Revision 19 for 'Hospital-acquired pneumonia'

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Hospital-acquired pneumonia

Hospital-acquired pneumonia (HAP) or nosocomial pneumonia is defined by the American Thoracic Society (ATS) guidelines as pneumonias that occur more than 48 hours after hospital administration but were not present at the time of admission.

Epidemiology

It can be a common cause of pneumonia in patients admitted to intensive care units (ICU) and those on mechanical ventilation (ventilator-associated pneumonia). While all ages and both sexes can be affected, elderly patients are more prone.

Pathology

Hospital acquired pneumonia is divided into:

  • early onset: within 4 days of admission
  • late onset: after day 5 of admission
Etiology

Hospital acquired pneumonia commonly results from colonized upper respiratory tract infections being aspirated into the lower respiratory tract and ascending infection from the stomach (i.e. ingested oropharyngeal secretions).

Common organisms for early onset type are Streptococcus pneumoniae and Haemophilus influenzae.

For late onset type, Staphylococcus aureus, Pseudomonas aeruginosaKlebsiella species and Acinetobacter are common.

Intubation and ventilatory support bypass normal defense mechanism predisposing patients to infection.

Radiographic features

It is essentially a clinical diagnosis with no specific features.

Plain radiograph

Areas of consolidation in unilateral or bilateral lung fields may be seen depending on severity. 

Treatment and prognosis

The early onset type has a better prognosis. High morbidity and mortality are seen patients with Hospital acquired pneumonia as they are already hospitalized for another condition. 

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