Ultrasound-guided Thyroid Cartilage Plane Block for Awake Intubation

Ultrasound-guided Thyroid Cartilage Plane Block for Patients With Awake Tracheal Intubation: a Randomized Controlled Trial

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 plate as an anatomical landmark. Local anesthetic is injected on the surface of the thyroid cartilage plate. 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, followed by an infusion at a rate of 0.3-0.6 μg/（kg·h） and intravenous injection of fentanyl at 0.1 μg/kg. 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）. 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 plate as an anatomical landmark. 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 in-plane or 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 3ml 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 oropharyngeal, 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.

Ultrasound-guided bilateral Thyroid Cartilage Plane Block is performed using the thyroid cartilage plate as an anatomical landmark. 3ml of 2% lidocaine is injected on the surface of the thyroid cartilage plate. Subsequently, perform fiberoptic bronchoscope-guided oropharyngeal, subglottic, and tracheal surface anesthesia. After completing surface anesthesia, perform fiberoptic bronchoscope-guided tracheal intubation, securing it properly.

Patients in the C Group receive airway surface anesthesia using the fiberoptic bronchoscope-guided local anesthetic spray method throughout the procedure.

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 in-plane or 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 3ml of 2% lidocaine on the surface of the thyroid cartilage plate.

The immediate comfort score upon intubation can reflect the effectiveness of superior laryngeal nerve block. A lower score indicates a better nerve block effect. 5 points for head or limb resistance movements,4points for verbal protests,3points for severe painful expressions,2points for mild painful expressions,1point for no response

T0: upon entry to the operating room,T1: before insertion of the tracheal tube,T2: immediately after tracheal tube insertion,T3: 5 minutes after successful intubation

T0: upon entry to the operating room,T1: before insertion of the tracheal tube,T2: immediately after tracheal tube insertion,T3: 5 minutes after successful intubation

The Ramsay Sedation Score is as follows: 6 points for unarousable, 5 points for slow response to stimulus, 4 points 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.

T0: upon entry to the operating room,T1: before insertion of the tracheal tube,T2: immediately after tracheal tube insertion,T3: 5 minutes after successful intubation

The neural blockade procedure time reflects the ease of the operation, with a shorter time indicating a simpler neural blockade procedure.

The patient's coughing upon contact of the fiberoptic bronchoscope with the vocal cords before intubation reflects the effectiveness of neural blockade. A lower degree of coughing indicates a better neural blockade effect. 1 point for no response, 2 points for mild cough, 3 points for severe cough.

The tolerance of the tube reflects the patient's tolerance to awake tracheal intubation. A higher level of tolerance indicates a better neural blockade effect. 3 points for severe resistance requiring immediate general anesthesia, 2 points for restlessness and mild resistance, 1 point for cooperation.

Pharyngeal pain and decreased vocal tone are used to assess postoperative complications of neural blockade.

Inclusion Criteria: Patients scheduled for awake tracheal intubation surgery 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 65 years. Gender is not restricted. ASA classification of I or II. Exclusion Criteria: Cardiovascular dysfunction or arterial aneurysms. Mental or neurological disorders or concomitant arterial aneurysms. Infection at the puncture site. Allergy to local anesthetics. Continuous use of antiplatelet or anticoagulant medications preoperatively. Hoarseness or coughing while drinking water. Bronchial asthma. Participation in other clinical trials within the previous 3 months before enrollment 9.r current participation in other clinical trials.

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Fowler JG, VanEenenaam DP Jr, Johnson KN, Courtemanche CD, Strathman AJ, Reynolds JE. Single midline injection for bilateral superior laryngeal nerve block. J Clin Anesth. 2020 Nov;66:109922. doi: 10.1016/j.jclinane.2020.109922. Epub 2020 Jun 6. No abstract available. Erratum In: J Clin Anesth. 2023 Jul 29;:111195.