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Community Acquired Pneumonia (CAP)
General Points - Community Acquired Pneumonia
- Over 300 patients a year are admitted to Christchurch Hospital with CAP. It can be a severe disease with mortality of around 5%.
- Clinical features and initial investigations seldom identify a causative agent so empiric therapy based on local epidemiological data and disease severity is typically required.
- S. pneumoniae is the most common causative pathogen in CAP (approx. 50% of cases).
- Early delivery of antibiotics is one of the few factors shown to favourably influence patient outcome - SO DON'T DELAY (delays increase mortality).
Diagnosis of Community Acquired Pneumonia
Investigations for Community Acquired Pneumonia
- Refer to the description of the CURB-age score.
- All patients with severe CAP (CURB-age score 3-5) should have blood drawn for blood culture - 2 sets before antibiotics (10 mL in each bottle).
Immunocompetent patients with mild to moderate CAP (CURB-age score 0-2) and no complications do not require blood cultures to be taken. However, blood cultures should still be taken from this group of patients if they have a prosthetic device, evidence of sepsis (fever >38.5°C, hypotension etc), history of possible bacteraemia (e.g., rigors), or suspicion of staphylococcal pneumonia.
- CXR - PA and lateral.
- CBC + diff.
- Na, K, urea, creatinine, glucose.
- Sputum sample for Gram stain:
- Rinse mouth out with water prior to collection.
- Prior antibiotic usage must be recorded.
- Sputum may be refrigerated (4°C) for up to 24 hrs, but must reach the lab within 4 hours of warming to room temperature.
- Consider whether specific tests are indicated (particularly in severe cases):
- Urinary pneumococcal antigen.
- Legionella - options include sputum for PCR, urinary antigen (L. pneumophila serogroup 1 only) and serology (acute and convalescent).
- ZN stain and culture for TB.
- Stains for Pneumocystis jirovecii (previously known as P. carinii) in induced sputum.
- Oximetry (or ABGs for severe cases or where there is chronic respiratory or cardiac disease.)
- Serology is unlikely to alter clinical management and is not recommended in routine practice.
- Throat and nasopharyngeal swabs for viral PCR especially if influenza is suspected.
Additional Investigations for Community Acquired Pneumonia
- Diagnostic pleurocentesis:
- Bronchoscopy. Indications include:
- Immunosuppressed patient.
- Life-threatening pneumonia.
- Multiple CXR changes.
- Deterioration despite appropriate initial treatment.
- Contact the Respiratory Physician on call.
Management of CAP
Resuscitate
- Airway
- Breathing
- Circulation
See The ABCs.
Severity assessment, site of care, and antibiotic selection
This is an essential aspect of the initial management of patients presenting with CAP. It should be used to guide admission decision, antibiotic selection, and site of inpatient care (Ward vs ICU).
In general, clinicians are poor at identifying both high risk and low risk CAP patients. In turn they tend to under-treat severe CAP with high mortality risk and over-treat mild CAP with low mortality risk. In response there are now 2 well-validated disease severity assessment tools for CAP, based largely around prediction of mortality to aid clinician decision making. The Pneumonia Severity Index (PSI) involves a 2 step process involving over 30 clinical variables. The CURB-age score is used in Christchurch largely due to ease of use.
CURB-age Score
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CURB-age score stratifies mortality risk with 5 variables (1 point each):
- C = Confusion (MSQ 8 or less, or new disorientation).
- U = Urea >7 mmol/L.
- R = Respiratory rate >30/min.
- B = Systolic BP <90 mm Hg or diastolic BP <60 mm Hg.
- Age = ≥65 years.
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If CURB-age score 0-1 (Mild CAP):
- Mortality <2%.
- Consider outpatient management if no significant comorbidity and adequate social supports.
 Use single agent oral antibiotic. Single agent oral antibiotic - CURB-age 0-1
- amoxicillin 500 mg po three times a day
OR
- doxycycline 200 mg po on day 1
- then 100 mg po once a day
If CURB-age score 2 (Moderate CAP):
- Mortality 5-10%.
- Inpatient management.
- Dual antibiotic therapy.
Dual antibiotic therapy - CURB-age 2
- amoxicillin 1 g iv eight hourly
- then 500 mg po three times a day
AND EITHER
- doxycycline 200 mg po on day 1
- then 100 mg po once a day
OR
- azithromycin 500 mg po once a day for 3 days
- Consider early switch to oral antibiotic - see below.
If CURB-age score 3-4 (Severe CAP):
- Mortality 10-50%.
- Inpatient management.
- Dual antibiotic therapy.
