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  1. What are common mimickers of hospital-acquired pneumonia (HAP)?

  2. Is an invasive sampling procedure necessary for accurate diagnosis?

  3. Which pathogens typically cause HAP?

  4. Which antibiotics are indicated for treatment?

  5. For how long should patients be treated?

  6. What can be done to prevent HAP?

More than 100 years ago, Sir William Osler noted the frequent mismatch between clinical and postmortem diagnoses of pneumonia. The disparity ran both ways: clinicians overdiagnosed the disease in patients without pneumonia, and failed to diagnose it in patients with demonstrable pneumonia at autopsy. Despite profound advances in the tools available to clinicians, including computed tomography scans, bronchoscopy, and advanced microbiological diagnostics, the diagnosis of hospital-acquired pneumonia (HAP), or pneumonia acquired more than 48 hours after hospital admission, continues to be elusive, partly because it has many mimickers, and partly because the population at risk tends to be very complex.

Misdiagnosis has three serious consequences: failure to treat truly infected patients early is associated with increased mortality, inappropriate use of antibiotics in uninfected patients needlessly promotes antibiotic resistant organisms including Clostridium difficile, and premature diagnostic closure delays detection and treatment of the patient's true cause of deterioration. Growing attention from legislators and quality improvement advocates has compounded the importance of accurate diagnosis. Some states now require hospitals to publicly report rates of ventilator-associated pneumonia (VAP), and some insurers have threatened to stop reimbursing hospitals for extra costs incurred due to VAP.

Health care–associated pneumonia is defined as pneumonia in a patient who has received health care as follows:

  • Hospitalization in an acute care hospital for 2 or more days within 90 days of the infection
  • Residence in a nursing home or long-term care facility
  • Administration of intravenous antibiotics, chemotherapy, or wound care within the past 30 days
  • Treatment with hemodialysis or attendance at a hospital-based clinic

These patients may present as outpatients, as general medical inpatients, or as ventilated patients in the intensive care unit. Although this chapter focuses primarily on VAP, since mechanically ventilated patients are at greater risk and better studied than other populations, the principles developed here are broadly applicable to all patients with health care–associated pneumonia.

Reported VAP rates have dropped dramatically over the past 20 years. Older literature reported VAP in 10% to 15% of ventilated patients, but more recent series report VAP in 5% or fewer of ventilated patients. The risk of VAP is primarily related to the duration of mechanical ventilation. Consequently, the risk of VAP is highest in burn and trauma units where mechanical ventilation tends to be prolonged (10.7 and 9.3 VAPs per 1000 ventilator-days in burn and trauma units, respectively), and lowest in units with fewer ventilator days per patient (2.5 VAPs per 1000 ventilator-days in medical and coronary units). On meta-analysis, an episode of VAP appears to extend intensive care length of stay by about 6 days, and doubles the risk of dying. The attributable cost of ...

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