eMedicine Specialties > Thoracic Surgery > Infection

Mediastinitis: Workup

Author: Dale K Mueller, MD, Associate Professor of Surgery, Section Chief, Department of Surgery, University of Illinois at Peoria; Co-Medical Director, Thoracic Center of Excellence, Vice-Chair, Department of Cardiovascular Medicine and Surgery, OSF St Francis Medical Center; Cardiovascular and Thoracic Surgeon, HeartCare Midwest, SC
Coauthor(s): Michael J Dacey, MD, Consulting Staff, Department of Internal Medicine, Division of Critical Care, Kent County Hospital
Contributor Information and Disclosures

Updated: Jun 4, 2009

Workup

Laboratory Studies

  • CBC count
    • CBC count shows leukocytosis, often with a left shift on the WBC count differential.
    • The hematocrit value decreases if bleeding has occurred.
    • The platelet count increases in the early stages of sepsis or decreases as sepsis worsens or disseminated intravascular coagulation occurs.
  • Blood cultures
    • Bacteremia can be observed and blood cultures should be obtained as clinically indicated.
    • Results from properly collected blood cultures should be reflexive in the workup when mediastinitis is considered, especially in the postoperative patient several days after cardiothoracic surgery in the presence of sepsis.
  • Gram stain: Samples of any sternal drainage should be sent for Gram stain and culture. This helps to establish a diagnosis and to tailor antimicrobial therapy. At operative exploration, additional cultures should be taken to direct antibiotic therapy.
  • Cultures of mediastinal pacing wires
    • Mediastinal pacing wires should be sent for culture if they are still present and no longer needed.
    • One study found that results from pacing wire culture have a sensitivity of 75%, a specificity of 83%, a positive predictive value of 12%, and a negative predictive value of 99%.15

Imaging Studies

  • Delays in the diagnosis of mediastinitis greatly increase morbidity and mortality. The condition is typically recognized because of high clinical awareness in susceptible populations. Occasionally, radiology studies, including chest CT scan, can be helpful in diagnosis if it is in question.8 Local wound exploration is the predominant method to distinguish between superficial wound infection and deep sternal wound infection.
  • Chest radiographs
    • Findings include pneumomediastinum and air-fluid levels within the mediastinum.
    • Air-fluid levels are often best seen on lateral films.
    • Mediastinal widening is not a reliable sign of mediastinitis, especially postoperatively.
  • CT scans
    • CT scans are more accurate for helping to identify air-fluid levels and pneumomediastinum. A CT scan image may demonstrate sternal separation and substernal fluid collections. These examinations can be helpful when the diagnosis is in question or in the late postoperative period. They should not take the place of prudent wound exploration to identify a deep sternal wound infection.
    • The later the scans are performed following surgery, the more accurate the results.16 If performed after the second postoperative week, CT scans have a sensitivity and specificity of almost 100%, although most wound infections occur prior to this time.16 The specificity of CT findings is clearly time-dependent.
    • CT findings consistent with mediastinitis can also be found in patients without sternal wound infections after cardiac surgery for as many as 21 days following the procedure. This makes integrating CT scan findings with clinical data and awareness critical.
  • MRI
    • MRI is poorly suited as a diagnostic modality in persons with mediastinitis. Postoperative patients may have sternal wires, vascular clips, metallic valves, and pacing wires that contraindicate MRI.
    • Also, logically performing an MRI study on an intubated, critically ill patient is difficult.
    • Findings from nuclear medicine scans/radioactive WBC scans involving labeled WBCs are reported to have very high specificity; however, few studies have been performed on postoperative patients.

Histologic Findings

As mediastinitis develops, an increasingly thick layer of fibrin is formed, causing the mediastinal structures to become progressively less mobile. As the infection spreads throughout the mediastinum through sinus tracts, a growing area of dead space develops beneath the sternum. The belief that this retrosternal dead space must be obliterated to achieve a cure after mediastinitis develops is becoming more popular.

A more indolent form of mediastinitis, termed chronic fibrosing mediastinitis, occurs as a complication of granulomatous infections, most commonly H capsulatum.11 Rupture of mediastinal lymph nodes and the release of caseous material generate an intense inflammatory reaction. The patient becomes symptomatic from obstruction of major mediastinal structures, especially the superior vena cava.

A significant minority of patients may be asymptomatic and present with an isolated mediastinal mass on chest radiograph.

