ORIGINAL ARTICLE

Acute mediastinitis. Restropective analysis of 21 cases^*

Marcelo Cunha Fatureto^I; Milton Alves das Neves-Junior^II; Thassio Cunha de Santana^II

^IMasters in Thoracic Surgery from the Faculdade de Medicina do Triângulo Mineiro (FMTM, Triângulo Mineiro School of Medicine), Uberaba (MG) Brazil
^IIMedical Student at the Faculdade de Medicina do Triângulo Mineiro (FMTM, Triângulo Mineiro School of Medicine), Uberaba (MG) Brazil

Correspondence

ABSTRACT

OBJECTIVE: To evaluate the epidemiological and clinical aspects of acute mediastinitis and to characterize its treatment.
METHODS: A retrospective study conducted through review of the medical charts of patients diagnosed with acute mediastinitis at the Hospital Escola da Faculdade de Medicina do Triângulo Mineiro (Triângulo Mineiro Medical School Hospital) between 1987 and 2004.
RESULTS: A total of 21 patients were studied. Most (76.2%) were male, and the mean age was 52.5 years. Six patients (28.6%) died. The most common cause (in 38.1%) was median sternotomy, followed by esophageal perforation (in 33.3%) and cervical infection (in 14.3%). Staphylococcus aureus and Staphylococcus epidermidis were the causative agents most frequently isolated. In most cases, the treatment of choice was antibiotic therapy accompanied by surgery. The most frequent complications of the acute mediastinitis were pleural effusions (in 23.8%) and osteomyelitis (in 19.0%). The average hospital stay was 26.6 days.
CONCLUSION: Acute mediastinitis is a serious complication of some diseases and procedures. Despite its low incidence, the mortality rate is high. Staphylococcus aureus and Staphylococcus epidermidis are the most common causative agents. The treatment used was antibiotic therapy accompanied by surgery.

Keywords: Mediastinitis/diagnosis; Mediastinitis/drug therapy; Mediastinitis/epidemiology; Mediastinitis/surgery; Mediastinitis/etiology. Drainage/methods; Anti-bacterial agents/therapeutic use; Empyema, pleural/etiology; Osteomyelitis/etiology; Respiratory insufficiency/etiology; Retrospective studies.

INTRODUCTION

Acute mediastinitis is defined as an inflammatory process ofthe connective tissue of the mediastinum.^(1-2) It isan entity whose incidence is low, ranging from 0.2% to 5% amongpatients submitted to median sternotomy,⁽³⁾ but whosemortality rate is high. In more recent studies, acutemediastinitis mortality has been estimated to range from 15.4% to50%.^(1,4) In some studies, mediastinitis was found tobe more prevalent among males.^(5-6)

There are several the factors that increase the risk fordeveloping acute mediastinitis. These include smoking, diabetesmellitus, chronic obstructive pulmonary disease, long-termcorticosteroid use and long stays in intensive careunits.⁽³⁾

Inflammation of the mediastinum may have several causes, chiefamong which are median sternotomy^(3,5) and esophagealperforation (Boerhaave's syndrome, dilatations, foreign bodies,etc.),^(7-10) as well as head and neck suppurationssuch as peritonsillar abscesses, deep cervical abscesses,etc.^(4,11-12) Other less common causes include pleuralempyema, osteomyelitis of the vertebrae and ribs, retroperitonealabscesses and subphrenic abscesses.⁽³⁾

Notable among the infectious agents found in cultures obtainedfrom inflamed mediastinal tissue are Staphylococcus aureus,Staphylococcus epidermidis, Pseudomonas sp and Escherichia coli,the last having been correlated with a high mortalityrate.^(3,5) However, in some cases, the exudate culturemay be negative, which is usually due to previous use ofantibiotics.⁽³⁾

There are several treatment options for acute mediastinitis.Drainage is necessary in order to remove the exudate containedwithin the mediastinal space. Antibiotic therapy, in combinationwith drainage, is introduced immediately after culturecollection, albeit empirically.

In addition to mediastinal drainage and antibiotic therapy,specific treatment of the cause of mediastinitis is requiredwhenever possible.⁽¹³⁾ In cases of suppuration in theneck area, removal of the necrotic tissue and drainage of thearea are performed.^(11-12) In cases of esophagealperforation, two methods of treatment have been proposed:cervical-access esophagectomy followed by cervical esophagostomyin combination with gastrostomy, or primary suture of the injuredwall.⁽⁹⁾

Various complications have been described in cases of acutemediastinitis, including renal insufficiency, respiratoryinsufficiency, sepsis and pleural empyema.^(5,8)

Within this context, our objective was to study theepidemiological and clinical aspects of acute mediastinitis inorder to better understand the disease. In addition, we evaluatedthe efficacy of the treatments proposed.

