Written by Clay Smith
Practicing to find the midpoint of the cricothyroid membrane with ultrasound is a much better way to learn than by using only external landmarks and no ultrasound.
- Wish you had a primer on performing a cric? Now you do.
- EMCrit has this video of the bougie-assisted technique.
Why does this matter?
The cricothyroid membrane may be difficult to palpate in some patients. Yet this is a critical skill in order to place a surgical airway in a "can't intubate, can't ventilate" scenario.
See below the surface
Anesthesia residents were randomized to practice neck palpation for the midpoint of the cricothyroid membrane with or without ultrasound. Then all residents used external palpation without ultrasound to make a mark on the neck of ten patients each. Unbeknownst to them, these patients previously had the gold-standard midpoint marked with invisible ink using ultrasound guidance. Those who were allowed to practice with the help of ultrasound performed much better when they had to find the midpoint without the help of ultrasound. The primary outcome was the percentage of attempts with the distance ≤5 mm measured from their mark of the midpoint compared to the gold-standard invisible ink mark. Those who practiced with ultrasound compared to those who did not were twice as accurate: 65% vs 30%, respectively. The ability to see below the surface with ultrasound and then correlate that to external landmarks is very helpful in being able to find the cricothyroid membrane when ultrasound is not available. This would be a great skill to practice on an ultrasound rotation or as part of an ultrasound course. I can't wait to practice this!
They used a portable system with a 10–5 MHz linear-array transducer. Here are some select images for the cited article.
Practice of Ultrasound-Guided Palpation of Neck Landmarks Improves Accuracy of External Palpation of the Cricothyroid Membrane. Anesth Analg. 2018 Jun 28. doi: 10.1213/ANE.0000000000003604. [Epub ahead of print]
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Reviewed by Thomas Davis
There was an excellent literature review this month in AJEM on ultrasound to determine landmarks prior to cricothyrotomy with excellent figures and step by step approach.