More on Mediastinitis

Overview: Mediastinitis
Workup: Mediastinitis
Treatment: Mediastinitis
Follow-up: Mediastinitis
Multimedia: Mediastinitis
References
[ CLOSE WINDOW ]

References

  1. Luckraz H, Murphy F, Bryant S, Charman SC, Ritchie AJ. Vacuum-assisted closure as a treatment modality for infections after cardiac surgery. J Thorac Cardiovasc Surg. Feb 2003;125(2):301-5. [Medline].

  2. MacIver RH, Stewart R, Frederiksen JW, Fullerton DA, Horvath KA. Topical application of bacitracin ointment is associated with decreased risk of mediastinitis after median sternotomy. Heart Surg Forum. 2006;9(5):E750-3. [Medline].

  3. Athanassiadi KA. Infections of the mediastinum. Thorac Surg Clin. Feb 2009;19(1):37-45, vi. [Medline].

  4. Jayakrishnan AG, Allan A, Forsyth AT, Desai JB. Sternal wound infections and internal mammary artery grafts. J Thorac Cardiovasc Surg. Jul 1993;106(1):181-2. [Medline].

  5. Ioannis K. Toumpoulisa, Nikolaos Theakosb and Joel Dunningc. Does bilateral internal thoracic artery harvest increase the risk of mediastinitis?. Interact CardioVasc Thorac Surg. 2007;6:787-791. [Medline].

  6. Farinas MC, Gald Peralta F, Bernal JM, et al. Suppurative mediastinitis after open-heart surgery: a case-control study covering a seven-year period in Santander, Spain. Clin Infect Dis. Feb 1995;20(2):272-9. [Medline].

  7. Milano CA, Kesler K, Archibald N, et al. Mediastinitis after coronary artery bypass graft surgery. Risk factors and long-term survival. Circulation. Oct 15 1995;92(8):2245-51. [Medline].

  8. Baldwin RT, Radovancevic B, Sweeney MS, et al. Bacterial mediastinitis after heart transplantation. J Heart Lung Transplant. May-Jun 1992;11(3 Pt 1):545-9. [Medline].

  9. Shaffer HA, Valenzuela G, Mittal RK. Esophageal perforation. A reassessment of the criteria for choosing medical or surgical therapy. Arch Intern Med. Apr 1992;152(4):757-61. [Medline].

  10. Sancho LM, Minamoto H, Fernandez A, et al. Descending necrotizing mediastinitis: a retrospective surgical experience. Eur J Cardiothorac Surg. Aug 1999;16(2):200-5. [Medline].

  11. Loyd JE, Tillman BF, Atkinson JB, Des Prez RM. Mediastinal fibrosis complicating histoplasmosis. Medicine (Baltimore). Sep 1988;67(5):295-310. [Medline].

  12. Konvalinka A, Errett L, Fong IW. Impact of treating Staphylococcus aureus nasal carriers on wound infections in cardiac surgery. J Hosp Infect. Oct 2006;64(2):162-8. [Medline].

  13. Saiki Y, Tabayashi K. [Use of a vacuum-assisted closure system for the treatment of mediastinitis after cardiac and aortic surgery]. Nippon Geka Gakkai Zasshi. Jan 2009;110(1):21-6. [Medline].

  14. Noji S, Yuda A, Tatebayashi T, Kuroda M. Vacuum-assisted closure for postcardiac surgery mediastinitis in a patient on hemodialysis. Gen Thorac Cardiovasc Surg. Apr 2009;57(4):217-20. [Medline].

  15. Maroto LC, Aguado JM, Carrascal Y, et al. Role of epicardial pacing wire cultures in the diagnosis of poststernotomy mediastinitis. Clin Infect Dis. Mar 1997;24(3):419-21. [Medline].

  16. Jolles H, Henry DA, Roberson JP, et al. Mediastinitis following median sternotomy: CT findings. Radiology. Nov 1996;201(2):463-6. [Medline].

  17. El Oakley RM, Wright JE. Postoperative mediastinitis: classification and management. Ann Thorac Surg. Mar 1996;61(3):1030-6. [Medline].

  18. Kalweit G, Huwer H, Straub U, Gams E. Mediastinal compression syndromes due to idiopathic fibrosing mediastinitis--report of three cases and review of the literature. Thorac Cardiovasc Surg. Apr 1996;44(2):105-9. [Medline].

  19. Weinzweig N, Yetman R. Transposition of the greater omentum for recalcitrant median sternotomy wound infections. Ann Plast Surg. May 1995;34(5):471-7. [Medline].

  20. Hountis P, Dedeilias P, Bolos K. The role of omental transposition for the management of postoperative mediastinitis: a case series. Cases J. Feb 23 2009;2(1):142. [Medline].

