Page 302 - Small Animal Internal Medicine, 6th Edition

274 PART II Respiratory System Disorders

abnormalities and laryngeal function. These procedures are
indicated in any dog or cat with clinical signs that suggest
VetBooks.ir upper airway obstruction or laryngeal or pharyngeal disease.
It should be noted that patients with increased respiratory
efforts resulting from upper airway obstruction might have
difficulty during recovery from anesthesia. For a period
between removal of the endotracheal tube and full recovery
of neuromuscular function, the patient may be unable to
maintain an open airway. Therefore laryngoscopy should not
be undertaken in these patients unless the clinician is prepared
to perform whatever surgical treatments may be indicated
during the same anesthetic period.
The animal is placed in sternal recumbency. Anesthesia
is induced and maintained with a short-acting injectable
agent without prior sedation. Propofol is commonly used.
Depth of anesthesia is carefully titrated, with just enough
drug administered to allow visualization of the laryngeal
FIG 17.1 cartilages; some jaw tone is maintained, and spontane-
Lateral radiograph of the neck, larynx, and pharynx ous deep respirations occur. Gauze is passed under the
showing normal anatomy. Note that the patient’s head and maxilla behind the canine teeth, and the head is elevated
neck are not rotated. The left and right osseous bullae,
mandibles, and frontal sinuses are all superimposed. by hand (preferred) or by tying the gauze to a stand (Fig.
Excellent visualization of the soft palate and epiglottis is 17.3). This positioning avoids external compression of
possible. Images obtained from poorly positioned patients the neck.
often result in the appearance of “lesions” such as masses Gentle retraction of the tongue with a gauze sponge
or abnormal soft palate because normal structures are should allow visualization of the caudal pharynx and larynx.
captured at an oblique angle or are superimposed on one Avoid distorting the normal anatomy with excessive retrac-
another. tion. A laryngoscope is used for proper illumination of this

FIG 17.3
Dog positioned with the head held off the table by gauze
FIG 17.2 passed around the maxilla and hung from an intravenous
Lateral radiograph of a dog with a neck mass showing pole. The tongue is pulled out, and a laryngoscope is used
marked displacement of the larynx. to visualize the pharyngeal anatomy and laryngeal motion.