Mediastinitis: ED-focused basics

Authors: Carling Macdonald1, Anthony Scoccimarro, MD2, and Muhammad Waseem, MD, MS1,2 (St. Georges University Grenada West Indies1; Lincoln Medical & Mental Health Center Bronx, New York2) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW Medical Center / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician at SAUSHEC)

A 54-year-old woman presents to the emergency department with shortness of breath and chest pain. She is tachycardic and febrile upon review of vital signs. On physical examination, increased fullness of her face is noted. She has a prior history of right upper lobe resection one month ago due to a lung mass. What could be her diagnosis?

What is Mediastinitis?

Mediastinitis is an infection involving the structures of the mediastinum.  The mediastinum is the space between the pleural sacs which extends from the diaphragm superiorly to the superior aperture of the thorax. In mediastinitis, the following structures can be involved: the heart and great vessels, esophagus, distal portion of the trachea and mainstem bronchi, vagus and phrenic nerves, thymus, and thoracic duct. It is a surgical emergency with potentially devastating consequences and serious threat to vital structures.

Who Gets It?

It results from either a breach in the integrity of mediastinal structures or spread to mediastinal structures from elsewhere in the body. Mediastinal infections may result from the following possible sources:

-Direct mediastinal injury (most common)

-Iatrogenic esophageal perforation

-Perforation of superior vena cava by a central venous catheter[1]

-Leakage from a migrated central venous catheter

-Hematogenous or lymphatic spread

-Infectious extension from potential spaces such as the carotid space, the prevertebral space, etc.

Traditionally, retropharyngeal or peritonsillar abscess, Ludwig’s angina, dental abscess, and other infections of the head and neck were common causes of acute mediastinitis. However, in the developed world, most cases of mediastinitis are due to a postoperative complication of cardiovascular or other thoracic surgical procedures.

Mediastinitis may be either acute or chronic. Usually, acute mediastinitis is fulminant, while chronic mediastinitis is an indolent infection. Generally, acute mediastinitis is due to a bacterial infection, and chronic mediastinitis is related to a granulomatous infection.

Acute mediastinitis can be due to esophageal perforation, cardiothoracic procedures, penetrating trauma, pneumonia, empyema, foreign body aspiration, or head and neck infections. Generally, esophageal perforation is due to iatrogenic injury. Chronic mediastinitis may follow acute mediastinitis. It can be fibrosing or granulomatous in nature, following infections, as in histoplasmosis, syphilis, tuberculosis, and coccidioidomycosis. Non-infectious granulomatous conditions such as sarcoidosis may also cause chronic mediastinitis.

Typical Presentation

The most common presentation is acute onset of fever, chest pain, dysphagia and respiratory distress. Dysphagia is characteristic of esophageal perforation. Patients with proximal perforations may present with cervical tenderness and subcutaneous emphysema, whereas distal perforation may result is abdominal symptoms which may mimic an acute abdomen. Respiratory distress may be due to pleural involvement. Bacteremia is common in postoperative mediastinitis.[2] Chest radiographs should be evaluated with care, as early signs of mediastinitis may be misinterpreted as postoperative collections of fluid and gas. It is often difficult to distinguish normal postoperative findings from superimposed infection on CT during the first few days following surgery. Generally, CT findings are nonspecific for up to the 14th postoperative day. However, after the first 2 weeks CT is more helpful in diagnosing mediastinitis.[3] Patients with chronically retained foreign bodies may be mistakenly thought to have asthma or reflux problems. The diagnosis can be delayed because symptoms may mimic many emergent conditions, such as myocardial infarction, aortic dissection, or pulmonary embolism.

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Acute mediastinitis on CT with  mediastinal gas and fluid (arrow), bilateral pleural effusions and pericardial effusion (yellow arrowheads). Image from http://www.radpod.org/2007/01/12/acute-mediastinitis/.

What is Poststernotomy Mediastinitis (PSM)?

