Hospital-acquired and ventilator-associated pneumonia

Whilst the majority of patients with pneumonia develop outside of hospital ('community-acquired) it is common for patients to develop significant chest infections whilst admitted. These require special consideration as the causative organisms (and hence recommend antibiotic regimes) are often different.

Definitions

• hospital-acquired pneumonia (HAP): pneumonia that occurs ≥ 48 hours after admission
• ventilator-associated pneumonia (VAP): pneumonia that develops ≥48 hours after endotracheal intubation

Common causative organisms

• Staphylococcus aureus (methicillin-sensitive, MSSA)
• methicillin-resistant Staphylococcus aureus (MRSA)
• Pseudomonas aeruginosa - particularly in ventilated patients, most common cause in patients ventilated > 5 days
• gram-negative bacilli (e.g. Escherichia coli, Klebsiella pneumoniae, Enterobacter spp, Acinetobacter spp) - particularly in late-onset HAP (after 4 days)
• polymicrobial infections
• multidrug-resistant (MDR) pathogens

Features

• clinical findings also seen with community-acquired pneumonia
  • cough
  • sputum
  • dyspnoea
  • fever
  • consolidation/infiltrates on chest x-ray
  • raised white cell count and CRP
• increased respiratory rate, decreased oxygenation saturations may be seen on observations charts
• ventilated patients may have
  • decreased tidal volume
  • increased inspiratory pressures
  • decreased oxygenation
• diagnosis is complicated by the fact that many hospitalised patients will have confounding features due to reason for underlying admission, e.g. dyspnoea or raised CRP

Investigations