Community Acquired Pneumonia in Adults
- Risk factors for CAP include:
- Age over 50 years, asthma, smoking, pre-existing COPD, DM, CRF, CCF, alcoholism, liver disease, neoplasia, stroke, seizures, aspiration, immunosuppression, institutionalisation, indigenous.
Johnson P, Irving L et al. Community-acquired pneumonia. MJA 2002; 176:341-347 [Reference]
- Note that a normal CXR in a bed-ridden patient with suspected pneumonia does not rule it out (NPV 65%) and so CT may be indicated to confirm.
Esayag Y, Nikitin I, Bar-Ziv J et al. Diagnostic value of chest radiographs in bedridden patients suspected of having pneumonia. Am J Med 2010;123:88.e1-88.e6. [Reference]
- Most common organism is Strep pneumoniae + causes most severe illness and deaths, especially in the elderly. Also Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella and H.influenzae (usually in COPD)
- Note rapid urinary antigen tests available for Strep pneumonia and Legionella, recommended in moderate to severe CAP.
- ‘Red flags’ for severe illness mandating admission include RR > 30/min, SBP < 90 mmHg, SaO2 < 92%, acute confusion, pH < 7.35, PaO2 < 60 mmHg and multilobar involvement on CXR.
- Australian-derived severity scoring system for use when CAP is confirmed on CXR, dichotomoised for patients more than 50 years or ≤ 50 yr, is known as SMART-COP, and is scored out of 11.
- A score of 3-4 gives a 1:8 risk of needing intensive respiratory or vasopressor support (IRVS).
- SMART-COP score ≥ 5 gives a 1:3 risk needing IRVS = severe CAP.
- Better predicts need for IRVS / ICU than the Pneumonia Severity Index (PSI) or CURB-65 score, which are more heavily dependent of age and co-morbid illness in predicting 30-day mortality.
Charles P, Wolfe R, Whitby M et al. SMART-COP: A tool for predicting the need for intensive respiratory or vasopressor support in community acquired pneumonia. Clin Infect Dis 2008;47:375-84. [Reference]
- Alternative scoring system is the 5-point CURB-65 score, with one point for each of Confusion, Urea > 7 mmol/l, Resp rate ≥ 30/min, Blood pressure low (SBP < 90 mmHg or DBP ≤ 60 mmHg), age ≥ 65 yr.
- Score 4 = 41.5%, and score 5 = 57% mortality or need for ICU.
- Score 0 or 1 = 0.7% and 3.2% mortality respectively.
- Thus score 0 or 1 patients could be treated at home, score 2 patients need hospital assessment and ≥ 3 are considered severe. Score ≥ 4 need referral to ICU.
Lim WS et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003;58:377-82. [Reference]
- Give empiric antibiotic treatment after 2 sets of blood cultures from separate venepuncture sites if severe (5-10% yield), and sputum if rapidly available (do not delay treatment to collect sputum, as yield ≤ 40% only).
- Mild CAP:
- Give amoxicillin 1 g PO 8-hourly for 5-7 days. Or if Mycoplasma pneumoniae, Chlamydophila pneumoniae or Legionella is suspected, use doxycycline 200 mg PO for first dose then 100 mg PO daily for 5 days instead, or clarithromycin 250 mg PO bd f or 5-7 days.
- Patients who fail to improve by 48 hours of amoxicillin PO should have doxycycline or clarithromycin added to their regime.
- If history of immediate hypersensitivity to penicillin, give doxycycline or moxifloxacin 400 mg PO daily, depending on local practice.
- Moderate severity CAP:
- Patients requiring hospital admission, give benzyl penicillin 1.2 g IV 6-hourly until significant improvement then change to amoxicillin 1 g PO 8-hourly for 7 days, plus either doxycycline 100 mg PO 12-hourly for 7 days or clarithromycin 500 mg PO 12-hourly for 7 days.
- Add gentamicin 5 mg/kg IV daily (assuming normal renal function) if Gram-negative bacilli are identified in blood or sputum. Alternatively, change the benzyl penicillin to ceftriaxone 1 g daily IV.
- If patient has immediate hypersensitivity to penicillin, substitute ceftriaxone 1 g daily IV for the penicillin, or use moxifloxacin 400 mg PO daily monotherapy as a single drug.
- Tropical areas, if the patient has risk factors for meliodosis (diabetes / alcohol / CRF / lung disease), give ceftriaxone 2 g daily IV plus gentamicin 5 mg/kg IV as a single dose.
- For both moderate and severe CAP admitted to hospital, consider use of oseltamivir 75 mg BD PO, particularly in ‘flu season.
- Severe CAP (SMART-COP score ≥ 5):
- Refer to HDU / ICU.
- Give ceftriaxone 1 g IV daily; or benzyl penicillin 1.2 g IV 4-hourly with gentamicin 5 mg/kg IV daily, plus with either azithromycin 500 mg IV daily.
- If significant renal impairment or penicillin allergy, use moxifloxacin 400 mg IV daily with azithromycin.
- Severe tropical pneumonia:
- Where Burkholderia pseudomallei (melioidosis) or Acinetobacter baumannii are prevalent, give meropenem 1 g IV 8-hourly plus azithromycin 500 mg IV daily.
Therapeutic Guidelines Ltd. Therapeutic Guidelines. Antibiotic; Version 14, 2010:221-258. [Reference]
- In HIV patients, pneumocystis jiroveci (carinii) pneumonia is the commonest AIDS-defining illness and cause of death. Also TB has 100-fold increased relative risk, and can not be excluded on CXR findings alone.
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: S27-72. [Reference] [Website]