Pneumonia

 

­­

Definition of pneumonia

• Infection of the lung parenchyma
• Usually bacterial

 

Epidemiology of pneumonia

•  Commonest infectious cause of death in the UK and USA

• Incidence – 5-11 per 1000 per year

• Worse during autumn and winter

 

Risk factors for pneumonia

• Age
• Aspiration (of gastric contents or oral secretions)
  • Usually gram negative organisms and anaerobes
• Immunosuppression
• Alcoholism
• Diabetes
• Smoking
• COPD
  • Haemophilus influenza, Moraxella catarrhalis
• Nursing home residents

 

Presentations of pneumonia

• Cough, usually productive
• Fever
• Shortness of breath
• Pleuritic chest pain
• Non-specific features, especially in the elderly e.g. confusion, weakness, malaise
• Associated features in specific causes (e.g. headache in mycoplasma)

 

Differential diagnosis of pneumonia

• Infective exacerbation COPD
• Infective exacerbation of bronchiectasis
• Malignancy
• Empyema
• Effusion

 

Common bacterial causes of pneumonia

• Strep pneumonia
• Haemophilus influenza
• Staph aureus
• Moraxella
• Chlamydia pneumoniae
• Chlamydia psittacosis
• Aspiration (usually anaerobes)
• Mycoplasma pneumonia
  • Young people
  • Headache, malaise and cough
  • WCC can be normal
  • Cold agglutinins in 50%
    • Other complications: pericarditis, myocarditis, erythema multiforme, D&V, meningoencephalitis
  • Treatment
    • Erythromycin
      • Doxy is second line
      • Has no cell wall, so penicillins and cephalosporin are useless
• Legionella
  • Middle-aged smokers (M>F 2:1)
  • Presentation
    • Mild WCC, hyponatraemia
    • Proteinuria and haematuria
  • Investigations
    • Urinary antigen is pretty easy
    • IgG and IgM titres in urine, blood or sputum
  • Treatment
    • Erythromycin (rifampicin if allergic)

 

Other causes of pneumonia

• Viral
  • Influenza
• Fungal
  • Aspergilloma
  • Invasive aspergillosis
    • Diffuse shadowing on CXR
  • ABPA
    • High IgE and abs to aspergillus (skin prick positive)
    • CXR: perihilar infiltrates
    • Sputum: hyphae
    • Biopsy: stains with H&E (unusual for a  fungi)
    • Treatment – Antifungals. Itraconazole in ABPA
• Eosinophilic pneumonia
  • Flitting peripheral X-Ray shadows
  • Large numbers of eosinophils on BAL
  • Treat with steroids
• Tropical pulmonary eosinophilia
  • Immune reaction wuceria bancroftii
  • Patchy infiltrates on CXR and all the other systemic pneumonia things including lymphadenopathy
  • Treatment: diethylcarbamizine
• Organising pneumonia (often cryptogenic)
  • Pneumonia, which then recurs on a different place.
  • Non-specific malaise and dry cough as well
  • CT: patchy avlveolar opacities (granulation tissue)
  • Treatment: steroids

 

 

Investigation of pneumonia

• Oxygen saturations
• Bloods
  • FBC, U&Es, LFTs, Clotting, CRP
  • Cultures
  • Venous/arterial blood gas
    •  ? metabolic acidosis, respiratory failure, lactate
  • Consider HIV testing
• Urinary antigen detection
  • Legionella
  • Pneumococcal
• CXR (although changes lag behind clinical illness).
  • Repeat at 6/52 after discharge to check full resolution and no remaining lesion, i.e. underlying Ca
  • Cavitation
    • Staph aureus, klebsiella, TB, apergilloma, anaerobes, pseudomonas
    • Malignancy, Wegener’s
• Sputum culture and sensitivity
• Respiratory viral screen
• Pleural fluid culture

 

CURB-65 severity assessment score for pneumonia

• CURB-65
  • Confusion: or new AMTS<8
  • Urea: ≥ 7mmol/l
  • Respiratory Rate: ≥ 30/min
  • Blood Pressure: Systolic ≤ 90 and/or diastolic ≤60
  • Age: ≥ 65
• 4 factors gives a mortality of 83%, 3 factors 33%, 2 factors 23%, one factor 8%, no factors 2.4%
• Should not be used as a substitute for clinical judgement – can sometimes over/under-estimate severity

 

Management of pneumonia

• ABCDE
  • Oxygen: aim sats > 92% (if no risk CO2 retention)
  • Iv access and bloods/cultures/sputum cultures/viral screen
  • CXR
  • ABG
  • IV fluids
• Analgesia/anti-pyretics
• Work out CURB-65
• Antibiotics
  • Guided  by clinical scenario, severity, and local protocols
  • Consider IV if:
    • Severe pneumonia
    • Reduced GCS
    • Loss of swallow reflex
    • Impaired absorption
  • Add anaerobic cover e.g. metronidazole if:
    • Possible aspiration
    • Suspicion of abscess
  • Duration
    • 5-7 days: non-severe, uncomplicated pneumonia
    • 10 days: severe pneumonia
    • 14-21: if staphylococcal, legionella or gram-neg suspected
  • Iv to oral switch
    • As soon as possible, especially if clinical improvement and apyrexial
  • Consider reasons for treatment failure if no improvement
    • Incorrect diagnosis
    • Secondary complication
    • Inappropriate antibiotics
    • Impaired immunity
      • Systemic: hypogammaglobulinaemia, HIV, Malignancy
      • Local: Bronchiectasis, aspiration, underlying malignancy
• May need NIV
  • Should only be done in a HDU/ITU setting as high risk of proceeding to require intubation
• Consider nutritional supplementation (?NG)

 

Further management of pneumonia

• Follow-up CXR at 6 weeks
• Vaccination
  • influenza and pnemococcal

 

Complications of pneumonia

• Parapneumonic pleural effusion
• Empyema (suspect if persistent fever and WBCs in spite of 4-5d appropriate Abx therapy)
• Lung abscess
• DVT (immobility)
• Septicaemia (and thus shock) , or septic emboli
• Post-infective bronchiectasis
• Acute renal failure (likely pre-renal)

 

Prognosis of Pneumonia

• Age adjusted death rates of between 1 and 24/ 100 000
• Up to 40% of UK adults with CAP require hospital admission
• Hospital mortality varies between 5-12%

 

Click here for medical student OSCE and PACES questions about Pneumonia

Common Pneumonia exam questions for medical students, finals, OSCEs and MRCP PACES

 

Click here to download free teaching notes on Pneumonia: Pneumonia

Perfect revision for medical students, finals, OSCEs and MRCP PACES