Discussion
This is the first study to report results according to airway management
for patients with DNM secondary to DNI. The airway should be carefully
monitored throughout the course of treatment with a flexible
laryngoscope. We found that orotracheal intubation should be the first
trial and delayed tracheotomy was better than early tracheotomy if
needed.
When it comes to DNM secondary to DNI, it is imperative to diagnose the
condition with CT (scanned from skull base to diaphragm) as quickly as
possible and conduct immediate surgical drainage with a synchronous
approach to the mediastinum.4 CT is important in
making a diagnose of DNM, in determining the level of infection and the
pathways of spread of infections from the neck to the mediastinum, and
in planning a successful treatment.5 High risk factors
for the development of DNM from DNI include older age (> 65
years), cervical necrotizing fasciitis, involvement of two or more
cervical spaces, the presence of comorbidities such as chronic renal
failure, diabetes mellitus, cardiovascular and pulmonary diseases,
C-reactive protein ≥30 mg/dL, and neutrophil to lymphocyte ratio ≥
13.6-8 In our study, 50% and 55 % of all patients
had DM and pulmonary diseases, respectively.
Propagation of infection in the cervical space readily descends into the
mediastinum as a result of gravity, respiration, and negative thoracic
pressure. It has been known that inflammation in the cervical space
readily descends into the mediastinum passing through potential space
such as retropharyngeal, pretracheal, and carotid spaces. It has been
reported that over 70% of cases of DNM spread via the retropharyngeal
space.9 However, in our case series, 18 (90%)
patients had involvement of the pretracheal space. The pretracheal space
leads from the thyroid cartilage and the thyroid gland to the
pericardium. Infection following this route can lead to suppurative
pericarditis and empyema. Therefore, is would be dangerous to undertake
tracheotomy if fulminant infection is present in the pretracheal space.
Primary surgical treatment for DNM secondary to DNI is aggressive
drainage. This surgical approach to the mediastinum depends on the
supra-carinal or the infra-carinal location of the
disease.10,11 The operator should have the ability to
open all relevant compartments. Failure of drainage can increase the
morbidity and mortality. Experienced surgeon could shorten the overall
general anesthetic time and decrease the morbidity and mortality.
According to one report including 185 cases of deep neck infection,
10.3% patients had upper airway obstructions.12 It
developed more frequently in patients with retropharyngeal space abscess
and Ludwig’s angina (36.4% and 27.3%). Three of 19 patients (15.8%)
died of airway obstruction. Therefore, airway management in deep neck
infection has been known as one of the most important determining
factors for mortality. Ludwig’s angina, known as a bilateral
inflammation of sublingual, submental, and submandibular spaces, is not
rare in severe DNI. The gold standard of airway management in Ludwig’s
angina is tracheotomy. However, Ludwig’s angina is not a risk factor for
DNM. In addition, not all included patients originated from Ludwig’s
angina in our series. Thus, we should consider individualized airway
management in DNI. In Ludwig’s angina, neck infection or edema is
usually confined to a suprahyoid lesion, rather than a descending
infection, and compressed upper airway including the oropharynx and the
larynx. On the other hand, in DNM secondary to DNI, neck edema literally
descends to the thoracic diaphragm. There has been no report about the
incidence of airway problems or management of patients with DNM.
In the airway management of a deep neck infection, tracheotomy has been
recommended if fiberoptic intubation is infeasible, if the clinician is
not skillful in the use of an awake fiberoptic intubation, or if
intubation attempts have failed.13 In the treatment of
DNM, tracheotomy is considered mandatory by some authors due to upper
airway obstruction and repeated aspiration during
swallowing.14 It is also suggested for the purpose of
avoiding endotracheal intubation since its accidental dislodgement of
the tube can be fatal because of the almost impossible task of
re-intubation if massive upper airway edema is present. However, Karkas
et al. have the development of tracheal stenosis in two (11.8%) of 17
patients after tracheotomy during DNM treatment.10 We
did not experience tracheal stenosis, although the potential of this
complication was higher in simultaneous (early) tracheotomy and
cervicotomy. A recent report observed that the presence of bacterial
biofilm and higher amounts of microbes in the tracheal tissue can
increase the rate of laryngotracheal stenosis.15 In
addition, tracheotomy is not always necessary because early cervical
drainage and anti-inflammatory therapy could prevent upper airway
obstruction in DNM.16 The present study also revealed
that tracheotomy rather enhanced contamination of the pretracheal space
and prolonged the duration of hospital stay. Among 7 (35%) patients
with tracheotomy, mortality rates of early tracheotomy and late
tracheotomy were 75% and 0%, respectively, with early tracheotomy
showing significantly higher mortality (p = 0.032 ). Therefore,
tracheotomy should be performed with great caution in patients with DNM.
Tracheotomy should be conducted when a long-term mechanical respiratory
support is needed after controlling neck infection. Close clinical and
radiological postoperative follow-up investigations are needed with
early surgical re-intervention if necessary. An infected wound caused by
sputum can be regarded as one of tracheotomy-related
complications.17 In the present study, one patient
with early tracheotomy developed communication between neck wound and
tracheal lumen. It also aggravated pulmonary complications such as
pneumonia. This patient could not survive from DNM. However, patients
who underwent late tracheotomy did not have any wound infection caused
by sputum because neck infection was controlled after the initial
operation. In addition, diffusion of sputum onto the neck and the
mediastinum can be prevented by suturing the tracheal wall with
surrounding tissues during a late tracheotomy.
Keeping orotracheal intubation was safe and adequate after the initial
surgery in our cases. The extubation was tried as early as possible
(within 12 to 24 h after the surgical procedure) in the ICU. Therefore,
endotracheal intubation should be performed as the first airway
management in DNM without prolonged intubation. Conducting orotracheal
intubation for an extended period is likely to cause complications such
as laryngotracheal stenosis, especially in deteriorated patients.
This study has some limitations. The retrospective design of our study
was its major inherent
limitation. In addition, statistical analysis was limited owing to our
small sample size. This is
because DNM secondary to DNI is a rare disease. To eliminate various
biases, a prospective
multicenter study for airway management in DNM is needed to render more
reliable results.