Are We Following the New Guidelines for Ventilator-Associated Pneumonia?
Abstract & Commentary
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Diagnostic methods and initial antibiotic regimens used in patients with ventilator-associated pneumonia vary a great deal, and few patients have therapy de-escalated as recommended in current practice guidelines.
Source: Kollef MH, et al. Clinical characteristics and treatment patterns among patients with ventilator-associated pneumonia. Chest. 2006;129:1210-1218. Erratum in: Chest. 2006;130:308.
In this prospective observational study, Kollef and associates enrolled patients with ventilator-associated pneumonia (VAP) in 20 ICUs across the United States in order to characterize the patients and the antimicrobial regimens used in treating them, as well as their mortality and lengths of stay. They describe the management and outcomes of this cohort of VAP patients in the context of the recently published American Thoracic Society/Infectious Disease Society of America guidelines.1
To be eligible for inclusion in the study, patients had to be older than 18 years of age, hospitalized > 48 h, mechanically ventilated, and able to meet the criteria for diagnosing VAP published by the American College of Chest Physicians.2 The latter allowed either a clinical diagnosis based on fever, leukocytosis, and/or sputum purulence, plus culture of an endotracheally suctioned sputum specimen, or an invasive diagnosis based on quantitative culture of bronchoalveolar lavage (BAL) specimens. The investigators recorded the initial antibiotic regimen used to treat the VAP, and any subsequent changes as culture results became available.
During the 20-month study period, the authors enrolled 398 patients who met their criteria for VAP. These patients comprised a broad spectrum of medical, cardiac, and surgical ICU patients, although none were trauma patients, and only 11 (2.8%) were admitted for COPD exacerbations. Mean (±SD) duration of mechanical ventilation prior to VAP diagnosis was 7.3 (6.9) days. The culture specimens were tracheal aspirates in 60% of cases and BAL fluid in 36%, with 4% having no microbiologic specimens collected. Most commonly identified organisms were methicillin-resistant Staphylococcus aureus (15%) and Pseudomonas aeruginosa (14%); no major organism was identified in 37% of the patients.
More than 100 initial antibiotic regimens were used to treat VAP in the 398 patients, including a single drug (in 28%) and combinations of 2 (46%) and 3 (23%) agents. Duration of therapy ranged from 0 to 51 days (mean, 12 6 days). Sixty two percent of patients experienced no escalation (that is, an upgrading of antimicrobial spectrum through a switch or addition of antibiotics) or de-escalation (a spectrum downgrading or reduction in antibiotics) during the course of therapy. De-escalation of therapy occurred in only 22% of patients.
One hundred of the 398 patients (25%) died. The mortality rate was lower among patients in whom de-escalation of therapy was done (17%), as compared to patients in whom no change was made (24%) or therapy was escalated (43%; P = 0.001).
Commentary
The diagnosis and management of VAP remain two of the most controversial topics in critical care. Whether an invasive (BAL, with quantitative culture) or noninvasive (tracheal suctioning, with qualitative culture) technique should be used to collect specimens has not been resolved, although the best available evidence is that some sort of cultures should be obtained before starting antibiotics, with the number and type of agents used being influenced by the individual hospital's current organism prevalence and "antibiogram," and therapy modified promptly according to the culture results.3 This study suggests that clinicians may not be doing a very good job of the latter, and that there is great variation in the choice of initial empiric antimicrobial therapy.
There are several features of this study that affect the generalizability of its results. For example, the 20 participating ICUs enrolled only about 400 patients with VAP over a 20-month period—an average of 1 per month per center—and in fact 173 of the patients (43%) were from just 2 participating ICUs. This means that many more cases of VAP must have occurred in the other 18 ICUs during the study period, and we do not know why they were not enrolled.
The higher mortality among patients whose antibiotic regimen was escalated or remained the same, as compared with that in the patients in whom de-escalation occurred, may in part reflect differences in severity of illness or other confounding factors. Nonetheless, insofar as the current guidelines1 reflect the best way to manage VAP, this study's results suggest that many—if not most—clinicians have not yet adopted them.
References
- American Thoracic Society. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005;171:388-416.
- Baselski VS, et al. The standardization of criteria for processing and interpreting laboratory specimens in patients with suspected ventilator-associated pneumonia. Chest. 1992;102(5 Suppl 1):571S-579S.
- Chastre J. Conference summary: ventilator-associated pneumonia. Respir Care. 2005;50:975-983.