The typical presentation is nonspecific chest pain weeks or months following sternotomy, primarily for cardiac surgery. The most common procedure is coronary artery bypass grafting (CABG), with a reported incidence of approximately 3%.[4] The most important clinical sign in PSM is painful sternal instability. However, not all patients with sternal dehiscence do have, or will develop, PSM.[5] In patients with PSM, signs of sternal wound infection or cellulitis, crepitus, and chest wall edema may be present. EKG changes are related to pericarditis or perimyocarditis and ST-segment elevation, mimicking an acute myocardial infarction.[6] Plain radiographs have limited value in post-operative mediastinitis due to post-surgical abnormalities. Usually, CT scan is required in differentiating superficial wound infections from deeper retrosternal infection. Literature supports timely initial debridement in mediastinitis patients. An initial debridement following the fourth day of hospital admission increases the odds of in-hospital mortality by 50 percent (odds ratio, 1.5; 95%; CI, 1.0 -2.1).[7] In order to improve long-term survival, patients with postoperative mediastinitis should undergo sternal closure within 72 hours after sternal debridement.[8] 

What is Fibrosing Mediastinitis?

This condition is also called sclerosing mediastinitis or mediastinal fibrosis. It is a rare disorder characterized by the invasive proliferation of fibrous tissue within the mediastinum. Its pathogenesis remains unknown. However, it is thought to represent an immune-mediated hypersensitivity response to Histoplasma capsulatum infection.[9] Fibrosing mediastinitis can be focal or diffuse. Initially, most patients are asymptomatic until symptoms develop due to invasion of mediastinal or adjacent structures. The presentation depends upon which structures of the mediastinum are involved, including superior vena cava syndrome, pulmonary venous or arterial obstruction, esophageal obstruction, and thoracic duct obstruction. It can be associated with a fibrotic process at another anatomic site, such as the retroperitoneum. Its diagnosis is based on the clinical presentation and radiographic findings of associated calcification.  Imaging is required to confirm the presence of an infiltrative process in the mediastinum. Biopsies may be contraindicated because of an increased risk of bleeding.

ED Management

All forms of mediastinitis are life-threatening and require prompt diagnosis and treatment, including surgical drainage and antibiotic administration. Treatment should be directed toward the primary cause. Administration of broad-spectrum antibiotics should be initiated. First-line agents are cefepime or ceftazidime plus metronidazole or clindamycin. For MRSA infections, vancomycin, linezolid, or daptomycin should be considered until culture results become available. Surgical consultation is needed, in so far as surgical drainage is the gold standard. Computed tomography is the preferred modality for imaging for all forms of mediastinitis. A plain chest radiograph may show mediastinal widening, air-fluid levels, and subcutaneous or mediastinal emphysema. In certain situations, a lateral chest radiograph may be obtained to reveal mediastinal gas, since it may not be evident on upright film. In addition, pleural effusion or pneumoperitoneum can be seen in the chest radiograph. For chronic mediastinitis, diagnostic evaluation should include a chest radiograph and contrast-enhanced CT or MRI. Vascular imaging may be obtained if vena caval obstruction or arterial involvement is suspected. Patients with chronic mediastinitis, should also be evaluated for tuberculosis and histoplasmosis. The mortality rate in postoperative mediastinitis is up to 50%.[10] In one study evaluating mortality of mediastinitis, approximately 20% died within 3 months of the initial surgery.[8]  The mortality rate for the average patient treated for mediastinitis decreased from 10.6% in 1998 to 3.1% in 2010.[7] The following predictors of death are identified in postoperative mediastinitis:[11]

-Delay >3 days in sternal closure after debridement

-Age > 65 years

-Stay in the ICU before sternal debridement

-Serum creatinine >2 mg/dL before debridement

-MRSA infection

 

Pearls/Pitfalls

-Generally, patients with mediastinitis have manifestations of systemic infection, such as fever, chills, etc.

Do not delay administering antibiotics if mediastinitis is suspected.

-Initial diagnosis is often clinical; no single test can confirm this diagnosis.

Any surgical procedure on the neck, including tracheostomy, could result in mediastinitis.

