VAT vs VAP: are we heading toward clarity or confusion?

Epidemiology of ventilator-associated tracheobronchitis and ventilator-associated pneumonia caused by multidrug-resistant Gram-negative bacteria at a tertiary care hospital in Thailand

Objectives

To investigate the epidemiology of MDR Gram-negative bacilli ventilator-associated tracheobronchitis (MDR GNB-VAT) and MDR GNB ventilator-associated pneumonia (MDR GNB-VAP) among mechanically ventilated patients.

Methods

We conducted a retrospective observational study among hospitalized patients who underwent continuous mechanical ventilation for ≥48 h at Siriraj Hospital, Thailand.

Results

During the 18 month study period, 1824 unique patients underwent continuous mechanical ventilation (12 216 ventilator-days). The cumulative incidences of MDR GNB-VAT and -VAP were 8.4% and 8.3%, respectively. The incidence rates of MDR GNB-VAT and -VAP were 12.52 and 12.44 episodes/1000 ventilator-days, respectively. Among those with VAT, the cumulative incidence and incidence rate of subsequent VAP development within 7 days were 11.76% and 2.81 episodes/1000 ventilator-days, respectively. The median durations of mechanical ventilation before having VAP and VAT were 9 and 12 days, respectively. Multivariate analysis identified three independently associated factors for patients having VAP compared with having VAT: underlying cerebrovascular disease [adjusted OR (aOR): 0.46; 95% CI: 0.27-0.78; P = 0.04], previous surgery (aOR: 0.68; 95% CI: 0.57-0.8; P < 0.001) and acute renal failure (aOR: 1.75; 95% CI: 1.27-2.40; P = 0.001).

Conclusions

The study revealed high incidences of MDR GNB-VAT and -VAP among mechanically ventilated patients. The independent risk factors for having VAP can help identify patients at risk for developing VAP and who need early weaning from mechanical ventilation.

Antibiotic therapy in ventilator-associated tracheobronchitis: a literature review

The concept of ventilator-associated tracheobronchitis is controversial; its definition is not unanimously accepted and often overlaps with ventilator-associated pneumonia. Ventilator-associated tracheobronchitis has an incidence similar to that of ventilator-associated pneumonia, with a high prevalence of isolated multiresistant agents, resulting in an increase in the time of mechanical ventilation and hospitalization but without an impact on mortality. The performance of quantitative cultures may allow better diagnostic definition of tracheobronchitis associated with mechanical ventilation, possibly avoiding the overdiagnosis of this condition. One of the major difficulties in differentiating between ventilator-associated tracheobronchitis and ventilator-associated pneumonia is the exclusion of a pulmonary infiltrate by chest radiography; thoracic computed tomography, thoracic ultrasonography, or invasive specimen collection may also be required. The institution of systemic antibiotic therapy does not improve the clinical impact of ventilator-associated tracheobronchitis, particularly in reducing time of mechanical ventilation, hospitalization or mortality, despite the possible reduced progression to ventilator-associated pneumonia. However, there are doubts regarding the methodology used. Thus, considering the high prevalence of tracheobronchitis associated with mechanical ventilation, routine treatment of this condition would result in high antibiotic usage without clear benefits. However, we suggest the institution of antibiotic therapy in patients with tracheobronchitis associated with mechanical ventilation and septic shock and/or worsening of oxygenation, and other auxiliary diagnostic tests should be simultaneously performed to exclude ventilator-associated pneumonia. This review provides a better understanding of the differentiation between tracheobronchitis associated with mechanical ventilation and pneumonia associated with mechanical ventilation, which can significantly decrease the use of antibiotics in critically ventilated patients.

Diagnosis and Treatment of Ventilator-Associated Infection: Review of the Critical Illness Stress-Induced Immune Suppression Prevention Trial Data

OBJECTIVES

The Critical Illness Stress-Induced Immune Suppression prevention trial was a randomized, masked trial of zinc, selenium, glutamine, and metoclopramide compared with whey protein in delaying nosocomial infection in PICU patients. One fourth of study subjects were diagnosed with nosocomial lower respiratory infection, which contributed to subjects receiving antibiotics 74% of all patient days in the PICU. We analyzed diagnostic and treatment variability among the participating institutions and compared outcomes between nosocomial lower respiratory infection subjects (n = 74) and intubated subjects without nosocomial infection (n = 1 55).

DESIGN

Post hoc analysis.

SETTING

Eight hospitals in the Collaborative Pediatric Critical Care Research Network.

PATIENTS

Critical Illness Stress-Induced Immune Suppression study subjects.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Variability across institutions existed in the frequency and manner by which respiratory secretion cultures were obtained, processed, and results reported. Most results were reported semiquantitatively, and both Gram stains and antibiotic sensitivities were frequently omitted. The nosocomial lower respiratory infection diagnosis was associated with increased PICU lengths of stay compared with those who were intubated without nosocomial infection (24 ± 19 vs 9 ± 6 d; p < 0.001) and antibiotic use (38 ± 29 vs 15 ± 20 antibiotics days; p < 0.001). Despite antibiotic treatment, the same bacteria persisted in 45% of follow-up cultures.

