Changes in electromyographic amplitudes but not latencies occur with endotracheal tube malpositioning during intraoperative monitoring for thyroid surgery: Implications for guidelines

Abstract

4. Laryngoscope, 127:2182-2188, 2017.

Continuous vagal monitoring value in prevention of vocal cord paralysis following thyroid surgery

“…Repetitive combined events have been found to be associated with subsequent vocal cord paralysis, but if they are recognized in the surgical trauma and reversed early, these nascent neurapraxia EMG events have been found to be reversible. Combined events more optimally track with neural injury, whereas endotracheal tube displacement or laryngeal retraction has been associated with amplitude changes without associated latency changes …”

Contralateral R1 and R2 components of the laryngeal adductor reflex in humans under general anesthesia

“…This new methodology has several technological limitations: craniocaudal or rotatory movements of the endotracheal tube during surgery can significantly impact vocal fold muscle recordings, a limitation common to all current vagal/RLN monitoring techniques that rely on endotracheal tube surface electrodes to record laryngeal responses. Some recent studies suggest that vertical and rotational endotracheal tube misplacement can reduce the amplitude of the vocal fold muscle responses as much as 80%, and normative human data on CMAP amplitude in response to RLN and vagus nerve stimulation is highly variable and much reduced compared to data obtained from animal studies with more precise control of tube placement . The LAR neuromonitoring method relies on tube electrodes for both stimulation and recording purposes, and thus is especially sensitive to any intraoperative changes in tube position.…”

Trans–thyroid cartilage recording for neural monitoring of the recurrent laryngeal nerve in thyroid surgery

“…High‐quality neural monitoring needs good contact between surface electrodes and vocal folds during surgery. Second, during surgery, there may be some tube displacement causing changes of EMG amplitude or even loss of signal owing to poor electrode–vocal cord contact . Thus, there is often a need to troubleshoot and resolve tube rotation and improper depth problems.…”