Pneumonia in Health Care

Curtis J. Coley II

Melissa A. Miller

EPIDEMIOLOGY

As health care and associated technology have advanced, delivery of care has expanded to include not only the traditional hospital setting but also to long- and short-term acute and chronic care settings as well as to the home. As a consequence, the concept of the traditional nosocomial infection has changed. One example of this is nosocomial pneumonia, which is now largely classified according to recommendations from the American Thoracic Society and Infectious Diseases Society of America.¹

Hospital-acquired pneumonia (HAP) is defined as pneumonia identified 48 hours or more after admission to the hospital, which was not incubating at the time of admission.
Ventilator-associated pneumonia (VAP) is defined as pneumonia in a patient who is currently intubated or who has been endotracheally intubated within the last 48 hours.
Health care-associated pneumonia (HCAP) can occur in any patient who was hospitalized in an acute care hospital for two or more days within 90 days of the infection; resided in a nursing home or long-term care facility; received intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of infection; or received hemodialysis in a clinic or hospital setting.

Pneumonia is the second most common nosocomial infection and associated with the highest potential morbidity and mortality.²^,³ HAP has been reported to occur at a rate between 5 and 10 cases per 1,000 hospital admissions, with the incidence increasing by 6- to 20-fold in mechanically ventilated patients. The incidence increases with duration of ventilation, and the risk is highest early in the hospital stay. It is estimated to be 3% per day during the first 5 days of mechanical ventilation, 2% per day during days 5 to 10, and 1% per day after this.⁴ It has been estimated that pneumonia accounts for 25% or more of nosocomial infections in the intensive care unit (ICU) and for 50% or more of antibiotics prescribed there.⁵ VAP is associated with longer length of stay in the ICU and an attributable cost of care ranging from $10,000 to over $40,000 per episode.¹ Also, VAP may lead to complications such as empyema, lung abscess, lengthy intubation times, and the need for additional procedures such as bronchoscopy and tracheostomy. Crude mortality associated with nosocomial pneumonia has been reported to be between 20% and 50% depending on the patient population under study and the infecting organism.¹^,²^,³ Increased mortality has been associated with cases complicated by bacteremia, especially with Pseudomonas and Acinetobacter species, medical (as opposed to surgical) illness, and ineffective empiric antibiotic therapy.¹

Important risk factors for HAP are often presented as those which are modifiable and those which are not.⁶

Modifiable risk factors include prolonged intubation and reintubation, oversedation, and continuous use of paralytic agents, which increase risk of aspiration. The use of H2 blockers and proton pump inhibitors for gastric acid suppression has also been suggested to increase risk.
Nonmodifiable risk factors include advanced age, low functional status, underlying illness and lung disease, impaired immunity, and a diagnosis of acute respiratory distress syndrome (ARDS).

CLINICAL PRESENTATION

In order for pneumonia to occur, there must be a shift in the balance between host defense and a pathogen’s ability to colonize and invade. Aspiration, which is common among seriously ill hospitalized patients, is the key pathogenic event, and depending on this balance, active infection may ensue. Clinical signs and symptoms may vary from patient to patient and include fever, tachypnea, increased oxygen requirement, cough, and increased production or a change in the character of sputum (including that suctioned from the endotracheal tube). In elderly patients, altered mental status may be a presenting symptom. Laboratory abnormalities may include an elevated white blood cell count with a neutrophil predominance.

Differential Diagnosis

The differential diagnosis for new pulmonary symptoms and fever in a hospitalized patient, including those receiving mechanical ventilation, is broad and includes pneumonia, aspiration pneumonitis, infectious tracheobronchitis, atelectasis, pulmonary embolism, and ARDS. Since the approach to management of each of these entities varies, it is important for the clinician to make the correct diagnosis and initiate appropriate therapy.

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