Download superior laryngeal nerve block using a novel ultrasound technique

1325235 - SUPERIOR LARYNGEAL NERVE BLOCK USING A NOVEL ULTRASOUND TECHNIQUE
Balvindar Kaur1, Raymond Tang1, Andrew Sawka1, Himat Vaghadia1
1. Department of Anaesthesia, University of British Columbia, Vancouver General Hospital, Vancouver,
BC, Canada
Introduction: We investigated the feasibility of performing ultrasound guided superior laryngeal nerve (SLN)
block using a novel ultrasound technique. To date, only a single case report performed this block under
ultrasound guidance, but the SLN was not visualized and surrogate landmarks were utilized.1,2 We
hypothesized that with the improvements in ultrasonographic technology, the SLN could be visualized to enable
accurate placement of the needle.
Methods: After ethics and institutional approval, a 8-15 MHz transducer (HST15-8/20 linear probe (Ultrasonix,
Richmond, BC, Canada) was used on 2 fresh unembalmed cadavers to identify the SLN nerve bilaterally.
Cadavers in the supine, neck extended position were scanned using the transducer placed in the transverse
position relative to the skin, to identify the greater cornu of hyoid bone and the superior lateral aspect of the
thyrohyoid membrane. By rotating the medial aspect of the probe cephalad, the SLN was identified. A needle
was inserted in-plane to the ultrasound beam, advanced to the SLN and 1ml of green dye was injected. Correct
dye placement was confirmed by a blinded anatomist. Dye spread was noted and photographed.
Results: In both cadavers, we confirmed successful bilateral dye placement on the SLN by anatomical
dissections.
Discussion: Visualization of the SLN has not been consistently successful leading some authors to advocate
use of the hyoid image or superior laryngeal artery as surrogate ultrasound landmarks for blockade of the nerve.
1,2 Current ultrasound technology has improved image processing and resolution and now made it possible to
identify and target the SLN accurately under ultrasound guidance. We propose that this method may be used in
humans to perform the block safely and successfully.
References: 1. Manikandan S, Neema PK, Rathod RC. Ultrasound guided bilateral superior laryngeal nerve
block to aid awake endotracheal intubation in a patient with cervical spine disease for emergency surgery.
Anaesthesia Intensive Care 2010; (28): 946-948
2. Green J.S., Tsui B.C.H. Applications of ultrasonography in ENT: Airway Assessment and Nerve Blockade.
Anesthesiology Clin 2010; (28): 541-553
3. Vaghadia H, Lawson R, Tang R, et al. Failure to visualize the superior laryngeal nerve using ultrasound
imaging. Anaesth Intensive Care 2010; 39(3): 503
Pre and post injection images with arrows indicating the SLN