The aim of this clinical trial is to compare the effectiveness and safety of ultrasound-guided thyroid cartilage plane approach with the superior laryngeal nerve space approach for superior laryngeal nerve block in awake tracheal intubation. Patients were randomized into the thyroid cartilage plane block group (T group) or the superior laryngeal nerve space block group (C group). In Group T, bilateral thyroid cartilage plane block was performed under ultrasound with thyroid cartilage as the landmark, and local anesthetic was injected on the surface of the thyroid cartilage. In Group C, local anesthetic was injected into the space between the thyrohyoid membrane and muscle groups above.
The investigators aim to evaluate whether the thyroid cartilage plane approach is not inferior to the superior laryngeal nerve space approach for ultrasound-guided superior laryngeal nerve block in awake tracheal intubation
Patients scheduled for awake tracheal intubation under general anesthesia.
Patients with difficult airways (e.g., limited cervical spine mobility, full stomach, partial airway obstruction, craniofacial deformities or trauma, micrognathia, mouth opening <3cm, Mallampati III or IV classification) posing challenges for mask ventilation or intubation.
Age between 18 and 85 years old.
Gender is not restricted.
Cardiovascular dysfunction or arterial aneurysms.
Mental or neurological disorders or concomitant arterial aneurysms.
Infection at the puncture site.
Allergy to local anesthetics.
Parallel
Ultrasound-guided bilateral Thyroid Cartilage Plane Block
Procedure/SurgeryUse a SonoSite high-frequency linear array transducer (5-13 MHz, SonoSite, USA). Placing the transducer parallel to the spine on one side of the neck, ensuring clear visualization of the thyroid cartilage under ultrasound. Using the out-of-plane technique to visualize the needle insertion path and tip. Once the needle tip contacts the cranial half of the thyroid cartilage, injecting 2.5ml of 2% lidocaine on the surface of the thyroid cartilage each side.
Ultrasound-guided bilateral Superior Laryngeal Nerve Space Block
Procedure/SurgeryUse a SonoSite high-frequency linear array transducer (5-13 MHz, SonoSite, USA). Placing the transducer parallel to the spine on one side of the neck, ensuring clear visualization of the superior laryngeal nerve space under ultrasound. Using the out-of-plane technique to visualize the needle insertion path and tip. 2% lidocaine 2.5ml was injected into the space between the thyrohyoid membrane and muscle groups above.
The proportion of patients with acceptable intubation conditions (AIC)
The evaluation of the intubation condition was based on the Cormack-Lehane classification, vocal cord movement, 5-point reaction scale, and severity of coughing. Clinically, AIC was defined when each part was scaled to Grade 1 or Grade 2. The proportion of AIC = number of participants with AIC/number of participants who received ATI in each group.
Quality of airway anesthesia
The quality of airway anesthesia assessed on a 5-point scale,Quality of airwayanesthesia was graded as: 0=no coughing or gagging in response to intubation, 1=mild coughing and/or gaggingthat did not hinder intubation, 2=moderate coughing and/or gagging that interfered minimally with intubation,3=severe coughing and/or gagging that made intubation difficult and 4=very severe coughing and/or gaggingthat required additional local anesthetic and/or change in technique.The lower grade means a better quality of airway anesthesia.
Mean Arterial Pressure
Stable blood pressure indicates a good neural blockade effect.
Heart Rate
Time Frame: T0: upon entry to the operating room,T1: before insertion of the tracheal tube,T2: immediatelyafter tracheal tube insertion,T3: 5 minutes after successful intubation
Ramsay Sedation Score
The Ramsay Sedation Score is as follows: 6 points for unarousable, 5 points for slow response to stimulus, 4points for asleep but easily aroused, 3 points for quiet and cooperative with orientation, 2 points for asleep,anxious, restless, and 1 point for asleep, agitated, and restless. Satisfactory sedation falls within 2-4 points,while oversedation is indicated by 5-6 points.
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