquired MRSA pneumonia has become more prevalent. This type of pneumonia historically affects younger patients, follows infection with influenza virus, and is often severe, requiring hospitalization and causing the death of a significant proportion of those affected. Ultimately, hospital-acquired MRSA and community-acquired MRSA are important causes of pneumonia and present diagnostic and therapeutic challenges. Rapid institution of appropriate antibiotic therapy, including linezolid as an alternative to vancomycin, is crucial. Respiratory infection-control measures and de-escalation of initial broad-spectrum antibiotic regimens to avoid emergence of resistant organisms are also important. This article reviews the clinical features of, diagnosis of, and therapies for MRSA pneumonia.

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

OBJECTIVE

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

PARTICIPANTS

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

EVIDENCE

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

CONSENSUS PROCESS

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

CONCLUSIONS

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

Diagnosis of ventilator-associated pneumonia: a systematic review of the literature

INTRODUCTION

Early, accurate diagnosis is fundamental in the management of patients with ventilator-associated pneumonia (VAP). The aim of this qualitative review was to compare various criteria of diagnosing VAP in the intensive care unit (ICU) with a special emphasis on the value of clinical diagnosis, microbiological culture techniques, and biomarkers of host response.

METHODS

A MEDLINE search was performed using the keyword 'ventilator associated pneumonia' AND 'diagnosis'. Our search was limited to human studies published between January 1966 and June 2007. Only studies of at least 25 adult patients were included. Predefined variables were collected, including year of publication, study design (prospective/retrospective), number of patients included, and disease group.

RESULTS

Of 572 articles fulfilling the initial search criteria, 159 articles were chosen for detailed review of the full text. A total of 64 articles fulfilled the inclusion criteria and were included in our review. Clinical criteria, used in combination, may be helpful in diagnosing VAP, however, the considerable inter-observer variability and the moderate performance should be taken in account. Bacteriologic data do not increase the accuracy of diagnosis as compared to clinical diagnosis. Quantitative cultures obtained by different methods seem to be rather equivalent in diagnosing VAP. Blood cultures are relatively insensitive to diagnose pneumonia. The rapid availability of cytological data, including inflammatory cells and Gram stains, may be useful in initial therapeutic decisions in patients with suspected VAP. C-reactive protein, procalcitonin, and soluble triggering receptor expressed on myeloid cells are promising biomarkers in diagnosing VAP.

CONCLUSION

An integrated approach should be followed in diagnosing and treating patients with VAP, including early antibiotic therapy and subsequent rectification according to clinical response and results of bacteriologic cultures.

Usefulness of procalcitonin for the diagnosis of ventilator-associated pneumonia

OBJECTIVE

To assess the predictive capacity for the diagnosis of ventilator-associated pneumonia (VAP) of serum procalcitonin levels before and on the day it is suspected.

DESIGN AND SETTING

Single-center observational study in the intensive care unit of a teaching hospital.

PATIENTS AND PARTICIPANTS

Consecutive patients whose serum procalcitonin levels were available on the day that VAP was clinically suspected (day 1) and at some time within the preceding 5 days ("before").

MEASUREMENTS AND RESULTS

Serum procalcitonin levels were determined on day 1 and "before". Among the 73 suspected episodes VAP was confirmed by quantitative bronchoalveolar lavage cultures in 32 and refuted in 41. Respective median "before" procalcitonin levels were 1.89 ng/ml (interquartile range 0.18-6.01) and 2.14 (0.76-5.75) in patients with and without VAP, but their respective median day-1 procalcitonin levels did not differ: 1.07 ng/ml (0.39-6.57) vs. 1.40 (0.67-3.39). On day 1 a 0.5 ng/ml procalcitonin threshold had 72% sensitivity but only 24% specificity for diagnosing VAP. Between "before" and day 1, procalcitonin increased in 41% and 15% of patients with and without VAP, respectively. Thus a procalcitonin rise on day 1, compared to its "before" level, had 41% sensitivity and 85% specificity for diagnosing VAP, with respective positive and negative predictive values of 68% and 65%.

CONCLUSIONS

Crude values and procalcitonin rise had poor diagnostic value for VAP in this particular setting and thus should not be used to initiate antibiotics when VAP is clinically suspected.

Healthcare-associated pneumonia: principles and emerging concepts on management

Healthcare-associated pneumonia (HCAP) is a relatively new entity that includes pneumonia occurring in healthcare settings other than acute-care hospitals. Many patients with HCAP are at greater risk for colonization and infection with multi-drug resistant (MDR) bacteria such as Pseudomonas aeruginosa, Gram-negative bacilli-producing extended-spectrum beta-lactamases and methicillin-resistant Staphylococcus aureus. Infections with these MDR pathogens require different empiric antibiotic therapy. To avoid initiation of inappropriate antibiotic therapy that may result in poorer patient outcomes, new principles for HCAP management were outlined in the 2005 American Thoracic Society and Infectious Diseases Society of America guidelines. These guidelines were suggested for patients assessed in acute-care hospitals and clinics, and may not be applicable for all patients with suspected HCAP in nursing homes and other long-term care settings. This review article addresses HCAP management strategies in both clinical settings.