Dual antibiotic therapy - CURB-age 3-4
- amoxicillin/ clavulanate 1 g/200 mg iv eight hourly then 500 mg/125 mg po three times a day
AND EITHER
- azithromycin 500 mg po once a day
OR
- clarithromycin 500 mg iv twelve hourly (for 1 or 2 doses then change to azithromycin 500 mg po once a day)
If CURB-age score 4-5 (very severe CAP):
- Consider ICU referral and wider spectrum antibiotic cover.
Wider-spectrum antibiotic cover
- amoxicillin/ clavulanate 1 g/200 mg iv eight hourly then 500 mg/125 mg po three times a day
AND
AND
- clarithromycin 500 mg iv twelve hourly
Follow clarithromycin iv with an early switch to
- azithromycin 500 mg po once a day
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Notes:
- When using clarithromycin, watch for drug interactions, e.g., warfarin.
- IV clarithromycin causes phlebitis and should be diluted in 250 mL sodium chloride 0.9% and given via a large vein over 30 minutes.
- If staphylococcal pneumonia suspected (multifocal pneumonia ± cavities) IV flucloxacillin 2 g q4h should be added to usual empiric therapy.
- If pneumonia due to Mycoplasma or Legionella species is suspected in mild/moderate CAP a macrolide should be added.
- If Legionella pneumonia is suspected and the patient's condition is deteriorating then start ciprofloxacin 750 mg q12h PO and contact Respiratory or Infectious Diseases Physician.
- If influenza diagnosed in the setting of CAP consider neuraminidase inhibitor therapy, e.g., oseltamivir if duration of symptoms is <48 hrs.
- Physiotherapy may be needed if sputum retention likely.
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Failure to respond to initial antibiotic and supportive therapy
- Consider the presence of penicillin resistant S. pneumoniae (PRSP) - consider the role of high dose penicillin.
- Alternate diagnoses.
- Resistant organism (always consider TB).
- Development of complication (e.g., complicated parapneumonic effusion/empyema).
- Alternate source of fever (e.g., drug or phlebitis).
Switch from IV to oral antibiotic therapy
Duration of IV antibiotic therapy has been shown to be the major determinant of length of hospital stay in Christchurch Hospital. Indications for switch from IV to oral:
- Clinical improvement:
- Haemodynamic stability.
- Temperature settling.
- Improved respiratory status.
- Able to tolerate oral therapy.
- Return to premorbid mental status.
Discharge planning
- Duration of therapy
- There is little scientific evidence for optimal duration of antibiotic therapy for CAP.
- Inpatient observation whilst on oral therapy in the absence of other medical issues is usually unnecessary.
- Recommendations:
- 7-10 days for uncomplicated pneumonia.
- 14-21 days for complicated disease (e.g., Legionella pneumonia, COPD, severe CAP).
At discharge:
- Appropriate oral antibiotic as above.
- Stop smoking - refer for smoking cessation programme.
- Check spirometry in all smokers and alert GP or refer to Respiratory Physician if significantly impaired.
- Instruct patient to contact their GP if they develop fever, chest pain or increasing dyspnoea.
- Follow-up should be arranged with either the GP or hospital team at 6 weeks to document recovery and exclude ongoing complications or alternate diagnoses.
- The role of the routine 6 week CXR remains uncertain. It is currently recommended locally that it should be undertaken if the patient remains unwell or has risk factors for underlying malignancy (significant smoking history, asbestos exposure). These will be funded through Community Referred Radiology.
- British Thoracic Society guidelines also include those over 50 years of age, however age alone is a controversial indication and not funded through Community Referred Radiology.
Note: CXR may take up to 3 months to clear especially in older patients and those with COPD.
Common Complications of Community Acquired Pneumonia
- Parapneumonic effusion - seen in up to 40% of cases. Should always be aspirated to exclude empyema and complicated parapneumonic effusions.
- Large simple parapneumonic effusions (>1/3 of hemi-thorax), all complicated parapneumonic effusions and all empyemas should be immediately referred to the Respiratory Service.
Other Considerations - Community Acquired Pneumonia
- Any pneumonia that doesn't resolve at usual rate - consider endobronchial obstruction, tuberculosis, or other diagnoses.
- Recurrent pneumonia in same segment - consider endobronchial obstruction, bronchiectasis, foreign body.
- Recurrent chest infections - consider immune status:
- IgG/IgA deficiency.
- Acquired Immunodeficiency Syndrome/HIV.
- Cystic fibrosis/bronchiectasis.
- Consider referral to a Respiratory Physician.
Topic Code: 1650