11. Ventilator Associated Pneumonia (VAP)

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 

Chastre J, Wolff M, Fagon JY, et al. Comparison of 8 vs 15 days of antibiotic therapy for ventilator-associated pneumonia in adults: a randomized trial. JAMA 2003; 290:2588-2598.  

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.