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Infectious Disease and Microbiology - Mediastinitis
Mediastinitis is a serious infection involving the mediastinum, the central compartment of the thoracic cavity. It may present as acute or chronic disease. Acute mediastinitis is a life-threatening condition often resulting from esophageal perforation, cardiothoracic surgery, trauma, or spread from nearby infections such as those of the head and neck. A particularly severe form is descending necrotizing mediastinitis, where infection spreads rapidly from the oropharynx into the chest. Chronic mediastinitis is less common and is typically associated with granulomatous diseases such as tuberculosis or histoplasmosis, or with retained foreign bodies.
Currently, most cases of mediastinitis occur as complications following cardiac surgery, especially after sternotomy. The incidence of post-surgical mediastinitis ranges from approximately 0.4% to 5%. Despite advances in surgical techniques and infection control, the incidence has remained stable due to increasing numbers of elderly and immunocompromised patients undergoing complex procedures. Risk factors include diabetes mellitus, obesity, chronic lung disease, prolonged surgical time, reoperation, and vascular comorbidities.
The pathophysiology involves invasion of the mediastinum by pathogens, leading to intense inflammation, fibrin deposition, and formation of abscesses. Infection can spread rapidly through fascial planes, creating extensive tissue damage and dead space beneath the sternum. Acute infections are usually polymicrobial. Common organisms include gram-positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis in post-surgical cases, while infections related to esophageal or oropharyngeal sources often involve gram-negative and anaerobic organisms. In severely ill patients, fungal pathogens like Candida and Aspergillus may also be involved.
Clinically, acute mediastinitis presents with fever, severe chest pain, dysphagia, and respiratory distress. Patients with esophageal perforation may also have epigastric pain. Physical findings can include a sternal click (indicating instability), crepitus due to subcutaneous air, and Hamman’s sign, a crunching sound heard over the chest. In contrast, chronic mediastinitis may initially be asymptomatic but later presents with symptoms due to compression of mediastinal structures, such as cough, dyspnea, or signs of superior vena cava syndrome.
Laboratory findings typically show leukocytosis and elevated inflammatory markers such as C-reactive protein. Blood cultures may be positive, especially in cases associated with head and neck infections. Imaging is essential for diagnosis. Chest radiographs may reveal mediastinal widening or air-fluid levels, while CT scans provide detailed visualization of fluid collections, gas, and the extent of infection. Diagnostic procedures such as CT-guided aspiration, mediastinoscopy, or thoracoscopy may be required to obtain microbiological samples.
Management of mediastinitis requires urgent and aggressive treatment. Broad-spectrum intravenous antibiotics should be initiated promptly and later tailored based on culture results. Common regimens include combinations of cephalosporins with anaerobic coverage or agents such as piperacillin-tazobactam. Coverage for MRSA may require vancomycin or linezolid. Therapy is typically prolonged, lasting several weeks.
Surgical intervention is critical and remains the cornerstone of treatment. Procedures include drainage of infected material, debridement of necrotic tissue, and sometimes more extensive approaches such as thoracotomy or video-assisted thoracic surgery. Negative pressure wound therapy may be used in postoperative cases. Supportive care, including airway management, oxygen therapy, and adequate nutrition, is essential.
The prognosis of mediastinitis is guarded, with mortality rates reaching up to 50%, especially in delayed or inadequately treated cases. Early diagnosis and prompt surgical drainage significantly improve outcomes. Complications can be severe and include sepsis, pleural empyema, sternal osteomyelitis, acute respiratory distress syndrome, thrombosis, and superior vena cava syndrome.
Mediastinitis is a serious infection involving the mediastinum, the central compartment of the thoracic cavity. It may present as acute or chronic disease. Acute mediastinitis is a life-threatening condition often resulting from esophageal perforation, cardiothoracic surgery, trauma, or spread from nearby infections such as those of the head and neck. A particularly severe form is descending necrotizing mediastinitis, where infection spreads rapidly from the oropharynx into the chest. Chronic mediastinitis is less common and is typically associated with granulomatous diseases such as tuberculosis or histoplasmosis, or with retained foreign bodies.
Currently, most cases of mediastinitis occur as complications following cardiac surgery, especially after sternotomy. The incidence of post-surgical mediastinitis ranges from approximately 0.4% to 5%. Despite advances in surgical techniques and infection control, the incidence has remained stable due to increasing numbers of elderly and immunocompromised patients undergoing complex procedures. Risk factors include diabetes mellitus, obesity, chronic lung disease, prolonged surgical time, reoperation, and vascular comorbidities.
The pathophysiology involves invasion of the mediastinum by pathogens, leading to intense inflammation, fibrin deposition, and formation of abscesses. Infection can spread rapidly through fascial planes, creating extensive tissue damage and dead space beneath the sternum. Acute infections are usually polymicrobial. Common organisms include gram-positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis in post-surgical cases, while infections related to esophageal or oropharyngeal sources often involve gram-negative and anaerobic organisms. In severely ill patients, fungal pathogens like Candida and Aspergillus may also be involved.
Clinically, acute mediastinitis presents with fever, severe chest pain, dysphagia, and respiratory distress. Patients with esophageal perforation may also have epigastric pain. Physical findings can include a sternal click (indicating instability), crepitus due to subcutaneous air, and Hamman’s sign, a crunching sound heard over the chest. In contrast, chronic mediastinitis may initially be asymptomatic but later presents with symptoms due to compression of mediastinal structures, such as cough, dyspnea, or signs of superior vena cava syndrome.
Laboratory findings typically show leukocytosis and elevated inflammatory markers such as C-reactive protein. Blood cultures may be positive, especially in cases associated with head and neck infections. Imaging is essential for diagnosis. Chest radiographs may reveal mediastinal widening or air-fluid levels, while CT scans provide detailed visualization of fluid collections, gas, and the extent of infection. Diagnostic procedures such as CT-guided aspiration, mediastinoscopy, or thoracoscopy may be required to obtain microbiological samples.
Management of mediastinitis requires urgent and aggressive treatment. Broad-spectrum intravenous antibiotics should be initiated promptly and later tailored based on culture results. Common regimens include combinations of cephalosporins with anaerobic coverage or agents such as piperacillin-tazobactam. Coverage for MRSA may require vancomycin or linezolid. Therapy is typically prolonged, lasting several weeks.
Surgical intervention is critical and remains the cornerstone of treatment. Procedures include drainage of infected material, debridement of necrotic tissue, and sometimes more extensive approaches such as thoracotomy or video-assisted thoracic surgery. Negative pressure wound therapy may be used in postoperative cases. Supportive care, including airway management, oxygen therapy, and adequate nutrition, is essential.
The prognosis of mediastinitis is guarded, with mortality rates reaching up to 50%, especially in delayed or inadequately treated cases. Early diagnosis and prompt surgical drainage significantly improve outcomes. Complications can be severe and include sepsis, pleural empyema, sternal osteomyelitis, acute respiratory distress syndrome, thrombosis, and superior vena cava syndrome.
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