A Wrap-Up on CAP

Monica Holmberg, PharmD, BCPS

Published Online: Thursday, January 1, 2009

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Dr. Holmberg is the pharmacy coordinator at Desert Vista Behavioral Health Center in Mesa, Arizona.

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Community-acquired pneumonia (CAP) is classified as an acute lower respiratory tract infection.¹ Of all the lower respiratory tract infections diagnosed each year, an estimated 5% to 10% are due to CAP.² It is responsible for 1.3 million hospitalizations annually in the United States, and its total yearly treatment costs are estimated to be $8.⁴ billion to $10 billion.^3,4 Worldwide, CAP represents the primary cause of death from an infectious agent and the sixth overall cause of death.² Other outcomes of CAP include increased length of hospital stay, medication toxicity, adverse drug events, microorganism resistance to antibiotics, readmissions, and changes in quality of life and patient satisfaction.⁴

Diagnosis

Although CAP affects the elderly more frequently, it is important to remember that patients of all ages are susceptible to the disease.¹ Diagnosis should be based on both the presence of clinical features (cough, fever, sputum, and pleuritic chest pain) and infiltrate on chest radiograph.⁴ Patients with CAP may describe other symptoms, such as shortness of breath, rigors, night sweats, or confusion. Additional signs include increased respiratory rate and focal chest signs, such as decreased expansion, dullness to percussion, decreased air entry, bronchial breathing, and crackles.¹

Treatment Settings

Treatment of CAP is specific to its setting (outpatients, intensive care unit [ICU] patients, and non-ICU inpatients). Location of treatment can be costly—inpatient costs for CAP are estimated to be 25 times the costs of outpatient care.⁴ Whether or not to admit a patient for inpatient treatment of CAP depends on clinical judgment, and clinicians may find it helpful to use an objective tool to assess the need for hospitalization. Either a severity-of-illness score, such as CURB-65, or a prognostic model, such as the pneumonia severity index (PSI), may help determine if a patient needs inpatient care.

• CURB-65 assesses 5 criteria: confusion; urea (blood urea nitrogen) >7 mmol/L or 20 mg/dL; respiratory rate >30 breaths/min; blood pressure <90 mm Hg systolic or 60 mm Hg diastolic; and age >65 years. If 2 or more criteria are met, the assessment is considered positive, and the patient should be considered for admission. If laboratory values are not available, an abbreviated assessment may be obtained based on the remaining 4 criteria; it is considered positive if any of the criteria are present.⁵
• PSI categorizes patients into 1 of 5 mortality risk classes based on age, gender, nursing home status, comorbidities, vital signs, laboratory tests, radiographic evaluations, and oxygenation status.^2,4 Outpatient treatment is considered appropriate for patients in class I or II. Patients in class III are recommended for shortstay or observation unit admission. Inpatient admission is recommended for patients in class IV or V.⁴

An admission to the ICU should be considered in patients on vasopressors due to septic shock or in patients requiring mechanical ventilation as a result of their respiratory failure.⁴

CAP: Identifying Its Cause

Although CAP can be caused by a wide range of organisms, specific pathogens are usually identified and associated with it. Common etiologies for outpatient CAP include Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, and respiratory viruses, such as influenza A and B, respiratory syncytial virus, and parainfluenza virus. Inpatient CAP in non-ICU patients is often due to infection with S pneumoniae, M pneumoniae, C pneumoniae, H influenzae, Legionella species, and respiratory viruses, or as a result of aspiration. Inpatient CAP in ICU patients is often associated with S pneumoniae, Staphylococcus aureus, Legionella species, gram-negative bacilli, or H influenzae.

Specific diagnostic testing (ie, sputum or blood culture) is not usually recommended for outpatient CAP; however, it may be warranted for inpatients in more critical condition.

If organisms are identified, the antibiotic regimens should be adapted to target the cultured organism as appropriate.

Drug-Resistant CAP

In recent years, drug-resistant S pneumoniae (DRSP) has made the empirical treatment of CAP more difficult. Patients at greater risk for DRSP include those who are <2 or >65 years of age, have received treatment with a beta-lactam or macrolide within the past 3 to 6 months, have alcoholism, have comorbidities, are using immunosuppressive therapies or have an immunosuppressive illness, or have had an exposure to a child in day care.⁵

CAP resulting from communityacquired methicillin-resistant S aureus (CA-MRSA) is still rare, but its incidence has been increasing lately and is expected to continue to rise. It has been found in both adults and children and seems to follow influenza. Patients with CA-MRSA have cavitary infiltrates without risk factors for aspiration. Both sputum and blood cultures are useful in diagnosis.⁴

The Pharmacist's Role

Pharmacists can play an important role in both inpatient and outpatient treatment of CAP. Areas for pharmacist intervention include:

• Monitoring antimicrobial therapy for appropriate treatment according to severity of disease
• Ensuring correct utilization of an antimicrobial agent based on patient history
• Recommending an appropriate antimicrobial agent based either on empirical therapy or in response to culture and sensitivity results
• Identifying patients in whom conversion from intravenous antibiotics to oral antibiotics may be warranted (hemodynamic stability, clinical improvement such as loss of fever, improved respiratory status, improved white blood cell count, ability to take oral medications)⁵
• Identifying patients at high risk for DRSP based on their medical history
• Counseling patients about their course of antibiotic therapy

CAP is a prevalent and potentially deadly disease, but it also is one that can be overcome by appropriate diagnosis, monitoring, and treatment. The pharmacist has the potential to participate with the medical team in both an outpatient and inpatient setting to help improve patient outcomes and restore patient quality of life.

Table (click on table for larger image)

References

1. Hoare Z, Lim W. Pneumonia: update on diagnosis and management. BMJ. 2006;332:1077-1079.
2. Armitage K, Woodhead M. New guidelines for the management of adult community-acquired pneumonia. Current Opinion in Internal Medicine. 2007;6:275-281.
3. Kanwar M, Brar N, Khatib R, Fakih G. Misdiagnosis of community-acquired pneumonia and inappropriate utilization of antibiotics: side effects of the 4-h antibiotic administration rule. Chest. 2007;131:1865-1869.
4. Mandell L, Wunderink R, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44(suppl 2):S27-S72.
5. Treatment of community-acquired pneumonia in adults. Available at: www.uptodate.com.