Continuing Education Activity

Mediastinitis is a severe and potentially life-threatening inflammation or infection that involves the mediastinum—the central compartment within the thoracic cavity. The mediastinum is bordered by the pleural sacs laterally, the thoracic outlet superiorly, and the diaphragm inferiorly. In addition, it contains vital structures such as the heart, great vessels, trachea, mainstem bronchi, esophagus, and major nerves. Mediastinitis can arise from various causes, and it is categorized into 3 main subtypes—postoperative mediastinitis, descending necrotizing mediastinitis, and fibrosing mediastinitis. Patients with mediastinitis typically present with severe chest pain, fever, and signs of systemic infection. Due to the presence of crucial structures within the mediastinum, the disease process is life-threatening and requires emergent intervention and treatment.

Diagnostic strategies involve prompt initial assessment of airway, breathing, and circulation, followed by imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) for accurate diagnosis. Initial treatment includes broad-spectrum antibiotics, later tailored based on culture results, and often requires surgical debridement. This activity offers a comprehensive overview of mediastinitis, covering its etiology, pathophysiology, clinical presentation, diagnostic strategies, and current treatment protocols. This activity provides interprofessional healthcare providers with the knowledge and skills required to manage mediastinitis effectively by emphasizing the importance of collaboration among healthcare specialists in delivering comprehensive care for patients with mediastinitis.

Objectives:

• Identify the key clinical symptoms and signs of mediastinitis to ensure prompt diagnosis.

• Implement evidence-based diagnostic strategies, including CT and MRI, to confirm the presence and extent of mediastinitis.

• Apply appropriate broad-spectrum antibiotic therapy initially and adjust based on culture results.

• Collaborate with thoracic surgeons, infectious disease specialists, and other multidisciplinary healthcare providers to develop a comprehensive treatment plan.

Introduction

Mediastinitis is a severe and potentially life-threatening inflammation or infection that involves the mediastinum. The mediastinum encompasses the space within the thoracic cavity, bordered by the pleural sacs laterally, the thoracic outlet superiorly, and the diaphragm inferiorly. The mediastinum contains many vital structures, including the heart, great vessels, trachea, mainstem bronchi, esophagus, phrenic nerve, vagus nerves, and thoracic duct. Although mediastinitis is uncommon, it should be considered in the differential diagnosis, as any infection involving these structures is life-threatening and requires immediate treatment.[1][2]

Mediastinitis has multiple etiologies, categorized into 3 subtypes—postoperative mediastinitis, descending necrotizing mediastinitis, and fibrosing mediastinitis. Postoperative mediastinitis is the most common, followed by descending necrotizing mediastinitis, both of which are typically acute and follow a more fulminant course. Fibrosing mediastinitis, the least common subtype, is a more chronic and indolent process.[3][4][5][6]

Etiology

Mediastinitis can be caused by various pathologies that breach the integrity of the mediastinal structures, including iatrogenic, traumatic, or infectious causes. Iatrogenic causes are common and typically involve complications from medical procedures, such as cardiac surgery, esophageal dilation, or endoscopic interventions, where inadvertent injury to the mediastinal tissues can introduce infection. Traumatic causes include direct physical injuries to the chest from accidents or penetrating wounds, which can disrupt the trachea or esophagus, leading to contamination of the mediastinum. Infectious causes often arise from nearby infections spreading to the mediastinum, such as in descending necrotizing mediastinitis, where infections from the oropharynx extend into the mediastinal space. Additionally, infections from other areas, such as pulmonary infections or complications from pancreatitis, can occasionally spread and cause mediastinitis.

Mediastinitis due to esophageal perforation can occur regardless of the perforation's cause, as the rupture allows gastric fluid to contaminate the mediastinum with digestive flora. This condition is often iatrogenic, accounting for 50% of cases, although it can also be spontaneous or traumatic.[7] Common causes include tracheal and/or esophageal rupture from endoscopic procedures, Boerhaave syndrome, and foreign body aspiration. Other rarer causes include direct traumatic injury, spread of pulmonary infection, and pancreatitis.[3][2][8]

Poststernotomy mediastinitis is an uncommon condition, occurring in 0.5% to 2.5% of cases.[9] Despite advances in surgical techniques, perioperative antibiotics, and guidelines aimed at preventing poststernotomy infections, the incidence of poststernotomy mediastinitis has remained consistent over the years. Notably, it is thought to be caused by the intraoperative introduction of infection or from infection of the surgical wound that seeds the mediastinum. Poststernotomy mediastinitis has also been referred to as deep sternal wound infection.[1][10]

