VOL 48: NOVEMBER • NOVEMBRE 2002 Canadian Family Physician • Le Médecin de famille canadien 1773
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défi clinique
défi clinique
T
his article discusses the current management of community-acquired pneumonia based on Canadian guidelines for initial management of community-acquired pneumonia from the Canadian Infectious Diseases Society and the Canadian Thoracic Society.1Who gets community-acquired pneumonia?
Anyone can get community-acquired pneumonia (CAP), but incidence rates are highest at the extremes of life. People between 4 and 45 years old have a 1/1000 chance of getting CAP. Between ages 46 and 65, the rate increases to almost 3/1000 people and then rises exponentially to as high as 17/1000 in those older than 65. Dementia, alcoholism, congestive heart failure, chronic obstructive pulmonary disease (COPD), and overcrowding are some of the factors
that increase the risk of developing pneumonia.
Causes of pneumonia There are more than 100 microbial causes of CAP. In most cases, no specific signs, symptoms, or laboratory or imaging features define a particular cause. Therefore, physicians should take an empiric approach to treat- ment based on the likeli- hood of specific pathogens, the severity of disease, and certain risk factors.
How do I diagnose CAP?
Patients presenting with fever, new cough producing
purulent sputum, and focal abnormalities on chest exami- nation should be suspected of having pneumonia. The reliability of history and physical examination alone, however, has not been prospectively tested and remains unknown. No combination of symptoms or signs allows pneumonia to be definitively diagnosed or excluded. If patients have normal vital signs and normal findings on physical examination, the proba- bility of their having pneumonia is low, and no further examination is needed (level III evidence).2
Should I order tests?
A chest radiogram is the standard way of confirming CAP and is recommended for routine evaluation of patients suspected of having the disease. Unless a patient looks sick (ie, heart rate > 100/min, respiratory rate > 24 breaths/min, and oral temperature > 38°C) or has comor- bid disease or radiographic evidence of risk factors for poor outcome (pleural effusion, multilobar disease, cavi- tary disease), routine labo- ratory assessment is not recommended, provided patients are ambulatory.
Patients sent to an emer- gency department should have complete blood count, electrolyte level, and liver and renal function tests, and oxygen saturation should be measured. Oxygen satu- ration levels can be used in the prediction rule devel- oped by Fine et al3 that has been prospectively validated for determining risk of mor- tality (level III evidence).
Just the Berries
Management of community-acquired pneumonia
Evidence-based update
Meyer Balter, MD, FRCPC
“Just the Berries” for Family Physicians originated at St Martha’s Regional Hospital in 1991 as a newsletter for members of the Department of Family Medicine. Its pur- pose was to provide useful, practical, and current informa- tion to busy family physicians. It is now distributed by the Medical Society of Nova Scotia to all family physicians in Nova Scotia. Topics discussed are suggested by family physicians and, in many cases, articles are researched and written by family physicians.
Just the Berries has been available on the Internet for sev- eral years. You can find it at www.theberries.ns.ca. Visit the site and browse the Archives and the Berries of the Week.
We are always looking for articles on topics of interest to family physicians. If you are interested in contributing an article, contact us through the site. Articles should be short (350 to 1200 words), must be referenced, and must include levels of evidence and the resources searched for the data.
All articles will be peer reviewed before publication.
Dr Balter is an Associate Professor of Medicine at the University of Toronto in Ontario.
1774 Canadian Family Physician • Le Médecin de famille canadien VOL 48: NOVEMBER • NOVEMBRE 2002 VOL 48: NOVEMBER • NOVEMBRE 2002 Canadian Family Physician • Le Médecin de famille canadien 1775
Should I send off a sputum sample?
There are some difficulties with use of sputum samples in outpatient settings. Many patients, especially elderly patients, cannot provide a sample. Sputum samples must be promptly (within 1 to 2 hours) transported to a laboratory; this is extremely difficult in outpa- tient settings. Finally, identifying an adequate sample containing more than 25 squamous epithelial cells per low-power field requires specially trained staff who are normally unavailable in community laboratories. In routine clinical practice, causative pathogens are found in < 25% of CAP cases and lead to a change in therapy in < 10% of cases (level III evidence).4
For most patients treated as outpatients, no spe- cific microbiologic investigations are recommended.
Exceptions include circumstances where infections with Mycobacterium tuberculosis, Pneumocystis cari- nii, or endemic fungi are suspected and where direct staining of sputum would be diagnostic.
How do the 2000 guidelines differ from the 1993 guidelines?
Simplified modifying factors. Many comorbid conditions considered in the 1993 guidelines (eg, congestive heart failure, renal failure, diabetes) are no longer important for choosing specific therapy for CAP (level IV evidence).5 Their importance now lies in their contribution to the pneumonia score that helps determine site of care. The main modifying fac- tors to consider include presence of COPD, recent use of antibiotics, and risk of aspiration.
Site of care. Physicians can use validated predic- tion rules to assess the likelihood of mortality in CAP patients (level III evidence).3 Although not neces- sarily tested for determining which patients can be safely treated as outpatients, the prediction rules do help guide decisions because patients with low risk of mortality can usually be treated as outpatients. An overall pneumonia-specific severity-of-illness score is cumbersome to calculate and probably not useful in outpatient settings. Low-risk patients can be identi- fied quickly in the office, however, and can be treated as outpatients assuming that their social situations make this feasible.
