Ventilator-associated pneumonia: what is new?

Improvements in pulmonary and general critical care reduces mortality following ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is the most common hospital-acquired infection in the intensive care unit, with substantial subsequent mortality. The mortality following VAP declined in the 1980s and 1990s. Experts suggest that little progress has been made in the outcomes from VAP since several novel interventions have failed. We nonetheless hypothesized that mortality following VAP has continued to decrease owing to advances in pulmonary critical care.

METHODS

We identified all adult patients with Centers for Disease Control and Prevention-defined, intensive care unit-acquired VAP between January 1, 1997, and December 31, 2008, from a prospectively collected database.

RESULTS

A total of 793 cases of VAP occurred in the study period. Cases were divided into four periods (1997-1999, 2000-2002, 2003-2005, or 2006-2008) to compare outcomes over time. Acute Physiology and Chronic Health Evaluation II scores were stable, while mortality was significantly lower in Period 4 when compared with Periods 1 and 2 (p = 0.004 and 0.009, respectively). A logistic regression model predicting death (c statistic = 0.871) revealed age (odds ratio, 1.03; 95% confidence interval, 1.02-1.05), Acute Physiology and Chronic Health Evaluation II score (1.09, 1.05-1.14), white blood cell count (1.03, 1.00-1.06), transplant recipient (3.45, 1.40-8.53), transfusions (3.25, 1.37-7.68), and pulmonary disease (3.01, 1.67-5.45) were independent predictors of death, as was the presence of trauma (0.10, 0.06-0.18), chronic steroid therapy (0.39, 0.17-0.91), and patient length of stay (0.99, 0.98-0.99), with odds ratios less than 1.0. In addition, those patients treated in Period 1 (2.23, 1.16-4.29) or Period 2 (2.13, 1.12-4.06) had twice the risk of death following an episode of VAP when compared with those treated in the most recent period.

CONCLUSION

We have shown that mortality following an episode of VAP continues to decrease over time and attribute this to advancements in pulmonary and general critical care rather than any specific interventions.

LEVEL OF EVIDENCE

Prognostic study, level II.

The pathogen of ventilator-associated pneumonia does not influence the mortality rate of surgical intensive care unit patients treated with a rotational antibiotic system

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the leading causes of morbidity in critically ill surgical patients. Certain pathogens (e.g., methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa) have been associated with an excess mortality rate from sepsis in several studies, but not in the surgical setting specifically or when protocol-driven antibiotic therapy is administered.

PURPOSE

We sought to determine which factors and, in particular, whether the individual pathogen affected the mortality rate in our surgical intensive care unit (ICU), where a rotational antibiotic system has been employed continuously since 1997. We hypothesized that the type of pathogen and illness severity were the primary influences on the mortality rate of patients with VAP.

METHODS

A total of 198 consecutive patients from a university surgical ICU, with clinical signs of VAP confirmed by quantified isolation of significant numbers of a pathogen (> or =10(4) colony-forming units [cfu]/mL) from bronchoalveolar (BAL) fluid obtained by fiberoptic bronchoscopy, were identified prospectively from January 2001 to November 2004. The data collected were age, sex, Acute Physiology and Chronic Health Evaluation (APACHE) III score, multiple organ dysfunction score, unit day of diagnosis, time (h) to antibiotic administration (TTA), appropriateness of initial therapy (AIT), unit and hospital length of stay, and mortality rate. Pathogens were classified as non-lactose-fermenting gram-negative bacilli (NGNB), lactose-fermenting gram-negative bacilli (LGNB), methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus, yeast, community-acquired pneumonia (e.g., Streptococcus pneumoniae), or other pathogens. Patients with a polymicrobial isolate were placed in the "other" category.

RESULTS

The overall mortality rate was 32.3% vs. 55% as predicted by APACHE III normative data. The overall AIT was 92%. The mortality rate for NGNB infections was 35.6% vs. 29.4% for LGNB infections (p = NS). By logistic regression, neither TTA, AIT, nor pathogen influenced the mortality rate.

CONCLUSIONS

The type of pathogen does not influence death in surgical ICU patients with VAP diagnosed rigorously and treated by a rotational antibiotic system. The high proportion of AIT as a result of the rotational antibiotic administration system optimizes bacterial killing and negates the impact of bacterial resistance, contributing to better outcomes.

Management of antibiotic resistance in the intensive care unit setting

Over the past few decades, an alarming increase of infections caused by antibiotic-resistant pathogens, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus species, carbapenem-resistant Pseudomonas aeruginosa, extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp., and multidrug-resistant Acinetobacter spp., has been observed, particularly in intensive care units. For clinicians, the rising resistance rate observed in nosocomial pathogens, when coupled with the lack of effective antimicrobials, represents the real challenge in the therapeutic management of critically ill patients. The contribution of clinicians in minimizing the increasing trend of resistance is represented by reduction of the patients' exposure to antibiotics, which reduces the resistance-selecting pressure, and by avoiding unnecessary antibiotic treatments. Recent issues on strategies to minimize resistance development and to appropriately manage critically ill patients with infections caused by multidrug-resistant organisms in the intensive care unit setting are discussed in this article.

Decrease of CD4-lymphocytes and apoptosis of CD14-monocytes are characteristic alterations in sepsis caused by ventilator-associated pneumonia: results from an observational study

Introduction

The present study aimed to investigate changes of the immune response between sepsis due to ventilator-associated pneumonia (VAP) and sepsis due to other types of infections.

Methods

Peripheral venous blood was sampled from 68 patients with sepsis within 24 hours of diagnosis; 36 suffered from VAP; 32 from other nosocomial infections, all well-matched for severity, age and sex. Blood monocytes were isolated and cultured with/without purified endotoxin (lipopolysaccharide (LPS)). Estimation of tumour necrosis factor alpha (TNFα) and interleukin-6 (IL-6) in cultures' supernatants was done by an enzyme immunoassay. Flow cytometry was used to determine subpopulations of mononuclear cells and apoptosis. To mimic pathogenesis of VAP, mononuclear cells of healthy volunteers were progressively stimulated with increased inocula of pathogens; apoptosis was determined.

Results

In patients with VAP, the absolute number of CD3(+)/CD4(+) lymphocytes was significantly lower (P = 0.034) and apoptosis of isolated monocytes was increased (P = 0.007) compared to other infections. TNFα and IL-6 production from LPS-stimulated monocytes was lower in patients with VAP-related sepsis than with sepsis due to other infections. Apoptosis of monocytes was induced after in vitro stimulation of mononuclear cells by a mechanism mimicking VAP.

Conclusions

Decrease of CD4-lymphocytes and immunoparalysis of monocytes are characteristic alterations of sepsis arising in the field of VAP.