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Pneumonia

 

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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%

 

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