The simple and the simpler in pneumonia diagnosis

In the absence of a perfect 'gold standard' for diagnosing pneumonia, comparing diagnostic performance between techniques remains controversial. El Solh and coworkers present a study evaluating use of quantitative endotracheal aspirate culture to enhance diagnostic accuracy in pneumonia patients admitted from nursing homes. We discuss the use of quantitative cultures and thresholds to differentiate between colonization and infection in pneumonia patients; we also consider the inaccuracy of diagnostic studies, which compromises the reproducibility of these data in clinical practice.

Is bronchoalveolar lavage with quantitative cultures a useful tool for diagnosing ventilator-associated pneumonia?

The results of a recently published Canadian study suggest that bronchoalveolar lavage and endotracheal aspiration are associated with similar clinical outcomes and similar overall use of antibiotics in critically ill patients with suspected ventilator-associated pneumonia (VAP). The study, however, does not provide convincing information on the best strategy to diagnose VAP, to accurately choose initial treatment and to exclude VAP in order to avoid administering antibiotics to patients without bacterial infection. In fact, this trial has several limitations or drawbacks: patients at risk for developing VAP due to Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus were excluded, far from the real-life scenario; a significant number of patients were receiving recent antimicrobial therapy at the time of sampling, with, consequently, difficult-to-interpret culture results; randomization of included patients for initial treatment – meropenem plus ciprofloxacin or meropenem alone – resulted in a high rate of inappropriate initial empirical therapy due to the absence of customization to local epidemiology; and the initial decision to treat and the re-evaluation at day 3 were, in fact, based on clinical judgment and not on direct examination and quantitative culture results. In summary, because antimicrobial treatment was initiated in all suspected patients and was rarely withheld in patients with negative cultures, the study does not suggest an appropriate strategy for improving the use of antibiotics in intensive care unit patients. Such a strategy has two requirements: immediate administration of adequate therapy in patients with true VAP, and avoidance of administering antibiotics in patients without bacterial infection.

Neumopatías hospitalarias en pacientes con ventilación mecánica

Las neumopatías son la primera causa de infección hospitalaria en reanimación. Las neumopatías hospitalarias en los pacientes con ventilación mecánica (NHPVM) ocurren después de al menos 48 horas de ventilación mecánica invasiva. Su mecanismo es multifactorial, pero la opinión predominante es que obedecen a una inhalación posterior a la colonización orofaríngea, gástrica o traqueal. El retraso en la manifestación permite clasificar las NHPVM en precoces o tardías según se desarrollen antes o después del 5.° día de ventilación mecánica. La clínica puede ayudar al diagnóstico, sobre todo mediante la CPIS (Clinical Pulmonary Infection Score) y también es útil el lavado broncoalveolar (LBA), que parece la mejor prueba para el diagnóstico microbiológico. El diagnóstico diferencial se plantea con una neumopatía no bacteriana o incluso no infecciosa (neoplásica, inflamatoria, fibrosante) en la que siempre debe plantearse la búsqueda de otro foco infeccioso en función de la orientación clínica inicial o del fracaso de la antibioticoterapia. El uso preferente de la ventilación no invasiva, cuando es posible, parece que ayuda a prevenir el desarrollo de la neumopatía hospitalaria. La posición inclinada 30-45° del paciente es la única medida preventiva verdaderamente validada en las NHPVM. El tratamiento curativo de las neumopatías bacterianas descansa por lo general en un tratamiento antibiótico doble, que puede orientarse por los datos de muestras obtenidas con métodos no invasivos como las aspiraciones traqueales efectuadas de forma periódica y sistemática. La duración del tratamiento es discutible, pero los últimos datos apoyan un tratamiento con antibióticos relativamente corto, de 8 días.

Polmoniti nosocomiali acquisite sotto ventilazione meccanica

Le polmoniti sono la prima causa di infezione nosocomiale in rianimazione. Le polmoniti nosocomiali acquisite sotto ventilazione meccanica (PNAVM) compaiono dopo almeno 48 ore di ventilazione meccanica invasiva. Il loro meccanismo è multifattoriale, ma predomina la nozione di inalazione che compare dopo una colonizzazione orofaringea, gastrica o tracheale. Il tempo di comparsa permette di classificare queste PNAVM come precoci o tardive a seconda che compaiano prima o dopo il 5° giorno di ventilazione meccanica. La diagnosi può essere aiutata dalla clinica, essenzialmente grazie al punteggio CPIS (Clinical Pulmonary Infection Score), e dal lavaggio broncoalveolare (BAL), che sembra l’esame più utile per la diagnosi microbiologica. La diagnosi differenziale con una pneumopatia non batterica o anche non infettiva (neoplastica, infiammatoria, fibrotica) o la ricerca di un altro focolaio infettivo devono sempre essere discusse in funzione dell’orientamento clinico iniziale o del fallimento della terapia antibiotica. Il ricorso preferenziale alla ventilazione non invasiva, quando possibile, sembra utile per prevenire l’insorgenza di una pneumopatia nosocomiale. La posizione semiseduta del paziente a 30–45° è la sola misura profilattica veramente validata di prevenzione delle PNAVM. Il trattamento curativo delle polmoniti batteriche si basa in genere su una doppia terapia antibiotica. Quest’ultima può essere orientata dai dati di prelievi non invasivi, come le aspirazioni tracheali, realizzate in modo periodico e sistematico. La durata del trattamento è discussa, ma gli ultimi dati sono in favore di una terapia antibiotica relativamente breve, di 8 giorni.

