Outcome assessment
bipolar, closed-loop muscle relaxation
MUSCLE RELAXATION
The NIM 3.0 nerve monitoring system (MedtROnic, Minneapolis, MN, USA) was employed for IONM. EMG signals were obtained with surface electrodes integrated (ETT, NIM Flex EMG tubes, Medtronic) and a handheld bipolar stimulating probe. The current amplitude and impulses have been set at 1 mA and 3 Hz, respectively. The timing of recording was as follows: Vagus nerve EMG amplitude after opening the lateral space between the thyroid and carotid sheath and before the initiation of thyroid dissection(record as V0), RLN EMG amplitude at first recognition(record as R0), RLN EMG amplitude after complete thyroid dissection(Repeat three times, record as Rn), and Vagus nerve EMG amplitude after thyroidectomy(Repeat three times, record as Vn). For those without satisfactory signals, muscle relaxant antagonist (sugammadex 2 mg/kg) was intravenously injected, and signal values were recorded 1 min later. If still not satisfied, the measurement was repeated after a few minutes.To reduce the deviation caused by measurement timing, The closed-loop muscle relaxation monitoring system and The NIM 3.0 nerve monitoring system were kept on during the operation. Anesthesiologists communicated with the surgeons before each measurement: The electrical stimulation of the RLN or vagus nerve was performed at the same time as the start button of the muscle relaxation monitoring system was pressed. The ulnar nerve stimulation interval is set to 15 s, and if TOFr values and EMG amplitude need to be measured again, the measurement can be repeated after 15 s.When unpaired TOFr and EMG data exist, this set of data will not be included in the analysis. Once TOFr or EMG values were not measured or judged as seriously biased by thyroid surgeons, the corresponding data will not be included in the analysis. All nerve stimulation signal analyses were defined as group VR. Subgroups were defined as follows: Vagus nerve stimulation data were included in Subgroup V. RLN stimulation data were included in Subgroup R; Nerve stimulation in patients with intraoperative sugammadex injection was defined as subgroup S; Nerve stimulation in patients without any muscle relaxant antagonist was defined as subgroup N–S. TOFr was divided into six intervals: TOFr = 0,0 < TOFr ≤ 0.5, 0.5 < TOFr ≤ 0.75, 0.75 < TOFr ≤ 0.85, 0.85 < TOFr ≤ 0.95, and 0.95 < TOFr ≤ 1. When TOFr exceeded 100%, it was classified as a 0.95 < TOFr ≤ 1 interval.