CONCLUSIONS

The Critical Illness Stress-Induced Immune Suppression data demonstrate that the nosocomial lower respiratory infection diagnosis is associated with longer lengths of stay and increased antibiotic use, but there is considerable diagnostic and treatment variability across institutions. More rigorous standards for when and how respiratory cultures are obtained, processed, and reported are necessary. Bacterial persistence also complicates the interpretation of follow-up cultures.

Incidence and outcomes of ventilator-associated tracheobronchitis and pneumonia

BACKGROUND

Prolonged intubation with mechanical ventilation carries a risk for ventilator-associated respiratory infections manifest as tracheobronchitis or pneumonia. This study analyzed natural history, incidence, and outcomes of patients developing ventilator-associated tracheobronchitis and pneumonia.

METHODS

We studied 188 mixed intensive care unit (ICU) patients intubated ≥48 hours for the development of tracheobronchitis defined as quantitative endotracheal aspirate ≥10(5) cfu/mL plus at least 2 clinical criteria (fever, leukocytosis, or purulent sputum). Pneumonia was defined as microbiologic criteria for tracheobronchitis and a new and persistent infiltrate on chest radiograph.

RESULTS

Airways of 41 (22%) patients became heavily colonized with a bacterial pathogen(s) at a concentration of ≥10(5) cfu/mL. Tracheobronchitis developed in 21 (11%) study patients, of which 6 (29%) later progressed to pneumonia. Including these 6 patients, 28 (15%) study patients developed pneumonia. Multidrug-resistant pathogens were isolated in 39% of pneumonia patients. Patients with tracheobronchitis and pneumonia had significantly more ventilator days and longer stays in the ICU (P ≤.02).

CONCLUSIONS

Approximately one third of tracheobronchitis patients later developed pneumonia. Patients with tracheobronchitis or pneumonia experienced significantly more ventilator days and longer ICU stays, but had no difference in mortality. Better patient outcomes and reduced health care costs may be achieved by earlier treatment of ventilator-associated respiratory infections, manifest as tracheobronchitis or pneumonia.

The diagnostic dilemma of ventilator-associated pneumonia in critically ill children

OBJECTIVE

A review of the existing literature on ventilator-associated pneumonia in children with emphasis on problems in diagnosis.

DATA SOURCES

A systematic literature review from 1947 to 2010 using Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Science using key words "ventilator associated pneumonia" and "children." Where pediatric data were lacking, appropriate adult studies were reviewed and similarly referenced.

STUDY SELECTION

Two hundred sixty-two pediatric articles were reviewed and data from 48 studies selected. Data from 61 adult articles were also included in this review.

DATA EXTRACTION AND SYNTHESIS

Ventilator-associated pneumonia is the second most common nosocomial infection and the most common reason for antibiotic use in the pediatric intensive care unit. Attributable mortality is uncertain but ventilator-associated pneumonia is associated with significant morbidity and cost. Diagnosis is problematic in that clinical, radiologic, and microbiologic criteria lack sensitivity and specificity relative to autopsy histopathology and culture. Qualitative tracheal aspirate cultures are commonly used in diagnosis but lack specificity. Quantitative tracheal aspirate cultures have sensitivity (31-69%) and specificity (55-100%) comparable to bronchoalveolar lavage (11-90% and 43-100%, respectively) but concordance for the same bacterial species when compared with autopsy lung culture was better for bronchoalveolar lavage (52-90% vs. 50-76% for quantitative tracheal aspirate). Staphylococcus aureus and Pseudomonas species are the most common organisms, but microbiologic flora change over time and with antibiotic use. Initial antibiotics should offer broad-spectrum coverage but should be narrowed as clinical response and cultures dictate.

CONCLUSIONS

Ventilator-associated pneumonia is an important nosocomial infection in the pediatric intensive care unit. Conclusions regarding epidemiology, treatment, and outcomes are greatly hampered by the inadequacies of current diagnostic methods. We recommend a more rigorous approach to diagnosis by using the Centers for Disease Control and Prevention algorithm. Given that ventilator-associated pneumonia is the most common reason for antibiotic use in the pediatric intensive care unit, more systematic studies are sorely needed.

Diagnosis, management and prevention of ventilator-associated pneumonia: an update

Ventilator-associated pneumonia (VAP) affects 10-20% of mechanically ventilated patients and is associated with increased morbidity and mortality and high costs. Early diagnosis is crucial for rapid appropriate antimicrobial therapy to be instituted, but debate remains as to the optimal diagnostic strategy. Noninvasive clinical-based diagnosis is rapid but may not be as accurate as invasive techniques. Increased use of biomarkers and advances in genomics and proteomics may help speed up diagnosis. Management of VAP relies principally on appropriate antimicrobial therapy, which should be selected according to individual patient factors, such as previous antibacterial therapy and length of hospitalization or mechanical ventilation, and local infection and resistance patterns. In addition, once bacterial culture and sensitivity results are available, broad-spectrum therapy should be de-escalated to provide a more specific, narrower-spectrum cover. Optimum duration of antibacterial therapy is difficult to define and should be tailored to clinical response. Biomarker levels may be useful to monitor response to therapy. With the high morbidity and mortality, prevention of VAP is important and several strategies have been shown to reduce the rates of VAP in mechanically ventilated patients, including using noninvasive ventilation where possible, and semi-recumbent positioning. Other potentially beneficial preventive techniques include subglottal suctioning, oral decontamination strategies and antimicrobial-coated endotracheal tubes, although further study is needed to confirm the cost effectiveness of these strategies.