Intraoperative monitoring of the vagus and laryngeal nerves with the laryngeal adductor reflex

Intraoperative monitoring of the vagus and laryngeal nerves with the laryngeal adductor reflex (LAR) is a promising technique for a wide spectrum of surgeries where sensory, motor, and brainstem pathways of the vagus nerve are at risk of injury. The LAR consists of ipsi- and contralateral short-latency R1 components and ipsi- and contralateral long-latency R2 components, relative to the stimulating side. If the patient is under total intravenous anesthesia, the R1 components can endure several hours of surgery, whereas the R2 components fade. We describe a new noninvasive endotracheal tube-based methodology to monitor the entire laryngeal reflex arc continuously without interference with the surgery. The correct choice of endotracheal tube size according to the patient’s laryngeal anatomy, gender, and correct positioning of the endotracheal tube electrodes relative to the relevant anatomical structures are essential for successful monitoring. Transient decreases in LAR amplitude correlate with surgical maneuvers that put traction on the nerve. If the amplitude decreases >60% of baseline, postoperative nerve and vocal fold dysfunction are likely.