319.1 🎓 醫孞生版

319.1.0.1 📌 䞀頁重點

319.1.0.1.1 Aspiration Pneumonia
319.1.0.1.1.1 Mechanism Spectrum

Chemical Pneumonitis (Mendelson Syndrome): - Acidic gastric contents (pH < 2.5) - Rapid lung injury (minutes-hours) - Sterile initial; bacterial superinfection can develop - Treatment: supportive; NOT routine antibiotics initially

Bacterial Aspiration Pneumonia: - 24-72 hours post-aspiration - Pathogen-driven infection - Polymicrobial (anaerobes + aerobes) - Treatment: antibiotics

319.1.0.1.1.2 Pathogens (Modern Understanding)

Anaerobes (traditional emphasis): - Peptostreptococcus - Fusobacterium - Prevotella - Bacteroides - Veillonella

Aerobes (Now Recognized as Common): - S. pneumoniae - H. influenzae - S. aureus (esp post-influenza) - GNR (Klebsiella, Pseudomonas, E. coli) - Mycoplasma (less common)

Hospital / Healthcare Setting: - More Pseudomonas + MRSA - Bacteroides + anaerobic GNR

319.1.0.1.1.3 Risk Factors

Altered Consciousness: - Stroke - Dementia - Drug intoxication - Seizure - General anesthesia - Coma

Dysphagia: - Stroke - Parkinson disease - ALS - Multiple sclerosis - Head + neck cancer - Esophageal motility disorders - Achalasia

Reduced Gag / Swallow: - Esophageal disease - Tracheoesophageal fistula - Cricopharyngeal dysfunction

Mechanical Factors: - NG / NJ tube - Endotracheal tube - Tracheostomy - Bedridden status

Other: - GERD - Chronic alcohol - Periodontal disease - Aging - Obesity (mild risk) - Bulbar dysfunction

319.1.0.1.1.4 Clinical Features

Witnessed Aspiration: - Coughing, choking during/after eating - Acute respiratory distress - Cyanosis if severe - Watch for chemical pneumonitis

Subacute Aspiration Pneumonia: - Insidious onset (days) - Fever, cough, sputum - Often dependent lung zones (RLL > LLL when supine, RUL when right side down) - Foul-smelling sputum (anaerobic)

Examination: - Crackles, decreased breath sounds - Egophony (consolidation) - Tachypnea, hypoxia

319.1.0.1.1.5 Imaging

Chest X-Ray / CT: - Dependent lung zone infiltrates: - Right upper lobe: aspiration in supine position with right side down - Right lower lobe + middle lobe: aspiration in semi-recumbent - Posterior segments lower lobes: aspiration in left lateral decubitus - Bilateral often - Consolidation, ground-glass, or both - Cavitation suggests abscess

319.1.0.1.1.6 Diagnosis
  • Clinical context (witnessed aspiration, dysphagia, altered mental status)
  • Radiographic findings (dependent lobes)
  • Sputum: anaerobes hard to culture; foul smell hints
  • Blood cultures (less often positive)
  • Bronchoscopy + BAL if uncertain
  • Modified barium swallow / FEES (fiberoptic endoscopic evaluation of swallowing) for swallowing assessment
319.1.0.1.2 Treatment
319.1.0.1.2.1 Chemical Pneumonitis (Acute Aspiration without Infection)

Initial Management: - Suctioning (acute) - O2 + supportive - Mechanical ventilation if respiratory failure - Watch for ARDS

No Routine Antibiotics: - Most resolve in 24-48 hours - Antibiotics if: - Fever, leukocytosis, persistent infiltrate > 48 hours - SIRS / sepsis features - Failure to improve

Steroids: not routinely; no clear benefit

319.1.0.1.2.2 Bacterial Aspiration Pneumonia

Outpatient / Community: - Amoxicillin-clavulanate (first-line) - OR Clindamycin (alternative) - OR Metronidazole + amoxicillin (combination) - Duration: 7-14 days

Inpatient: - Ampicillin-sulbactam (Unasyn) - Piperacillin-tazobactam (Zosyn) - Metronidazole + ceftriaxone OR - Carbapenem (severe / MDR risk)

Hospital-Acquired (HAP): - See Ch317 - Cover Pseudomonas + MRSA if applicable

Penicillin Allergy: - Clindamycin + ceftriaxone - Carbapenem (carbapenem-allergy rare)

MRSA Risk: - Add vancomycin or linezolid

319.1.0.1.3 Lung Abscess
319.1.0.1.3.1 Definition
  • Localized necrotic + suppurative collection > 2 cm
  • Communication with airway (cavitation with air-fluid level)
  • Most often aspiration + anaerobes
319.1.0.1.3.2 Etiology