Descending necrotizing mediastinitis, originating from oropharyngeal infections, occurs when the infection spreads from the cervical area to the mediastinum. This condition affects approximately 2% to 5% of deep neck infections, such as neck abscesses, Ludwig's angina, and other dental infections. Commonly, odontogenic or pharyngeal sources cause inflammation via the fascial planes, impacting the posterior mediastinum.[4][11]

Fibrosing mediastinitis, although believed to be idiopathic, has been associated with both infectious and noninfectious processes. Potential infectious causes include histoplasmosis and tuberculosis, linked to an immune-mediated hypersensitivity reaction.[12] Noninfectious causes include sarcoidosis, retroperitoneal fibrosis, and Riedel thyroiditis.[13]

Epidemiology

The exact incidence and prevalence of mediastinitis cases are not well documented. Postoperative mediastinitis has a relatively low incidence, ranging from 0.3% to 5%, with an average of 1% to 2% at most facilities.[14][15] Higher incidence rates have been associated with cardiac transplant surgeries, coronary artery bypass graft (CABG) with thoracic aortic surgery, and CABG with valvular surgery. Lower incidence rates have been found with isolated CABG, valvular repairs, and thoracic repairs.[14][16] 

Previously, descending necrotizing mediastinitis comprised 70% of mediastinitis cases; however, a significant decrease in incidence is observed due to advancements in imaging and antibiotics.[17] Regarding fibrosing mediastinitis, associations with a granulomatous subtype are observed, which is more frequently found in North America, where there is a higher prevalence of Histoplasma capsulatum.[13][18]

Pathophysiology

Mediastinitis is due to a breach in the mediastinal structures from an inciting incident, including a direct injury or secondary to an acute infectious process. Postoperative mediastinitis is often linked to intraoperative contamination, although infection can also spread postoperatively from an infected surgical wound into the mediastinum. Most cases are caused by gram-positive bacteria, particularly Staphylococcus aureus and coagulase-negative Staphylococcus, accounting for 60% to 80% of cases. Infections linked to S aureus frequently result from intraoperative contamination by the surgeon or surgical staff who are carriers or from the patient’s own nares. Coagulase-negative Staphylococcus, commonly found in skin flora, frequently infects surgical wounds due to its ubiquitous presence on the skin. Although S aureus and coagulase-negative Staphylococcus are the most common causes, other gram-positive and gram-negative bacteria and fungi (rarely) can also be causative agents.[10][14][19]

Descending necrotizing mediastinitis is characterized by the spread of infection from the pharynx, odontogenic sources, or cervical areas into the mediastinum. The disease can extend through the deep fascial planes and typically affects the posterior mediastinum. In addition, the disease presents with manifestations such as cellulitis, abscess formation, sepsis, and necrosis, marking a fulminant and severe course.[11] Polymicrobial infection accounts for approximately 58% of cases, with the remainder being solely gram-positive organisms, including Streptococcus and anaerobes. In patients with diabetes, Klebsiella and other gram-negative enterobacteria can be causative agents.[4]

Although the exact pathophysiology of fibrosing mediastinitis is unknown, it has been shown to have multiple variants, including a granulomatous and a non-granulomatous form, which can then be divided into either diffuse or focal distributions.[20] Some forms, especially those associated with histoplasmosis, are believed to be due to a delayed immune-mediated hypersensitivity response. Histoplasmosis and tuberculosis have been closely associated with the focal form, while the diffuse form is linked with autoimmune syndromes.[13]

History and Physical

Patients with acute mediastinitis typically appear ill and may report symptoms such as dysphagia, chest pain, fever, and respiratory distress. Obtaining a thorough history, including recent surgeries or infections, along with a comprehensive medical, travel, and social history, is crucial to assessing risk factors associated with the development of mediastinitis.

When evaluating a patient for postoperative mediastinitis, it is essential to document important risk factors such as diabetes, obesity, smoking, renal failure, and an immunocompromised state. Additionally, obtaining a detailed surgical history is critical, as patients with longer surgical times, repeated thoracic surgeries, or excessive cautery might have an increased predisposition to developing postoperative mediastinitis. Findings obtained during physical examination of patients suspected of mediastinitis often include sternal instability, wound discharge, tenderness, and pain. Mediastinitis should be considered in patients experiencing unexplained slow postoperative recovery. Although mediastinitis can present up to a year after surgery or longer, most cases occur within 30 days of the surgery.[14][15][16][19]

If descending necrotizing mediastinitis is suspected, it often indicates an inadequately treated head or neck infection that has subsequently spread to the mediastinum. In addition to the previously mentioned symptoms, these patients may present with dyspnea, and on physical examination, signs of cervical or thoracic pain with crepitus and erythema may be noted.

