Pneumonia Lecture

Pneumonia Overview

  • Acute infection of lung parenchyma
    • Symptoms: lower respiratory tract infections (LRTI)
    • Diagnosed through chest radiology
    • Abnormal auscultation findings: decreased breath sounds, rales, crackles, dullness.

Types of Pneumonia

  • Community-Acquired Pneumonia (CAP)
    • Occurs outside hospital or within 48 hours of admission.
  • Hospital-Acquired Pneumonia (HAP)
    • Develops > 48 hours after hospital admission, not incubating at the time of admission.
  • Ventilator-Associated Pneumonia (VAP)
    • Occurs > 48 hours after endotracheal intubation.

Risk Factors for Pneumonia

  • CAP Risks:
    • Advanced age (≥ 65), immunosuppressive therapy, underlying lung diseases (e.g., COPD, asthma), environmental exposures, poor oral health, smoking, excessive alcohol use.
  • HAP Risks:
    • Advanced age, witnessed aspiration, prolonged lying position, use of certain medications (antacids, H2-antagonists, proton pumps), extra invasive devices, recent IV antibiotics.
  • VAP Risks:
    • Same as HAP, plus the presence of an endotracheal tube and ICU therapies.

Epidemiology & Mortality

  • CAP: Approx. 6 million cases annually, significant hospitalizations (1.4 million).
    • 30-day mortality rates: 2.8% in adults <60 years, 26.8% in older patients with comorbidities.
  • HAP/VAP: Mortality rate from 24-76% (higher in ICU).

Pathophysiology

  • Fluid or pus-filled alveoli disrupt gas exchange leading to pneumonia diagnosis.

Common Pathogens and Diagnosis

  • CAP:
    • Outpatient: Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, respiratory viruses.
    • Inpatient: More severe pathogens like Legionella species and Staphylococcus aureus.
  • HAP/VAP: Common pathogens include MRSA and multidrug-resistant organisms.

Clinical Presentation

  • Symptoms: fever, chills, dyspnea, cough, rust-colored sputum, pleuritic chest pain.
    • Possible nonspecific symptoms include confusion and lethargy.

Diagnosis Process

  • Combination of clinical signs, symptoms, imaging (gold standard: chest x-ray), and laboratory investigations (CBC, sputum culture).
    • Radiologic findings: infiltrates, lobar consolidations, cavitations should be checked.
  • Culture and Sensitivity: Important for tailoring antibiotic therapy.

Severity Assessment

  • Pneumonia Severity Index (PSI): Predict mortality risk and manage outpatient versus inpatient treatment.
    • CURB-65 Score: Considers confusion, urea levels, respiratory rate, blood pressure, age.

Empiric Treatment Strategies

  • Outpatient Treatment (No risk factors):
    • Preferred: Amoxicillin 1 g PO q 8h.
    • Alternatives: Doxycycline or Macrolide.
  • Inpatient Treatment:
    • Non-severe cases: Ceftriaxone or Ampicillin-sulbactam + Macrolide.
    • Severe cases: Initiate combination therapies targeting likely pathogens.

Monitoring and De-escalation

  • Monitor clinical response: WBC, symptoms, chest x-ray improvement, and adjust therapy based on culture results.
  • Duration of treatment: typically 5-7 days if the patient is improving.

Preventative Measures

  • Vaccination (PCV13, PPSV23), annual influenza vaccination, smoking cessation, lifestyle changes.

Complications

  • Potential complications include sepsis, pleural effusion, lung abscess, and ARDS.