Ultrasound-guided Thyroid Cartilage Plane Block for Patients With Awake Tracheal Intubation: a Randomized Controlled Trial
Phase: NA
Conditions: Superior Laryngeal Nerve Block
Sponsor: Nanjing First Hospital, Nanjing Medical University

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Protocol
Ultrasound-guided thyroid cartilage plane block for patients with awake tracheal
intubation: a randomized controlled trial
August 29, 2023

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One: Background
Traditional surface anesthesia, administered via fiberoptic bronchoscope
spray, is limited by the penetration of airway secretions and local
anesthetics. Excessive airway secretions can significantly compromise the
effectiveness of surface anesthesia. Moreover, the vicinity of the glottis is
rich in neural fibers, making the airway highly sensitive. During
fiberoptic bronchoscope spray, patients often experience coughing and
even laryngospasm. In contrast, thyroid cartilage plane block circumvents
these limitations and offers a more precise method of airway blockage.
In recent years, both international and domestic research has focused
extensively on blocking the superior laryngeal nerve. Blocking the
superior laryngeal nerve can significantly reduce stimulation to the
tongue base and pharynx during laryngoscopy, diminish the irritation
caused by the endotracheal tube to the trachea, mitigate stress responses,
and minimize adverse cardiovascular effects. This technique provides a
reliable airway management method for clinical anesthesia and ICU
tracheal intubation
[1]. Research by Mathur et al. demonstrated that
ultrasound-guided superior laryngeal nerve block provides effective
airway anesthesia during fiberoptic bronchoscopy and reduces the
incidence of adverse reactions such as coughing [2]. Additionally, superior
laryngeal nerve block is widely applied in managing challenging airways,
such as in patients with severe acute pharyngitis, cervical spine injuries,

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awake tracheal intubation, percutaneous tracheostomy, laryngoscopy
examinations, treatment of chronic pharyngitis, and neurogenic cough.
However, the method of performing nerve blocks through surface
anatomy localization has its drawbacks, including inaccurate positioning,
low success rates, poor safety, and unsatisfactory outcomes. Some
researchers argue that using the thyrohyoid membrane as a target for
ultrasound-guided superior laryngeal nerve block can be challenging.
Traditional ultrasound-guided superior laryngeal nerve block methods
often rely on the thyrohyoid membrane and the superior thyroid artery as
ultrasound landmarks, injecting local anesthetic solution beneath the
thyrohyoid membrane and adjacent to the superior thyroid artery.
However, locating the thyrohyoid membrane and the small superior
thyroid artery can be extremely challenging, especially for beginners.
Even experienced clinicians, despite their familiarity with anatomy and
skill, can struggle to identify these structures under ultrasound. Therefore,
there is a pressing need for simpler, more precise, and easier-to-locate
methods of superior laryngeal nerve block in clinical practice.
In our preliminary research, while performing superior laryngeal nerve
block, we observed that the injected solution could spread along the
surface of the thyroid cartilage plate, extending towards the thyrohyoid
membrane. Given that the solution could reach the superior laryngeal
nerve from the surface of the thyroid cartilage, we propose that injecting

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local anesthetic solution on the surface of the thyroid cartilage can
effectively block the superior laryngeal nerve, a technique we refer to as
"Thyroid Cartilage Plane Block." This method offers the advantage of
easy identification of the thyroid cartilage under ultrasound, making it
more convenient to perform than traditional methods. Therefore, this
study aims 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.
Two: Research Objectives
1. Primary Objective: To evaluate the effectiveness of ultrasound-guided
Thyroid Cartilage Plane Block for superior laryngeal nerve blockade.
2. Secondary Objectives: To assess the safety and ease of performance of
ultrasound-guided Thyroid Cartilage Plane Block for superior laryngeal
nerve blockade.
Three: Research Design, Methods, and Study Steps
1. Research Design
Select patients undergoing elective awake tracheal intubation surgery and
randomly assign them to two groups using a random number table. The
control group will receive surface anesthesia of the throat using local
anesthetic sprayed via fiberoptic bronchoscope, while the experimental
group will undergo ultrasound-guided Thyroid Cartilage Plane Block.