Primary (Aspiration): - Most common - Anaerobes + S. aureus + GNR - Often single - Right lung > left

Secondary: - Septic pulmonary embolism (S. aureus, esp from endocarditis, IVDU) - Necrotizing pneumonia (Klebsiella, S. aureus, Acinetobacter) - Bronchial obstruction (cancer, foreign body) - Trauma - Immunocompromise (aspergillosis, mucormycosis) - TB / NTM (cavitary)

319.1.0.1.3.3 Clinical
  • Chronic cough (often foul, putrid sputum)
  • Fever (often low-grade chronic)
  • Weight loss
  • Night sweats
  • Hemoptysis (15-30%)
  • Pleuritic chest pain
  • Clubbing (chronic)
319.1.0.1.3.4 Imaging
  • CXR: cavity with air-fluid level
  • CT: defines size + location + multifocality
  • Often dependent areas
  • Right lower lobe + right upper lobe (posterior segment) common
319.1.0.1.3.5 Workup
  • Bronchoscopy: for foreign body, mass, biopsy
  • Sputum cultures (aerobic + anaerobic)
  • Blood cultures
  • Echocardiogram (right-sided endocarditis source)
  • HIV testing in select
319.1.0.1.3.6 Treatment

Antibiotics: - Amoxicillin-clavulanate or piperacillin-tazobactam (covers anaerobes) - Clindamycin alternative - Carbapenem for severe / MDR - Duration: 4-6 weeks (often longer than CAP) - IV initially → switch to PO - Adjust per cultures

Drainage: - Usually NOT needed (spontaneous drainage via airway) - Percutaneous catheter drainage: for large, persistent, or refractory abscess - Surgical resection: rare; for malignancy suspicion or recurrence

Bronchoscopy: - Diagnostic: rule out foreign body, mass, infection - Therapeutic: limited - Beware bronchopulmonary spillage during procedure

Underlying Cause Treatment: - Endocarditis (if septic emboli source) - Foreign body removal - Aspiration prevention

319.1.0.1.3.7 Outcomes
  • 80-90% resolve with antibiotics
  • Mortality 5-15%
  • Worse: immunocompromised, large abscess, sepsis
319.1.0.1.4 Anaerobic Pleuropulmonary Infections (Spectrum)
319.1.0.1.4.1 Necrotizing Pneumonia
  • Multiple smaller cavitations
  • Aggressive infection
  • Similar antibiotic management; often longer
319.1.0.1.4.2 Empyema
  • See Ch311
  • Anaerobes + aerobes common
  • Drainage + antibiotics
319.1.0.1.4.3 Bronchopleural Fistula
  • Complication
  • Difficult to close
  • Surgical management
319.1.0.1.5 Aspiration Prevention
319.1.0.1.5.1 Swallowing Evaluation
  • Speech-language pathologist (SLP)
  • Modified barium swallow
  • FEES (fiberoptic endoscopic evaluation of swallowing)
319.1.0.1.5.2 Strategies
  • Modified diet (thickened liquids, pureed)
  • Head of bed elevation ≥ 30° during meals + post-prandial
  • Smaller, slower meals
  • Oral hygiene
  • Swallowing exercises (CTAR, Shaker exercise)
  • NG tube placement check before feeding
  • PEG tube for severe dysphagia (debated benefit in dementia)
319.1.0.1.5.3 Stroke Care Bundle (Class I)
  • NPO until swallow assessment
  • Dysphagia screening within 24 hours
  • SLP referral if abnormal
319.1.0.1.5.4 Reflux Management
  • PPI for severe GERD
  • Lifestyle (avoid late meals, weight loss)
  • Fundoplication for severe
319.1.0.1.5.5 Other Prevention
  • Acute care of cricopharyngeal dysfunction
  • Esophageal dilation for stricture
  • Surgery for tracheoesophageal fistula
  • Treat underlying neurologic disease

319.1.0.2 🩺 床邊速查

  • Aspiration pneumonia = polymicrobial (anaerobes + aerobes); dependent lobes
  • Mendelson syndrome = chemical pneumonitis from gastric acid; no routine abx
  • Treatment: amoxicillin-clavulanate / pip-tazo (anaerobic cover)
  • Lung abscess: cavity + air-fluid level; 4-6 week antibiotics; drainage usually not needed
  • Septic pulmonary embolism: S. aureus (endocarditis, IVDU); multiple cavitations
  • Prevention: SLP evaluation, thickened liquids, HOB elevation, oral hygiene