Pneumonia

• • 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

Epidemiology

• • 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

Symptoms and Signs

• • Fever

  • Increase and change in character of sputum

  • Hypoxia

  • Decreased breath sounds over affected region of lung

  • Tachypnea

Laboratory Findings

• • Leukocytosis

  • Hypoxemia

Imaging Findings

• • Pulmonary infiltrate on chest film or CT scan

• • 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

• • 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

• • 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

Medications

• • Antibiotics

Treatment Monitoring

• • Clinical improvement

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

Complications

• • Empyema

  • Lung abscess

Prognosis

• • Associated mortality, 20-50%

  • Excess risk of death, 33%

Prevention

• • Avoid supine positioning

  • Prompt extubation

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

References