Mediastinitis

Synonym: Mediastinal infection

This is inflammation and infection affecting the mediastinum and its pleura. It is a life-threatening condition and requires urgent surgical and medical intervention to treat it. It may occur due to pathology affecting structures within the mediastinum, or infection descending from the oropharynx, when it is known as descending necrotising mediastinitis. Its most common causes are oesophageal rupture, or following cardiothoracic surgical intervention. Descending necrotising mediastinitis comes about because of the descent of infection in the fascial planes surrounding the oropharynx (the so-called parapharyngeal spaces). There is usually a polymicrobial infection with organisms such as Staphylococci, Streptococci, Bacteroides, Fusobacterium and Peptostreptococci.¹

The rate of mediastinitis following cardiothoracic surgery is around 1%.² There are no population-based figures for the incidence of mediastinitis following oesophageal rupture, which may occur as a spontaneous phenomenon, following ingestion of a foreign body, or rarely as a complication of endoscopy. It is a relatively rare phenomenon in patients who have not undergone surgery. In the antibiotic era, descending necrotising mediastinitis is exceedingly rare, but is still seen in some developing countries as a complication of head and neck infections.¹

Risk factors¹

• Commoner in men
• Commoner in middle age
• Commoner in diabetics
• Commoner in immunocompromised
• Commoner among drug users

• Oesophageal perforation due to foreign body ingestion
• Spontaneous oesophageal perforation
• Iatrogenic oesophageal perforation due to:
  • Endotracheal intubation
  • Bronchoscopy
  • Cardiothoracic surgery
  • Upper GI endoscopy
• Descending necrotising mediastinitis due to:
  • Pharyngitis
  • Tonsillitis and peritonsillar abscess
  • Otitis media
  • Sinusitis
  • Dental abscess
  • Sialadenitis
• Mediastinal infection with TB or fungi (incredibly rare)

The symptoms can be of gradual onset and sufferers may have been unwell for a few days before presentation to their GP or emergency department. There may be a history of:

Symptoms

• Fever and/or rigors
• Shortness of breath
• Retrosternal chest pain, usually pleuritic, that may radiate to the neck or upper 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 occur due to the onset of systemic sepsis.

Signs

• Systemically unwell
• Fever
• Oedema and/or erythema of neck and face
• Crepitus may affect skin of 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.

• Pulmonary embolism (on basis of symptoms)
• Myocardial infarction (on basis of symptoms)
• Pneumomediastinum³
• Mediastinal tumour and/or superior vena cava syndrome
• Cellulitis of the neck
• Necrotising fasciitis affecting the neck
• Pneumonia ± empyema or lung abscess
• Mediastinal tuberculosis
• Fibrosing mediastinitis (rare fibrotic reaction to granulomatous diseases such as histoplasmosis).

• White cell count often elevated with neutrophils predominating
• Blood cultures may reveal septicaemia
• Swabs should be taken of any obvious sources of sepsis in the mouth or neck tissues
• ABGs – ? significant hypoxia
• X-ray of the neck and chest – widening of the precervical, retropharyngeal and pre/paratracheal soft tissues with linear air shadows and/or fluid levels
• CXR – can show lower lobe consolidation and pleural effusion
• CT of thorax – can better delineate mediastinal abnormalities
• CT of neck/head may find evidence of source of descending infection
• MRI of head, neck and thorax are increasingly popular to diagnose and delineate the underlying cause of the condition.

• Patients with mediastinitis can be critically ill so initial management should focus on protecting the airway, maintaining adequate oxygenation with supplementary oxygen, adequate ventilation and vigorous intravenous fluid resuscitation.
• Where the patient has significant and worsening hypoxia, intubation and artificial ventilation may be required – seek senior anaesthetic/medical/A&E advice.
• Intubation is likely to be difficult to achieve if there is swelling of the cervical tissues 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.
• High-dose intravenous antibiotics – usually a combination of broad-spectrum cephalosporins and metronidazole; microbiological advice may be necessary on the most appropriate antimicrobial agent(s), due to the polymicrobial nature of the infection.
• 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.
• Surgery usually consists of urgent thoracotomy or access via a cervical approach; drainage of pus and necrotic material with tissue debridement, plus closure of any oesophageal rupture, or drainage of any cervical infective focus.⁴
• Patients are often severely ill and require management on intensive care.

• Overwhelming sepsis leading to multi-organ failure and death
• Respiratory failure leading to death
• Pericarditis
• Secondary pneumonia
• Lung abscess
• Empyema
• Pneumomediastinum, pneumoperitoneum and pneumothorax causing significant haemodynamic compromise.

Mortality is high and up to 50% in some series. Minimum reported mortality is in the order of 20%.¹