Page 118 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 8 · Surgery of the extrathoracic trachea

A general physical examination should proceed, with medical management alone. However, these authors agreed
particular attention to the respiratory and cardiovascular that surgery can play a role when conservative manage-
VetBooks.ir and murmurs may reveal underlying pulmonary or cardiac to medical management after some years of successful
ment fails and that animals could fail to continue to respond
systems. Careful thoracic auscultation for crackles, wheezes
conservative therapy.
disease that may be amenable to medical therapy. The neck
is gently palpated to search for compressive masses.
Surgical treatments, including dorsal membrane
Manual tracheal palpation often induces a cough and may plic ation, chondrotomy, and tracheal resection and anas -
reveal a flaccid, collapsible trachea. to mosis, have been described. However, the most com -
monly performed procedure is the use of extraluminal
Imaging poly propylene ring prostheses. Regardless of the technique
Survey lateral radiography of the entire trachea should used, serious complications are not uncommon, even in the
include the cervical region and thorax (see Figure 8.10ac). hands of trained surgeons. For this reason, one cannot
Requesting three views is advised, with the forelimbs overemphasize the importance of identifying and treating
pulled caudally in one lateral radiograph and cran ally in concurrent causes of respiratory distress, and recommend-
i
the contralateral radiograph to ensure that an unob- ing surgery only for those animals that have failed to
structed view of the entire trachea is obtained. Otherwise, respond to aggressive conservative therapy and for whom
the forelimbs will always be positioned over the thoracic tracheal collapse is the primary cause of their clinical signs.
inlet, obscuring this most commonly affected region.
Whilst radiography is often diagnostic for collapse, fluor- Extraluminal polypropylene ring prostheses
oscopy is preferred to standard radiography to eval uate Indications: Animals determined to be relatively good
the trachea throughout all phases of respiration. Whenever anaesthetic and surgical candidates, with cervical
possible, fluoroscopy during a coughing episode is most
tracheal collapse extending no further caudally than the
useful to reveal dynamic collapse under more extreme second intercostal space, are candidates for extraluminal
physiological airway pressures; however, this is rarely per-
prostheses. Buback et al. (1996) reported excessive
formed if treatment is not imminent. morbidity rates when attempting to place prosthetic rings
Tracheobronchoscopy is considered by some as the on the thoracic trachea; it is, therefore, not recommended
‘gold standard’, particularly for evaluation of the mainstem at this time. More recently, Becker et al. (2012) have chal-
bronchi and for the collection of samples for cytology lenged this statement, demonstrating that some dogs with
and culture. Tracheoscopy also permits ‘grading’ of the
combined cervical and intrathoracic collapse may benefit
tracheal collapse: grades 1, 2, 3 and 4 indicate a progres- from cervical rings, especially if the clinical signs are
sive decrease in tracheal lumen size from 25% reduction mostly inspiratory.
through 50% and 75% to almost 100%. Unfortunately,
tracheobronchoscopy requires general anaesthesia, which Prosthesis preparation: Prosthetic rings can be purchased
is often dangerous for animals in respiratory distress. commercially or manually crafted from a polypropylene
General blood tests, including a complete blood count syringe case or syringe. The size of the intended recipient
and biochemistry panel, should be performed, as should a
will determine which of these is most appropriate. A saw,
cardiac evaluation when necessary and oral/laryngeal dental drill or pipe cutter can be used to cut the syringe or
examination whenever possible. The latter is typically syringe case into sections that are 5–8 mm wide, with
performed during an intervention to avoid an unnecessary approximately five holes and one open end. Sandpaper or a
anaesthetic episode.
dental drill burr is recommended to smooth any rough
edges before use. These techniques are described in detail
Conservative management elsewhere (Hobson, 1976). The pros theses can be auto-
Aggressive medical management with corticosteroids, anti- claved and stored for future use. Commercially available
tussives, bronchodilators and/or sedatives/tranquillizers is tracheal ring prostheses are now recommended.
always recommended prior to surgical treatment for tracheal
collapse if there is no imminent threat of airway obstruction. Technique: When possible, a brief oral/laryngeal examin-
The role of antibiotics remains unclear. Johnson and ation and tracheoscopy are performed under sedation,
Fales (2001) reported that 86% of cases of tracheal collapse followed by rapid induction of anaesthesia. Although un-
in dogs had positive cultures obtained via trach eo- common in the authors’ opinion, concurrent laryngeal par -
l
bronchoscopy. This finding, however, might be attributed a ysis would be important to address simultaneously and
to oropharyngeal contamination, as cytological evidence identify prior to surgical manipulation of the trachea. More
of inflammation was rare and mixed bacterial populations commonly, long soft palates are identified that might require
were common. Normal dogs often have positive cultures partial staphylectomy. Peri operative antibiotics are recom-
(Johnson and Fales, 2001). Antibiotics may be indicated if mended, as the tracheal lumen is not a sterile environment,
clinical signs suggest infection or a single bacterial popu- and full-thickness sutures and a prosthesis will be placed.
lation is cultured. The patient is placed in dorsal recumbency with dorso-
It is also imperative to manage obesity, to limit expo- flexion of the neck as it is draped over a towel or sandbag
sure to second-hand smoke and to replace neck leads with the forelimbs pulled caudally. This position increases
with harnesses to help reduce clinical signs. Medical man- exposure to the trachea as well as elevating it to a more
agement for this disease has been described elsewhere, superficial location.
and readers are referred to these sources for a complete A ventral midline cervical incision, from the caudal
list of options (Fossum, 2002; Mason and Johnson, 2004). larynx to the thoracic inlet, exposes subcutaneous tissues
and the paired sternohyoid muscles, which are carefully
Surgical treatment separated with sharp and blunt dissection. It is imperative
for the surgeon to identify the delicate segmental tracheal
The indication(s) for surgical management of tracheal blood supply located in the lateral pedicles (Figure 8.11a). In
collapse are still under debate. White and Williams (1994) addition, care must be taken to avoid the recurrent laryngeal
l
reported a >70% long-term response (>12 months) with nerve, located in the lateral pedicle along the dorso ateral

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