Pneumonia and Respiratory Infections: 2012 Review
(More PulmCCM Topic Updates)
This review document on pneumonia and respiratory infections is updated periodically as new research findings are published. The listed date reflects its most recent update. Please suggest important articles for inclusion in future updates, either in the comments section below or by email.
The Distal Lung Is Not Sterile (As Was Supposed)
Charlson et al carefully protected bronchoscopes from contamination during insertion, and performed bronchoalveolar lavage on healthy volunteers. Contrary to the previous belief that the distal lung is sterile, in fact it contained the same spectrum of bacteria as the upper respiratory tract, but at less than 1% of the quantitative counts (2-4 log difference). Nosocomial pathogens were even isolated from some healthy volunteers’ distal lungs. Future studies will further characterize this normal lung microbiome and its potential contribution to pneumonia pathogenesis. [Charlson AJRCCM 2011]
Community-Acquired Pneumonia Update
The Evidence for CAP Guidelines and Performance Measures is Weak
Wilson and Schunemann examined the literature forming the basis for community-acquired pneumonia performance measures and clinical practice guidelines. Overall, the evidence supporting the Joint Commission’s 6 core performance measures was poor. Only influenza vaccination and using guideline-compliant antibiotics for community acquired pneumonia were supported by moderate or better-strength evidence. The other Joint Commission core measures, including antibiotics within 6 hours, smoking cessation counseling, and pneumococcal vaccination, had little evidence to justify their use as measures of hospital or physician performance. [Wilson, AJRCCM 2011]
Failed Intervention Randomized Trials in CAP
Randomized controlled trials testing tissue factor pathway inhibitor (CAPTIVATE) and another testing recombinant surfactant protein C aerosols in patients with community acquired pneumonia were negative. PROWESS-SHOCK, testing activated protein C and including many patients with community acquired pneumonia, was also negative.
Corticosteroids in ARDS from H1N1 Viral Pneumonia
Two large multicenter observational trials, while not conclusive and vulnerable to confounding by severity of illness, were concordant in the finding that providing corticosteroids to patients with ARDS from pneumonia due to H1N1 influenza was associated with harms. [Brun-Buisson AJRCCM 2011; Kim AJRCCM 2011]
Inhaled Steroids for COPD Raise Risk of Pneumonia — But Reduce Its Severity?
Several observational studies have suggested that the use of inhaled corticosteroids for chronic obstructive pulmonary disease (COPD) increases the risk for community acquired pneumonia. Chen et al analyzed Veterans Administration databases and found among patients with COPD admitted to VA hospitals with community acquired pneumonia, use of inhaled steroids was associated with a lower risk of mortality and need for mechanical ventilation. This promotes the dual hypothesis that inhaled steroids may increase the risk for pneumonia, yet reduce its severity when it does occur. This would also be congruent with the observations from the TORCH trial (NEJM), in which COPD patients randomized to inhaled steroid/LABA had an increased risk for pneumonia, but still had an almost-significant reduction in mortality compared to placebo users. [Chen AJRCCM 2011]
Hospital-Acquired Pneumonia and Ventilator-Acquired Pneumonia (VAP) Update
New Devices May Reduce Risk for VAP
A device to continuously maintain endotracheal tube cuff pressure above 25 cm H2O reduced VAP rates significantly (to 10%) in a randomized trial [NseirAJRCCM 2011]. In a multicenter randomized trial and a meta-analysis, intermittent subglottic suction of secretions with a special endotracheal tube likewise reduced late-onset VAP (to 19%) [Muscedere Crit Care Med 2011]. These and other technological advances in endotracheal tubes that may reduce the risk of VAP were reviewed by Fernandez et al in Chest 2012.
VAP’s Attributable Mortality Is Only 1%?
Because the risk of ventilator-associated pneumonia increases with severity of illness, the true mortality attributable to VAP is unknown and subject to constant dispute. A large multicenter French study concluded that VAP was nearly harmless in and of itself, with only a 1% excess mortality contributed by the ventilator-associated pneumonia itself.
These authors included 4,479 ventilated patients and used a novel methodology to (they claimed) better control for severity of illness and the evolution of VAP and critical illness through time, as compared to previous flawed studies. In that paper, the mortality of patients with VAP was 24%, while that of those matched patients without VAP was 23%. [Bekaert AJRCCM 2011]
As with all other studies past, present, and future in this Bermuda Triangle of medical research, conclusions and extrapolations must be limited by epidemiologic factors (there were very few cases of MRSA pneumonia, for example) and those inherent to VAP research (no gold standard for diagnosis).
Induced Hypothermia After Out-of-Hospital Cardiac Arrest: New Risk Factor for VAP?
In a French multicenter study, 65% of patients with out-of-hospital cardiac arrest developed VAP. They had increased lengths of stay but no increase in mortality; therapeutic hypothermia was the only independent risk factor. [Perbet AJRCCM 2011]
Aerosolized Antibiotics Only For VAP?
In a 40-patient randomized pilot study, giving aerosolized ceftazidime and amikacin only (nothing IV) was equally efficacious as intravenous ceftazidime/amikacin at eradicating Pseudomonas from the lung in patients with VAP; however, 3 of the aerosol group had recurrent infection (vs. 1) and one had a cardiac arrest from the equipment occluding the airway. [Lu AJRCCM 2011]
Guideline-Compliant Antibiotics for VAP Can Be Harmful?
A controversial study observed that patients receiving ATS/IDSA guideline-compliant antibiotics for HAP, HCAP, or VAP had increased mortality compared to patients receiving guideline-noncompliant antibiotics. This was nonrandomized, observational, and did not control for timing of therapy or include deescalation of antibiotics in its definition of guideline-compliance. [Kett Lancet ID 2011]
Other recent studies suggested that guideline-compliant antibiotics might be harmful, and/or that patients meeting definitional criteria for HAP/HCAP/VAP per IDSA/ATS guidelines can be successfully treated with guideline-noncompliant antibiotic regimens, such as community-acquired pneumonia antibiotic regimens. [Grenier J Antimicrob Chemother 2011; Chalmers Clin Infect Dis 2011; Attritdge ERJ 2011]
With gratitude to: Wunderlink RG, Niederman MS. Update in Respiratory Infections 2011. AJRCCM 2012;185:1261-1265.