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Pneumonia

Pneumonia is an acute LRTI that leads to fluid and blood cells leaking into the alveoli. This causes lung tissue to become consolidated, therefore impairing gas exchange. It's classified into:

  • CAP - Developed outside hospital

  • HAP - Developed > 48hrs after hospital admission

  • Aspiration

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Lobar pneumonia - Heart, Lung and Blood Institute

Risk factors for it include:

  • Elderly

  • Smoking

  • Co-morbidities e.g. asthma, cystic fibrosis, COPD, DM, HF

  • Unsafe swallow e.g. post-stroke, myasthenia gravis, MND

  • Immunocompromised e.g. HIV


Complications - Sepsis, Pleural effusion, Empyema - pus in pleural space, Lung abscess


Differentials - COPD, Asthma, Pulmonary oedema, Bronchiectasis, PE, Lung ca.


Causes

The most common cause of it is Streptococcus pneumoniae (50%). Other common causes are Haemophilus influenzae (20%) and Pseudomonas aeruginosa.


Atypical pneumonia - This is where the causative organisms can’t be cultured in the normal way or detected with a gram stain. These organisms don’t respond to penicillins, but can be treated with macrolides, fluoroquinolones, or tetracyclines. The 5 causes of this are - Legions of Psittaci MCQ:

  • Legions - legionella (infected water/air)

  • Psitacci - chlamydia psittaci (infected birds)

  • Mycoplasma pneumoniae (“target lesions” rash)

  • Chlamydydophila pneumoniae

  • Q fever (coxiella burnetii) (animal exposure)


Fungal pneumonia - Most common in immunocompromised patients e.g. HIV/AIDS. Treated with Co-trimoxazole.


CURB65 Severity Score

This is used to assess the severity of a CAP.

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Interpretation of the Score:

  • 0-1 = Outpatient care

  • 2 = Consider inpatient admission

  • 3+ = Inpatient admission with consideration for ICU if score 4/5


Investigations

  • Basic obs (RR, BP, O2)

  • Bloods - FBC (WCC), U&Es (Urea), LFTs, CRP

  • Sputum and blood cultures if febrile

  • Urine - Testing for legionella/pneumococcal antigens

  • CXR - Consolidation, Lobar/multi-lobar cavitation, Pleural effusion

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AP chest X-ray of a 76 year old woman, who developed cough and labored breathing. - Mikael Häggström

Management

Mild - Oral Amoxicillin TDS for 5 days (Macrolide/doxycycline if pen allergic)


Moderate/severe - Amoxicillin + Macrolide for 7-10 days


N.B. If treatment is unsuccessful or the patient is pen allergic, the Amoxicillin can be switched out for Metronidazole.




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