Community-Acquired Pneumonia

MARK LOEB, M.D., Assistant Professor, McMaster University, Hamilton, Canada

Questions Addressed

• What are the effects of antibiotics in outpatient settings?
• What are the effects of treatments in people admitted to the hospital?
• What are the effects of treatments in people in intensive care?
• What are the effects of guidelines?
• What are the effects of preventive interventions?

Summary of Interventions Treatment Likely to be beneficial Prompt administration of antibiotics in people severely ill with community-acquired pneumonia Unknown effectiveness Bottle blowing Specific combinations of antibiotics in intensive care settings Guidelines for treating pneumonia (for clinical outcomes) Unlikely to be beneficial New antibiotics versus older antibiotics in outpatient settings, unless microbes are resistant to older drugs New antibiotics versus older antibiotics in the hospital, unless microbes are resistant to older drugs Intravenous antibiotics versus oral antibiotics in immunocompetent people in the hospital without a life-threatening illness Prevention Beneficial Pneumococcal vaccine in immunocompetent adults Likely to be beneficial Influenza vaccine in elderly people Unknown effectiveness Pneumococcal vaccine in chronically ill, immunosuppressed, or elderly people Related topics covered in Clinical Evidence Antivirals for influenza To be covered in future issues of Clinical Evidence Other antiviral treatments

Definition Community-acquired pneumonia is pneumonia contracted in the community rather than in the hospital.

Incidence/Prevalence In the northern hemisphere, community-acquired pneumonia affects about 12 per 1,000 people a year, particularly during winter and at the extremes of age (incidence: <1 year of age, 30 to 50 per 1,000 a year; 15 to 45 years of age, 1 to 5 per 1,000 a year; 60 to 70 years of age, 10 to 20 per 1,000 a year; 71 to 85 years of age, 50 per 1,000 a year).^1-6

Etiology/Risk Factors More than 100 microorganisms have been implicated in community-acquired pneumonia, but most cases are caused by Streptococcus pneumoniae.^4-7 Smoking is probably an important risk factor.⁸

Prognosis Severity varies from mild to life-threatening illness within days of the onset of symptoms. One systematic review (search date 1995, 33,148 people) of prognosis studies for community-acquired pneumonia found overall mortality to be 13.7 percent, ranging from 5.1 percent for ambulant people to 36.5 percent for people requiring intensive care.⁹ The
following prognostic factors were significantly associated with mortality: male sex (overall risk [OR]: 1.3; 95 percent confidence interval [CI]: 1.2 to 1.4); pleuritic chest pain (OR: 0.5; 95 percent CI: 0.3 to 0.8 [i.e., lower mortality]); hypothermia (OR: 5; 95 percent CI: 2.4 to 10.4); systolic hypotension (OR: 4.8; 95 percent CI: 2.8 to 8.3); tachypnea (OR: 2.9; 95 percent CI: 1.7 to 4.9); diabetes mellitus (OR: 1.3; 95 percent CI: 1.1 to 1.5); neoplastic disease (OR: 2.8; 95 percent CI: 2.4 to 3.1); neurologic disease (OR: 4.6; 95 percent CI: 2.3 to 8.9); bacteremia (OR: 2.8; 95 percent CI: 2.3 to 3.6); leukopenia (OR: 2.5; 95 percent CI: 1.6 to 3.7); and multilobar radiographic pulmonary infiltrates (OR: 3.1; 95 percent CI: 1.9 to 5.1).

Clinical Aims Treatment: to cure infection; to prevent death; to alleviate symptoms; to enable return to normal activities; and to prevent recurrence, while minimizing adverse effects of treatments.

Prevention: to prevent onset of pneumonia.

Clinical Outcomes Clinical cure (defined as return to premorbid health status); relief of symptoms; admission to hospital; complications (empyema, endocarditis, lung abscess); death; adverse effects of antibiotics.

Evidence-Based Medicine Findings

SEARCH DATE: CLINICAL EVIDENCEUPDATE SEARCH AND APPRAISAL
JULY 2001

Treatment

ANTIBIOTICS IN OUTPATIENTS

One systematic review comparing different oral antibiotics in outpatient settings has found cure or improvement in more than 90 percent of people.

