Overview

Mediastinitis is inflammation or infection of the mediastinum. The mediastinum is the area within the thoracic cavity, surrounded by the pleural sacs on the sides, the thoracic outlet above, and the diaphragm below. The mediastinum contains numerous essential structures such as the heart, major blood vessels, trachea, bronchi, esophagus, phrenic nerve, vagus nerves, and thoracic duct.

Even though mediastinitis is rare, it must be considered in the differential diagnosis, since any infection affecting the mentioned structures is deemed as life-threatening and needs urgent treatment.¹

Causes

Most cases of acute mediastinitis were caused by esophageal perforation and the extension of infection from retropharyngeal or odontogenic infections. Currently, due to progress in surgical techniques, the majority of mediastinitis cases arise as a complication of: 

• Endoscopic surgeries and esophageal procedures 
• Perforation from a foreign body
• Esophageal rupture
• Infection
• Pulmonary infections disseminated to the mediastinum, and post-operative complications especially after cardiac surgeries

Esophageal perforation and rupture is not a frequent problem and the risk factors are related to the problem but in children, it is highly recognisable to carry increased rates of morbidity and mortality. It can potentially and quickly cause mediastinitis, sepsis, and also multi-organ failure directing children to weak prognoses like morbidities and even death (in 9-41% of cases) despite advanced support in the intensive care unit.

As previously stated, the absence of serosa and a loose areolar connective tissue increases the risk of the oesophagus rupturing or perforating which can allow bacteria and digestive enzymes to enter the mediastinal and subphrenic spaces. This can result in mediastinitis and more serious issues such as empyema, abscess, and sepsis. Concerning the most common cause (77%), iatrogenic etiologies of mediastinitis, esophagectomy, and cases of esophagogastrectomy often experience post-operative complications that are typically life-threatening. 

Anastomotic leaks at the surgical site are the primary cause of mediastinitis. The leakage varies from being symptomless and only detectable in contrast to x-ray scans to severe occurrences with sepsis and failure of multiple organs. At present, the main reason for esophageal perforation in children is usually iatrogenic.

The initial occurrence of iatrogenic esophageal perforation was documented in a neonate in 1961 after a rigid rubber catheter was inserted for respiratory suctioning. Currently, the main reasons for this situation are endoscopic tools, oral intubation, Bougie expansion, respiratory suction devices, and nasogastric tube placement. Even though iatrogenic esophageal perforations are uncommon (0.6%), they result in mortality for 28% of children according to a report from 1987. Inserting a nasogastric tube, intubation, or nasotracheal suctioning are the top reasons for esophageal perforation in premature and low birth weight infants weighing under 1500 grams.

The thoracic oesophagus is a common site of perforation in children due to iatrogenic causes and a case series reports a higher rate of perforation in the upper third of the organ. The pharyngoesophageal junction is the most common site of perforation in neonates due to its narrowness causing potential perforation during intubation attempts. Additionally, this condition may be caused by the compressed posterior esophageal wall pressing against the cervical vertebrae when attempting to intubate children with their necks in hyperextension.²

Clinical features

Postoperative mediastinitis is typically characterised by signs such as:

• Tenderness in the area
• Wound opening 
• Heightened redness of the wound with or without pus 
• Unstable sternum (with movable edges coming together) 
• Restricted neck movements
• Difficulty opening the mouth 
• Non-purulent throat inflammation 
• Chest pulling in, and crackling sounds in the lower parts of the lungs when listened to with a stethoscope

The location of the perforation plays a crucial role in the impact it has on the patient, including manifestations of respiratory distress like increased heart rate and rapid breathing. The utilisation of additional muscles is frequently observed in instances of thoracic puncture. Additional indicators such as chest discomfort and subcutaneous emphysema commonly go along with it.

Esophageal perforation may occur in newborns who experience excessive saliva, coughing, or blueness during feeding after a challenging placement of an endotracheal tube or nasogastric tube.³

Babies may just get cranky and show expiratory grunting noises. A fever typically appears 5 days post-surgery, while local symptoms develop around 9 days post-surgery.²

In older kids, symptoms may manifest at a later time; one study found infections were typically identified 15 days after surgery. Infections caused by Nocardia, Rhodococcus, Candida species, or nontuberculous mycobacteria, may start slowly, occasionally with incubation periods lasting more than 30 days.

