Comprehensive Overview of Pneumonia

Oct 30, 2024

Lecture Notes on Pneumonia

Introduction

  • Topic: Pneumonia
  • Discussion will cover:
    • Pathophysiology (Pathophys)
    • Classifications based on microbes, acquisition, and location
    • Features and complications
    • Diagnostics and treatment

Pathophysiology

  • Pneumonia: Inflammation/infection of lung tissue due to pathogens (bacterial, viral, fungal)
  • Common route: Aspiration (oral pharyngeal, gastric)
  • Reflex mechanisms: Cough, gag, swallowing reflexes
  • Factors affecting aspiration:
    • CNS diseases: Stroke, seizures, Parkinson’s, MS, ALS
    • CNS depression: Opioids, benzodiazepines, sedation, alcohol

Microbial Concerns with Aspiration

  • Klebsiella: Common in alcohol users, CNS issues
  • Anaerobes: From GI tract
  • Staphylococcus aureus: Associated with aspiration

Inhalation as a Cause

  • High population density areas risk:
    • Mycoplasma pneumoniae, Chlamydia, Influenza
    • Legionella from contaminated water sources

Fungal Infections

  • Geographic-specific fungal infections:
    • Coccidioidomycosis: Southwestern US
    • Histoplasmosis: Ohio/Mississippi River Valleys
    • Blastomycosis: Eastern US

Impaired Mucociliary Clearance

  • Diseases affecting mucus clearance:
    • Cystic fibrosis, Bronchiectasis, COPD, smoking
  • Pseudomonas: High risk in CF and bronchiectasis
  • Haemophilus influenza, Moraxella catarrhalis: COPD
  • Legionella: Risk in elderly smokers

Hematogenous Spread

  • IV drug users at risk for Staphylococcus aureus spreading to lungs
  • Post-influenza risk for Staphylococcus aureus infection

Immune System Involvement

  • Immunocompromised patients (HIV, CKD, diabetes, alcoholics) are at risk
  • Pseudomonas, Legionella, PJP in HIV (CD4 < 200)

Acquisition Types

  • Community-acquired pneumonia (CAP): <2 days in hospital or outpatient
    • Commonly Streptococcus pneumoniae
  • Hospital-acquired pneumonia (HAP): >2 days in hospital
    • Risk for MRSA, Pseudomonas

Clinical Features

  • Typical pneumonia: High-fever, rigors, productive cough, pleuritic chest pain
  • Atypical pneumonia: Upper respiratory symptoms (headache, sore throat, earaches)
  • Physical exam findings: Consolidation (dull percussion, positive egophony)

Complications

  • Parapneumonic effusion, Empyema, Lung abscess
  • Risk of ARDS and sepsis

Diagnostics

  • CAP: Consider respiratory viral panel, CBC, BMP (hyponatremia for Legionella), urinary antigens
  • HAP: Check for resistant pathogens

Imaging

  • Chest X-ray initially, CT if needed
  • Lobar pneumonia: Consolidated area
  • Bronchopneumonia: Patchy, scattered opacities
  • Interstitial pneumonia: Fine reticular markings

Treatment

  • Antibiotics vary by pneumonia type:
    • CAP outpatient: Macrolides (azithromycin) or doxycycline
    • CAP inpatient: Fluoroquinolones or macrolides with beta-lactam
    • CAP ICU: Beta-lactam with macrolide/fluoroquinolone
    • HAP: Target MRSA (vancomycin), Pseudomonas (piperacillin-tazobactam)
    • PJP in HIV: Treat with Bactrim

Prevention

  • Vaccinations: Pneumococcal vaccines (PCV13, PPSV23)