ANTIBIOTICS IN HOSPITALIZED PATIENTS

Randomized controlled trials (RCTs) found no significant difference between new and older antibiotics in cure of people with community-acquired pneumonia admitted to the hospital. However, most trials were small and were designed to show equivalence between treatments rather than superiority of one over another.

INTRAVENOUS VS. ORAL ANTIBIOTICS

Two RCTs found that, in immunocompetent people admitted to the hospital who were not suffering from life-threatening illness, intravenous antibiotics were no more effective than oral antibiotics and increased the length of hospital stay.

BOTTLE BLOWING

One unblinded RCT found limited evidence that bottle blowing physiotherapy (blowing bubbles via a narrow tube inserted in water) plus early mobilization plus encouragement to regularly sit up and take deep breaths versus early mobilization alone significantly reduced hospital stay.

ANTIBIOTICS IN ICU PATIENTS

We found no RCTs comparing one combination of antibiotics versus another in intensive care units.

EARLY VS. LATE ANTIBIOTICS

Two retrospective studies found that prompt administration of antibiotics significantly improved survival.

GUIDELINES

One systematic review comparing a guideline incorporating early switch from intravenous to oral antibiotics and/or early discharge strategies versus usual care has found no significant difference in clinical outcomes.

Prevention

INFLUENZA VACCINE

One RCT found that influenza vaccine versus placebo significantly reduced the incidence of influenza in people
60 years and older. Another RCT found that intranasal live vaccine plus parenteral vaccine versus parenteral vaccine alone significantly reduced the incidence of influenza A in elderly people. Two RCTs found that the offer of vaccination of health care workers versus no offer of vaccination significantly reduced mortality in elderly people in long-term care hospitals.

PNEUMOCOCCAL VACCINE

One systematic review has found that pneumococcal vaccination versus no vaccination significantly reduces pneumococcal pneumonia in immunocompetent people, but found no significant difference between pneumococcal vaccination versus no vaccination in elderly people or people likely to have an impaired immune system.

The author has received a research grant from Bayer, and has spoken at events sponsored by Bayer, Janssen Ortho, Pfizer, and Abbott, and attended conferences sponsored by Aventis.

Adapted with permission from Loeb M. Community acquired pneumonia. Clin Evid 2002;7:1358-68.

REFERENCES

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2. Murphy TF, Henderson FW, Clyde WA, Collier AM, Denny FW. Pneumonia: an 11 year study in a pediatric practice. Am J Epidemiol 1981;113:12-21.
3. McConnochie KM, Hall CB, Barker WH. Lower respiratory tract illness in the first two years of life: epidemiologic patterns and costs in a suburban pediatric practice. Am J Public Health 1988;78:34-9.
4. Porath A, Schlaeffer F, Lieberman D. The epidemiology of community-acquired pneumonia among hospitalized adults. J Infect 1997;34:41-8.
5. Jokinen C, Heiskanen L, Juvonen H, Kallinen S, Karkola K, Korppi M, et al. Incidence of community-acquired pneumonia in the population of four municipalities in eastern Finland. Am J Epidemiol 1993;137:977-88.
6. Houston MS, Silverstein MD, Suman VJ. Risk factors for 30-day mortality in elderly patients with lower respiratory tract infection. Arch Intern Med 1997;157:2190-5.
7. Bartlett JG, Mundy LM. Community-acquired pneumonia. N Engl J Med 1995;333:1618-24.
8. Almirall J, Gonzalez CA, Balanco X, Bolibar I. Proportion of community-acquired pneumonia attributable to tobacco smoking. Chest 1999;116:375-9.
9. Fine MJ, Smith MA, Carson CA, Mutha SS, Sankey SS, Weissfeld LA, et al. Prognosis and outcomes of patients with community-acquired pneumonia: a meta-analysis. JAMA 1995;274:134-41.

This is one in a series of chapters excerpted from Clinical Evidence, published by the BMJ Publishing Group, Tavistock Square, London, United Kingdom. Clinical Evidence is published in print twice a year and is updated monthly online. The complete text for this topic, as well as additional information, is available to subscribers at www.clinicalevidence.com. This series is part of AFP's CME. See "Clinical Quiz" on page 21.