Tracheal intubation in the thyroid surgical position improves recurrent laryngeal nerve monitoring: a dual-centre randomised trial.

BACKGROUND: Intraoperative neuromonitoring (IONM) is a critical adjunct in thyroid surgery to preserve recurrent laryngeal nerve (RLN) function. This study aims to evaluate whether tracheal intubation in the thyroid surgical position enhances IONM signal quality compared to the standard supine position. METHODS: In this dual-centre, parallel-group, randomised trial, 184 adults scheduled for elective thyroidectomy requiring IONM were allocated 1:1 to intubation in either the thyroid surgical position or the conventional supine position. The modified intention-to-treat cohort comprised 167 participants (85 vs 82) with an assessable baseline vagus response (V1). The primary outcome was the incidence of satisfactory electromyography (EMG) signals, defined as an initial vagus nerve EMG amplitude exceeding 500 μV when stimulated at 1.0 mA. Secondary outcomes included EMG signal amplitude, intubation-related metrics (e.g., Cormack-Lehane grades, intubation difficulty scale scores, intubation time, and depth of intubation), postoperative complications (e.g., lip lesions, dental injury, postoperative nausea and vomiting, dizziness, and headache), and clinician satisfaction with patient positioning and mask ventilation. RESULTS: Satisfactory V1 signals occurred in 82/85 patients (96.47 %) in the thyroid-surgical-position group versus 70/82 (85.37 %) in the supine group (relative risk 1.13; 95 % CI 1.03-1.24; P = 0.0145). Intubation time and Cormack-Lehane grades did not differ significantly, but the Thyroid Surgical Position Group required deeper EMG tube insertion (22 cm [21-23] vs. 22 cm [21-22]; median differences 1.1, 95% CI 0-1; P = 0.046). Postoperative complications did not differ significantly between groups (all P > 0.05). Clinician satisfaction scores were significantly higher in the Thyroid Surgical Position Group (median 9 vs. 5; median differences 4, 95% CI 3-4; P < 0.0001). Mask ventilation satisfaction was also rated higher in the Thyroid Surgical Position Group (median 9 vs. 8; median differences 1, 95% CI 0-1 P < 0.0001). CONCLUSIONS: Tracheal intubation in the thyroid surgical position significantly improves IONM signal quality and clinician satisfaction without increasing intubation difficulty or postoperative complications. Adopting this simple positioning strategy can optimise EMG tube placement and enhance the reliability of IONM during thyroid surgery.