Ultrasound-guided thyroid cartilage plane block for superior laryngeal nerve blockade in awake fiberoptic tracheal intubation: combined cadaveric validation and randomized clinical trial

Background: The thyroid cartilage plane (TCP) block is a novel approach for superior laryngeal nerve (SLN) block in awake tracheal intubation (ATI). We aimed to evaluate the efficacy and safety of TCP block for ATI. Materials and methods: Our study included a cadaver dissection and a clinical study. Detailed anatomical dissections were performed on two fresh cadavers after a bilateral TCP block with methylene blue. Sixty patients scheduled for ATI were randomized to receive either bilateral TCP block (TCP group) or fiberoptic bronchoscope-assisted topical anesthesia (FIB group) to anesthetize the vocal cords. A 22-gauge needle was advanced targeting the thyroid cartilage laminae, followed by injection of 2.5 ml lidocaine in the TCP group. Lidocaine spray was applied to anesthetize the remainder of the airway. The primary outcome was quality of airway anesthesia grade during intubation (0, excellent; 1, good; 2, fair; 3, poor; 4, very poor), with secondary outcomes including hemodynamic profile, Ramsay sedation score, and incidence of airway hemorrhage and SLN injury. Results: The methylene blue stained all the internal branches of SLN, with one external branch not stained. In the clinical study, the quality of airway anesthesia was significantly better in the TCP group than in the FIB group (median [IQR], 0 [0–0] vs 1 [0–2], difference [95% CI]: 1 [0–1], P < 0.001). Mean arterial pressure and HR were better maintained during intubation in the TCP group ( P < 0.05). Neither airway hemorrhage nor nerve injury was observed. Conclusion: Ultrasound-guided TCP block is an effective and safe approach for the SLN blockade, providing an alternative for ATI.