-Post-sternotomy mediastinitis may mimic acute myocardial infarction.[12]

-Hodgkin’s disease may resemble sclerosing mediastinitis.[13]

-Fibrosing mediastinitis may result in superior vena cava syndrome.[14],[15]

-Fibrosing mediastinitis may mimic sarcoidosis.[16]

-Mediastinitis may result in airway compromise; consider early protection of the airway.

-Mediastinitis may be mistaken for many conditions, such as pneumonia, acute coronary syndrome, etc.

-Spontaneous esophageal rupture may be mistaken for an abdominal catastrophe.

-Consider tertiary center referral, if resources are not optimal.

-The key to an optimal outcome is early diagnosis and aggressive treatment.

 

References / Further Reading

[1] Valat P, Pellerin C, Cantini O, Jougon J, Delcambre F, Morales P, Janvier G. Infected mediastinitis secondary to perforation of superior vena cava by a central venous catheter. Br J Anaesth. 2002 Feb;88(2):298-300.

[2] Kohman LJ, Coleman MJ, Parker FB Jr. Bacteremia and sternal infection after coronary artery bypass grafting. Ann Thorac Surg 1990; 49:454.

[3] Jolles H, Henry DA, Roberson JP, Cole TJ, Spratt JA. Mediastinitis following median sternotomy: CT findings. Radiology. 1996 Nov;201(2):463-466

[4] van Wingerden JJ, Ubbink DT, van der Horst C, de Mol B. Poststernotomy mediastinitis: a classification to initiate and evaluate reconstructive management based on evidence from a structured review. J Cardiothorac Surg 2014;9:179

[5] Boiselle PM, Mansilla AV, White CS, Fisher MS. Sternal dehiscence in patients with and without mediastinitis. J Thorac Imaging 2001;16:106–110

[6] Catarino PA, Westaby S. Postcardiac surgery mediastinitis mimicking acute inferior myocardial infarction. J Card Surg 2000;15:309–312

[7] Aliu O, Diaz-Garcia RJ, Zhong L, McGlinn E, Chung KC. Mortality trends and the effects of debridement timing in the management of mediastinitis in the United States, 1998 to 2010. Plast Reconstr Surg. 2014 Sep;134(3):457e-463e.

[8] Karra R, McDermott L, Connelly S, Smith P, Sexton DJ, Kaye KS. Risk factors for 1-year mortality after postoperative mediastinitis. J Thorac Cardiovasc Surg. 2006 Sep;132(3):537-543

[9] Peikert T, Colby TV, Midthun DE, Pairolero PC, Edell ES, Schroeder DR, Specks U. Fibrosing mediastinitis: clinical presentation, therapeutic outcomes, and adaptive immune response. Medicine (Baltimore). 2011 Nov;90(6):412-422

[10] Risnes I, Abdelnoor M, Almdahl SM, Svennevig JL. Mediastinitis after coronary artery bypass grafting risk factors and long-term survival. Ann Thorac Surg 2010; 89:1502.

[11] Karra R, McDermott L, Connelly S, et al. Risk factors for 1-year mortality after postoperative mediastinitis. J Thorac Cardiovasc Surg 2006; 132:537.

[12] Catarino PA, Westaby S. Postcardiac surgery mediastinitis mimicking acute inferior myocardial infarction. J Card Surg. 2000 Sep-Oct;15(5):309-312

[13] Flannery MT, Espino M, Altus P, Messina J, Wallach PM. Hodgkin’s disease masquerading as sclerosing mediastinitis. South Med J. 1994 Sep;87(9):921-923

[14] Bays S, Rajakaruna C, Sheffield E, Morgan A. Fibrosing mediastinitis as a cause of superior vena cava syndrome. Eur J Cardiothorac Surg. 2004 Aug;26(2):453-455

[15] Esquivel L, Diaz-Picado H. Fibrosing TB mediastinitis presenting as a superior vena cava syndrome: a case presentation and echocardiogram correlate. Echocardiography. 2006 Aug;23(7):588-591

[16] Ferrer Galván M, Rodríguez Portal JA, Serrano Gorarredona MP, Gómez Izquierdo L. Fibrosing mediastinitis mimicking sarcoidosis. Clin Respir J. 2015 Jan;9(1):125-128

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