Aspiration pneumonia and pneumonitis

Background

Lobes of the lung with related anatomy.
  • Difficult to predict which patients with pneumonitis will go on to develop pneumonia, aspiration alone does not cause pneumonia
  • Witnessed aspiration key to distinguishing between the two
  • Aspiration pneumonitis
    • Inflammatory chemical injury of tracheobronchial tree and pulmonary parenchyma
    • Due to inhalation of regurgitated sterile gastric contents
    • Must aspirate at least 20-30mL of gastric contents with pH <2.5
    • Usually resolves after 24-48 hrs with supportive care only
    • Can lead to aspiration pneumonia due to pulmonary defense mechanism injury
  • Aspiration pneumonia
    • Alveolar space infection secondary to inhalation of pathogenic material from oropharynx
    • Result of a complex interplay of the aspirated material, aspirated volume, pH, patient physiology and pulmonary defense mechanisms
    • Increased in patients with periodontal disease, chronic colonization of upper airways, or taking PPI/H2-blockers
    • Accounts for up to 20% of community-acquired pneumonia in elderly, majority of nursing home-acquired pneumonia
    • Microbiology

Risk factors

  • Advanced age
  • Altered level of consciousness
  • Anatomic abnormality of upper airway
  • Dementia
  • Esophageal disorders
  • Gastroesophageal reflux
  • Neuromuscular disease
  • Poor oral hygiene
  • Prior history of aspiration
  • Prolonged supine position
  • Retained gastric material
  • Tube feedings

Clinical Features

Differential Diagnosis

Acute dyspnea

Emergent

Non-Emergent

Evaluation

Aspiration pneumonia in a ventilated person with a central line and nasogastric tube.
Chest X-ray of the patient showing (left) multifocal patchy consolidation consistent with aspiration pneumonitis and (right) the decreased extent of pulmonary opacification in both central lung areas 3 days after initiation of the treatment.

Work-Up

  • CXR
    • Unilateral focal or patchy consolidations in dependent lung segments
    • Right lower lobe is most common area; bilateral patterns can also be seen
    • Lower lobe infiltrate when aspiration occurs in upright position
    • Upper lobe infiltrate when aspiration occurs in recumbent position
  • CT
    • Increased sensitivity, specificity, and overall accuracy compared to CXR
    • Reasonable to obtain even if CXR negative if clinical suspicion is high
    • Aspiration is a risk factor for pulmonary abscess formation

Management

Aspiration pneumonitis

  • Suction upper airway if aspiration is witnessed
  • Caused by aspiration of gastric contents. Usually resolves in 24-48 hrs w/o treatment
  • Antibiotics only recommended if symptoms persist >48hr
    • Same as those for community-acquired aspiration pneumonia below

Aspiration pneumonia

  • Treat same as community acquired pneumonia (see below)
    • Routinely adding anaerobic coverage beyond the standard empiric treatment for community-acquired aspiration pneumonia is no longer recommended unless lung abscess, empyema, healthcare-associated, periodontal disease, or SBO[1]

Outpatient

Coverage targeted at S. pneumoniae, H. influenzae, M. pneumoniae, C. pneumoniae, and Legionella

Healthy[2]

No comorbidities (chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia) and no risk factors for MRSA or Pseudomonas aeruginosa (include prior respiratory isolation of MRSA or P. aeruginosa or recent hospitalization AND receipt of parenteral antibiotics (in the last 90 d))

  • Amoxicillin 1 g three times daily (strong recommendation, moderate quality of evidence), OR
  • Doxycycline 100 mg twice daily (conditional recommendation, low quality of evidence), OR
  • Macrolide in areas with pneumococcal resistance to macrolides <25% (conditional recommendation, moderate quality of evidence).
  • Duration of therapy 5 days minimum

Unhealthy[2]

If patient has comorbidities or risk factors for MRSA or Pseudomonas aeruginosa

  • Combination therapy:
    • Amoxicillin/Clavulanate
      • 500 mg/125 mg TID OR amox/clav 875 mg/125 mg BID OR 2,000 mg/125 mg BID. Duration is for a minimum of 5 days and varies based on disease severity and response to therapy; patients should be afebrile for ≥48 hours and clinically stable before therapy is discontinued[3]
    • OR cephalosporin
    • AND macrolide
      • Azithromycin 500 mg on first day then 250 mg daily
      • OR clarithromycin 500 mg BID OR clarithromycin ER 1,000 mg daily (strong recommendation, moderate quality of evidence for combination therapy)
    • OR doxycycline 100 mg BID (conditional recommendation, low quality of evidence for combination therapy)
  • Monotherapy: respiratory fluoroquinolone (strong recommendation, moderate quality of evidence):