  21. Chase CW, Franklin JD, Guest DP, Barker DE. Internal fixation of the sternum in median sternotomy dehiscence. Plast Reconstr Surg. May 1999;103(6):1667-73. [Medline].

  22. Zec N, Donovan JW, Aufiero TX, et al. Seizures in a patient treated with continuous povidone-iodine mediastinal irrigation. N Engl J Med. Jun 25 1992;326(26):1784. [Medline].

  23. Loop FD, Lytle BW, Cosgrove DM, et al. J. Maxwell Chamberlain memorial paper. Sternal wound complications after isolated coronary artery bypass grafting: early and late mortality, morbidity, and cost of care. Ann Thorac Surg. Feb 1990;49(2):179-86; discussion 186-7. [Medline].

  24. Gadek JE, DeMichele SJ, Karlstad MD, et al. Effect of enteral feeding with eicosapentaenoic acid, gamma-linolenic acid, and antioxidants in patients with acute respiratory distress syndrome. Enteral Nutrition in ARDS Study Group. Crit Care Med. Aug 1999;27(8):1409-20. [Medline].

[ CLOSE WINDOW ]

Further Reading

[ CLOSE WINDOW ]

Keywords

mediastinitis, cardiac surgery, heart transplant, surgical complication, operative complication, surgery, postoperative complications, esophageal perforation, postoperative infection, tracheobronchial perforation, progressive odontogenic infection, Ludwig angina, lung infection, chronic fibrosing mediastinitis, granulomatous infections, Staphylococcus aureus, S aureus, Staphylococcus epidermidis, S epidermidis, Candida, Histoplasma capsulatum, H capsulatum, Mycobacterium tuberculosis, M tuberculosis, gram-positive cocci, mediastinal disease, mediastinum disease, open heart surgery, open heart operations, open-heart surgery, open-heart operations

[ CLOSE WINDOW ]

Contributor Information and Disclosures

Author

Dale K Mueller, MD, Associate Professor of Surgery, Section Chief, Department of Surgery, University of Illinois at Peoria; Co-Medical Director, Thoracic Center of Excellence, Vice-Chair, Department of Cardiovascular Medicine and Surgery, OSF St Francis Medical Center; Cardiovascular and Thoracic Surgeon, HeartCare Midwest, SC
Dale K Mueller, MD is a member of the following medical societies: American College of Chest Physicians, American College of Surgeons, American Medical Association, American Medical Writers Association, Chicago Medical Society, Illinois State Medical Society, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Coauthor(s)

Michael J Dacey, MD, Consulting Staff, Department of Internal Medicine, Division of Critical Care, Kent County Hospital
Disclosure: Nothing to disclose.

Medical Editor

Benson B Roe, MD, Emeritus Chief, Division of Cardiothoracic Surgery, Emeritus Professor, Department of Surgery, University of California at San Francisco Medical Center
Benson B Roe, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for Thoracic Surgery, American College of Cardiology, American College of Surgeons, American Heart Association, American Medical Association, American Society for Artificial Internal Organs, American Surgical Association, California Medical Association, Society for Vascular Surgery, Society of Thoracic Surgeons, and Society of University Surgeons
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Shreekanth V Karwande, MBBS, Chair, Professor, Department of Surgery, Division of Cardiothoracic Surgery, University of Utah School of Medicine and Medical Center
Shreekanth V Karwande, MBBS is a member of the following medical societies: American Association for Thoracic Surgery, American College of Chest Physicians, American College of Surgeons, American Heart Association, Society of Critical Care Medicine, Society of Thoracic Surgeons, and Western Thoracic Surgical Association
Disclosure: Nothing to disclose.

CME Editor

Paolo Zamboni, MD, Professor of Surgery, Chief of Day Surgery Unit, Chair of Vascular Diseases Center, University of Ferrara, Italy
Paolo Zamboni, MD is a member of the following medical societies: American Venous Forum and New York Academy of Sciences
Disclosure: Nothing to disclose.

Chief Editor

Mary C Mancini, MD, PhD, Professor, Department of Surgery, Louisiana State University Health Sciences Center
Mary C Mancini, MD, PhD is a member of the following medical societies: American Association for Thoracic Surgery, American College of Surgeons, American Surgical Association, Phi Beta Kappa, Society of Thoracic Surgeons, and Southern Surgical Association
Disclosure: Nothing to disclose.

 
 
HONcode

We subscribe to the
HONcode principles of the
Health On the Net Foundation

All material on this website is protected by copyright, Copyright© 1994- by Medscape.
This website also contains material copyrighted by 3rd parties.

DISCLAIMER: The content of this Website is not influenced by sponsors. The site is designed primarily for use by qualified physicians and other medical professionals. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.