Purulent Pericarditis

Purulent pericarditis is bacterial (rarely fungal) infection of the pericardial space with a purulent effusion. It is uncommon in the antibiotic era (under 1% of pericarditis), but it is rapidly fatal untreated and still carries a mortality of about 20 to 40% when treated.

Spread is from a contiguous focus (pneumonia, empyema or lung abscess; most common in adults), by bacteraemia, from cardiac surgery or penetrating trauma, from a myocardial or valve ring abscess in endocarditis, from subdiaphragmatic infection, or after oesophageal perforation.

Risk factors are an existing pericardial effusion, immunosuppression, HIV infection, malignancy, alcohol use disorder, uraemia and dialysis, and chest surgery.

Usual organisms are Staphylococcus aureus, Streptococcus pneumoniae and other streptococci, Gram negative bacilli (including Haemophilus influenzae in children), anaerobes, and Neisseria meningitidis. Fungi (Candida, Aspergillus) occur in immunocompromised patients.

Tuberculous effusions can also be purulent and must be considered where tuberculosis is common.

Pathophysiology. Inflammatory exudate with fibrin and neutrophils accumulates, forms loculations and thickens the pericardium. Tamponade develops rapidly, and constrictive pericarditis follows in a substantial minority of survivors. Sepsis and organ failure add to mortality.

• Fever (often over 38.5 degrees Celsius), rigors, tachycardia, dyspnoea, and sweating. Chest pain may be absent or masked by the primary source.
• Pericardial rub (often absent), raised venous pressure, pulsus paradoxus, muffled heart sounds and hypotension when tamponade is present.
• Features of the source: pneumonia, empyema, wound infection, endocarditis.
• ECG: sinus tachycardia, low voltage and ST elevation or non-specific change. Electrical alternans in large effusions.

Red flags.

• Fever with tamponade features
• Sepsis, hypotension or lactate over 2 mmol/L
• Recent chest or cardiac surgery, trauma or oesophageal procedure
• Pneumonia or empyema with a new effusion or an enlarging cardiac silhouette
• Immunosuppression or HIV infection
• Gas within the pericardium (fistula or gas forming organism)
• Persistent fever 48 to 72 hours after drainage and antibiotics

• Blood cultures (3 sets) before antibiotics. Full blood count, CRP, procalcitonin, lactate, creatinine, liver function, HIV test.
• Echocardiography. Effusion size, fibrin strands, loculations, thick pericardium, tamponade (right atrial and ventricular collapse, respiratory variation in inflow), and endocarditis.
• CT chest. Thickened enhancing pericardium, gas, loculated collections, empyema, mediastinitis, and oesophageal or other source.
• Pericardiocentesis or surgical drainage with fluid analysis. Gram stain, aerobic and anaerobic culture, fungal culture, acid fast stain and Xpert MTB/RIF Ultra, cell count (neutrophil predominant), glucose (low), protein (high), LDH (high), adenosine deaminase, and cytology. Obtain fluid before antibiotics when the patient is stable.
• Cause workup: transoesophageal echocardiography for endocarditis, and contrast swallow or endoscopy when oesophageal rupture is possible.

Differential diagnosis.

• Viral or idiopathic pericarditis
• Tuberculous pericarditis
• Malignant, uraemic and radiation pericardial effusion
• Post-myocardial infarction and post-pericardiotomy syndromes
• Mediastinitis or sternal wound infection after surgery
• Endocarditis with a ring abscess
• Pneumonia with pleural effusion
• Myocarditis
• Sepsis from another source with pericardial effusion from heart failure
• Systemic lupus erythematosus and other autoimmune serositis

Early complete drainage plus antibiotics. Emergency.