Inpatient

  • Monotherapy or combination therapy is acceptable
  • Combination therapy includes a cephalosporin and macrolide targeting atypicals and Strep Pneumonia[4]
  • Adjunctive corticosteroids in severe CAP: The SCCM 2024 Focused Update strongly recommends corticosteroids for hospitalized adults with severe bacterial CAP (strong recommendation, moderate certainty)[5]
    • CAPE COD trial (NEJM 2023): Hydrocortisone 200 mg IV daily (50 mg q6h) in severe CAP requiring ICU/intermediate care → ↓ 28-day mortality (6.2% vs 11.9%, NNT ~18), ↓ intubation, ↓ vasopressor use[6]
    • Duration: 200 mg/day for 4–7 days based on clinical improvement, then tapered (total 8–14 days)
    • Excluded patients already in septic shock
    • No recommendation for or against steroids in less severe CAP[5]
    • Avoid in influenza pneumonia (without bacterial superinfection)[2]
  • Duration: Minimum 5 days; continue until clinically stable (temp ≤37.8°C, HR ≤100, RR ≤24, SBP ≥90, SpO2 ≥90% on RA, tolerating PO, baseline mental status) for ≥48 hours[2]
  • De-escalation: If empiric MRSA or Pseudomonas coverage was started, de-escalate to standard CAP therapy within 48 hours if cultures/MRSA nasal PCR are negative and patient is improving[2]

Community Acquired (Non-ICU)

Coverage against community acquired organisms plus M. catarrhalis, Klebsiella, S. aureus[2]

ICU, Low Risk of MRSA/Pseudomonas

ICU, Risk of Pseudomonas (without MRSA risk)

2019 guidelines recommend single antipseudomonal β-lactam (changed from double gram-negative coverage in 2007 guidelines)[2]

ICU, Risk of MRSA

Add MRSA coverage to appropriate regimen above[2]

  • Vancomycin 15–20 mg/kg IV q8-12h (target AUC/MIC 400-600) OR Linezolid 600 mg IV q12h
  • MRSA nasal PCR has a high negative predictive value (~95%); if negative, MRSA coverage can be safely discontinued[7]

Hospital Acquired Pneumonia (HAP)

Pneumonia developing ≥48 hours after hospital admission in non-intubated patients[8]

High risk of MRSA or high mortality risk (ventilatory support for HAP or septic shock)
Low risk of MRSA and low mortality risk

Ventilator Associated Pneumonia (VAP)

Pneumonia developing ≥48 hours after endotracheal intubation[8]

High risk of MRSA or IV antibiotics in the last 90 days or unit MRSA prevalence >10-20% or unknown
Low risk of MRSA and Pseudomonas (no risk factors for antimicrobial resistance, unit MRSA <10-20%)
  • Single antipseudomonal β-lactam monotherapy (from list above) is acceptable[8]
  • Duration: 7 days recommended[8]


Disposition

  • Generally admit all patients with aspiration pneumonia
  • For aspiration pneumonitis, consider discharge if:
    • Otherwise healthy and non-toxic
    • Give outpatient antibiotics if symptomatic for >48hrs
  • For aspiration pneumonitis, consider admission for:
    • Chronically ill or immunocompromised
    • Nursing home patient

See Also

References

  1. ↑ Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45–e67.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67
  3. ↑ IDSA. Mandell 2007
  4. ↑ Chokshi R, Restrepo MI, Weeratunge N, Frei CR, Anzueto A, Mortensen EM. Monotherapy versus combination antibiotic therapy for patients with bacteremic Streptococcus pneumoniae community-acquired pneumonia. Eur J Clin Microbiol Infect Dis. Jul 2007;26(7):447-51
  5. ↑ 5.0 5.1 Chaudhuri D, Nei AM, Rochwerg B, et al. 2024 Focused Update: Guidelines on Use of Corticosteroids in Sepsis, Acute Respiratory Distress Syndrome, and Community-Acquired Pneumonia. Crit Care Med. 2024;52(5):e219-e233.
  6. ↑ Dequin PF, Meziani F, Quenot JP, et al. Hydrocortisone in Severe Community-Acquired Pneumonia. N Engl J Med. 2023;388(21):1931-1941.
  7. ↑ Parente DM, Cunha CB, Engemann AM, et al. The Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening to Rule Out MRSA Pneumonia: A Diagnostic Meta-analysis With Antimicrobial Stewardship Implications. Clin Infect Dis. 2018;67(1):1-7.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Kalil AC, Metersky ML, Klompas M et al. 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. Clin Infect Dis. 2016 Sep 1;63(5):e61-e111.
  9. ↑ Luther MK, Timbrook TT, Caffrey AR, Dosa D, Lodise TP, LaPlante KL. Vancomycin Plus Piperacillin-Tazobactam and Acute Kidney Injury in Adults: A Systematic Review and Meta-Analysis. Crit Care Med. 2018;46(1):12-20.
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