Pneumonia, Nosocomial (Hospital-Acquired & Ventilator-Associated)

Key Features

Essentials of Diagnosis

• Hospital-acquired pneumonia (HAP) is diagnosed in patient with clinical features and imaging consistent with pneumonia, occurring > 48 hours after admission to the hospital, and excluding any infections present at the time of admission

• Ventilator-associated pneumonia (VAP) requires clinical features concerning for new pneumonia with positive respiratory samples developing > 48 hours following endotracheal intubation and mechanical ventilation

General Considerations

• Most common organisms in HAP

  • Staphylococcus aureus (both methicillin-sensitive S aureus and methicillin-resistant S aureus)

  • Pseudomonas aeruginosa

  • Gram-negative rods, including non–extended-spectrum β-lactamase (non-ESBL) producing and ESBL-producing (Enterobacter species, Klebsiella pneumoniae, and Escherichia coli)

• Organisms seen in VAP

  • Acinetobacter species

  • Stenotrophomonas maltophilia

• Anaerobic organisms may also cause pneumonia in the hospitalized patient

  • Bacteroides

  • Anaerobic streptococci

  • Fusobacterium

• Uncommon causes of nosocomial pneumonias

  • Mycobacteria

  • Fungi

  • Chlamydiae

  • Viruses

  • Rickettsiae

  • Protozoal organisms

Clinical Findings

Symptoms and Signs

• Nonspecific

• However, two or more clinical findings (fever, leukocytosis, purulent sputum, worsening respiratory status) along with one or more new or progressive pulmonary opacities on chest imaging are characteristic features

• See also Pneumonia, Community-Acquired

Differential Diagnosis

• Heart failure

• Atelectasis

• Aspiration

• Acute respiratory distress syndrome (ARDS)

• Pulmonary thromboembolism

• Pulmonary hemorrhage

• Medication reactions

Diagnosis

Laboratory Tests

• Blood cultures identify the pathogen in up to 15–20% of cases

• Complete blood count and chemistry tests

  • Not helpful in identifying the etiologic agent

  • However, can assist in determining illness severity and complications

• Gram stains and other examinations of respiratory secretions and cultures of respiratory secretions are controversial but may be useful in guiding antibiotic therapy

• Serum procalcitonin levels are not sufficiently sensitive to rule out HAP or VAP but may allow discontinuation of antibiotic therapy

Imaging Studies

• Radiographic findings

  • Nonspecific

  • Range from patchy opacities to lobar consolidation to diffuse alveolar or interstitial opacities

Diagnostic Procedures

• When HAP is suspected in a patient who subsequently requires mechanical ventilation, secretions may be obtained by

  • Spontaneous expectoration

  • Sputum induction

  • Nasotracheal suctioning

  • Endotracheal aspiration (qualitative or semiquantitative samples)

    • More likely to return nonpathogenic organisms

    • Thus, associated with higher antibiotic exposure (without improvement in mortality)

  • Bronchoscopic sampling of the lower airways secretions (quantitative samples): increases cost and patient risk

• Invasive qualitative sampling is universally recommended when

  • The patient is not improving with initial therapy directed at the expected or isolated pathogens

  • An opportunistic pathogen is suspected in an immunocompromised person

Treatment

Medications

• See Tables 9–11 and 30–5

• Treatment is usually empiric and should be started as soon as the diagnosis is suspected

• No consensus regimens exist, but ...