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Pneumonia is a common disease that requires a deep understanding of pathophysiology, epidemiology, and pharmacology to properly manage.
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Diagnostic strategies for pneumonia range from simple to highly complex depending on disease severity and likelihood of altering the empiric antibiotic regimen.
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Pneumonia management plans are tailored to each individual patient encounter and incorporate knowledge of health care setting, pathogen type, and risk factors for antibiotic resistance.
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Complications from
Community-acquired Pneumonia and Hospital-acquired Pneumonia
Section snippets
Key points
Pathophysiology
Pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and gram-negative bacilli typically enter the lower respiratory tract through aspiration of oropharyngeal secretions. Microaspiration can occur on a regular basis, even in healthy individuals and particularly during sleep, but progression to pneumonia is rare. Progression largely depends on the inoculum of pathogenic bacteria, volume of aspirate, frequency of aspiration, and virulence of aspirated bacteria relative to the host
Epidemiology
Pneumonia remains a leading cause of hospitalization and death worldwide. In 2015, pneumonia was the eighth leading cause of death in the United States,1 the fourth leading cause of death worldwide, and leading cause of death in low-income countries.7 However, the true incidence of CAP is likely underestimated. Patients with mild infections are less likely to seek medical attention and diagnosis may therefore go unrecognized.
Clinical presentation
The classic or typical presentation of pneumonia is characterized by the acute onset of infectious lower respiratory tract symptoms in conjunction with consistent radiographic findings. Fever, cough, pleurisy, dyspnea, and increased sputum production are common symptoms of pneumonia. In many patients, the presentation of pneumonia can be atypical and characterized predominantly by nonrespiratory symptoms such as malaise, myalgia, confusion, and diarrhea. In elderly individuals, this type of
Imaging
Radiographic evidence of parenchymal lung involvement is needed to establish the diagnosis of pneumonia. The radiographic appearance of pneumonia can be highly variable (Fig. 1). Although computed tomography (CT) is the gold standard for detection of pulmonary infiltrates, plain chest radiographs are more frequently obtained, especially in the outpatient setting. Although CT imaging can elucidate more specific findings than plain chest radiography (see Figs. 1D–F), it also exposes patients to
Severity Scores
Severity scoring indices seek to standardize the decision to treat patients with CAP in the outpatient versus inpatient settings by predicting mortality. Determination of disease severity is often the first branch point in the management algorithm for CAP (Fig. 3). The PSI (Pneumonia Severity Index) and CURB-65 (confusion, urea nitrogen, respiratory rate, blood pressure, age ≥ 65 years) scoring systems are the most widely used of these tools. The PSI includes 20 different variables and may be
Complications
Complications of pneumonia frequently occur. Although not all cases of pneumonia require pulmonary consultation, when complicating factors are evident at the time of initial presentation or arise during treatment, consultation with a pulmonary specialist should be considered (Box 1).
Parapneumonic effusions frequently complicate pneumonia. Most of these are sterile inflammatory exudates and do not require a change in management. However, when microorganisms transit into the pleural space, a more
Prevention
For pneumonia prevention, behavioral risk factors such as smoking and alcoholism should be addressed. Vaccines for influenza and S pneumoniae are routinely used in select patient populations. Annual influenza vaccination is recommended in all individuals more than 6 months of age with priority given to older adults, immunocompromised patients, those with medical comorbidities, and health care workers.57
Conjugate (PCV13) and polysaccharide (PPSV23) vaccines against S pneumonia are available.
Outcomes
Mortality from CAP in the ambulatory, inpatient, and ICU settings is approximately 5%, 15%, and 36%, respectively.61 Overall mortality is approximately 10%, with half of the deaths occurring after hospital discharge.62 Gram-negative organisms and S aureus have the highest mortalities.61 Thirty-day readmission rates are between 7% and 18% and result from both recurrent pneumonia as well as exacerbations of preexisting comorbidities.63, 64, 65 Patients who survive beyond 30 days have
Summary
Although pneumonia is a commonly encountered problem in clinical practice, variability in presentation, causative organism, and severity make appropriate diagnosis and treatment extremely challenging. There have been many recent advances in diagnostic techniques such as PCR testing and point-of-care ultrasonography, but recommendations for antimicrobial treatment are largely unchanged in the last decade. Particular attention should be paid to multidrug resistance and development of
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Disclosure: The authors have no financial conflicts of interest.