Ultrasound-guided Thyroid Cartilage Plane Block for Awake Intubation

The goal of this clinical trial is to investigate the clinical effectiveness and safety of superior laryngeal nerve block through surface injection of local anesthetic solution on the thyroid cartilage in patients undergoing general anesthesia with endotracheal intubation. The main questions it aims to answer are the effectiveness of ultrasound-guided Thyroid Cartilage Plane Block for superior laryngeal nerve blockadethe and the safety and ease of performance.

All patients are divided into the Thyroid Cartilage Plane Block Group (T Group) and the Control Group (C Group). Patients in the C Group receive airway surface anesthesia using the fiberoptic bronchoscope-guided local anesthetic spray method throughout the procedure. In the experimental T Group, ultrasound-guided bilateral Thyroid Cartilage Plane Block is performed using the thyroid cartilage as an anatomical landmark. Local anesthetic is injected on the surface of the thyroid cartilage.

Compare the following parameters between the two groups: duration of the blocking procedure, Ramsay Sedation Score, patient coughing upon contact of the fiberoptic bronchoscope with the vocal cords before intubation, comfort score immediately after intubation, and tracheal tube tolerance after successful intubation.

Select 60 patients undergoing elective awake tracheal intubation surgery. Instruct patients to fast （no food or drink） for 8 hours before the procedure. Upon admission to the operating room, monitor patients' ECG （electrocardiogram）, BP （blood pressure）, and SpO2 （pulse oxygen saturation）. Establish intravenous access in the upper extremities and administer normal saline solution. Administer a loading dose of dexmedetomidine at 0.5 μg/kg over 5 minutes and remifentanil 0.5μg.kg-1, followed by an infusion at a rate of 0.3-0.6 μg/（kg·h） , 0.1μg.kg-1.min-1 by micropump infusion respectively. Perform radial artery puncture and catheter placement for invasive arterial pressure monitoring. Use a computer-generated random number table to allocate patients into two groups in a 1:1 ratio. To ensure objectivity, a nurse not involved in the study prepares sealed opaque envelopes containing the group assignments. All patients are divided into the Thyroid Cartilage Plane Block Group （T Group） and the Control Group （C Group）. All patients received topical oral and pharyngeal anesthesia using 2.4% lidocaine spray administered by an experienced anesthesiologist. The pharyngeal surface was sprayed twice, with each spray lasting one second, and repeated after a 5-minute interval. Each spray contained approximately 16 mg lidocaine. Patients in the C Group receive airway surface anesthesia using the fiberoptic bronchoscope-guided local anesthetic spray method throughout the vocal cord and tracheal with 5 ml 2% lidocaine respectively. In the experimental T Group, ultrasound-guided bilateral Thyroid Cartilage Plane Block is performed using the thyroid cartilage plate as an anatomical landmark.2.5 ml 2% lidocaine local anesthetic is injected on the surface of the thyroid cartilage plate. The blocking procedure is as follows: Use a Sonosite high-frequency linear array transducer (5-13 MHz, Sonosite, USA). Place the transducer parallel to the spine on one side of the neck, ensuring clear visualization of the thyroid cartilage plate under ultrasound. Employ ultrasound-guided out-of-plane techniques to display the needle insertion path and tip. Once the needle tip contacts the upper half of the thyroid cartilage plate, inject 2.5ml of 2% lidocaine on the surface of the thyroid cartilage plate （the dosage is consistent with the commonly used local anesthetic volume for classic superior laryngeal nerve block methods in clinical practice）. Subsequently, perform fiberoptic bronchoscope-guided subglottic, and tracheal surface anesthesia. After completing surface anesthesia, select an appropriate-sized tracheal tube and perform fiberoptic bronchoscope-guided tracheal intubation, securing it properly.

Eligibility Criteria:
Inclusion Criteria:

1. Patients scheduled for awake tracheal intubation surgery under general anesthesia.
2. 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.
3. Age between 18 and 65 years.
4. Gender is not restricted.
5. ASA classification of I or II.

Exclusion Criteria:

1. Cardiovascular dysfunction or arterial aneurysms.
2. Mental or neurological disorders or concomitant arterial aneurysms.
3. Infection at the puncture site.
4. Allergy to local anesthetics.
5. Continuous use of antiplatelet or anticoagulant medications preoperatively.
6. Hoarseness or coughing while drinking water.
7. Bronchial asthma.
8. Participation in other clinical trials within the previous 3 months before enrollment 9.r current participation in other clinical trials.