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How to Perform a Transtracheal Wash in the Field
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1. Introduction
The transtracheal wash (TTW) is a relatively noninvasive procedure that can be easily performed in the field. This is the ideal method for collecting respiratory secretions for culture in cases of suspected bacterial pneumonia. First described in horses in the early 1970s,1 the TTW procedure requires few supplies and can be performed in the sedated or unsedated horse depending on temperament.2–6 TTW avoids the need for an endoscope and reduces the chance of culturing upper respiratory flora by directly sampling the lower respiratory tract.7 Despite the ease of TTWs, many practitioners are hesitant to perform these procedures. It is the authors’ hope that practitioners will become reacquainted with this underutilized skill.
Respiratory secretions are brought up from the lungs via mucocilliary clearance; thus, samples obtained from the tracheal puddle represent secretions from all areas of the lungs.5 A TTW is especially indicated in cases when localized lung pathology is suspected (e.g., an abscess or discrete pneumonia), because more directed respiratory sampling such as a bronchoalveolar lavage may obtain a false-negative culture result if a nonaffected portion of the lung is inadvertently sampled.8
It is highly recommended that TTWs be performed before commencing antibiotic therapy to increase the chance of identifying the causative bacterial pathogen. The TTW fluid may also be submitted for cytology, and reference ranges have been described.9–11 However, cells from the upper airway may be present in the tracheal puddle, and results may not be purely representative of the lower airway.7,8
2. Materials and Methods
Supplies (Fig. 1):
- Sedation
- Clippers
- Surgical scrub
- Alcohol
- 4 x 4 gauze
- 2% lidocaine neat
- 3- or 5-mL syringe
- 25-gauge needle
- Sterile gloves
- #15 scalpel blade
- Transtracheal wash aspiration kita
- If no kit available (Fig. 2):
- Introduction catheter: 12-gauge intravenous catheterb
- Flushing catheter: #5 or #6 French polypropylene urinary catheterc, 45 cm long for foals and 100 cm for adults
- If no kit available (Fig. 2):
- 60-ml syringes (2)
- 20-gauge needles for drawing up saline and lidocaine
- Sterile physiological saline
- Self-adhesive elastic bandaged
- Culture media swab or vial
- Red and purple top tubes
3. Preparation of the Patient—Sedation
Depending on the horse’s temperament and severity of illness, sedation may or may not be required or recommended to perform a TTW. If the horse is prone to moving around, light sedation or a twitch may help reduce the chance of contamination during the procedure. Because you will be in a relatively dangerous spot while performing the procedure, personal safety must always be a concern. Light sedation with xylazine and butorphanol is usually sufficient for the procedure because the procedure itself is not lengthy. The addition of butorphanol will also decrease the cough reflex. Coughing during the procedure will displace the tracheal puddle, making it more difficult to aspirate the fluid and potentially increasing the risk of contamination from the upper airways.
4. Preparation of the Site
Palpate the ventral midline of the horse’s neck. The sternocephalicus muscles will overlie the trachea caudally. As the muscles run cranially they move abaxially and lie lateral to the trachea, which allows for easy palpation of the tracheal rings. The TTW site is approximately halfway between the larynx and the point at which the rings can no longer be palpated because of the overlying sternocephalicus muscles. This will likely be approximately 1/3 to 1/2 the way down the neck. The area should be clipped and aseptically prepared. The authors prefer a wide clip area so that the trachea can be grasped and stabilized while maintaining sterility of the non-dominant hand. The horse’s mane should be braided or taped out of the way to ensure it will not contaminate your TTW site or hands during the procedure.
The lidocaine can be instilled into the TTW site at this point and followed by a second prep of the area. After donning sterile gloves, it could also be drawn up and infiltrated into the site using aseptic technique. When infiltrating the site with lidocaine, first create a bleb under the skin and then direct the needle slightly deeper to infiltrate the tissues adjacent to the trachea.
5. Transtracheal Wash Procedure
If possible, a small table or counter with the sterile field should be available within arm’s reach of the horse. All of the supplies should be prepared and organized before commencing the procedure. Sterile gloves should be donned at this point if they have not been donned already. Using aseptic technique, 20 to 30 mL of sterile saline is drawn up into each of two 60-mL syringes and placed onto the sterile field. Palpate the trachea and relocate the TTW site. Palpate the space between the two tracheal rings and make a small incision with the #15 scalpel. The incision is vertical—approximately 1 to 2 cm long or twice as long as the TTW introduction needle (or catheter)—along the skin over the middle of the trachea. If using an intravenous (introduction) catheter and polypropylene urinary (flushing) catheter instead of a TTW kit, this is a good time to ensure that the flushing catheter fits in the lumen of the introduction catheter (it would be very frustrating to find this out after the introduction catheter is positioned in the horse). [...]
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