Look at the right hand diagram for details on attaching the electrode to the endotracheal tube. The left hand diagram shows the normal anatomy of the recurrent laryngeal nerves.
Select the correct size of electrode according to the endotracheal tube being used.
Attach the electrode to the endotracheal tube as shown in the instructions for use. If the edge of the electrode is placed against the weld of cuff to tube, the black lines on some tubes will remain visible. Do not grease the tube until the electrode is attached. Ensure that the tabbed side of the electrode is attached first – the other side will overlap the tab.
Intubate as normal, get the patient onto the operating table, shoulder bag in place, neck extended, then check that the electrode is between the cords. If the electrode is next to the weld of the cuff, then in women the tube should be at 19cm, and in men at 20cm (allow for patient variation).
Connect the cable – it can fit either way round. The 2 yellow wires form 1 channel, the 2 blue wires form the 2nd channel. The green connector can go to either of the Reference connectors on the preamp, leaving 1 connector empty.
Set the stimulator to 30Hz and 2mA. It should not be necessary to change this value.
Use the bipolar probe P/N 3601-00.
Surgical Procedure Information
Thyroid surgery carries a small risk (1-3%) of permanent injury to the recurrent laryngeal nerves (RLN) which control the vocal cords. Damage to these nerves can lead to hoarseness, difficulty with speech, swallowing and compromise of the airway. More frequent is a subtle change to the voice timbre, which can be serious for those using their voices professionally.
The surgeon can be at the site of the nerve within 30 minutes, so it is especially important that the patient is not paralysed at this point.
Because of the nature of the electrode and the manipulation of the larynx during the surgey, movement artifacts are common. The purpose of the monitoring it to help identify the RLN using the stimulating probe. Once identified, the surgeon can stay away from it.
The nerve is usually identified at Berry’s ligament or in the esophagotracheal groove.
The RLN appears to behave differently from the facial nerve in that it has a distinct threshold below which it will not stimulate. It is recommended that the stimulator be set at 2mA as this threshold varies and can be as high as 1.5mA.
Products & consumables able to be used for this procedure include: