Ventilator-associated pneumonia in adults: a narrative review

Abstract

Ventilator-associated pneumonia (VAP) is one of the most frequent ICU-acquired infections. Reported incidences vary widely from 5 to 40% depending on the setting and diagnostic criteria. VAP is associated with prolonged duration of mechanical ventilation and ICU stay. The estimated attributable mortality of VAP is around 10%, with higher mortality rates in surgical ICU patients and in patients with mid-range severity scores at admission. Microbiological confirmation of infection is strongly encouraged. Which sampling method to use is still a matter of controversy. Emerging microbiological tools will likely modify our routine approach to diagnosing and treating VAP in the next future. Prevention of VAP is based on minimizing the exposure to mechanical ventilation and encouraging early liberation. Bundles that combine multiple prevention strategies may improve outcomes, but large randomized trials are needed to confirm this. Treatment should be limited to 7 days in the vast majority of the cases. Patients should be reassessed daily to confirm ongoing suspicion of disease, antibiotics should be narrowed as soon as antibiotic susceptibility results are available, and clinicians should consider stopping antibiotics if cultures are negative.

Keywords: Antibiotics; Bronchoalveolar lavage; Bronchoscopy; Endotracheal aspirate; Incidence; Mechanical ventilation; Mortality; Multiple-drug resistance; Prevention; Treatment; Ventilator-associated pneumonia; epidemiology.

Fig. 1

Chest X-rays and CT-scan of a 65-year-old man who developed ventilator-associated pneumonia. Chest X-ray performed the day VAP was suspected seems normal (a), whereas the CT-scan performed the same day showed consolidation of the left inferior lobe (b, d). Bronchoalveolar lavage yielded 10⁵Enterobacter aerogenes. The next day, chest X-ray showed progression of pulmonary infiltrates (c). VAP diagnosis based on chest X-ray would have been delayed

Fig. 2

Chest X-ray of a 35-year-old woman with H1N1 influenza-associated acute respiratory distress syndrome (“white lungs”). She developed fever, leukocytosis, purulent tracheal secretions and bronchoalveolar lavage (obtained during fiber optic bronchoscopy) yielded 10⁵Pseudomonas aeruginosa. Chest X-ray was unchanged (same chest X-ray since 1 week) and obviously not useful for suspecting/diagnosing ventilator-associated pneumonia

Fig. 3

Schematic representation of VAP diagnosis and treatment. Clinical suspicion of VAP refers to the association of some of the following criteria: fever, purulent sputum, leukocytosis, impaired oxygenation, unexplained hypotension or shock, new (or progression of) pulmonary infiltrates on chest X-ray (not always observed). Empirical treatment takes into account the underlying disease and its severity, the presence of risk factors for multiple-drug-resistant pathogens (antibiotic therapy in the previous 90 days, hospital stay > 5 days, septic shock at VAP onset, ARDS prior to VAP onset, acute renal replacement therapy prior to VAP onset, previous colonization with MDR pathogen) and local pattern of antimicrobial susceptibility. Immunocompromised patients, patients with empyema, lung abscess or necrotising pneumonia should receive prolonged antimicrobial course [38]

Fig. 4

Current and potential future workup processes for identification of pathogens responsible for VAP. To date, it takes 48–72 h. to identify pathogen responsible for ventilator-associated pneumonia (VAP) and its susceptibility to antibiotics (purple boxes), delaying the definitive, targeted treatment at that time (green boxes). Awaiting these results, physicians prescribe empiric broad-spectrum antimicrobial treatment. The use of specific, targeted polymerase chain reaction (PCR) may allow shortening this time to 24–36 h., but for specific pathogens and specific resistance mechanisms. A potential future workup process will be to use multiplex PCR (blue box) to identify within less than 6 h pathogens responsible for VAP and their resistance to antimicrobials