Pneumonia

Definition

Pneumonia is a lower respiratory tract infection characterised by inflammation of interstitial tissue and/or alveolar space of lungs.

Categories according to timing:

  • Community Acquired Pneumonia (CAP)
    • Pneumonia in a patient in the community or hospitalised for less than 48 hours
  • Hospital Acquired Pneumonia (HAP)
    • Pneumonia that develops in a patient who has been hospitalised for more than 48 hours
  • Ventilator Associate Pneumonia
    • Pneumonia that develops in a patient who has been intubated for more than 48 hours
  • Aspiration Pneumonia
    • Pneumonia developed after contents from the stomach or mouth enters the lungs
    • Abscess likely and foul-smelling sputum

 

Categories according to anatomy:

  • Lobar Pneumonia
    • Pneumonia localised to one pulmonary lobe
  • Bronchopneumonia
    • Pneumonia localised to bronchioles and adjacent alveoli
  • Interstitial Pneumonia
    • Pneumonia causing fibrosis of interstitial tissue
  • Cryptogenic Organising Pneumonia (COP)
    • Inflammatory tissue present in bronchioles and alveoli
    • Although classified as pneumonia, it is non-infectious
    • Only diagnosed when other causes of pneumonia are eliminated

 

Categories according to clinical presentation:

  • Typical
    • Productive cough present
    • Common pathogens:
      • Streptococcus pneumoniae (most common lobar pneumonia)
      • Moraxella catarrhalis, Hemophilus influenzae (COPD exacerbations)
      • Staphylococcus aureus (IV drug users)
      • Klebsiella pneumoniae (alcoholics, aspiration pneumoniae, diabetics, malnourished)
  • Atypical
    • Dry cough
    • Auscultation unremarkable
    • Common pathogens:
      • Mycoplasma pneumoniae
      • Chlamydophila pneumoniae
      • Legionella pneumophila
Etiology
  • Impaired mucociliary escalator causing stasis/accumulation of secretions (smoking, CF, bronchiectasis)
  • Immunocompromised (Pneumocystis jirovecii, Aspergillus fumigatus, candida species, CMV)
  • Poor cough/gag reflex or increased risk of aspiration (stroke, GORD, low GCS)
  • Obstruction like space-occupying lesions
Clinical Features
  • Cough ± sputum
  • Shortness of breath
  • Fever/ chills/ rigors
  • Pleuritic chest pain
  • Papular rash
  • Diarrhoea
  • Neurological changes
Investigations
  • Vitals signs
  • Glasgow Coma Scale (GCS): to assess neurological changes
  • FBE: elevated neutrophil count
  • CRP: elevated
  • UEC: presence of uraemia demonstrates high severity
  • Sputum MCS and blood culture if febrile
  • ABG and PCR if suspecting viral illness
  • CXR for new/persistent infiltrate
Management
  • O2, IV fluids and salbutamol if necessary
  • Antibiotics:
  Low severity Moderate severity High severity 
 CAP Amoxicillin if typical; Doxycycline OR Clarithromycin if atypical Benzylpenicillin PLUS Doxycycline OR Clarithromycin Ceftriaxone
HAP Amoxicillin PLUS Clavulanate  Amoxicillin PLUS Clavulanate Piperacillin PLUS Tazobactam OR Cefepime
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