Influence of an Endotracheal Tube with Polyurethane Cuff and Subglottic Secretion Drainage on Pneumonia

RATIONALE

Subglottic secretion drainage (SSD) appears to be effective in preventing ventilator-associated pneumonia (VAP), primarily by reducing early-onset pneumonia; but it may not prevent late-onset pneumonia. We tested the hypothesis using an endotracheal tube incorporating an ultrathin polyurethane cuff (which reduces channel formation and fluid leakage from the subglottic area), in addition to an SSD lumen, which would reduce the incidence of late-onset VAP.

OBJECTIVES

To compare the incidence of VAP, using an endotracheal tube with polyurethane cuff and subglottic secretion drainage (ETT-PUC-SSD) versus a conventional endotracheal tube (ETT-C) with polyvinyl cuff, without subglottic secretion drainage.

METHODS

Clinical randomized trial in a 24-bed medical-surgical intensive care unit. Patients expected to require mechanical ventilation for more than 24 hours were randomly assigned to one of two groups: one was ventilated with ETT-PUC-SSD and the other with ETT-C.

MEASUREMENTS AND MAIN RESULTS

Tracheal aspirate samples were obtained during endotracheal intubation, then twice per week and finally on extubation. VAP was found in 31 of 140 (22.1%) patients in the ETT-C group and in 11 of 140 (7.9%) in the ETT-PUC-SSD group (P = 0.001). Cox regression analysis showed ETT-C as a risk factor for global VAP (hazard ratio [HR], 3.3; 95% confidence interval [CI], 1.66-6.67; P = 0.001), early-onset VAP (HR, 3.3; 95% CI, 1.19-9.09; P = 0.02), and late-onset VAP (HR, 3.5; 95% CI, 1.34-9.01; P = 0.01).

CONCLUSIONS

The use of an endotracheal tube with polyurethane cuff and subglottic secretion drainage helps prevent early- and late-onset VAP. Clinical trial registered with www.clinicaltrials.gov (NCT 00475579).

Health technology assessment in critical care

BACKGROUND

Heath technology assessments (HTAs) evaluate the benefits and costs of devices for monitoring and therapy (and their associated requirements for human resources) which contribute to the high expense associated with ICU admission.

DISCUSSION

Given the limited resources available for health care and increasing demands, funds spent inefficiently or unnecessarily on technologies in the ICU may threaten the sustainability of the health care system or prevent other potentially cost-effective devices from being introduced into clinical care. We discuss the factors impeding the conducting of HTAs in the ICU and suggest strategies for change.

CONCLUSIONS

Despite the need for HTAs of ICU devices only few have been conducted. They should be undertaken more frequently, and their results used to influence clinical practice and hospital and regional-level policy decisions.

Impact of a protocol for prevention of ventilator-associated pneumonia

BACKGROUND

Several interventions have been shown to be effective in reducing the incidence of ventilator-associated pneumonia (VAP), but their implementation in clinical practice has not gained widespread acceptance.

OBJECTIVE

To determine the impact of a protocol that incorporates evidence-based interventions shown to reduce the frequency of VAP on the overall rate of VAP, early-onset VAP, and late-onset VAP in the intensive care unit (ICU) of a tertiary care adult teaching hospital.

METHODS

This pre- and postintervention observational study included mechanically ventilated patients admitted to the Montreal General Hospital ICU between November 2003 and May 2004 (preintervention) and between November 2004 and May 2005 (postintervention). A multidisciplinary prevention protocol was developed, implemented, and reinforced. Rates of VAP per 1000 ventilator-days were calculated pre- and postprotocol implementation for all patients, for patients with early-onset VAP, and for those with late-onset VAP.

RESULTS

In the pre- and postintervention groups, 349 and 360 patients, respectively, were mechanically ventilated. Twenty-three VAP episodes occurred in 925 ventilator-days (crude incidence rate 25 per 1000) in the preintervention period. Following implementation, the VAP rate decreased to 22 episodes in 988 ventilator-days (crude incidence rate 22.3 per 1000), corresponding to a relative reduction in rate of 10.8% (p < 0.001). The incidence of early-onset VAP decreased from 31.0 to 18.5 VAP per 1000 ventilator-days (p < 0.001), while the incidence of late-onset VAP increased from 21.9 to 24.1 VAP per 1000 ventilator-days (p < 0.001). However, when all covariates were adjusted, the impact of the prevention protocol was not statistically significant.

CONCLUSIONS

Implementation of a VAP prevention protocol incorporating evidence-based interventions reduced the crude incidence of VAP, early-onset VAP, and late-onset VAP. However, when covariates were adjusted, the beneficial effect was no longer observed. Further research is needed to assess the impact of such measures on VAP, early-onset VAP, and late-onset VAP.