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Eur J Cardiothorac Surg 1999;16:200-205
© 1999 Elsevier Science NL

Descending necrotizing mediastinitis: a retrospective surgical experience

Thoracic Surgery and Otorhinolaryngology Divisions, Hospital das Clinicas, University of São Paulo Medical Center, São Paulo, Brazil

Corresponding author. Rua Dr. Diogo de Faria, 964 Vila Clementino, São Paulo, SP, Brasil, CEP 04037-003. Tel./fax: +55-11-2826365

	Abstract

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 
Objective: Descending necrotizing mediastinitis (DNM) is a primary complication of cervical or odontogenical infections that can spread to the mediastinum through the anatomic cervical spaces. We reviewed the last 10 years of our surgical experience in DNM and commented on early diagnosis and aggressive surgical treatment in these patients. Methods: Five males (71%) and two females (29%), mean age 34 years, with DNM, were surgically treated. Primary oropharyngeal infection occurred in three (43%) and odontogenic abscess in four (57%) patients. All had serious cervical and mediastinal infections with severe respiratory and hemodynamic repercussions, i.e. bacteremia, systemic arterial hypotension and obnubilation. Diagnosis was confirmed by computerized chest tomography. Results: All patients underwent surgical drainage of the cervical region by bilateral transverse cervicotomy with debridement of the necrotic and infected tissues, associating ample mediastinal drainage with or without thoracotomy. Six patients (86%) evolved well and were discharged after a mean of 35 days. Two patients (29%) required reoperation due to local surgical complications: empyema and dehiscence of the sternum. One patient (14%) died on the second postoperative (p.o.) day due to renal and respiratory insufficiency. Cultures of DNM showed the development of associated aerobic and anaerobic flora in 71% of the operated patients and only aerobic in 29%. Conclusion: Early diagnosis by CAT scan of the neck and thorax aids in rapid indication of a surgical approach of DNM. Performing ample cervicotomy with mediastinal drainage generally associated with thoracotomy can significantly reduce the mortality rate for this condition to 14%.

Key Words: Descending necrotizing mediastinitis • Mediastinitis • Necrotizing fasciitis

	1. Introduction

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 
Acute mediastinitis is a severe infection of the mediastinal connective tissue which fills the interpleural mediastinal space and its thoracic anatomic structures. It is most often caused by perforation of the esophagus or infection after sternotomy in cardiac surgery [8] and can also occur as a complication of primary oropharyngeal infection progressing to the cervical region and spreading through the fascia to the mediastinum. In the latter case, the disease is known as descending necrotizing mediastinitis (DNM) [5,7]. Diagnostic criteria for DNM were defined by Estrera et al. [5] in 1983. DNM is a rare disease, but, highly fatal in all its clinical forms. Various reports place the mortality rate as high as 50% [4,6–8,13]. We recently reviewed our 10 years experience of surgical management of DNM. Utilization of computerized tomography for early diagnosis of DNM and aggressive surgery for ample mediastinal drainage chiefly using thoracotomy has also significantly reduced our mortality rate to 14%.

	2. Patients and methods

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 
Between 1986 and 1997, seven patients with DNM were managed at this institution. Estrera and colleagues criteria were applied in all patients [5] and included: clinical manifestations of a severe oropharyngeal infection; radiological demonstration of mediastinitis; demonstration of necrotizing mediastinal infection at operation or autopsy or both; proof of a relationship between oropharyngeal infection and DNM.

Five males (71%) and two females (29%) ranging in age from 9 to 71 years were treated. The primary oropharyngeal infection was 57% (4/7) for odontogenic abscesses and 43% (3/7) for peritonsillar abscesses (Ludwig Angina). Mean interval between onset of the oropharyngeal infection and hospitalization was 10 days. All patients were referred to our service without prior treatment at other services. Only three out of the seven were empirically given non-hormone antiinflammatory medications prescribed by laymen.

On admission to our service four blood cultures were collected during the first 12 h. The patients were immediately placed on broad spectrum antibiotics preoperatively for gram positive aerobic and anaerobic bacteria. Medication included 20 million IU crystalline penicillin/day and 2.4 g/day of clindamycin, at least 24 h prior to surgery. Tissue specimens from the cervical and mediastinal regions obtained intraoperatively were cultured for aerobic and anaerobic germs and the results used for specific antibiotic therapy.

Antibiotic therapy was maintained for a minimum of 15 days. In order to discontinue this therapy the patients needed to be without signs of toxemia (fever, tachycardia, and dehydration) for at least 48 h and to display a normal white blood cell count.

The oropharyngeal infection was controlled while the patients was hospitalized and before discharge. Treatment a included odontological, drainage of case a cervical abscess and antibiotic therapy similar to that used for DMN.