Fibrosing mediastinitis often progresses insidiously, leading many patients to be asymptomatic initially. When symptoms do appear, common presentations include cough, shortness of breath, pleuritic chest pain, hemoptysis, fever, or weight loss.[21] These individuals may have a history of recurrent lung infections. As the disease advances, an obstructive or compressive pattern may develop, affecting organs within the mediastinum. Patients may present with airway or vascular compromise, such as in superior vena cava syndrome. A comprehensive history, including travel history, is essential due to its association with conditions such as histoplasmosis and tuberculosis.[13]

Evaluation

In cases of suspected mediastinitis, patients should undergo a prompt primary assessment of the airway, breathing, and circulation. If necessary, resuscitative measures should be prioritized over laboratory workup and imaging. Once the patient is stabilized, obtaining critical imaging is crucial for diagnosis. While a chest radiograph may reveal signs of mediastinal widening or pneumomediastinum, it often lacks detail in showing the full extent of the disease process.[15] Comparatively, computed tomography (CT) and magnetic resonance imaging (MRI) are better diagnostic tools for evaluating mediastinitis.

Postoperative mediastinitis can be challenging to assess with imaging due to physiological changes observed postoperatively in radiographic studies. The sensitivity and specificity of CT will notably improve after 14 days following surgery.[22] Mediastinal aspiration can also be performed to aid in the diagnosis.[15][23] 

For descending necrotizing mediastinitis, imaging may reveal a widened mediastinum, increased fat density within the mediastinum, air-fluid levels indicating abscess formation, or pleural effusions often associated with mediastinitis. If the pericardium is affected, findings may include thickening, pericardial effusion, or pneumopericardium.[4] In addition, a CT of the cervical area should be obtained to identify the primary source of infection.[2]

Laboratory studies for acute mediastinitis may reveal leukocytosis, elevated C-reactive protein, and increased procalcitonin levels. Blood cultures should be obtained, especially in patients suspected of postoperative mediastinitis, as bacteremia is frequently associated with the disease.[15][23]

Fibrosis mediastinitis most commonly manifests as an infiltrative mass on CT, which distorts the mediastinal fat planes and extends into surrounding mediastinal structures. The condition can manifest as diffuse involvement or localized to a specific area. Additionally, it may present with calcifications on imaging, particularly when associated with histoplasmosis. Localized masses are often found in the hila, paratracheal, or subcarinal areas.[21] In addition, commonly present symptoms include narrowing of the tracheal, bronchial, pulmonary artery, and superior vena cava or esophagus, as well as pulmonary infiltrates, pulmonary volume loss, collapse, or hyperlucency.[24] Chest radiographs typically show abnormalities in these patients, although findings may be subtle. Mediastinal widening with distortion of the mediastinal interfaces is frequently noted. In cases where pulmonary vessel involvement leads to pulmonary hypertension, peribronchial cuffing and septal thickening may be present. Pleural effusions are less often seen.[21]

Treatment / Management

Treatment for acute mediastinitis usually focuses on the early initiation of antibiotics and surgical debridement as necessary.[3][14][25] Antibiotics should initially be broad-spectrum and subsequently tailored based on culture results.

Various surgical approaches exist for mediastinitis, ranging from minimally to maximally invasive, selected based on the extent and severity of the condition. Following surgical intervention, it is crucial to conduct repeat CT scans, closely monitor laboratory parameters, and frequently reassess the patient's clinical status to evaluate the need for further surgical intervention. Patients with mediastinitis necessitate ongoing evaluation and treatment in an intensive care unit.[2]

The exact pathogenesis of fibrosing mediastinitis remains unknown, leading to a lack of standardized treatment regimens.[13] Although evidence supporting successful medication therapies is limited, current strategies often involve immunosuppressants, corticosteroids, or antifungals due to the limited treatment options available for these patients.[20] Surgical interventions, such as decompressive procedures such as stent placement or bypasses of affected structures, should be considered for symptomatic patients.[13][26][27]

Differential Diagnosis

When evaluating a patient suspected of having mediastinitis, it is crucial to consider a comprehensive differential diagnosis, as this condition can overlap with other thoracic and systemic disorders. Accurate and prompt differentiation among these conditions is essential to ensure appropriate and timely treatment.

The differential diagnoses of mediastinitis include, but are not limited to, the following conditions:

• Coronary artery disease
• Acute coronary syndrome
• Pulmonary embolism
• Pneumothorax
• Aortic dissection
• Cellulitis
• Localized infection in the head or neck
• Tumor or mass [8][13][15]

Prognosis

Postsurgical and descending necrotizing mediastinitis are both associated with high morbidity and mortality if not treated early. They are considered life-threatening conditions, with descending necrotizing mediastinitis having a mortality rate of 20% to 40% despite current treatments.[3][2] Advancements in surgical management techniques and improved evaluation and treatment regimes have led to a reported mortality rate for postsurgical mediastinitis of 1% to 14%, an improvement from past rates of 12% to 50%.[28]

Comparatively, fibrosing mediastinitis generally carries a better prognosis when unilateral involvement is present compared to bilateral involvement.[26] However, despite its relatively slow progression, patients often succumb to recurrent pneumonia or pulmonary heart disease associated with fibrosing mediastinitis.[13]

Complications

Mediastinitis can lead to severe and potentially life-threatening complications if not promptly diagnosed and treated. Immediate intervention is crucial to mitigate these risks and improve patient outcomes.

