- Community-acquired pneumonia (CAP) is an acute infection of the pulmonary parenchyma associated with a constellation of suggestive features and accompanied by the presence of an acute infiltrate demonstrable on chest radiograph—with or without supporting microbiological data—in a patient not hospitalized or residing in a long-term care facility.
- Clinical features include cough, fever, sputum production and pleuritic chest pain
- Initial site of treatment—outpatient, or inpatient in a ward or intensive care unit (ICU)—is one of the most important clinical decisions in managing patients with CAP, often determining:
- Selection and route of administering antimicrobial agents
- Intensity of medical observation, and
- Use of medical resources
- Almost all major decisions in the management of CAP depend on initial assessment of severity.
- Prognostic models such as the Pneumonia PORT Severity Index (PSI) (see Table 1) or severity of illness scores such as CURB-65 (confusion, urea nitrogen, respiratory rate, low blood pressure, age ≥ 65 years) (see Table 1A) can be used to help determine the site of care.
- Such scores should be supplemented by physician determination of subjective factors, including:
- Ability to safely and reliably take oral medication
- Availability of outpatient support resources
- Direct admission to an ICU is recommended for patients who present with 1 major or 3 of the minor criteria for severe CAP (Table 2):
- Major criteria
- Septic shock requiring vasopressors
- Acute respiratory failure requiring intubation and mechanical ventilation
- Minor criteria
- Respiratory rate ≥ 30 breaths/min
- PaO2/FiO2 ratio ≤ 250
- Multilobar infiltrates
- Uremia (blood urea nitrogen [BUN] level ≥ 20 mg/dL)
- Thrombocytopenia (platelet count < 100,000 cells/mm3)
- Leukopenia (white blood cell [WBC] count < 4000 cells/mm3)
- Hypotension requiring aggressive fluid resuscitation
- Hypothermia (core temperature, < 36°C)
- Major criteria
- Diagnostic testing should be done for specific pathogens that would significantly alter empirical management decisions of patients with CAP, when the presence of such pathogens is suspected on the basis of clinical and epidemiologic clues:
- These tests are optional for outpatients with CAP.
- An aggressive approach to diagnostic testing is warranted in patients with severe CAP.
- The first treatment dose for hospitalized patients should be given in the emergency department (ED) as soon as possible after the diagnosis of CAP is made.
- Empiric therapy for outpatients (Table 4) should consider:
- If previously healthy and no use of antimicrobials within previous 3 months
- If presence of comorbidities or use of antimicrobials within the previous 3 months
- If from a region with a high rate of infection with macrolide-resistant S. pneumoniae
- Empiric therapy for inpatients (Table 4) should consider:
- In medical wards:
- Prior antimicrobials within the past three months?
- In ICU:
- Is Pseudomonas or community-acquired methicillin-resistant S. aureus (CA-MRSA) infection an issue?
- β-Lactam allergy?
- In medical wards:
- Recommendations are generally for a class of antibiotics rather than for a specific drug, unless outcome data clearly favor one drug.
- More potent drugs are given preference because they may decrease the risk of selecting for antibiotic resistance.
- Patients with CAP should be treated for a minimum of 5 days, should be afebrile for 48-72 hours, and should have no more than one CAP-associated sign of clinical instability before stopping therapy. Longer durations of therapy may be needed if initial therapy was not active against the identified pathogen or if complicated by extrapulmonary infection such as meningitis or endocarditis or associated with bacteremia.
- Prevention of CAP:
- Inactivated influenza vaccine* for persons age > 50 years, others at risk for influenza complications, household contacts of high-risk persons, and healthcare workers as recommended by the Advisory Committee on Immunization Practices (ACIP), Centers for Disease Control and Prevention.
- Intranasal live attenuated vaccine* for certain persons age 2-49 years without chronic underlying diseases, including immunodeficiency, asthma, or chronic medical conditions.
- Healthcare workers in inpatient, outpatient, or long-term care facilities should receive annual immunization.
- Pneumococcal polysaccharide vaccine* for persons age ≥ 65 years and those with selected high-risk concurrent diseases, according to ACIP guidelines.
- Smoking cessation should be a goal, particularly for hospitalized patients with CAP.
* In the United States, check http://www.cdc.gov/flu/professionals/index.htm for interim recommendations about influenza vaccination during the 2012-2013 season.
Diagnosis and Assessment of Disease
Table 1A. CURB-65 Severity Scores for CAP
Table 2. Criteria for Severe CAPa
|Respiratory ratec ≥ 30 breaths/min|
|PaO2/FiO2 ratioc < 250|
|Uremia (BUN level > 20 mg/dL)|
|Leukopeniad (WBC count < 4000 cells/mm3)|
|Thrombocytopenia (platelet count < 100,000 cells/mm3)|
|Hypothermia (core temperature < 36°C)|
|Hypotension requiring aggressive fluid resuscitation|
|Invasive mechanical ventilation|
|Septic shock with the need for vasopressors|
b Other criteria to consider include hypoglycemia (in nondiabetic patients), acute alcoholism/alcoholic withdrawal, hyponatremia, unexplained metabolic acidosis or elevated lactate level, cirrhosis, and asplenia.
c A need for noninvasive ventilation can substitute for a respiratory rate > 30 breaths/min or a PaO2/FiO2 ratio < 250.
d As a result of infection alone.