METHODS

We carried out a retrospective study through review of themedical charts of patients diagnosed with acute mediastinitis atthe Hospital Escola da Faculdade de Medicina do TriânguloMineiro (Triângulo Mineiro School of Medicine TeachingHospital) between 1987 and 2004. This review was carried out inthe Department of Information and Methods of the hospital. Thefollowing data were registered: gender, age, risk factors foracute mediastinitis, etiologies of this pathology, infectiousagents that cause mediastinitis, treatment employed,complications, length of hospital stay and patient condition atdischarge.

The present study was appraised and approved by the Ethics inResearch Committee of the Triângulo Mineiro School ofMedicine.

In order to analyze the data obtained, we used the methods offrequency counting and percentage, in addition to calculation ofmeans and standard deviations. Comparison between the variableswas carried out using the chi-square test - or Fisher's exacttest when one of chi-square cells was smaller thanfive.⁽¹⁴⁾

RESULTS

A total of 21 patients diagnosed with acute mediastinitis werestudied. Of those, 16 (76.2%) were male and 5 (23.8%) werefemale. The mean age of the patients was 52.5 years (±17.096), ranging from 23 to 79 years of age. Of the 21 patientsstudied, 6 died, resulting in a general mortality rate of28.6%.

Most of the patients (52.4%) presented no risk factors.However, 38.1% were smokers, and smoking has been identified inthe literature as a risk factor for the condition.

The most common cause of acute mediastinitis was median sternotomy (in 38.1%), closely followed by esophageal perforation (in 33.3%). The causes of esophageal perforation were found to be: post-endoscopic upper-digestive tract rupture/dilatation (3 cases), spontaneous perforation (Boerhaave's syndrome; 2 cases), traumatic perforation (1 case) and perforation by a foreign body (1 case). Head and neck infections accounted for 3 (14.3%) of the cases. Of those 3, 2 were cases of deep cervical abscess and 1 was a case of Ludwig's angina (Figures 1, 2 and 3). Mediastinoscopy, pyopericarditis and pleural empyema were each responsible for 1 case (4.8%).

Culture of the exudates revealed that the acute mediastinitiswas caused by a single microorganism in 42.9% of the cases and bymultiple microbes in 23.8%. In 33.3% of the cases, thedisease-causing agent was not isolated. There were nostatistically significant differences between the number ofmicroorganisms present in the cultures and the mortality rate (p= 0.51). The agents S. aureus and S. epidermidis were found in 7cases each, whereas Pseudomonas sp., E. coli, Klebsiellapneumoniae, Enterococcus cloacae, Proteus sp. and Acinetobactersp were found in 1 case each.

Antibiotic therapy was used exclusively in only 1 case (4.8%).Antibiotic therapy in combination with mediastinal drainage wasused in 9 cases (42.9%) and antibiotic therapy in combinationwith specific treatment of the cause of mediastinitis was used in4 cases (19.0%). A combination of antibiotic therapy, mediastinaldrainage and specific treatment of the cause was used in 7 cases(33.3%).

In our facility, antibiotic therapy is administered(empirically) immediately after collection of the material forculture. We typically use a broad-spectrum antimicrobialcombination in order to eliminate gram-positive, gram-negativeand anaerobic microorganisms. After the result of the culture isknown, the antibiotic therapy is adjusted according to the resultobtained in the exam. For gram-positive microorganisms, we useeither oxacillin (especially in patients whose culture waspositive for S. aureus, which is sensitive to this antimicrobialagent) or vancomycin. For gram-negative microorganisms, we use acombination of cefepime, ceftriaxone (or ceftazidime) andamikacin (or gentamicin), the first three also attackinggram-positive microorganisms. For anaerobic microorganisms, weuse clindamycin or metronidazole.

When the cause of the mediastinitis was median sternotomy,less invasive treatments were typically adopted. Of the 8 caseswith this etiology, 5 were submitted only to antibiotic therapy(using one of the regimens described above) and extensivemediastinal drainage. Drainage of the incision site, totalsternum removal and partial sternum removal (the last two both incombination with a chest muscle flap) were used in 1 case each.In this group (patients with median sternotomy-relatedmediastinitis), the mortality rate was 25%, which is very similarto the overall mortality rate.

When the etiology of mediastinitis was esophageal perforation,either primary closure or proximal esophagostomy, involvinggastrostomy and esophagectomy, was used. In 3 of the 7 cases ofesophageal perforation, the second option was used, and 1 deathoccurred. In the 4 remaining cases, primary closure was theprocedure chosen, and 2 of these patients died. Among thepatients with mediastinitis resulting from esophagealperforation, the mortality rate was 42.9%, which is high incomparison to the overall mortality rate.

For cases in which mediastinitis was caused by cervicalabscess, the procedure used was always surgical drainage,provided that collection did not extend beyond thebrachiocephalic veins. Among such cases, the mortality rate was33.3%.

In the 3 cases of mediastinitis caused by other etiologies, nodeaths occurred (in these cases, there was no specific treatmentof the cause).