Diagnosis was obtained by CT scan of the cervical and mediastinal regions. Broad bilateral transverse cervicotomies (Kocher incision) were accomplished, with debridement of necrotic infected tissue, leaving the incision open for healing by second intention.

Four patients submitted to mediastinal drainage without opening the chest cavity comprised Group I. Three patients submitted to opening of the chest cavity and drainage through the opening of the mediastinal space consisted of Group II. Underwater sealed drainage was used on all patients realized with no. 38 French multiperforated pleural drainage tubes. Irrigation with saline within the mediastinum as recommended by Marty-Ane et al. [8] and Santos et al. [11] was dispensed with.

	3. Results

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 
Mean time between hospitalization on our service and diagnosis of DNM was three days. An oropharyngeal infection was suspected in all patients with marked cervical disease, local pain and widespread inflammatory infiltrate in the skin with crepitation (subcutaneous emphysema), suggestive of infection by gas-producing bacteria in 57% (4/7). The patients also complained of moderate dyspnea and hypoxia with radiological signs suggestive of descending mediastinitis (widening of the mediastinum) in 57% (4/7). All the diagnoses of DNM were made by CT scan. Typical mediastinal abscess images either with air-fluid level or mediastinal emphysema or both (Figs. 1–3) confirmed the diagnosis of DNM. Two of the blood cultures in patient no. 3, demonstrated Staphylococcus aureus and Bacteroides fragilis. Staphylococcus aureus was present in the blood culture of patient no. 7. Blood cultures in the other five patients were negative.

View larger version (96K): [in this window] [in a new window]   Fig. 1. CT scan of the cervical region with abscess and collection of gas (arrow).

View larger version (95K): [in this window] [in a new window]   Fig. 2. CT scan of the chest displaying collection of gas in the anterior mediastinal space (arrow).

View larger version (101K): [in this window] [in a new window]   Fig. 3. CT chest scan displaying abscess in the anterior mediastinum (arrow).

3.2. Bacteriological culture
Eighty-six percent (6/7) of cultures displayed polymicrobial flora (8), with 71% (5/7) demonstrating aerobic and anaerobic bacteria. The most common microorganisms cultured from material obtained from the mediastinum were: Pseudomonas aeruginosa in 71% (5/7), Staphylococcus aureus in 57% (4/7) and Enterobacter cloacae in 43% (3/7), Acinetobacter caloaceticus 29% (2/7), Escherichia coli in 14% (1/7) and Serratia marcencis 14% (1/7) (Table 3). In these cultures, the most common anaerobic microorganism was Bacteroides fragilis in 71% (5/7).

	4. Discussion

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 
Nowadays, acute mediastinitis secondary to primary oropharyngeal or odontological infections is very rare. It is more common in developing countries due to the poor economic conditions and consequently lack of medical resources for prevention and treatment of dental and oropharyngeal diseases. Hence, it is still possible to come across cases with DNM secondary to oropharyngeal infections (Ludwig Angina) and lesions of the dental arcades with secondary infections, especially of the second and third lower molars progressing to a descending and rapid mediastinal infection [14,15].

Pearse [10] in 1938, was the first author to describe this type of mediastinitis secondary to oropharyngeal infections reporting a mortality rate of up to 50%. According to Moncada et al. [9], 70% of cervical infections depend on the toxicity of the infecting bacteria and their inroad through the retropharyngeal space, spreading with the help of gravity, ventilation and negative intrathoracic pressure [12]. In patients in poor physical conditions suffering from malnutrition, diabetes mellitus, alcoholics, drug addicts, and in the immunosuppressed, the incidence of DNM is much greater than in the general population [7]. Late diagnosis is the principal reason for the high mortality in DNM. The diagnosis is suspected when the patient complains of chest pain, dyspnea and fever with marked associated toxemia. Radiological study frequently demonstrates widening of the upper mediastinum, pneumomediastinum or abscess which obliterates the retrosternal space and the retrocardiac silhouette but frequently these clinical findings appear in the late stage of the infection. Possible chest or mediastinal drainage and tracheostomies prior to the infection can render the interpretation of these tomographic images difficult.

CT scan is useful for early diagnosis of DNM demonstrating gas infiltration or edema in soft tissues of the mediastinum and the presence of fluid collections typical of mediastinal abscess with or without gas bubbles (Figs. 1–3). Preoperative cervicothoracic tomography exhibits the extent of the necrosis and locates these lesions for orienting surgical drainage. It is also useful for p.o. follow-up, as exemplified by our study. Immediately p.o., one of our patients developed fever and the tomogram demonstrated a probable empyema in the posterior right pleural cavity requiring a new drainage on the 10th p.o. day.

