Written by Megan Hilbert
Ultrasonography can assist in identification of cricothyroid membrane for scalpel cricothyroidotomy pre-planning but should not be used in completion of the procedure itself.
Why does this matter?
A failure of 15% first pass success rate in ED intubation attempts can result in a cannot intubate-cannot oxygenate (CICO) scenario. Based on its speed and reliability, scalpel cricothyroidotomy is recommended in these situations, but misidentification of the membrane by palpation increases risk of adverse outcomes, especially when landmarks are not palpable. POCUS has been shown to help find and mark the cricothyroid membrane.
Impalpable = Impossible?
This was a prospective randomized control trial that included evaluation of scalpel cricothyroidotomy technique in Emergency Medicine and Anesthesia residents (n = 42) in a CICO simulation using a porcine model with impalpable landmarks. Primary outcome evaluated was size of vertical incision with secondary evaluation of procedural completion time, severity of tissue injury, and correct tube placement. Participants underwent a 1 hour teaching session and simulation 1 week later.
Current airway guidelines recommend an 8-10cm vertical incision from the sternal notch. The ultrasound group in this study was able to achieve similar success rates and degree of tissue injury to the non-ultrasound group, with a significantly smaller vertical incision: median (IQR), 35.0 (15,40) vs 65.0 (52,100) mm, p =0.02. The ultrasound group took a longer time to complete the procedure: median (IQR), 200.5 (126,267) vs 93.5 (71.0,167.5) seconds, p=0.04.
In a situation where time is of the essence, ultrasound may theoretically prevent adverse outcomes related to a larger incision size (ie: damage to surrounding structures) but too greatly increases time to completion of this life-saving intervention. As such, it may be beneficial in pre-procedural planning but should not be used in the completion of the procedure itself.
Role of ultrasonography in an impalpable tissue larynx model during a simulated front-of-neck access scenario: a randomized simulation study. CJEM. 2022 Nov 8. doi: 10.1007/s43678-022-00399-6. Epub ahead of print.