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Emergency Ultrasound

Ask The Expert

Section edited by Rob Bramante, MD


“What can I do to make it easier to drain a peritonsillar abscess using ultrasound?”

Bob Gekle, MD, RDMS, FACEP
Associate Program Director, Emergency Medicine Residency
Associate Director, Emergency Ultrasound
Assistant Professor, NY Institute of Technology
Good Samaritan Hospital Medical Center
Progressive Emergency Physicians, PLLC

Sonographic diagnosis of peritonsillar abscess is well established as a standard in emergency medicine. Typically these are diagnosed with an endocavitary probe. It is also recommended that the drainage of a peritonsillar abscess be done under dynamic ultrasound guidance when diagnosed. The reason for this is two-fold. 1. There is less of a chance of missing the abscess, which is a known possibility with a blind approach and 2. The carotid artery, which usually lies just posterior to the tonsil can be avoided.

Many emergency physicians and residents have come to me explaining that this is a difficult proposition given that most of these patients are presenting with trismus and pain. It has been recommended to start the examination with cetacaine or benzocaine spray to the area. However, one has to remember that the effective dose of these medications when viscous or aerosolized is variable and there is the possibility of iatrogenic methemoglobinemia. The minimum amount possible to achieve anesthesia and prevent the gag-reflex of the area should be used. Other practitioners have described using viscous lidocaine or even aerosolized injectable lidocaine. I recommend discussing with a toxicologist if you are going to perform the latter, as this is definitely an “off-label” usage of the medication.

After significant anesthesia of the area, the endocavitary probe is inserted and the fluid collection, usually with surrounding hyperemia, is visualized. It has been recommended to do a guided needle placement to drain the abscess. Again, this is sometimes easier said than done, as the endocavitary probe can be quite large in relation to the patient’s oral cavity. Remember that many patients with this pathology have significant oropharyngeal swelling.

If available, a “hockey-stick” high-frequency linear probe has demonstrated some success, and some physicians prefer it to the endocavitary probe as it has a small footprint and can be inserted within the oropharynx with greater success than the endocavitary probe in some patients. Many emergency departments do not have the hockey stick probe and so other approaches have been described.

When direct sonographic visualization of the needle placement is not possible, an approach that I have found is to use a video laryngoscope to assist in this ultrasound guided procedure. Once the area is significantly anesthetized, the procedure is as follows. Have the patient sitting up with his/her head resting against the stretcher. Use the endocavitary probe to visualize the abscess. Measure the depth of the abscess. Insert a video laryngoscope and point it directly at the site of the endocavitary probe’s contact with the mucosa. Then remove the endocavitary probe. Use the video laryngoscope and needle aspirate at the visualized site, inserting the needle as deep as was measured with the endocavitary probe. Prior to inserting the needle, it is important to remember that when a video laryngoscope is inserted with a patient sitting up, it is the “upside-down” view of what is used for intubation, so the right side will appear on the left and the left on the right.

It sounds like it would be cumbersome, but remember that most video laryngoscopes are much thinner than an endocavitary probe, and its placement is limited to the oral cavity, not the pharynx. With this procedure, one does not “turn the corner” to visualize the vocal cords. It is only cumbersome for the few seconds when both the endocavitary probe and the laryngoscope are in the mouth at the same time. In addition, the laryngoscope handle can be used just as with intubation to move the tongue out of the way and facilitate much greater visualization.

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