• Drainage. Pericardiocentesis under ultrasound control for tamponade or when the effusion is free. Leave a drain and irrigate with saline several times daily. Pus is often thick and loculated, so most patients need surgical drainage: subxiphoid pericardiotomy or pericardial window, with thoracoscopic or open washout, and pericardiectomy for loculated disease, failure of drainage, persistent sepsis or developing constriction. Instillation of a fibrinolytic agent into the pericardium is used for fibrinous collections when surgery is not possible, but evidence is limited and no uniform dose is established.
• Haemodynamics. Intravenous fluid to maintain preload. Avoid diuretics and vasodilators, and avoid positive pressure ventilation where possible, because it reduces preload. Noradrenaline 0.05 microgram/kg/min intravenously, titrated to a mean pressure of 65 mm Hg, usual maximum 0.5 microgram/kg/min, for hypotension, as a bridge to drainage.
• Empirical antibiotics intravenously after blood cultures and without waiting for pericardial fluid:
  • Community acquired: vancomycin 25 to 30 mg/kg as a loading dose (maximum 3 g), then 15 to 20 mg/kg every 8 to 12 hours (usual maximum 2 g for each dose), adjusted to a trough of 15 to 20 mg/L or an AUC of 400 to 600 mg·h/L, lengthening the interval and using levels in renal impairment. Plus ceftriaxone 2 g every 24 hours.
  • Healthcare associated, post-surgical, or risk of Pseudomonas: vancomycin (25 to 30 mg/kg loading dose, maximum 3 g, then 15 to 20 mg/kg every 8 to 12 hours with levels) plus piperacillin-tazobactam 4.5 g every 6 hours (4.5 g every 8 hours at creatinine clearance 20 to 40 mL/min, and every 12 hours under 20 mL/min), or meropenem 1 g every 8 hours (1 g every 12 hours at creatinine clearance 26 to 50 mL/min, 500 mg every 12 hours at 10 to 25 mL/min, 500 mg every 24 hours under 10 mL/min).
  • Add metronidazole 500 mg every 8 hours when an anaerobic or abdominal or oesophageal source is likely.
  • Add antifungal cover for immunosuppression, prolonged hospital stay or Candida risk: caspofungin 70 mg as a loading dose, then 50 mg once daily (35 mg in moderate liver impairment).
• Directed therapy after culture: flucloxacillin 2 g every 4 hours (maximum 12 g daily) or cefazolin 2 g every 8 hours for methicillin susceptible staphylococci; benzylpenicillin 2.4 g every 4 hours or ceftriaxone for susceptible streptococci and pneumococci; vancomycin continued for methicillin resistant staphylococci; Gram negative cover by susceptibility.
• Duration. Evidence is limited. Treat for 3 to 4 weeks intravenously from effective drainage, and for 4 to 6 weeks for S. aureus bacteraemia, endocarditis, incomplete drainage or persistent fever. Candida needs at least 4 to 6 weeks.
• Specific causes. Treat the source (empyema drainage, surgery for oesophageal perforation or abscess, valve surgery for endocarditis). Where tuberculosis is possible, send fluid for Xpert and start isoniazid 5 mg/kg (maximum 300 mg), rifampicin 10 mg/kg (maximum 600 mg), pyrazinamide 25 mg/kg (maximum 2 g) and ethambutol 15 mg/kg, each orally once daily, with pyridoxine 25 mg once daily, while results are pending.
• Corticosteroids are not used for bacterial pericarditis.

Special groups. Children: ceftriaxone 50 mg/kg every 12 hours (maximum 2 g for each dose) plus vancomycin 15 mg/kg every 6 hours (maximum 2 g for each dose, levels directed), with early surgical drainage. Renal impairment: adjust piperacillin-tazobactam, meropenem and caspofungin to the creatinine clearance bands given for each drug, and adjust vancomycin to trough levels.

Monitoring. Haemodynamics, temperature, drain output and neurological state in intensive care. Daily CRP and white cell count until falling, repeat blood cultures until negative, vancomycin levels and creatinine twice weekly. Echocardiography at 48 to 72 hours, at 2 to 4 weeks, at 3 months and at 6 months for loculation and constriction.

Referral and escalation. Refer urgently to cardiothoracic surgery and infectious diseases. Escalate for tamponade, sepsis, persistent fever after drainage, constriction, or a suspected perforation or fistula.