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

Key Features

Essentials of Diagnosis

• Hospital-acquired pneumonia (HAP) occurs more than 48 hours after admission to the hospital or other health care facility and excludes any infection present at the time of admission

• Ventilator-associated pneumonia (VAP) develops more than 48 hours following endotracheal intubation and mechanical ventilation

• At least two of the following are present

  • Fever

  • Leukocytosis

  • Purulent sputum

• New or progressive parenchymal opacities on chest radiograph

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 extended spectrum beta-lactamase (ESBL)- producing and non–ESBL-producing organisms (eg, 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) in the setting of a new or progressive pulmonary opacity on chest radiograph were approximately 70% sensitive and 75% specific for the diagnosis of VAP in one study

• Colonization of the pharynx and possibly the stomach with bacteria is the most important step in the pathogenesis of nosocomial pneumonia

• See also Pneumonia, Community-Acquired

Differential Diagnosis

• Heart failure

• Atelectasis

• Aspiration

• Acute respiratory distress syndrome (ARDS)

• Pulmonary thromboembolism

• Pulmonary hemorrhage

• Drug reactions

Diagnosis

Laboratory Tests

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

• Arterial blood gases help define illness severity and the need for assisted ventilation

• 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

Imaging Studies

• Radiographic findings

  • Nonspecific

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

Diagnostic Procedures

• With suspected HAP, secretions obtained by spontaneous expectoration, sputum induction, nasotracheal suctioning and endotracheal aspiration in a patient who subsequently requires mechanical ventilation should be cultured

• For patients with suspected VAP, endotracheal aspiration using a sterile suction catheter with semi-quantitative cultures of lower respiratory tract secretions is the recommended method of evaluation

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 guidelines separate patients by disease severity

• Duration ...