Respiratory

Community-Acquired Pneumonia

An acute infection of the lung parenchyma acquired outside hospital that fills alveoli with inflammatory exudate and impairs gas exchange. Confirm the syndrome, assess severity and sepsis risk, and start appropriate antibiotics promptly.

In a nutshell

Community-acquired pneumonia fills alveoli and impairs gas exchange. Confirm the syndrome, score severity with CRB65 or CURB65 while using clinical judgement, start severity-appropriate antibiotics promptly, escalate sepsis or respiratory failure, and safety-net the slower recovery.

Classic presentation

Acute fever, cough, sputum, breathlessness or pleuritic pain with focal chest signs and possible hypoxaemia, although older or immunosuppressed patients may present with confusion or decompensation.

Key points

Pneumonia is alveolar consolidation, not simply airway narrowing. Focal bronchial breathing, dullness and crackles reflect fluid-filled lung.
Use CRB65 in primary care and CURB65 in hospital. CRB65 0 is low risk, 1 or 2 intermediate, and 3 or 4 high; CURB65 0 or 1 is low, 2 intermediate, and 3 to 5 high. Clinical judgement can override a reassuring score.
In hospital, establish the diagnosis and start antibiotics within 4 hours. Use oral antibiotics first line when the patient can take them and severity permits.
Adult low and moderate severity treatment is amoxicillin 500 mg three times a day for 5 days, adding clarithromycin when atypical pathogens are suspected. High severity uses co-amoxiclav plus a macrolide; levofloxacin 500 mg twice daily is an alternative for penicillin allergy with microbiology advice. See BNF and NICE NG250 for current doses and patient-specific adjustments.
Consider intravenous hydrocortisone for 4 to 7 days or until discharge in adults with high-severity CAP in hospital. Do not extend corticosteroid use to routine low- or moderate-severity disease.
Do not routinely perform microbiology in low-severity adult CAP. Consider cultures and urinary antigen tests in moderate or high severity when the results can guide treatment or de-escalation.
Reassess rapid deterioration or lack of improvement within 3 days. Do not routinely order a post-discharge chest X-ray; consider it at 6 weeks for cancer or underlying respiratory risk, persistent symptoms or unexplained weight loss.

First-line investigation

Clinical assessment plus chest X-ray in hospital, with CRB65 or CURB65 severity scoring and targeted microbiology or blood tests according to severity.

Management

Stabilise and choose the care setting

Use ABCDE, assess oxygenation and sepsis, and use CRB65 or CURB65 with clinical judgement. Refer or admit for high risk, severe physiology, complications, inability to take oral treatment or an unsafe home setting.^1,3

Confirm and start treatment

In hospital, establish the diagnosis including chest X-ray and start antibiotics within 4 hours. Use oral treatment first line when feasible and collect targeted samples according to severity.¹

Use severity-led antibiotics

Use amoxicillin for low and moderate severity, add a macrolide when atypical pathogens are suspected, and use co-amoxiclav plus a macrolide for high severity. Check BNF and local microbiology advice for allergy, interactions, renal function and resistant organisms.^1,4,6,8,9

Treat high-severity complications

Escalate sepsis, respiratory failure, shock, empyema and abscess urgently. In hospital adults with high-severity CAP, consider adjunctive corticosteroid treatment for 4 to 7 days or until discharge.^1,3,11

Reassess and safety-net

Review intravenous treatment by 48 hours, stop adult antibiotics after 5 days if clinically stable, reassess if symptoms worsen or fail to improve within 3 days, and reserve a 6-week chest X-ray for selected higher-risk or non-resolving cases.^1,2

Exam traps

A low CRB65 or CURB65 does not overrule severe hypoxaemia, shock, pleural complications or major comorbidity.
Do not use CURB65 in children; paediatric pneumonia uses age, work of breathing, oxygenation, hydration, feeding and clinical judgement.
Levofloxacin in the current NICE adult table is 500 mg twice a day for 5 days, not once a day, but it requires fluoroquinolone safety checks and microbiology advice. See BNF and NICE NG250 for the current regimen.
Do not routinely give corticosteroids for low- or moderate-severity CAP.
A persistent cough after treatment can be normal, but rapid deterioration or no improvement within 3 days requires reassessment.
Routine follow-up chest X-ray is no longer recommended for every adult discharged after pneumonia.

Illustrations

Alveolar consolidationDiagram contrasting normal air-filled alveoli with alveoli flooded by inflammatory exudate, fibrin and neutrophils in pneumonia.PassFinals · original

Community-acquired pneumonia on chest X-rayAnnotated frontal chest radiograph showing dense right upper-lobe air-space consolidation in community-acquired pneumonia.Mikael Häggström, M.D., Wikimedia Commons · CC0

Severity and treatment pathwayFlow diagram linking clinical assessment and CRB65 or CURB65 to outpatient treatment, hospital antibiotics, critical care escalation and follow-up.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.