Definition
- Pneumonia in a patient who has been on a mechanical ventilator >48 hours.
- Diagnosis: clinical diagnosis with no standard definition, but in general:
- New or worsening CXR infiltrate.
PLUS at least two of the following:
- Purulent secretions.
- Leukocytosis or leukopenia.
- Fever.
- Worsening oxygenation/ventilator settings.
Epidemiology
- Occurs in 9-27% of mechanically ventilated patients, with about five cases per 1000 ventilator days.
- Most common nosocomial infection in the ICU.
- 1-3% risk of VAP per day that the patient is intubated (highest early in the course of hospitalization).
Etiology and Risk Factors
- Pathophysiology: colonization (oropharynx and ETT) → bypass of normal protective upper airway reflexes → microaspiration.
- Patient-related risk factors: age >70 years, serum albumin <2.2 mg/dl, ARDS, COPD, coma, sinusitis, stroke.
- Timing of VAP and MDR risk factors:
- Early (≤5 days of hospitalization): CAP organisms such as Strep pneumo, H flu.
- Late (>5 days of hospitalization): nosocomial pathogens such as MRSA, Pseudomonas.
- Other risk factors for MDR VAP: IV antibiotics in past 90 days, ARDS before VAP, acute RRT before VAP.
- Iatrogenic risk factors: duration of intubation, H2 blockers, proton-pump inhibitors, paralytics, excessive sedation, RBC transfusions, nasogastric tube, supine position, re-intubation.
Evaluation
- Imaging: CXR should be the first step in evaluation of suspected VAP.
- Microbiologic data can be obtained through various sampling methods. Gram stain should show many PMNs and may reveal a dominant organism. Specimens should be submitted for culture.
- Tracheal aspirates: sensitive (90%), but not specific (50%).
- Mini-bronchoalveolar lavage (mini-BAL):
- Blind sampling (via lavage) of lower airways with a protected catheter.
- Contraindications: FiO2 ≥0.8 or PEEP >14, high ICP, INR ≥2, platelets ≤50K, severe COPD.
- Data show that mini-BAL and tracheal aspirate are roughly equivalent, though mini-BAL is more helpful for patients with indwelling tracheostomy.
- Bronchoscopy with BAL: sensitive (82-91%) and specific (78-89%).
- Invasive, similar sensitivity/specificity to mini-BAL for VAP, but facilitates evaluation for alternative diagnoses and identification of atypical organisms such as PJP pneumonia where sputum culture is inadequate. Particularly useful in immunocompromised hosts.
- Does not improve mortality, length of stay, duration of ventilation, or ICU stay.
Management
- If high clinical suspicion, initiate empiric therapy with broad-spectrum antibiotics tailored to local resistance patterns (consult your local pharmacist or www.ucsf.edu/idmp).
- Narrow antibiotics within the first 48-72 hours based on microbiologic data.
- Length of treatment: 2016 VAP guidelines recommend seven-day course, same as other types of HAP (hospital-acquired pneumonia).
- Failure to improve after 2-3 days of adequate antibiotic therapy (empirically broad or culture-driven) should raise suspicion for an alternative or concurrent diagnosis or antibiotic-resistant organisms.
Prevention
- Reduce airway colonization: oral decontamination, silver ETT reduces VAP but does not affect mortality, ICU stay or intubation duration (NASCENT study). Digestive tract decontamination not standard practice in US.
- Prevent aspiration: elevated HOB, subglottic suctioning. No evidence that monitoring gastric volume with NG tube reduces VAP.
- Minimize duration of mechanical ventilation.
- Some evidence that sucralfate for stress ulcer prophylaxis decreases VAP compared to PPI or H2 blockers. No difference in GIB (though trend to higher rates in sucralfate) or mortality rates.
- Frequent changing of ventilator circuit does not prevent VAP.
Key Points
- VAP develops after >48 hours of mechanical ventilation.
- A normal chest radiograph excludes VAP.
- Patients with suspected VAP and an abnormal CXR should have microbiologic sampling.
- Prevention measures should be instituted for patients with prolonged ventilation.
- Consider alternative diagnoses in patients who do not improve with 2-3 days of antibiotics.
Keywords: VAP, ventilator-associated pneumonia, pneumonia
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Hunter JD. Ventilator associated pneumonia. BMJ 2012;344:e3325
Klompas, M. Does This Patient Have Ventilator-Associated Pneumonia? JAMA 2007; 297(14):1583-93.
Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clinical Infectious Diseases, Volume 63, Issue 5, 1 September 2016, Pages e61–e111.
Prod'hom G, et al. Nosocomial pneumonia in mechanically ventilated patients receiving antacid, ranitidine, or sucralfate as prophylaxis for stress ulcer. A randomized controlled trial. Ann Intern Med. 1994;120(8):653.
Reignier J, et al. Effect of not monitoring residual gastric volume on risk of ventilator-associated pneumonia in adults receiving mechanical ventilation and early enteral feeding: a randomized controlled trial. JAMA. 2013 Jan;309(3):249-56.