Community acquired pneumonia

Definition: 
Pneumonia is the inflammation of the terminal bronchioles and alveoli, characterised by consolidation of the affected part by inflammatory cells, exudate and fibrin. Pneumonia is most commonly caused by infection.

Community acquired pneumonia is defined as pneumonia presenting in the community or in the first 2 days of hospital admission. Pneumonia occurring after this time is more likely to be hospital acquired and caused by a different set of mircoorganisms.

Causes: 
The most common causes of community accquired pneumonias is streptococcus pneumoniae. (up to 60% depending on study)

Other causes include:
Haemophillus influenzae
Viral
Moraxella
and gram -ve bacteria
Staphylococcus aureus

Atypical:
Zoonotic - Chlamydia psittaci (birds), Francisella tularensis (rabbits/rodents), Coxiella Burnetii (cats, cattle, sheep)
Azoonotic- Chlamydophilia pneumoniae, Mycoplasma pneumonniae, Legionnaire's disease

Presentation: 
Fever, Cough productive of green sputum, malaise and pleuritic chest pain.

Other symptoms:
Myalgia, rigors, shaking chills, headache, abdominal pain, nausea and comiting, diarrhoea, anorexia and weight loss.

Rust/green coloured sputum - points to strep pneumoniae
Green sputum: pseudomonas haemphilus and pneumococcal species
red currant jelly sputum - points to klebsiella
Foul smelling/bad tasting sputum - points to anaerobic infections.

Signs:

• hyper or hypothermia
• Tachypnoea
• Use of accessory respiratory muscles
• Tachyacardia
• Central cyanosis
• Altered mental state
• Altered breath sounds - bronchial breathing, crackles, wheezes
• Dullness to percussion
• Pleural rub
• Lymphadenopathy
• tracheal deviation

Differential diagnosis
Acute exacerbation of COPD or Acute asthma
Non-pneumonic lower respiratory tract infection eg. acute bronchitis
Other conditions causing dyspnoea or coughing

Community management:
Diagnosis: Chest X Rays which is the gold standard in hospital is rarely availiable in the community. Diagnosis is therefore frequently dependent on history and examination of the patient.

The diagnosis is most likely if:
The symptoms present acutely/for a short duration
There are systemic symptoms and signs (eg. fever/tachycardia etc)
There are new focal chest signs

Determining how ill a patient is and whether antibiotic treatment is needed is more important than a solid diagnosis of pneumonia.

Investigations:

• Pulse oximetry
• Routine bloods such as FBC are usually not necessary
• Microbiological tests are not usually routinely needed as they take too long and don't affect acute management.
• If TB is suspected or infection does not resolve with antibiotics sputum culture may be considered
• swabs for atypical pathogens or viral causes may be considered in epidemics.
• Chest x ray is not necessary unless it affects acute management, reveiw is not satisfactory or another underlying lung pathology is suspected.

Management
Stratified by CRB-65 score AND clinical judgement

Factors to consider in managing at home or in hospital: 

Social circumstances/support

comorbid illnesses

If treating at home: 

• Give general advice- rest, drink plenty of fluids, stop smoking. 
• Antibiotics: Amoxicillin 500mg 3 times daily OR doxycycline and clarithromycin if sensitive to penicillins.
• Analgesia as needed : NSAIDs and Paracetamol, opiates with care (for CO2 retention) if needed. 
• Oxygen, fluids and nebulised saline if needed. 
• Review patient within 48 hours and refer to hospital if worsening or not improving. 
• Advise to return if not resolved in 3 weeks. 

Admitting to hospital:

In life threatening illness antibiotics should be given in the community.  (Penicillin G 1.2 g IV or 1g amoxicillin orally)

If delays in treatment/admission is expected, antibiotics may also be given in the community.

Inpatient/Hospital management:
investigations:

• Oxygen saturation, Arterial blood gases where necessary
• Bloods: Full blood count - raised white cells, CRP, Liver function tests, Urea and electrolytes (for baseline and severity scoring) , blood cultures preferably before antibiotics in moderate to severe patients.
• Chest X Ray- all patients within 4 hours.
• Microbiological tests:
• Low severity - none routinely
• Moderate: sputum sample, blood cultures before antibiotics, pneumococcus urine antigen, pleural fluid (if present), legionella investigations if indicated.
• Severe: Sputum sample or other respiratory sample, blood cultures, pneumococcal urine antigen, pleural fluid (if present), legionella investigations and atypical

Diagnosis: Primarily by chest x ray

Severity assessment:

Confusion
Urea
Respiratory Rate
Blood pressure

65 years of age or over

0-1 low severity
2 moderate
3-5 severe
And clinical judgement

Management: 

• Monitor: at least twice daily observations.
• Appropriate oxygen therapy
• Antibiotics: as soon as diagnosis is made- aim within 4 hours of arriving at the hospital.
• Mild: oral amoxicillin
• Moderate: oral amoxicillin and macrolide eg. clarithromycin
• Severe: IV coamoxiclav and clarithromycin
• Add macrolide, doxycycline or flouroquinolone if treatment fails.
• Change to oral antibiotics if improving and apyrexial for >24 hours and pick narrow spectrum antibiotics when sensitivities come back.
• Assessed for fluid requirements
• Prophylaxis for venous thromboembolism with low molecular weight heparin in immobile patients
• Nutritional support
• Teaching Airway clearance techniques if necessary
• Appropriate help in severe pneumonia
• 
  
• Reviewed within 24 hours of discharge
• CRP and Chest x ray should be repeated if patient is not improving within 3 days.
• Review at 6 weeks after discharge

http://www.brit-thoracic.org.uk/Portals/0/Guidelines/Pneumonia/CAPQuickRefGuide-web.pdf
http://emedicine.medscape.com/article/234240-overview#aw2aab6b9
http://emedicine.medscape.com/article/300157-clinical#a0256
http://www.patient.co.uk/doctor/Pneumonia.htm
http://www.thepcrj.org/journ/view_article.php?article_id=687