Page 329 - Small Animal Internal Medicine, 6th Edition

CHAPTER 20 Diagnostic Tests for the Lower Respiratory Tract 301

VetBooks.ir TC

CC

T

A B

FIG 20.13
(A) When a transtracheal wash is performed, the animal is restrained in a comfortable
position with the nose pointed toward the ceiling. The ventral neck is clipped and
scrubbed, and the clinician wears sterile gloves. The cricothyroid ligament is identified as
described in (B). After an injection of lidocaine, the needle of the catheter (whether a
through-the-needle catheter as is shown here, or an over-the-needle catheter as described
in the text) is placed through the skin. The larynx is grasped firmly with the fingers and the
thumb at least 180 degrees around the airway. The needle can then be inserted through
the cricothyroid ligament into the airway lumen. (B) The lateral view of this anatomic
specimen demonstrates the trachea and larynx in a position similar to that of the dog in
(A). The cricothyroid ligament (arrow) is identified by palpating the trachea (T) from
ventral to dorsal until the raised cricoid cartilage (CC) is palpated. The cricothyroid
ligament is the first depression above the cricoid cartilage. The cricothyroid ligament
attaches cranially to the thyroid cartilage (TC). The palpable depression above the thyroid
cartilage (not shown) should not be entered.

catheter and the syringe can make it easier to connect and Endotracheal Technique
disconnect the syringe. Aspirations should be forceful and The endotracheal technique is performed by passing a 5F red
should be repeated at least five or six times, so that small rubber or male dog urinary catheter through a sterilized
volumes of airway secretions that have been aspirated into endotracheal tube. The length of the catheter must be suffi­
the catheter are pulled the entire length of the catheter into cient to extend beyond the end of the endotracheal tube by
the syringe. several centimeters and to nearly reach the carina.
The procedure is repeated using additional boluses of The animal is anesthetized with a short­acting intrave­
saline until a sufficient amount of fluid is retrieved for analy­ nous agent to a sufficient depth to allow intubation. Propofol
sis. A total of 2 to 3 mL of turbid fluid is adequate in most or, in cats, a combination of ketamine and acepromazine or
instances. The clinician does not need to be concerned about diazepam is effective. Premedication with atropine, particu­
“drowning” the animal with infusion of the modest volumes larly in cats, is considered to minimize contamination of the
of fluid described because the fluid is rapidly absorbed into trachea with saliva. Cats with lower respiratory tract disease
the circulation. Failure to retrieve adequate volumes of may have airway hyperreactivity and generally should be
visibly turbid fluid can be the result of several technical dif­ administered a bronchodilator before the tracheal wash. Ter­
ficulties, as outlined in Fig. 20.14. butaline (0.01 mg/kg) can be given subcutaneously to cats
The catheter is removed after sufficient fluid is collected. not already receiving oral bronchodilators. It is also prudent
A sterile gauze sponge with antiseptic ointment is then to keep a metered dose inhaler of albuterol at hand to be
immediately placed over the catheter site, and a light bandage administered through the endotracheal tube or by mask if
is wrapped around the neck. This bandage is left in place for breathing becomes labored or wheezes are auscultated.
several hours while the animal rests quietly in a cage. These A sterilized endotracheal tube should be passed without
precautions minimize the likelihood that subcutaneous dragging the tip through the oral cavity. The animal’s mouth
emphysema or pneumomediastinum will develop. is opened wide with the tongue pulled out, a laryngoscope