Acute mediastinitis. Lection for students of 5 course

1. Chief of hospital surgery

Acute
mediastinitis.
Lection for students of 5 course

2. Acute mediastinitis

is most often the result of bacterial infection
of the mediastinum. Mediastinitis may be
associated with empyema and subphrenic
abscess.

3. Causes acute mediastinitis

The most common cause is oesophageal
perforation.
Esophageal perforation may complicate
esophagoscopy or insertion of a
Sengstaken-Blakemore or Minnesota tube
(for esophageal variceal bleeding). It may
occur with vomiting (Boerhaave's
syndrome). Patients with esophageal
perforation are generally acutely ill, with
severe chest pain and dyspnea due to
mediastinal infection and inflammation

4. Causes acute mediastinitis

The other causes that are much less common
include:
postoperative infection, particularly following median
sternotomy;
leakage from the oesophagus into the mediastinum
through a necrotic neoplasm;
traumatic rupture tracheobronchial tree;
extension of infection from adjacent anatomical regions,
particularly the nasopharynx or teeth, and occasionally
from adjacent structures such as the lungs, pleura,
pericardium and mediastinal lymph nodes.

5. Symptoms

patients present with chills
chest pain
high fever
tachycardia

6. Diagnostic

Chest radiography may show mediastinal
widening and findings of mediastinal abscess
including gas bubbles or airfluid level.
Pneumothorax and pneumomediastinum are
frequently associated in case of oesophageal
perforation.
CT is more sensitive than chest radiography for
detecting the presence and extent of mediastinal
fluid collections and the presence of extraluminal
gas (Fig.1).

7. Diagnostic

CT scan in a patient with a mediastinal fluid
collection located within the retrosternal space.
The collection is circumscribed by a rim of
contrast enhancement and contains a small gas
bubble (arrow). This appearance corresponded to
a poststernotomy mediastinal abscess

8. Complications of mediastinitis

Abscess formation
Empyema
Esophagocutaneous fistulas
Sternal osteomyelitis
Pericardial tamponade

9. Complications of mediastinitis

Common complications of mediastinitis result
from extension of the infectious process into
contiguous structures and spaces.
Thus, abscess formation and empyema are
relatively common complications of acute
mediastinitis of any cause. Late complications of
acute mediastinitis resulting from esophageal
perforation include esophagocutaneous,
esophagopleural, and esophagobronchial fistulas.
Sternal osteomyelitis is a common complication
of mediastinitis after a cardiothoracic operation
but is an infrequent complication of nonsurgical
causes of mediastinitis; therefore, it would be
unlikely to occur in this patient.

10. Complications of mediastinitis

Pericardial effusion and subsequent tamponade
can result from direct extension of the infectious
process into the pericardial space but can also
occur as a secondary inflammatory response to
infection. The incidences of pericardial effusion,
abscess, and empyema formation all increase if
treatment is delayed.
Soon after admission of this patient, clinical signs
of tamponade developed, including a pulsus
paradoxus, worsening dyspnea, and increased
jugular venous pressure.

11. Complications of mediastinitis diagnostic

Echocardiography demonstrated a
moderate to large circumferential pericardial
effusion.
Pericardiocentesis was subsequently
performed; 500 mL of serous fluid was
drained, and a percutaneous pigtail catheter
was placed for continued drainage.
The patient also underwent thoracentesis for
diagnostic and therapeutic purposes.

12. Complications of mediastinitis diagnostic

Laboratory analysis of the recovered fluid
revealed pericardial and pleural exudates,
with total nucleated cell counts of
2.55×109/L (91% neutrophils) and
6.9×109/L (81% neutrophils), respectively.
Gram stain, fungal and acid-fast stains, and
cultures of the recovered fluid were
negative.

13. Treatment

open surgical drainage and débridement are
necessary to prevent serious morbidity and
mortality. The importance of early diagnosis and
surgical management has been clearly
documented. Delay in treatment can result in
extensive local advancement within as short a
time span as 12 hours and is associated with a
steep increase in mortality.
The antibiotic treatment in this patient was
sufficiently broad to cover organisms commonly
implicated in acute mediastinitis but was unable to
curtail the rapid progression of the infection.

14. Treatment

Percutaneous catheter drainage has been used in
less urgent clinical settings, often as a temporizing
measure, but open surgical drainage remains the
standard of therapy. Although the initial
Gastrografin swallow study failed to document an
esophageal perforation, the working hypothesis
was that a small perforation during the patient’s
recent EGD led to the patient’s subsequent
mediastinal infection. Because of the deteriorating
clinical situation, observation or repeated attempts
to document an esophageal perforation would be
of no value.

15. Treatment

The patient underwent an open thoracotomy
with drainage and removal of right
paratracheal and subcarinal abscesses,
aggressive irrigation, and pericardiotomy.
Bronchoscopy and rigid esophagoscopy
done at the initiation of the procedure
demonstrated no visible fistulas or other
abnormalities. Thoracotomy disclosed a
large mediastinal mass superior to the
azygos vein and a second large mass in the
subcarinal space.

16. Chronic fibrosing mediastinitis

Chronic fibrosing mediastinitis usually is
due to TB or histoplasmosis but can be due
to sarcoidosis, silicosis, or other fungal
diseases. Patients develop an intense
fibrotic process that leads to compression of
mediastinal structures that can lead to the
superior vena cava syndrome, tracheal
stenosis, or obstruction of the pulmonary
arteries or veins.