Key Facts

Pneumonia is an acute lower respiratory tract infection causing inflammation and consolidation of the lung parenchyma. It remains a major cause of morbidity and mortality, particularly in the elderly, immunocompromised, and those with chronic diseases.

Epidemiology

• Incidence: 5-11 per 1,000 adults per year in the UK
• ~300,000 adults diagnosed annually in the UK
• ~29,000 deaths per year in England and Wales from pneumonia
• 6th leading cause of death in the UK
• 5-10% mortality for hospitalised CAP; <1% for community-managed CAP

Aetiology

Community-acquired pneumonia (CAP):

• Streptococcus pneumoniae (30-40%) — most common
• Haemophilus influenzae (5-10%)
• Mycoplasma pneumoniae (5-15%, epidemic every 4 years)
• Staphylococcus aureus (1-5%, post-influenza)
• Legionella pneumophila (2-5%)
• Chlamydophila pneumoniae, Moraxella catarrhalis, respiratory viruses

Hospital-acquired pneumonia (HAP):

• Gram-negative bacilli (E. coli, Klebsiella, Pseudomonas)
• Staphylococcus aureus (including MRSA)
• Anaerobes

Pathophysiology

• Pathogen reaches alveoli via inhalation, aspiration, or haematogenous spread
• Alveolar macrophages and neutrophils mount inflammatory response
• Exudate fills alveoli → consolidation → impaired gas exchange
• Four pathological stages: congestion → red hepatisation → grey hepatisation → resolution
• Complications: parapneumonic effusion, empyema, lung abscess, ARDS, sepsis

Typical Presentation

• Cough (productive with purulent or rusty sputum)
• Fever and rigors
• Pleuritic chest pain
• Breathlessness
• Malaise and myalgia

Clinical Signs

• Pyrexia (>38°C)
• Tachypnoea, tachycardia
• Reduced chest expansion on affected side
• Dull percussion note
• Bronchial breathing over consolidation
• Increased tactile vocal fremitus
• Coarse crackles

Atypical Presentations

• Elderly: confusion, falls, functional decline without fever
• Immunocompromised: indolent course, atypical organisms
• Atypical pneumonia: dry cough, headache, myalgia, extrapulmonary features

Red Flags

• CURB-65 score ≥3 (severe pneumonia)
• SpO₂ <92% or PaO₂ <8 kPa
• Bilateral or multilobar involvement
• Systolic BP <90 mmHg
• Confusion (new onset)
• Age >65 years
• Significant comorbidities
• Failure to respond to initial antibiotics within 48-72 hours

Bedside

• Pulse oximetry: SpO₂ on air
• ABG: if SpO₂ <92% or severe pneumonia
• Urinary antigens: pneumococcal and Legionella (moderate-severe CAP)
• Sputum sample: MC&S before antibiotics if possible

Bloods

• FBC: leucocytosis (or leucopenia in severe sepsis)
• CRP: elevated; useful for monitoring response
• U&Es: urea (CURB-65 component), renal function
• LFTs: baseline; abnormal in Legionella, Mycoplasma
• Blood cultures: x2 before antibiotics in moderate-severe
• Procalcitonin: may guide antibiotic duration
• HIV test: consider in all pneumonia patients aged 15-59 (NICE)

Imaging

• Chest X-ray: within 4 hours of admission — lobar consolidation, air bronchograms, parapneumonic effusion
• Follow-up CXR at 6 weeks: confirm resolution, exclude underlying malignancy (especially smokers >50 years)
• CT chest: if non-resolving, complicated, or alternative diagnosis suspected

Special Tests

• Pleural fluid aspiration and analysis: if significant effusion (pH, glucose, protein, LDH, MC&S, cytology)
• Bronchoscopy with BAL: if immunocompromised, non-resolving, or unusual organism suspected
• Atypical serology: Mycoplasma IgM, Chlamydophila, Legionella if clinical suspicion

Non-pharmacological

• Oxygen therapy (target SpO₂ 94-98%, or 88-92% if at risk of hypercapnia)
• IV fluids if dehydrated or unable to take oral
• Chest physiotherapy for sputum clearance
• VTE prophylaxis for inpatients (enoxaparin 40mg SC OD)

Pharmacological

NICE CG191 — empirical antibiotics for CAP:

Low severity (CURB-65 0-1, treat in community):

• Amoxicillin 500mg TDS for 5 days
• If penicillin allergic: doxycycline 200mg loading then 100mg OD, or clarithromycin 500mg BD

Moderate severity (CURB-65 2, consider hospital):

• Amoxicillin 500mg TDS PO + clarithromycin 500mg BD PO for 5 days
• If penicillin allergic: doxycycline 200mg then 100mg OD

High severity (CURB-65 3-5, hospital/ICU):

• Co-amoxiclav 1.2g IV TDS + clarithromycin 500mg IV BD
• Or piperacillin-tazobactam 4.5g IV TDS + clarithromycin 500mg IV BD if very severe
• Step down to oral when improving (typically 48-72 hours)

Specific organisms:

• Legionella: clarithromycin/azithromycin ± rifampicin (notify PHE)
• MRSA: vancomycin or linezolid
• Pseudomonas: piperacillin-tazobactam or meropenem

Surgical/Interventional

• Chest drain: for empyema or large complicated parapneumonic effusion
• CT-guided drainage: for lung abscess not responding to antibiotics

Referral Criteria

• CURB-65 ≥2: hospital admission
• CURB-65 ≥3: ICU assessment
• Non-resolving pneumonia at 6 weeks: urgent CXR, consider CT and respiratory referral
• Recurrent pneumonia in same lobe: bronchoscopy to exclude obstruction

• Community-managed CAP: mortality <1%
• Hospitalised CAP: mortality 5-10%
• ICU-admitted CAP: mortality 25-50%
• 30-day mortality by CURB-65: score 0 (~0.7%), 1 (~3.2%), 2 (~13%), 3 (~17%), 4 (~41.5%), 5 (~57%)
• Pneumococcal bacteraemia increases mortality 2-3 fold
• Most patients show clinical improvement within 48-72 hours of appropriate antibiotics
• CXR changes may take 6-8 weeks to resolve completely
• Long-term: pneumonia survivors have increased cardiovascular risk for 1-2 years post-event

CURB-65 Score

Management by CURB-65 Score

Light's Criteria (Exudative Effusion)