Complications of acute mediastinitis included pleural empyema(23.8%), osteomyelitis (19%), respiratory insufficiency (9.5%)and others (19.1%). In 28.6% of the cases, there were nocomplications.

The mean length of hospital stay among patients diagnosed withacute mediastinitis was 26.6 days (± 19.), ranging from 6to 77 days.

DISCUSSION

Acute mediastinitis continues to be a much feared complicationof various diseases and procedures. In our study, as well as inthe literature, the incidence of the disease was low (1.17 casesper year in our hospital), although the mortality rate was quitehigh.^(1,4)

Notable among the causes of acute mediastinitis are the casesresulting from median sternotomy. Since the number of cardiacsurgical procedures using this approach is on the rise, thisetiology has become the most important and also the most widelystudied.^(3,5-6) However, esophageal perforation shouldnot be forgotten since it is responsible for the highestmortality rates.^(7-10,15)

Among the infectious agents involved, S. aureus and S.epidermidis are the most frequently found. Similar results havebeen reported in the literature, and some studies have also shownthat the isolation of E. coli is correlated with a high mortalityrate.^(3,5) It is important to bear in mind that theculture of the exudates may be negative, which is typicallyattributable to prior use of antibiotics.⁽³⁾

The treatment of acute mediastinitis is based on three basicpoints: antibiotic therapy, extensive drainage of the mediastinalcavity and treatment of the specific cause.⁽¹³⁾ Incases of mediastinitis occurring as a complication of mediansternotomy, the literature indicates that the prognosis is betterwhen the patient is submitted to a specific treatment, withdrainage of the incision site and omental flaprotation.^(3,5) However, despite the small number ofcases in our study, this type of treatment did not reduce themortality rate among these patients.

Another controversial point is the treatment of choice foresophageal perforation, especially in cases of Boerhaave'ssyndrome. Some authors prefer primary resection of the esophagus,whereas others believe superior esophagectomy to be theideal.^(8-9) In our study, both types of treatmentpresented similar prognoses.

Considering the data found in our study and that in theliterature,^(1,6) we believe that it is important toconsider a diagnosis of acute mediastinitis for all patientssubmitted to median sternotomy or to any esophageal manipulationand presenting subsequent fever or other signs of significantinfection, especially (in those submitted to esophagealprocedures) around the head and neck. The great diagnosticchallenge continues to be spontaneous esophageal perforation(Boerhaave's syndrome), which manifests only as a nonspecifichistory of vomiting and signs of toxemia. It is important toemphasize that, in these cases, a better prognosis is closelycorrelated with early diagnosis.^(8-9)

As soon as there is clinical suspicion, a chest X-ray shouldbe requested. This may reveal signs of mediastinitis or itscomplications, such as mediastinal emphysema and pleuraleffusion. Tomography of the chest using a window for themediastinum complements the chest X-ray, revealing mediastinalabscesses, emphysemas, sternal involvement, etc., in moredetail.^(1,6) In suspected cases of Boerhaave'ssyndrome, a contrast esophagogram is extremely important since itconfirms the diagnosis by showing the extravasation of thecontrast medium into the mediastinum.

The most important laboratory exams are culture andantibiogram of the mediastinal secretion. Control exams should berequested in order to detect complications such as renalinsufficiency as early as possible.

In our facility, after collection of material for culture,empirical antibiotic therapy is initiated and continues until theresult of the antibiogram is known. Generally, this initialtreatment is oriented according to the etiology. In cases ofmedian sternotomy-related acute mediastinitis, the initialantibiotic therapy includes the administration of oxacillin and athird-generation or higher cephalosporin (ceftriaxone, cefepimeor ceftazidime), combined or not with an aminoglycoside (amikacinor gentamicin). In cases of cervical abscesses, we administered athird-generation or higher cephalosporin combined withclindamycin. Finally, in cases of esophageal perforation, acombination of crystalline penicillin, clindamycin (ormetronidazole) and an aminoglycoside is the treatment used.Boerhaave's syndrome constitutes an exception, in which, due toits severity and usually late diagnosis, we opt for a combinationof a third-generation or higher cephalosporin, combined withclindamycin and oxacillin or even vancomycin.

In conclusion, acute mediastinitis is a severe complication ofsome diseases and procedures. Despite a low incidence, themortality rate is high. Hospital stays are longer among patientswith mediastinitis resulting from infection with S. aureus and S.epidermidis, which are the most common etiologic agents.

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Correspondence to
Marcelo Cunha Fatureto
Av. Leopoldino de Oliveira 4458, apto. 401, Centro
Uberaba, MG. CEP: 38060-000
Tel: 55 34 3332-2155
E-mail: mfat@terra.com.br

Submitted: 19 January 2005. Accepted, after review: 18 April 2005.

* Study conducted at the Faculdade de Medicina do Triângulo Mineiro (FMTM, Triângulo Mineiro School of Medicine), Uberaba (MG) Brazil.