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  • • Leading cause of death from nosocomial infection

    • Aspiration of gastric contents in patients with impaired airway protective defenses, due to intubation or level of consciousness, plays central role in pathogenesis

    • Diagnosis can be difficult to distinguish from other likely causes of postoperative or post-injury infection

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Epidemiology

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  • • Majority of cases occur outside of ICU

    • Incidence 4-7/1000 admissions

    • 13-18% of all nosocomial infections

    • 25% of ICU patients will develop pneumonia

    • 75% of critically ill patients have oropharynx colonized with pathogenic bacteria within 48 hours

    • Gram-negative bacilli predominate (Pseudomonas, E coli, Serratia, H influenzae, Enterobacter, Klebsiella, etc)

    • Risk factors include:

    • -Old age

      -Mechanical ventilation

      -Head injury

      -H2-receptor antagonists or proton pump inhibitors

      -Frequent ventilator setting changes

      -Winter months

      -Large volume aspiration of gastric contents

      -Thoracic surgery

      -Chronic lung disease

    • Intubation increases risk by 6- to 20-fold

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Symptoms and Signs

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  • • Fever

    • Increase and change in character of sputum

    • Hypoxia

    • Decreased breath sounds over affected region of lung

    • Tachypnea

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Laboratory Findings

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  • • Leukocytosis

    • Hypoxemia

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Imaging Findings

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  • • Pulmonary infiltrate on chest film or CT scan

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  • • Chest film infiltrate has positive predictive value (PPV) of 64% at best

    • Sputum Gram stain is unreliable

    • Protected brush specimen (PBS) has sensitivity of 64-100% when > 1000 CFU/mL detected on culture

    • Bronchoalveolar lavage (BAL) has sensitivity of 72-100% when > 10,000 CFU/mL detected

    • BAL cell count with < 50% polymorphonuclear leukocytes (PMNs) nearly excludes pneumonia

    • Atelectasis

    • Pulmonary embolus

    • Other likely causes of fever in patient's clinical situation

    • Lung tumor, in appropriate clinical circumstance

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  • • Chest x-ray

    • CBC

    • Sputum Gram stain and culture

    • Blood culture

    • Consider BAL or PBS to improve sensitivity and specificity

    • Serial imaging exams may be helpful to reveal evolution of infiltrate

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  • • Consider prior antibiotic exposure when choosing therapy

    • Empiric coverage must be appropriate for patient and unit endogenous flora

    • Early and appropriate antibiotic coverage is essential

    • Duration of treatment is 10-14 days with some recommending longer courses for Pseudomonas, S aureus, and Acinetobacter

    • Respiratory therapy to assist patient to clear secretions essential

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Medications

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  • • Antibiotics

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Treatment Monitoring

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  • • Clinical improvement

    • Resolution of tachypnea, hypoxemia and leukocytosis; radiographic changes often lag behind clinical improvement

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Complications

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  • • Empyema

    • Lung abscess

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Prognosis

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  • • Associated mortality, 20-50%

    • Excess risk of death, 33%

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Prevention

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  • • Avoid supine positioning

    • Prompt extubation

    • Vigorous respiratory therapy and early ambulation to preserve pulmonary clearance mechanisms

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References

Kozlow AH et al. Epidemiology and impact of aspiration pneumonia in patients undergoing surgery ...

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