Pneumonia
Description
Acute infection of the lung parenchyma with new radiographic infiltrate.
Classify by where it was acquired - this drives the antibiotic
| Definition | |
|---|---|
| CAP | Acquired outside hospital |
| HAP | >=48 h after admission |
| VAP | >=48 h after intubation |
| Aspiration | Pneumonitis (chemical) vs pneumonia (infective) |
| Immunocompromised | Widened differential: PJP, CMV, fungi, Nocardia, mycobacteria |
- "Healthcare-associated pneumonia" (HCAP) has been abandoned - it over-treated with broad-spectrum agents without benefit
Radiological patterns
- Lobar - alveolar filling, air bronchograms. Strep pneumoniae, Klebsiella
- Bronchopneumonia - patchy, multilobar. Staph, H. influenzae, anaerobes
- Interstitial - diffuse, "atypical"/viral pattern. Mycoplasma, viruses, PJP
- Cavitating - Staph aureus, Klebsiella (upper lobe, "bulging fissure"), anaerobes, TB, Nocardia
- The radiographic pattern does not reliably predict the organism - do not prescribe on it alone
*Aspiration pneumonitis vs aspiration pneumonia*
- Pneumonitis = acute chemical injury from gastric acid; rapid onset (within hours), often fever and infiltrate, radiographically indistinguishable from pneumonia
- *Does not require antibiotics* - it is a chemical burn
- In practice, when the distinction is unclear, start antibiotics and review at 24-48 hours, stopping if the picture resolves
- Pneumonia = bacterial infection following aspiration of oropharyngeal flora; develops over days
- Dependent segments: right lower lobe (upright), posterior segments of upper lobes / superior segments of lower lobes (supine)
- Anaerobes are less important than once taught; routine anaerobic cover is no longer recommended unless there is abscess, empyema or necrotising disease
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