Low-risk patients. Low-risk patients:
• are younger than 50 years;
• have no neoplastic, cerebrovascular, renal, or liver diseases and no congestive heart failure; and
• have normal mental status and vital signs (pulse
<125 beats/min, respiratory rate <30/min, systolic
blood pressure >90 mm Hg, and body temperature above 35°C and below 40°C).
Antimicrobial therapy. Macrolides or fluoroquino- lones can be an important part of initial antimicrobial therapy. The bacterial organisms responsible for most CAP cases (Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella spe- cies, and Haemophilus influenzae) are usually suscep- tible to these two classes of medication. Inclusion of a macrolide or fluoroquinolone in initial empiric treat- ment of CAP is associated with improved survival rates (level III evidence).6
How do I treat CAP patients?
Treatments listed here are based on level IV evidence.5 Outpatients with no modifying factors. Treatment of choice is a macrolide (erythromycin, azithromycin, or clarithromycin). For patients intolerant of or aller- gic to macrolides, doxycycline is a second choice.
Outpatients with modifying factors. Patients with COPD who have not had antibiotics or oral steroids within the past 3 months: Because of the increased risk of H influenzae (not sensitive to erythromycin), extended-spectrum macrolides (azithromycin or clar- ithromycin) are recommended. Doxycycline is again a second choice for patients allergic to or intolerant of macrolides.
Patients with COPD who have had antibiotics or oral steroids within the past 3 months: Because these patients are at increased risk of infection with Gram- negative rods along with the more common CAP pathogens, respiratory fluoroquinolones (levofloxa- cin, moxifloxacin, or gatifloxacin) are recommended.
An alternative regimen is a macrolide combined with either amoxicillin-clavulanate or a second-generation cephalosporin (eg, cefuroxime, cefprozil).
Suspected macroaspiration: For patients with peri- ods of decreased consciousness (due to seizures, drug overdoses, alcohol consumption, or neurologic diseases affecting the swallowing mechanism), anti- biotics with enhanced activity against anaerobes should be considered. Amoxicillin-clavulanate with or without a macrolide is the first choice. An appropri- ate alternative would be a third-generation fluoroqui- nolone plus either metronidazole or clindamycin.
Nursing home residents: Because these patients are at risk of enteric Gram-negative rod infections in addition to more common pathogens, first choice of treatment is a respiratory fluoroquinolone alone or amoxicillin-clavulanate combined with a macrolide. A
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défi clinique
1774 Canadian Family Physician • Le Médecin de famille canadien VOL 48: NOVEMBER • NOVEMBRE 2002 VOL 48: NOVEMBER • NOVEMBRE 2002 Canadian Family Physician • Le Médecin de famille canadien 1775
second-generation cephalosporin with a macrolide is an alternative.
Patients hospitalized on medical wards. Treatment is directed at bacteremic pneumococcal pneumonia as well as infection with H influenzae, enteric Gram- negative bacilli, or severe atypical infections (legionella, chlamydia). Monotherapy with a respiratory fluoroqui- nolone is the first choice. An alternative regimen is a macrolide combined with a second-, third-, or fourth- generation cephalosporin.
Conclusion
An empiric approach to CAP therapy is recommended.
Physicians should consider:
• confirming the diagnosis with a chest radiogram;
• testing all patients for S pneumoniae and atypical infections (legionella, mycoplasma, chlamydia);
• specific comorbid illnesses, especially COPD and a predisposition to aspiration;
• determining site of care (outpatient, inpatient, or nursing home); and
• where the pneumonia was acquired (community at large or nursing home).
Acknowledgment
I thank Dr Dennis Bowie, Consultant Respirologist at the Queen Elizabeth II Health Sciences Centre in Halifax, NS, for reviewing the draft of this article.
References
1. Canadian Infectious Diseases Society, Canadian Thoracic Society. Canadian guide- lines for the initial management of community-acquired pneumonia. Clin Infect Dis 2000;31:383-421.
2. Metlay JP, Kapoor WN, Fine MJ. Does this patient have community-acquired pneumonia? Diagnosing pneumonia by history and physical examination. JAMA 1997;278:1440-5.
3. Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia.
JAMA 1997;336:243-50.
4. Woodhead MA, Arrowsmith J, Chamberlain-Webber R, Wooding S, Williams I.
The value of routine microbial investigation in community-acquired pneumonia.
Respir Med 1991;85:313-7.
5. Mandell LA, Marrie TJ, Grossman RF, Chow AW, Hyland RH. Canadian guidelines for the initial management of community-acquired pneumonia: an evidence-based update by the Canadian Infectious Diseases Society and the Canadian Thoracic Society. The Canadian Community-Acquired Pneumonia Working Group. Clin Infect Dis 2000;31:383-421.
6. Houck PM, MacLehose RF, Niederman MS, Lowery JK. Empiric antibiotic therapy and mortality among medicare pneumonia inpatients in 10 western states:
1993, 1995 and 1997. Chest 2001;119:1420-6.
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