Electromyography Endotracheal Tube in Thyroid Surgery

This video explains how electromyography endotracheal tubes work during thyroid surgery. Also known as, EMG ET tubes, these are a type of Intraoperative Neuromonitoring (IONM) which serve a big role preventing nerve injury by monitoring recurrent laryngeal nerve activity. Placement of the tube during intubation is important as the surface electrodes should be in contact with the vocal cords. Incorrect placement would render the tube ineffective and could cause damage to the nerve. Both, macintosh and video laryngoscopes can be used if there is poor visibility during intubation.

During surgery the tube may shift from its correct position for several reasons, primarily movement of the neck, so it’s important to check its correct placement throughout the duration of surgery. The tube itself has electrodes located at the tip. These electrodes come into contact with the vocal cords and detect electrical signals produced by the nerves. These signals are transmitted to a monitoring system which allows for continuous monitoring throughout the surgery. Once the EMG ET tube is properly placed, it can detect electrical signals produced by the nerve by using a stimulation probe. Whenever the nerve is stimulated surgeons and anesthesiologists can view the signals on a screen and listen to the sounds produced by pressing directly above the vocal cords.

The EMG signals are transmitted to a real-time monitoring system which helps surgeons view the signals on a screen and evaluate nerve integrity. During surgery this feedback helps surgeons adjust their technique to avoid nerve damage. Stimulation of the nerve creates a sinusoidal wave on the nerve integrity monitor along with an audible signal confirming its intactness. These waveforms, also known as electromyograms. In a normal resting state, should show very little electrical activity. The intensity can be seen by the amplitude of the wave. And the duration can provide information about the speed of muscle activation. A decrease or loss of EMG signals in response to nerve stimulation can indicate nerve damage or irritation.

Thyroid Cyst Removal with Hemithyroidectomy

This video shows a thyroid cyst removal that resulted in a hemithyroidectomy. The patient is placed under general anesthesia and intubated using a mac video laryngoscope and an EMG endotracheal tube. The ET tube has 4 stainless steel wire electrodes which touch the vocal cords for monitoring during surgery. After video intubation electrode placement is verified by direct stimulation of the area.

The surgeon makes a curvilinear skin crease incision in the front of the neck, to minimize the visibility of a scar. Afterwards, subplatysmal flaps are elevated and the midline raphe is dissected exposing the sternohyoid muscle, which is retracted laterally, and the sternothyroid muscle that is dissected off the left thyroid gland.

The thyroid cyst is found superficial and dissected, keeping in mind that anything suspicious for the recurrent laryngeal nerve is stimulated prior to dissection. The cyst is ruptured and sent for frozen pathology. The results returned as thyroid, so the surgeon proceeded with a hemithyroidectomy. The superior and inferior parathyroids were identified and dissected free. Hemostasis was achieved with electrocautery and confirmed with Valsalva. Strap musculature platysma and skin are closed. And lastly, mastisol and steri-strips are placed perpendicular to the wound.

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