Translational Study to Standardize the Safe Use of Bipolar Forceps, LigaSure™, Sonicision™ and PlasmaBlade™ Around the Recurrent Laryngeal Nerve in Thyroid Surgery

Purpose: We investigated the function of the recurrent laryngeal nerve (RLN) in a live porcine model during adjacent activation with bipolar forceps (BF), LigaSure™ small jaw (LSJ), Sonicision™ and PlasmaBlade ™ (PB) devices. Methods: Each of the energy-based devices (EBD) was activated for 3 seconds at different power settings at 5, 3, 2, and 1 mm from the RLN. Nerve root function and thermal spread were measured by continuous intraoperative neuromonitoring and in-frared thermal imagingResults: BF: The EMG amplitude decreased to 87% of baseline at a standardized dis-tance. The highest thermal reading was 120°C at 1 mm (average 80.7°C). LSJ: EMG amplitudes were 99% (5mm), 90% (3mm) and 66% (2mm) of the baseline amplitude. At 1mm, the temperatures of the RLN surface and the LSJ tip reached 80.6°C and 100.8°C, respectively. Sonicision™: Under both the minimum and maximum settings, EMG amplitudes remained above 80% of the baseline amplitude. The highest temper-atures of the device tip and RLN surface were 135°C and 117.3°C, respectively, at 1 mm. PB: The temperatures of the device tip and RLN surface increased gradually with an increase in the setting (tip 38.3°C to 163.8°C; nerve 34.8°C to 46.2°C). Loss of nerve function occurred at settings 9 and 10. There were no changes in the latency profile under any of the applications. Conclusions: RLN roots were exposed to increased temperatures when EBDs were applied at close spacing. The results suggest that these 4 EBDs are unsafe when ap-plied at a distance of 1-3 mm from the RLN due to their effects on both EMG and temperature.