Pleural Effusion & Empyema

Effusion + ongoing sepsis after pneumonia = sample the fluid — antibiotics cannot sterilise an empyema. US-guided aspiration: pH, protein/LDH (Light's criteria), glucose, culture, cytology. pH <7.2 (infected) or frank pus → chest drain in the…

BTS Pleural Disease Pathway

The pathway

1 · Suspect & image

Stony dull base + fever after pneumonia
CXR then bedside US — volume, loculation, echogenicity

2 · US-guided tap

pH (gas analyser), protein + LDH (paired serum), glucose, Gram/culture, cytology
Frank pus = empyema — diagnosis made

3 · Light's criteria

Exudate if pleural/serum protein >0.5 or LDH >0.6 or pleural LDH >2/3 ULN
Transudate → treat cause (HF, cirrhosis)

4 · Drain if indicated

pH <7.2, pus, or organisms → US-guided 12–14Fr drain
Triangle of safety, above the rib
Max ~1–1.5L first hour (re-expansion oedema)

5 · Antibiotics

Cover anaerobes: co-amoxiclav ± metronidazole (local policy)
Prolonged course (weeks) for empyema

6 · Escalate failures

Loculated + septic at 48–72h → intrapleural tPA + DNase (MIST2) or VATS
CT to check drain + anatomy

Drugs

Drug	Dose	Route	Notes
Co-amoxiclav	1.2g TDS	IV	Empyema cover incl. anaerobes — follow local policy.
Metronidazole	500mg TDS	IV	Added anaerobic cover per policy.
Alteplase (tPA) + DNase	10mg + 5mg BD ×3 days intrapleural	Intrapleural	MIST2 regimen for loculated empyema — specialist-directed.
Lidocaine 1%	Local infiltration	SC	For drain insertion.

When to escalate

pH <7.2 or pus — drain today, not tomorrow,Septic at 48–72h with loculations — respiratory + thoracic surgery,Unilateral effusion in smoker/cancer risk — cytology + CT BEFORE full drainage, pleural MDT,Massive effusion with mediastinal shift — controlled urgent drainage

Reference: BTS Pleural Disease Guideline 2023 / MIST2 (NEJM 2011)

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