Mediastinitis is an infection affecting the mediastinum. It can be a life-threatening condition and requires urgent surgical and medical intervention. Mediastinitis may be due to:
- Infection originating from structures within the mediastinum.
- Infection descending from the oropharynx through the fascial planes in the neck (eg the carotid space, the prevertebral space). This descending infection is known as descending necrotising mediastinitis.
- A rare fibrotic reaction to granulomatous diseases such as histoplasmosis. This is known as fibrosing mediastinitis.
- Mediastinitis is a relatively rare phenomenon in patients who have not undergone cardiothoracic surgery or another intervention. The rate of mediastinitis following cardiothoracic surgery was around 1% in one study of 10,000 patients.
- Patients who have undergone a heart transplant are at much higher risk.
- Since the introduction of antibiotics, descending necrotising mediastinitis has become rare in developed countries. In developing countries, mediastinitis is still a common complication of head and neck infections.
Mediastinitis originating from structures within the mediastinum
- Oesophageal rupture is the most common cause of mediastinitis. This may be due to:
- Blunt trauma to the chest/abdomen can cause mediastinitis.
- There may be direct spread of infection into the mediastinum from:
- Pulmonary infection.
- Osteomyelitis of the sternoclavicular junction.
- Granulomatous disease (including tuberculosis) in the mediastinal lymph nodes.
Descending necrotising mediastinitis
This may originate from:
- Tonsillitis, peritonsillar abscess and parapharyngeal abscess.[6, 7, 8]
- Otitis media.
- Dental abscess.
- Infection after head and neck surgery.
There is usually a polymicrobial infection with organisms such as Staphylococcus spp., Streptococcus spp., Bacteroides spp., Fusobacterium spp., Peptostreptococcus spp. and Pseudomonas aeruginosa. Meticillin-resistant S. aureus (MRSA) may be implicated when mediastinitis occurs after cardiothoracic surgery. Mediastinitis may also be caused by tuberculosis and fungal infections.
Onset can be insidious and patients may have been unwell for a few days before presentation to their GP or emergency department. There may be a history of:
- Recent cardiothoracic surgery or instrumentation.
- Upper GI endoscopy.
- Recent dental or oropharyngeal infection.
- Upper respiratory tract infection.
- Ingestion of a foreign body (particularly button batteries by young children, which may cause oesophageal rupture).
- Fever and/or rigors can occur.
- Shortness of breath may be present.
- Retrosternal chest pain, usually described as pleuritic, may radiate to the neck or back.
- There may be a sensation of soreness or congestion in the neck if the condition is due to descending infection.
- The patient may notice that their neck is swollen.
- Confusion or disorientation may be present due to the onset of systemic sepsis.
- There may be evidence of sternal wound infection and sternal instability post-cardiothoracic surgery.
- The patient can be systemically unwell and shocked.
- Fever may be evident.
- Oedema and/or erythema of the neck and face may be found.
- There may be crepitus of the skin of the chest and neck due to surgical emphysema.
- The mouth should be examined for evidence of pharyngeal infection or foreign bodies.
- Localised or diffuse swelling of the neck may be seen.
- Cranial nerve deficits may occur.
- Auscultation of the heart may reveal a crunching sound.
- Pulmonary embolism.
- Myocardial infarction.
- Spontaneous pneumomediastinum.
- Mediastinal tumour and/or superior vena cava syndrome.
- Cellulitis of the neck.
- Necrotising fasciitis affecting the neck.
- Pneumonia ± empyema or lung abscess.
- Mediastinal tuberculosis.
- FBC: white cell count is usually elevated.
- Blood cultures should be taken.
- Swabs of any obvious sources of sepsis in the mouth or neck tissues should be taken.
- X-ray of the neck and chest may show widening of the pre-cervical, retropharyngeal and paratracheal soft tissues. Pneumomediastinum and air-fluid levels may be seen on CXR. Mediastinal widening may be seen but is not a reliable sign.
- CXR may show lower lobe consolidation and/or pleural effusions.
- CT/MRI scan of the thorax can better delineate mediastinal abnormalities and may find evidence of the source of descending infection.
- Patients with mediastinitis can be critically ill. Initial management should focus on resuscitation, including protecting the airway, maintaining adequate oxygenation with supplementary oxygen, ensuring adequate ventilation and vigorous intravenous fluid resuscitation.
- Patients are often severely ill and require management within intensive care.
- Where the patient has significant and worsening hypoxia, intubation and artificial ventilation may be required.
- Intubation is likely to be difficult to achieve so experienced anaesthetic input may be needed; emergency cricothyroidotomy/tracheostomy may be necessary.
- The patient's respiratory status must be stabilised before sending for investigations such as CT/MRI scan.
- High-dose broad-spectrum intravenous antibiotics should be started as soon as possible.
- Broad-spectrum therapy is indicated and drugs used initially include piperacillin with vancomycin, or ceftazidime with vancomycin, or vancomycin with a quinolone and clindamycin. An aminoglycoside may be added.
- Microbiological advice may be necessary as to the most appropriate antimicrobial agent(s), due to the polymicrobial nature of the infection.
- Antibiotic regimes will be to be altered in line with results of culture results when available.
- Surgical referral is an urgent priority. Transfer to a cardiothoracic surgical centre is likely to be needed with advice from ENT surgery in cases of descending infection.
- Extensive and aggressive debridement of necrotic tissues with exploration of all mediastinal fascial spaces may be required.
- Surgery usually consists of urgent thoracotomy or access via a cervical approach. Drainage of pus and necrotic material with tissue debridement is carried out as well as closure of any oesophageal rupture, or drainage of any cervical infective focus.
- Overwhelming sepsis leading to multi-organ failure and death.
- Adult respiratory distress syndrome.
- Respiratory failure leading to death.
- Secondary pneumonia.
- Pleural effusions and empyema.
- Pneumomediastinum, pneumoperitoneum and pneumothorax.
- A recent review found an overall mortality of 11.1% (but is up to 50% in some series). In the presence of comorbid conditions, the mortality rate may be as high as 67%.
- Studies of descending necrotising mediastinitis in the last decade indicate mortality rates ranging between 11.1-34.9%.
- High clinical suspicion in susceptible individuals, early diagnosis and prompt aggressive management are the best way to reduce morbidity and mortality.[3, 6]
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- Mueller DK et al; Mediastinitis, Medscape, June 2009
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- Gerazounis M, Athanassiadi K, Kalantzi N, et al; Spontaneous pneumomediastinum: a rare benign entity. J Thorac Cardiovasc Surg. 2003 Sep 126(3):774-6.
- Chen KC, Chen JS, Kuo SW, et al; Descending necrotizing mediastinitis: a 10-year surgical experience in a single institution. J Thorac Cardiovasc Surg. 2008 Jul 136(1):191-8. Epub 2008 May 22.
- Ridder GJ, Maier W, Kinzer S, et al; Descending necrotizing mediastinitis: contemporary trends in etiology, diagnosis, Ann Surg. 2010 Mar 251(3):528-34.
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