Typical
- Abrupt onset of fever, cough, pleuritc chest pain and breathlessness.
- Strep pneumoniae - 40-50% of all cases - 75% will have rusty sputum, 70% pleuritic chest pain, 30% abnormal LFT's and there is a well recognised association with herpes labialis
- Haemophilus influenzae - 5-25% (Type B accounts form 95% of human H.Inf infections)
- Staphylococcus aureus 2%
Extra-pulmonary complications of mycolasma pneumonia
- Myocarditis & pericarditis
- Erythema muliforme
- Haemolytic anaemia and throbocytopaenia
- Myalgia and arthralgia
- GI disturbances
Atypical
- More insidious over several days, with less pyrexia, less sputum and milder respiratory impairment.
- Mycoplasma pneumoniae 6% - often affects young people particularly when living in crowded conditions. 50% will show evidence of haemolysis
- Chlamydia pneumoniae 3%
- Moraxella catarrhalis
- Coxiella burnetti 1%
- Legionella 2% - often assocaited with confusion and GI symptoms
Patients showing any two of the following three criteria will have a mortaility of 20%
- RR > 30 bpm
- Diastolic bp 60 mmHg
- Urea > 7 mmol/l
Indicators of severe CAP
History
- Age > 60
- Severe concurrent illnes
- Alcoholic
Clinical examination
- AF
- Confusion
- Daistolic bp < 60 mmHg
- RR > 30
Investigations
- Urea > 7 mmoll-1
- 4*109 < WCC > 20*109
- PO2 8kPa
- Acidosis
- Serum albumin < 35 g/dl
- Mulilobular X-ray shaddowing
Microbiological features
- Bacteraemia
- Legionairre's disease
- Staphylococcus or Gram -ve infection
Investigations
- FBC - WBC almost invaribaly > 15*109 in pneumococcal pneumonia, but often normal in atypicals. Evidence of haemolysis suggests cold agglutinin formation and is present in 50% of cases of Mycoplasma.
- CXR / AGB
- U&Es - 50% of patients with pneumococcal pneumonia have deranged LFT's
- Sputum MC&S - 50% of patients with pneumococcal pneumonia will have a positive culture.
- Urine for Legionella antigen
- Initial serology for atypicals (Mycoplasma IgG/IgM - antibodies to Legionella & Chlamydia on immunofluoresence)
Practical Emergency Medicine
Treatment
Patients who do not show markers of severe disease can be treated with oral antibiotics.
Previously healthy chest
No markers of severe disease: amoxycillin
Severe disease: Benzypenicillin or amoxcillin iv (500 mg tds -> 1g qds)
Add flucloxacillin if Staph aureus suspected (e.g. influenza or measles)
Add erythomycin if Mycoplamsa pneumoniae or Legionalla suspected.
Previoulsy unhealthy chest
No markers of severe disease: Augmentin
otherwise
Community acquired: Flucloxacillin + amoxycillin or erythromycin alone.
Hospital acquired: Broad spectrum cephalosporin.
BNF 5