The majority of these infections are polymicrobial aerobic and anaerobic exemplifying the oropharyngeal flora. Chow et al. [3], report the presence of anaerobic bacteria in 94% of their patients, with 52% of them displaying mixed polymicrobial infections and 88% aerobic polymicrobial infections. According to Wills and Vernon [14], three or four types of different aerobic bacteria may be found in the same culture. In the review by Wheathey et al. [13], 69% of cases displayed mixed polymicrobial infections. Estrera et al. [5] mentioned that the most common anaerobic bacteria are Streptococcus anaerobius, Bacteroides and Fusobacterium sp. In our experience Bacteroides fragilis was the most common anaerobic bacteria (71%) and Pseudomonas aeruginosa the most numerous aerobic bacteria (43%). Our results were very similar to those mentioned by Marty-Ane et al. [8].

Some authors [1,12] feel that the toxicity and invasion of the infection could be associated to symbiosis between the anaerobic and aerobic gram negative bacteria. It is also simple to spread the infection through the spaces between the cervical fascia of the throat and chest, providing an excellent medium for bacterial growth principally by anaerobic bacteria. The polymicrobial infection must be treated quickly using combined antibiotic therapy without awaiting the results of bacterial culture and respective susceptibility tests. The antibiotics can be modified later depending on the results of the latter test. Antibiotic therapy is incapable of eradicating the infection if it is not associated with aggressive surgical drainage both in the cervical as well as in the thoracic region [2].

The neck is usually approached by broad anterior cervicotomy, bilateral as far as the sternocleidomastoid muscles. The cervical layers are opened by anatomic dissection with debridement of all necrotic tissue and ample drainage, always leaving the incision open for healing by second intention. The anterior mediastinum can be approached by finger dissection through the cervicotomy and by this maneuver attaining the pretracheal space up to the level of the distal trachea. The posterior mediastinum can be approached by dissection of the descending retropharyngeal space, this descending mediastinal drainage is the management most often employed by various authors for DNM [5,8,13]. Mediastinal drainage can also be accomplished by minor procedures, i.e. mediastinoscopy or videothoracoscopy jointly with cervical drainage always guided by CT scans. However, there are no articles reporting this therapy.

Anterior mediastinotomy concomitant with subxiphoid drainage can in some cases promote adequate drainage in mediastinitis involving the anterior mediastinum. In addition posterior mediastinal abscesses can be drained through posterior mediastinotomy by extrapleural dissection. Right posterolateral thoracotomy also provides a broad approach to all the mediastinal spaces: anterior and posterior, pleural cavity and pericardium, permitting excellent local drainage. Various authors [1,4,5,8,13] agree that the best surgical approach for mediastinal drainage in DNM depends on the size of mediastinal necrosis. If only the upper mediastinum above the carina is involved, mediastinal transcervical drainage is sufficient. However, in extensive necroses the latter should be associated with right posterolateral thoracotomy for a better outcome. Estrera et al. [5] have established that if the descending mediastinitis extends below the tracheal bifurcation anteriorly or at the level of the fourth thoracic vertebra posteriorly, mediastinal drainage should be associated with a transthoracic approach.

We agree that mediastinal drainage for DNM requires aggressive surgical management with a systemic surgical and a transthoracic approach through a right posterolateral thoracotomy. It provides an excellent approach to all the mediastinal spaces permitting complete debridement of all necrotic tissue, ample drainage of the pleural cavity and even of the pericardium if necessary using pleural drainage tubes throughout the longitudinal length of the mediastinum.

We do not routinely irrigate the mediastinal cavity for fear of contamination. It is our point of view that this procedure has not been scientifically proven as completely effective. As a matter of fact our rates of morbidity and mortality are comparable to those reported in the literature [8,11,13] of those who use irrigation. Hence we consider irrigation of the mediastinal space an optional procedure.

Currently, we consider CAT scan of the cervical and thoracic regions the diagnostic method of choice for indication and operative strategy as well as for clinical follow-up.

In our experience, management of DNM should always be surgical with broad, extensive, open cervicotomy together with ample mediastinal drainage and associated thoracotomy whenever possible for adequate drainage of all mediastinal compartments. Antibiotic therapy should always be chosen based on sensitivity results of cervical and tissue cultures obtained from intraoperative mediastinal specimens.

	Footnotes

 
Presented at the 12th Annual Meeting of the European Association for Cardio-thoracic Surgery, Brussels, Belgium, September 20–23, 1998.

	References

Top Abstract 1. Introduction 2. Patients and methods 3. Results 4. Discussion References

 

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