Sedated Laryngeal Exam

Sedated laryngeal exam is a practical procedure used to further evaluate patients with stridor.  Stridor is a higher-pitched noisy breathing that originates at the level of the larynx or below (as opposed to stertor, which occurs above the level of the larynx and is typically lower in pitch).

The most common reason for a sedated laryngeal exam is for a patient with suspected laryngeal paralysis; however, upper airway partial obstruction with a mass or foreign body, abscess, or laryngeal collapse are other potential causes.  Always have the owner keep their phone on while you do a laryngeal exam, as you may find things you need to deal with right then and there.

These patients can easily go into crisis with small amounts of heat, stress, or exertion.  I schedule these for first thing in the morning and go straight from the owner to IV catheter to procedure to limit the stress of being in hospital.  On the other end, I like the owner to be free to come pick up relatively quickly after the procedure, to avoid a hospital stay and the associated stress leading to post-extubation crisis.

The main (but generally low) risk of a laryngeal exam is difficulty safely extubating the patient.  Similar to a brachycephalic patient, they can experience trouble maintaining their airway when they are sedate.  It is important to warn the owner of this risk of the procedure (and document that you warned them), and to maintain the endotracheal tube for as long as possible.  I like to recover these patients propped up in sternal with a towel under their chin (but not pressing on their neck).

Unlike most procedures, here we want to AVOID medications that interfere with muscle contraction (no benzodiazepines), most medications that cause respiratory depression (opioids,) and most medications that cause sedation, particularly irreversible sedation (partial mu opioids, acepromazine).

Procedure prep:

• Place an IV catheter (no pre-medications)
• Patient should be in sternal recumbency and pre-oxygenated
• Have at the ready:
  • Gauze to hold patient’s tongue
  • Tongue depressor (or two taped end-to-end together to make an extra-long tongue depressor) to push the soft palate dorsally
  • Laryngoscope
  • Endotracheal tubes
  • IV catheter flush
  • Propofol
  • Doxapram
    • Dose is 1.1 mg/kg IV, but the cheater way to do it is 2 ml IV for a big dog, 1 ml IV for a medium dog

Procedure:

1. Give propofol slowly IV to effect.  You are looking for no jaw tone but still breathing.  Because there are no pre-meds, it will take much more propofol than you usually use!
2. Have your assistant hold the upper jaw and pull tongue out and ventrally with gauze.
3. Place laryngoscope on tongue and epiglottis to view arytenoids.  Use tongue depressor to push soft palate dorsally for full view.
4. Observe whether (or not) patient is taking deep breaths.  Panting or quick shallow breaths are not helpful!  If the breaths are shallow or panting, give doxapram; it will take effect quicky.
5. Have assistant call out “IN” every time the patient breaths in.  This is extremely helpful to trigger you to know when the arytenoids should be opening.  Many laryngeal paralysis dogs have paradoxical movement, where the arytenoids collapse inward on inhalation. If you don’t know when the patient is breathing in, you may mistake this cycle (of slightly open then collapsed into the lumen) for normal laryngeal movement.  With laryngeal paralysis, the vocal folds also often contribute to a small airway by collapsing inward on inhalation.
6. After evaluation of the arytenoids, the laryngeal lumen, and the start of the trachea, intubate and perform a thorough oral and oropharyngeal exam for masses, swellings, and/or foreign bodies.
7. Wake the patient up in sternal recumbency with the chin propped up.  Maintain the tube with partial or full cuff inflation for as long as possible.

Visuals:

Pictured in the photo below are the items I like to have ready along with my endotracheal tube: Laryngoscope, saline catheter flush, doxapram, propofol, and a “double” tongue depressor.

In this video, propofol has been given sufficient for an exam, but the patient is not taking deep breaths that would help with evaluation.

In this video, doxapram IV has been added to promote deep breaths.  The assistant is calling out “IN” when the patient breathes in.  Without the assistant telling when “IN” is, you might be fooled by the movement here.  However, with the assistant calling out “IN,” you realize that this patient is actually moving both the vocal folds and the arytenoids INTO the lumen during inspiration.  This is laryngeal paralysis with paradoxical movement, and is a likely major reason why the disease seems to progress.

#practicepearls #videotutorials

 About the Guide: Jess Barrera, DVM, MS, DACVS-SA, ACVS Fellow Surgical Oncology

Dr. Jessica Barrera graduated vet school from Colorado State in 2006. She then did a rotating internship at Animal Surgical and Emergency Center, then a surgery internship at Oregon State University, then back to Colorado State University for small animal surgery residency as well as a one year fellowship in surgical oncology. She's currently in private specialty practice in Northern Colorado consisting of ~60% surgical oncology, ~20% minimally invasive soft tissue and orthopedics, and ~20% other soft tissue and orthopedics. Her professional passion (besides being in the operating room) is encouraging, supporting, and bringing confidence general practitioners in the realm of surgery.