Complications of mediastinitis may include the following:

• Pericarditis
• Myocarditis
• Recurrent pneumonia
• Lung abscess
• Pleural effusion
• Sepsis
• Obstructed airway
• Severe bleeding or hemoptysis
• Cor pulmonale
• Multiorgan failure
• Scarring and fibrosis
• Chronic pain
• Complications from surgical treatment or debridement [14][4][21]

Consultations

Managing mediastinitis often requires a multidisciplinary approach due to the complexity and potential severity of the condition. Although consultations vary depending on the subtype of mediastinitis, possible consultants are as follows: [4]

• Thoracic surgeon
• Infectious disease specialist
• Dentist
• Intensivist
• Anesthesiologist
• Otolaryngologist
• Radiologist
• Plastic surgeon

Deterrence and Patient Education

Preventing mediastinitis, particularly in individuals undergoing thoracic surgeries or invasive procedures, relies significantly on deterrence and patient education. Educating patients about adhering to preoperative and postoperative care instructions can significantly reduce the risk of infection. This includes emphasizing proper wound care, recognizing early signs of infection such as redness, swelling, or fever, and encouraging prompt medical attention if symptoms develop. Healthcare providers should emphasize the importance of hand hygiene and maintaining a clean environment to minimize infection risks. Additionally, informing patients about potential complications and the necessity of follow-up appointments ensures ongoing monitoring and early intervention if issues arise. Comprehensive patient education and adherence to preventive measures are crucial in significantly reducing the incidence of mediastinitis.

Intraoperative and postoperative measures that can reduce the incidence of mediastinitis include maintaining a complete aseptic technique and ensuring meticulous hemostasis and proper closure of the sternum. The administration of prophylactic intranasal mupirocin to S aureus carriers postoperatively can mitigate the risk of surgical site infection. In addition, topical application of bacitracin ointment on the sternotomy site after cardiac surgery can reduce the risk of mediastinitis.

Enhancing Healthcare Team Outcomes

Mediastinitis, a rare but life-threatening disease, demands a collaborative effort from an interprofessional healthcare team to ensure patient-centered care, optimize outcomes, promote patient safety, and enhance team performance. Physicians play a critical role in diagnosing and managing mediastinitis, utilizing their clinical skills in differential diagnosis, evidence-based treatment selection, and surgical interventions when necessary. Promptly obtaining necessary consults is crucial when mediastinitis is suspected, particularly from a cardiothoracic surgeon, as an emergent surgical intervention may be required. Other consultants are also vital in providing comprehensive care.

Advanced practitioners, including nurse practitioners and physician assistants, contribute by providing comprehensive assessments, monitoring patient progress, and facilitating continuity of care across different healthcare settings. Nurses are instrumental in mediastinitis care, overseeing wound management, administering medications, and educating patients and families on postoperative care protocols. Pharmacists ensure appropriate antibiotic therapy, monitor drug interactions, and educate healthcare providers on medication use and safety. Their expertise in pharmacology contributes to optimizing therapeutic outcomes while minimizing adverse effects.

Early broad-spectrum antibiotics should be initiated alongside prompt imaging, typically a CT scan.[3] After surgical intervention, intensive postoperative care is essential. While in the critical care unit, the healthcare team should closely monitor patients, as delayed healing or worsening symptoms may indicate the need for repeat surgery. Clinicians should maintain a low threshold for further treatment.[4]

The most critical aspect of improved outcomes is prevention. For surgeries, evaluating risk factors and attempting to modify them for a more favorable outcome are helpful. Sterile techniques and preventing contamination during surgery are crucial. Prophylactic antibiotics have also been shown to be beneficial.[14] Patients should receive adequate infection treatment and thorough follow-up to prevent descending necrotizing mediastinitis.

As with other thoracic surgeries, the preoperative diagnostic process involves assessing operability and resectability and devising a comprehensive reconstruction plan. Ideally, these evaluations should be conducted by multidisciplinary teams comprising thoracic surgeons, plastic surgeons, anesthesiologists, and physiotherapists.[27] Care coordination is essential in organizing services across disciplines, ensuring seamless transitions between acute care, rehabilitation, and outpatient settings. Effective coordination facilitates continuity of care, reduces hospital readmissions, and supports recovery in patients with mediastinitis.