Pneumonia, Ventilator-Associated

by Henry F. Chambers, M.D. last updated 2020-08-04 10:00:28.214337-04:00 © Antimicrobial Therapy, Inc.
Ventilator-associated bacterial pneumonia (VAP or VABP), ventilated hospital-acquired bacterial pneumonia (HBAP)

Clinical Setting

  • Ventilator-associated bacterial pneumonia (VAP or VABP), ventilated hospital-acquired bacterial pneumonia (HBAP). Defined as pneumonia that develops ≥ 48 hours of mechanical ventilation.
  • Empiric therapy:
    • Diagnostic criteria:
      • Clinical suspicion and presence of new or progressive pulmonary infiltrates on chest radiograph PLUS two of the following:
        • Fever
        • Peripheral leukocytosis
        • Purulent tracheal secretions
      • Proposed surveillance diagnostic criteria: Clin Infect Dis 57:1742, 2013.
  • Empiric therapy for ventilated hospital-acquired bacterial pneumonia
  • Culture, gram strain of tracheal aspirate or lavage fluid should be performed in all cases of suspected VAP.
  • Differential diagnosis includes:
    • Non-bacterial pathogens
    • Fever due to ischemia, malignancy, drug-induced pneumonia
    • Infiltrates due to congestive heart failure
    • For full list: Scand J Infect Dis 46:868, 2014.
  • 2017 European Guidelines: (Eur Respir J 2017; 50: 1700582). 2016 IDSA Guidelines: Clin Infect Dis 63:e61, 2016 (full article); executive summary: Clin Infect Dis 63:575, 2016.
  • For prophylaxis, see Comments

Etiologies

  • Early-onset (<5 days in the hospital, no other risk factors for multi-drug resistant (MDR) organisms)
    • Strep. pneumoniae
    • H. influenzae
    • Enteric gram-negative bacilli
  • Late-onset (≥ 5 days in the hospital, risk factors of MDR organisms present)
    • Staph. aureus (often MRSA)
    • Gram-negative enterics (often multi-drug resistant)
      • E. coli
      • Klebsiella pneumoniae
      • Enterobacter sp.
      • Serratia marcescens
      • Pseudomonas aeruginosa
      • Acinetobacter baumannii

Primary Regimens

  • Low risk of MRSA (ICU prevalence <10-20%), no risk factors for MDR pathogens,
  • More severe disease, i.e., sepsis, hypotension, rapid progression of infiltrates on chest radiograph indicating high risk of mortality; MDR risk factor, MRSA prevalence >10-20%
  • Duration of therapy: See Antimicrobial Stewardship

Alternative Regimens

  • Linezolid 600 mg IV q12h can be substituted for Vancomycin
  • Substitute Ceftazidime-avibactam 2.5 gm IV infused over 2 hours q 8h for Cefepime, Piperacillin-tazobactam or Meropenem if carbapenem-resistant enterobacteriaceae is suspected
  • Aztreonam 2 gm IV q8h instead of cefepime, piperacilli-tazobactam, or meropenem for patients with severe IgE-mediated hypersensitivity to beta-lactams.  However, unlike these other agents, aztreonam is not active against S. aureus or S.pneumoniae and hence should add vancomycin pending culture results.
  • Ceftolozane-tazobactam 3 g IV q8h covers pseudomonas and ESBL-producing Enterobacteriaceae (Lancet Infect Dis 2019 Dec;19(12):1299-1311).

Antimicrobial Stewardship

  • If  S. aureus nares screen is negative for MRSA no need to empirically cover for MRSA, and if coverage initiated, de-escalation  is safe with a negative predictive value of 96.1% (Clin Infect Dis 2019 Oct 1. pii: ciz974. doi: 10.1093/cid/ciz974). 
  • Duration of therapy is not well defined.
    • For relatively susceptible pathogens treat for 8 days.
    • For Staph. aureus, MRSA in particular, or more resistant organisms (e.g., Pseudomonas, Acinetobacter, Stenotrophomonas) treat for longer, e.g., 14 days.
    • Alternatively, can trend serum procalcitonin levels
    • Retrospective cohort study found that 1-3 days of therapy was as effective as > 3 days for patients with suspected VAP and minimal and stable ventilator settings defined as daily minimum PEEP of ≤5 cm H2O and daily minimum FiO2 <40% for at least 3 days from the first day of antibiotics (Clin Infect Dis 64:870, 2017).

Comments

  • If MDR pathogens are suspected, initial coverage should be broad and then streamlined based on culture and susceptibility results.
  • In literature review, ESKAPE pathogens etiologic in 80% of patients: Curr Opin Pulm Med 20:252, 2014.
  • Risk factors for MDR organisms:
    • Antimicrobial therapy in preceding 90 days.
    • Current hospitalization of 5 days or more.
    • Septic shock at time of VAP
    • Acute renal replacement therapy prior to onset of VAP
    • Antibiotic resistance prevalent in the community or specific hospital unit
  • Empiric regimen of choice may vary based on local prevalence and susceptibility of pathogens, known prior colonization with MDR organisms, prior treatment history, severity of illness.
  • Prevention/prophylaxis of VAP (Am J Infect Control 42:34, 2014):
    • Elevate head of bed by 30º or more.
    • Remove NG endotracheal tubes as soon as possible.
    • Continuous subglottic suctioning (Crit Care Med 43:22, 2015; Crit Care Med 43:227, 2015).
    • Chlorhexidine oral care.
    • Silver-coated endotracheal tubes may reduce incidence of VAP: JAMA 300:805, 2008; JAMA 300:842, 2008.
    • Prevention of VAP in patients with post cardiac arrest and targeted hypothermia management (N Engl J Med. 2019; 381:1831-1842). 
      • Multicenter, double-blind, randomized , placebo-controlled trial in adults (where available)
        • VAP in first 7 days: Placebo: 34%; Amoxicillin-clavulanatae 19 %, p 0.03
  • Imipenem-cilastatin-relebactam now FDA approved for hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia.