3 DISCUSSION
The formation of a tracheocutaneous fistula following a thyroidectomy
may be secondary to several etiologies. It has been previously reported
following radiation therapy2, iatrogenic tracheal
injury, prolonged intubation following procedure, infection of surgical
site, excessive cautery on tracheal wall4, or pressure
induced ischemia3. Many surgeons attempt to minimize
excessive cautery around the trachea to prevent necrosis, using cautery
on a lower setting when necessary4. Some authors
report tracheomalacia as a potential cause of tracheal necrosis as
thyroid tissue may act as framework for the trachea, causing tracheal
collapse when removed.1
In our case we postulate the formation of a seroma postoperatively
potentially led to a pressure induced necrosis of the anterior tracheal
wall. Only one case has been reported to our knowledge of tracheal
necrosis in the setting of a post-operative seroma. The pathogenesis of
a seroma induced pressure necrosis is likely similar to the hypothesized
manner in which elevated cuff pressure leads to tracheal necrosis. The
hypothesis is the cuff pressure exceeds perfusion pressure of tracheal
mucosa, resulting in pressure necrosis.5 The other
manner in which tracheal necrosis may have occurred is due to disrupting
the blood supply to the tracheal wall. Blood supplying the trachea stems
from the inferior thyroid artery. These branches can be very delicate
and easily interrupted with cauterization during removal of thyroid
tissue.5 The largest risk factor in this patient for
tracheal necrosis would be the need for a second procedure for complete
removal of thyroid tissue. Compared to a single procedure, a two-step
procedure would increase the amount of time intubated and lead to repeat
use of cautery around anterior tracheal wall. Other common risk factors
for tracheal necrosis that were not a factor in our patient include
post-operative infection, large thyroid goiter that might have
compromised tracheal blood supply, marked bleeding during procedure
leading to excessive cauterization for hemostasis, prior chemoradiation,
among others.7