Mediastinitis is an infection involving the connective mediastinal tissue that fills the interpleural spaces and surrounds the mediastinal organs. It can be acute or chronic.

Fibrosing mediastinitis

Sclerosing mediastinitis

Granulomatous mediastinitis

Acute mediastinitis (Box E1) occurs most frequently as a postoperative infection after a median sternotomy and can be a life-threatening infection. Most infections are bacterial in nature. Causes and clinical settings for mediastinitis are summarized in Table E1.

Chronic mediastinitis is a chronic form of infection in the mediastinum characterized by an invasive and compressive inflammatory infiltrate. It is mostly caused by fungi and some bacteria.

• Patients with acute mediastinitis present with acute onset of fever, tachycardia, chest pain, dysphagia, or respiratory distress. There may be signs of sternal wound infection or cellulitis and/or crepitus and edema of the chest wall.
• Patients with chronic mediastinitis are mostly asymptomatic until symptoms develop related to invasion or obstructions of structures within the mediastinum or adjacent to the mediastinum, such as cough, dyspnea, wheezing, chest pain, dysphagia, or hemoptysis. Complications of chronic or sclerosing mediastinitis include:
• Superior vena cava syndrome. Histoplasma is the most common nonmalignant cause of this syndrome, marked by edema of face, neck, and torso; neck vein distention; and headache
• Pulmonary venous or arterial obstruction
• Esophageal obstruction, cor pulmonale, constructive pericarditis
• Thoracic duct obstruction

Acute mediastinitis:

• Related to head and neck infections or esophageal perforation
  1. Anaerobic bacteria: Peptostreptococci, Veillonella, Fusobacterium, Actinomyces, Prevotella, Eubacterium, Bacteroides
  2. Aerobic bacteria: Streptococcus, Staphylococcus, Corynebacterium, Moraxella, enteric gram-negative rods
  3. Fungi: Candida albicans
• Related to cardiothoracic surgery
  1. Gram-positive bacteria: Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus, Streptococcus
  2. Gram-negative bacteria: Escherichia coli, Enterobacter, Klebsiella, Proteus, Pseudomonas, other Enterobacteriaceae
  3. Fungi: Candida albicans

Chronic mediastinitis:

• Histoplasma capsulatum, a dimorphic fungus, is the most common and can cause mediastinal granuloma or fibrosing mediastinitis. A leakage of fungal antigens from lymph nodes into the mediastinal space is believed to cause a hypersensitivity reaction and subsequent exuberant fibrotic response.
• Other: Mycobacterium tuberculosis, Nocardia, actinomycosis, aspergillosis.

For chronic mediastinitis:

• Tumors that can also cause superior vena cava syndrome (e.g., Hodgkin and non-Hodgkin lymphomas, mesothelioma)
• Sarcoidosis
• Behçet syndrome
• Mediastinal fibrosis associated with radiation
• Silicosis

• CBC with differential, C-reactive protein, and procalcitonin can point to bacterial infection.
• Obtain cultures: Aerobic and anaerobic bacteria and fungi, intraoperatively or of any purulent drainage.
• Pathologic examination: Distinguish between cancer and infection for chronic mediastinitis and allow for specific fungal stains on tissues.

Chest x-ray: Can show diffuse mediastinal widening or evidence of mediastinal abscess, including gas bubbles or fluid level. Pneumomediastinum (Fig. E1) or pneumothorax can be seen with esophageal perforation (Table E3).

Chest computed tomography (CT) (Fig. E2): Can show the same as x-ray but is more sensitive in determining degree of mediastinal involvement and may guide drainage procedures for treatment or diagnosis.

MRI may be superior to CT for sclerosing mediastinitis.

Surgery remains the gold standard treatment of mediastinitis for optimal drainage and debridement.

• Open techniques: Debridement of infected tissue and open packing of the wound with delayed closure or use of vacuum-assisted closure for acute mediastinitis
• Closed techniques: Debridement of infected tissues, closure of the sternum, and postoperative irrigation through drainage tubes for acute mediastinitis

• Intravenous antibiotics: Also a cornerstone of therapy but without surgery may fail. Broad-spectrum antibiotics should be used until cultures are finalized. Combination of piperacillin-tazobactam or meropenem plus vancomycin offers good initial coverage for acute mediastinitis. Other options include ciprofloxacin or cefepime for gram-negative rods, linezolid for gram-positive bacteria, metronidazole for anaerobic bacteria.
• Therapy is 2 to 3 wk, but some cases may require 4 to 6 wk.

There is no definitive cure for chronic fibrosing or sclerosing mediastinitis. Antifungal agents and steroids generally do not work. The goal of therapy is to palliate symptoms by relieving airway, vascular, or esophageal obstruction. Surgery in patients with extensive fibrosis has high morbidity and mortality.

Patients may need extensive wound care and possible vacuum-assisted closure and prolonged intravenous antibiotics.

• Thoracic surgeon and/or head and neck surgeon for surgery and debridement
• Infectious diseases consultant for antibiotic selection and long-term management

Histoplasma capsulatum is a dimorphic fungus found commonly in bird and bat fecal material and is most prevalent in the Ohio and Mississippi river valleys of the United States.

Antibiotic prophylaxis should be given within 60 min before incision for surgeries requiring sternotomy. Options include cefazolin 1 g intravenous (IV) if <80 kg and 2 g if >80 kg, or cefuroxime 1.5 g IV. If the patient is penicillin allergic or has a history of methicillin-resistant S. aureus (MRSA) infection or surgery is to be done in a hospital where MRSA infection is common, use vancomycin 1 g IV.