Topical anesthesia application is the most inexpensive and the most neglected procedure in a voice lab. The laryngologist who can — and frequently does — anesthetize the vocal cords will offer patients many more answers than one who does not.
Lidocaine Is the Laryngologist’s Best Friend
Four percent lidocaine applied onto the vocal cords provides dense anesthesia. Two percent lidocaine also works. I avoid benzocaine as it seems very uncomfortable when sprayed. It is possible to make life more comfortable for your patient by using a combination formula in the nose, consisting of 4% lidocaine, neosynephrine (or oxymetazolone), stevia (adds a touch of sweetness) and peppermint (for flavor). Being kind to your patient contributes to their relaxation and an improved view for the endoscopist.
The other act of kindness is to place the lidocaine/decongestant mixture onto the nasal mucosa at the beginning of an exam, allowing 5 or more minutes for the topical decongestant and anesthetic to work. While lidocaine is frequently used in the nose and posterior pharynx, it really adds to video resolution when placed onto the structures of the larynx.
Techniques for Applying Lidocaine to the Larynx
Curved Abraham Cannula (Transoral)
The most common technique I use is to drip lidocaine transorally. Typically I place 4 cc of 4% topical lidocaine into a syringe attached to a curved Abraham cannula. I spray the posterior pharynx and caution the patient about the effects of topical anesthesia — including the initial bitter taste, then the lump-in-throat sensation. He will feel unable to swallow, and it is acceptable to spit out saliva while he is numb. The throat will feel swollen — it is not. It may feel like he is not breathing, since air will no longer be sensed as it passes over the vocal cords. It is all an illusion. Prepping the patient helps manage the sensations.
A curved cannula is passed through the mouth past the base of the tongue and tip of the epiglottis. About 1 cc is dripped into the laryngeal introitus. When it touches the trachea, the patient coughs and the lidocaine is sprayed around the throat, beginning the process of anesthesia. About 30 seconds later, I ask the patient to phonate and I drip a second cc of lidocaine onto the closed and vibrating vocal cords. This creates a laryngeal gargle as the lidocaine bubbles on the surface of the vocal cords until the patient runs out of air, then often coughs. After another minute, a third and if needed a fourth cc of lidocaine can be dripped onto the vibrating vocal cords. Usually 3–4 cc are adequate to pass an endoscope into the larynx, touching the vocal cords if needed. I can typically pass the endoscope through the trachea to the carina with this method of anesthesia.
With this method, the topical anesthetic can be dripped blindly — and if a laryngeal gargle is heard, the medication was placed in the correct location. Alternatively, a flexible endoscope positioned in the nasopharynx can be used to monitor and confirm application directly onto the vocal cords.
Mucosal Atomization Device (MAD)
Other options for topical anesthesia include using an atomizer, such as the disposable MAD® device. With the flexible cannula, lidocaine can be aimed at the larynx. Initially spray about 1 cc, allowing some anesthesia to set in — then repeat one to three more times. This spraying can be done blindly or under direct visualization with an endoscope in the nose.
Catheter Through the Nose
A colleague places a small 10 French suction catheter through the nose and applies the lidocaine through this catheter onto the vocal cords, generating a laryngeal gargle.
Transcricothyroid Membrane Injection
If the patient cannot tolerate any of these methods, I apply 3 cc of injectable lidocaine with epinephrine using a ½-inch, 25-gauge needle passed through the cricothyroid membrane. This is injected all at once into the subglottic airway and the patient coughs, effectively spraying the medication over the vocal cords and onto the upper larynx and pharynx. I use this as a backup method because passing the needle through the mucosa typically generates a small amount of bleeding which can interfere slightly with the visual exam — and many individuals do not like needles. However, this technique is quicker than the dripping techniques.
Through a Working-Channel Endoscope
If I am going to utilize a procedure endoscope with a secondary channel anyway, I will drip the lidocaine through the accessory channel directly onto the vocal cords while the patient is phonating. This also generates a laryngeal gargle.
Topical anesthesia is the poor man’s high-definition endoscope. For the terrible gagger, with a combination of topical anesthesia and patience, there is no one I have not been able to examine.
What You Learned
- 4% lidocaine onto the vocal cords is transformative — it is the most underused technique in the voice lab, enabling close-up examination that is otherwise impossible.
- The laryngeal gargle confirms correct placement — if the lidocaine was dripped in the right location, the patient will produce a characteristic bubbling cough.
- Prep the patient for the sensations — explaining the lump-in-throat, inability to sense swallowing, and feeling of not breathing converts a frightening experience into an expected one.
- Multiple techniques exist for difficult exams — the transcricothyroid membrane injection is the fastest backup for the patient who cannot tolerate transoral application.
- Topical anesthesia enables optical biopsy — getting the endoscope close enough to map capillary architecture and define tumor margins requires anesthesia that eliminates the gag reflex.