Pyopneumothorax

Pus and air in the pleural space: an empyema with a communication to the airway (bronchopleural fistula) or gas forming organisms. It is a medical and surgical emergency.

• Causes: pneumonia and lung abscess rupturing into the pleura, tuberculosis (cavity rupture), post-operative complication (after lung resection or pneumonectomy, empyema with fistula in about 2 to 5% of pneumonectomies), infected spontaneous pneumothorax or haemopneumothorax, oesophageal rupture, trauma, subphrenic abscess, and necrotising pneumonia in children (Staphylococcus aureus).
• Organisms: Streptococcus pneumoniae, Staphylococcus aureus (including methicillin resistant strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, other Gram negative bacilli, anaerobes, Mycobacterium tuberculosis, and fungi in immunosuppressed patients.
• Mortality is about 10 to 20% (higher in elderly patients, immunosuppression, post-pneumonectomy and delayed treatment).

• Fever, rigors, sweats, productive cough with purulent sputum (if fistula), pleuritic chest pain, breathlessness, weight loss and malaise.
• Signs: succussion splash, dullness with tympany over the air, reduced breath sounds, tachycardia, toxicity, and in post-pneumonectomy patients new fever, cough with serous fluid (the fistula) and drop in the fluid level.
• Differential diagnosis: lung abscess with an air fluid level, infected bulla, simple hydropneumothorax, subphrenic abscess, infected pneumatocele, tuberculous cavity with effusion and diaphragmatic hernia.
• Complications: sepsis and septic shock, respiratory failure, aspiration of pus into the healthy lung, tension pyopneumothorax, empyema necessitans (extension through the chest wall), osteomyelitis of ribs, chronic empyema with fibrothorax, and death.

• Erect chest X-ray: air fluid level with pleural line. CT chest with contrast: pleural enhancement ("split pleura sign"), loculation, fistula, underlying abscess or tumour, and bronchoscopy to locate the fistula and exclude obstruction or foreign body.
• Pleural fluid: pus, pH less than 7.2, glucose less than 2.2 mmol/L, LDH greater than 1000 U/L, Gram stain, aerobic and anaerobic culture in blood culture bottles, acid fast smear, Xpert MTB/RIF and mycobacterial culture, and amylase.
• Blood tests: full blood count, CRP, procalcitonin, creatinine, albumin, glucose, HIV test, blood cultures.
• Sputum culture and Xpert MTB/RIF; methylene blue instilled in the pleura (post-operative) or bronchoscopic instillation of dye to demonstrate a fistula.

• Immediate: oxygen, IV fluids, analgesia, and IV antibiotics at once after cultures.
• Antibiotics (IV for 2 to 4 weeks and then oral to complete at least 4 to 6 weeks, guided by drainage and clinical response):
  • Piperacillin tazobactam 4.5 g IV every 6 to 8 hours, or ceftriaxone 2 g IV daily plus metronidazole 500 mg IV every 8 hours, or co-amoxiclav 1.2 g IV every 8 hours.
  • Add vancomycin 15 to 20 mg/kg IV every 8 to 12 hours (trough 15 to 20 mg/L) or linezolid 600 mg every 12 hours for suspected methicillin resistant Staphylococcus aureus.
  • Add an anti-pseudomonal agent (cefepime 2 g every 8 hours or meropenem 1 g every 8 hours) in hospital acquired or post-operative infection.
  • Oral step down for stable patients: co-amoxiclav 625 mg three times daily, or clindamycin 300 to 450 mg four times daily with ciprofloxacin 500 to 750 mg twice daily when Gram negative organisms are involved.
  • Avoid aminoglycosides, which penetrate pus poorly.
• Drainage (the central treatment):
  • Large bore chest drain 24 to 32 French (or ultrasound guided 12 to 14 French with regular saline flushes, 20 to 30 mL every 6 to 8 hours, when pus is thin) connected to an underwater seal with the tube positioned at the dependent site.
  • Apply suction at 10 to 20 cmH2O only when the leak is small; a large fistula with suction diverts ventilation and can cause failure to oxygenate; if the leak is large and the patient is breathless, avoid suction and keep the drain at low resistance.
  • Drain slowly if the empyema is very large.
  • Intrapleural alteplase 10 mg plus dornase alfa 5 mg (each in 30 to 50 mL saline, clamped for 1 hour) twice daily for 3 days for loculated collections without a large fistula (evidence is limited when a fistula is present).
• Surgery:
  • Video assisted thoracoscopic or open decortication with fistula closure when drainage fails after 5 to 7 days, or sooner in sepsis or necrotising disease.
  • Closure of the bronchial stump or fistula with a buttress of muscle (serratus anterior or latissimus dorsi), omentum or intercostal flap; endobronchial valves or glue for patients unfit for surgery (evidence is limited).
  • Open window thoracostomy (Eloesser flap) with packing for chronic empyema with fistula in unfit patients, and Clagett procedure (open window drainage with antibiotic irrigation and later closure with muscle flap) for post-pneumonectomy empyema with fistula.
  • Thoracoplasty for chronic residual space.
  • Operative mortality about 5 to 15% (higher after pneumonectomy).
• Tuberculous pyopneumothorax: rifampicin 10 mg/kg (maximum 600 mg), isoniazid 5 mg/kg (maximum 300 mg), pyrazinamide 25 mg/kg (maximum 2 g) and ethambutol 15 mg/kg (maximum 1.2 g) daily for 2 months, then rifampicin and isoniazid daily for 7 months or more, with pyridoxine 25 to 50 mg daily, plus drainage and surgery for persistent fistula. In HIV start antiretroviral therapy within 2 to 8 weeks; with rifampicin use dolutegravir 50 mg twice daily.
• Ventilated patient with fistula: low tidal volumes (4 to 6 mL/kg), shortest inspiratory time, lowest effective pressures, early extubation, and independent lung ventilation or high frequency ventilation in refractory cases (evidence is limited).
• Supportive care: nutrition (30 to 35 kcal/kg/day with 1.2 to 1.5 g/kg/day of protein), enoxaparin 40 mg SC daily, physiotherapy, analgesia (paracetamol 1 g four times daily, ibuprofen 400 mg three times daily with food if the kidneys allow, morphine 2.5 to 5 mg as needed), and correction of anaemia and diabetes.
• Special groups:
  • Children: ceftriaxone 50 to 100 mg/kg/day (maximum 4 g) with clindamycin 10 to 13 mg/kg every 8 hours or flucloxacillin 50 mg/kg every 6 hours; early thoracoscopic debridement.
  • Pregnancy: ceftriaxone, ampicillin sulbactam, or piperacillin tazobactam; avoid fluoroquinolones, tetracyclines and, where possible, metronidazole in the first trimester.
  • HIV and immunosuppression: test for tuberculosis and fungi, and use broad cover.
  • Renal impairment: adjust piperacillin tazobactam, vancomycin and other doses.
• Red flags: sepsis, tension pyopneumothorax, large air leak, haemoptysis, empyema necessitans, failure to improve at 5 to 7 days.
• Follow up: daily review in hospital; remove the drain when drainage is less than 50 to 100 mL/day, the fluid is clear, there is no leak and the lung is expanded; chest X-ray at discharge, 2 weeks and 6 weeks; lung function and CT at 3 months for residual pleural thickening.