Infections linked to these organisms may show minimal local symptoms (such as only serosanguineous drainage), with little to no fever present.

Diagnosis

Doctors can frequently diagnose mediastinitis by assessing symptoms in patients with conditions that could lead to the condition, such as those who exhibit symptoms of mediastinitis after undergoing a chest or oesophagus procedure or who have tuberculosis or a similar slow-progressing infection.

When mediastinitis becomes acute, signs are always sufficiently acute to make physicians inclined to consider the possibility in persons who cannot relate possible causes such as patients who are drunk and cannot recall having vomited profusely or children who might have ingested a corrosive substance or a button battery.⁴

A chest x-ray and typically a CT scan are used to confirm the diagnosis. If mediastinitis occurs after median sternotomy, doctors might use a needle to extract fluid from the chest through the breastbone for examination under a microscope (aspiration biopsy).

A certain diagnosis can be achieved by conducting Gram and acid-fast stains and cultures for bacteria, mycobacteria, and fungi on specimens obtained through CT-guided aspiration.

Lab findings are expected to show an increase in white blood cells, elevated levels of neutrophils, high C-reactive protein levels, and a positive rapid antigen detection test.²

Treatment

Mediastinitis after cardiac surgery usually calls for forceful mediastinal drainage and surgical debridement.

Incision, drainage, wound packing, and antibiotics can be effective for superficial infections in the mediastinum. In cases of severe infections, debridement, mediastinal irrigation, and antimicrobial therapy may be required to remove infected and damaged tissue.

Typically, surgical debridement (accompanied by closed-tube irrigation) and systemic antimicrobial treatment are usually enough. In severe infection, it is appropriate to leave the wound open and resuturing it in the later days, secondary closure.

When treating postoperative mediastinitis, it is important to choose empiric medications based on the common pathogens linked to cardiac surgical site infections at the hospital and the patient's bacterial makeup if it is known; treatment that works against S. aureus and coagulase-negative staphylococci should be given.

It is common to use vancomycin and a third- or fourth-generation cephalosporin together as an empiric regimen. There have been no research studies done to determine the best treatment plan or length of antibiotic therapy for mediastinitis, but typically a 3 to 8-week course is advised, depending on the seriousness of the infection and bone involvement. Topical antibiotics are not recommended.

Sternal osteomyelitis can be associated with the most critical and extensive deep mediastinitis infections most commonly following surgery involving a median sternotomy. The pathogens likely to cause sternal osteomyelitis are the same as those causing mediastinitis and these include S. aureus and coagulase-negative staphylococci. Management of sternal osteomyelitis involves removing infected bone and at least four to six weeks of antibiotic treatment.^2,3

Prevention

Although placebo-controlled trials have not shown that antimicrobial prophylaxis reduces the risk of mediastinitis, it is still commonly used in the perioperative setting due to the severity of this infection. Facilities with reduced mediastinitis rates utilise:

• Strict perioperative adherence to careful aseptic technique: focus on surgical techniques such as controlling bleeding and accurately closing the sternum; interventions targeted to identify risk factors.
• Intraoperative ultraviolet, disinfection of postoperative patients, negative pressure wound therapy, selective preoperative decolonization, and chlorhexidine washes of patients who are S. aureus carriers have been recommended by some authorities to prevent such infections.³

Summary

Mediastinitis is a condition that may involve inflammation and/or infection of the mediastinum which is a central part of the body containing the heart, its vessels, and the respiratory tract. The main problems are related to the validity of their oesophagus, endoscopic procedures, and other surgical procedures; postoperative causes. It may manifest in local tenderness, chest pain, and respiratory deterioration. In terms of diagnosis, methods such as chest X-rays and CT scans are used, in addition to checking for infection markers in the body. Management entails incision and drainage as well as the use of antimicrobials as part of the debridement of the affected limb. The preventive measures should include observations of strict asepsis and ensuring that all possibilities of being in this category are eliminated. In particular, mediastinitis is an emergency, thus, early diagnosis and treatment should be compulsory.