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The sample size for the study is determined based on the results of a pilot
study. The primary outcome measure is the success rate of superior
laryngeal nerve blockade. With a statistical power of 1-β=0.9 and a
significance level of α=0.05, a sample size of n=25 is calculated.
Assuming a dropout rate of 10%, the final sample size for each group is
determined to be 30 cases.
2. Research Methods
The study will clinically evaluate the effectiveness, safety, and ease of
performing Thyroid Cartilage Plane Block.
3. Study Steps
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

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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 3 ml 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

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it properly.
4. The research flowchart is as follows:
Four: Patient Selection
Inclusion Criteria: We will select 60 patients who meet the following
criteria for inclusion in the study:
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: Patients meeting any of the following criteria will be
excluded from the study:
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.

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Hoarseness or coughing while drinking water.
Bronchial asthma.
Participation in other clinical trials within the previous 3 months
before enrollment or current participation in other clinical trials.
3. Study Termination Criteria
The study may be terminated under the following circumstances:
1）Any medical condition or event occurs during the study that poses a
potential risk to the continued participation of the research subjects.
2）Subjects receive anesthetic regimens other than the specified airway
surface anesthesia rescue protocol, or if they are unable to complete the
trial according to the study protocol for any reason.
3 ）The investigator determines that other circumstances warrant
discontinuation from the trial.
4 ）
Poor effectiveness of airway surface anesthesia, resulting in the
patient's inability to tolerate awake tracheal intubation, or patient refusal
to proceed.
Five: Alternative Diagnostic and Therapeutic Methods
In cases where the airway surface anesthesia is ineffective, and patients
are unable to tolerate intubation, we will proceed with additional airway
surface anesthesia using 2% lidocaine via a fiberoptic bronchoscope
through an epidural catheter to enhance airway surface anesthesia.

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Six: Assessment Parameters and Timing
Primary Outcome:
Record the comfort score immediately after intubation (5 points:
resistance movement of the head or limbs; 4 points: verbal protest; 3
points: severe painful expression; 2 points: slight painful expression; 1
point: no response).
Secondary Outcomes:
1. Record the duration of the blocking procedure (from the start of
ultrasound probe positioning to completion of drug administration).
2. Record the following parameters at specific time 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):

Mean Arterial Pressure (MAP)

Heart Rate (HR)

Ramsay
Sedation
Score
(6
points:
unarousable;
5
points:
arousable but slow response to stimulation; 4 points: asleep but brisk
response to stimulation; 3 points: asleep with a moderate response to
command; 2 points: calm and cooperative with orientation; 1 point:
anxious, restless, or agitated. Sedation satisfaction is defined as 2-4
points, while oversedation is defined as 5-6 points).
3. Record the number of cases with reduced voice tone before intubation.

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4.
Document
patient
coughing
upon
contact
of
the
fiberoptic
bronchoscope with the vocal cords before intubation (1 point: no response,
2 points: mild cough, 3 points: severe cough).
5. Assess the tolerance of the tracheal tube after successful intubation (3
points: strong resistance requiring immediate general anesthesia; 2 points:
restlessness and mild resistance; 1 point: cooperative).
6. Record adverse reactions such as coughing and nausea/vomiting during
intubation.
7. Document post-extubation throat pain, voice tone reduction, and voice
tone reduction at 24 hours post-operation.
8. Assessment of superior laryngeal nerve blockade effectiveness based
on clinical diagnostic criteria:

Inability to produce high-pitched sounds, monotone voice.

Morphological changes in the vocal cords observed during
laryngoscopy (e.g., irregular vocal cord surface, wrinkles, malposition,
reduced mobility).

Absence of neural reflex upon touching the mucosa above the
vocal cords.

Meeting two of the above diagnostic criteria indicates successful
superior laryngeal nerve blockade.
9. Record adverse reactions such as local anesthetic toxicity, local
hematoma at the puncture site, and infections.

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10. Record patient satisfaction.
Seven: Efficacy Assessment Criteria
Record the duration of the blocking procedure (from the start of
ultrasound probe positioning to completion of drug administration).
Ramsay Sedation Score (6 points: unarousable; 5 points: arousable
but slow response to stimulation; 4 points: asleep but brisk response
to stimulation; 3 points: asleep with a moderate response to command;
2 points: calm and cooperative with orientation; 1 point: anxious,
restless, or agitated. Sedation satisfaction is defined as 2-4 points,
while oversedation is defined as 5-6 points).
Patient coughing upon contact of the fiberoptic bronchoscope with the
vocal cords before intubation (1 point: no response, 2 points: mild
cough, 3 points: severe cough).
Comfort score immediately after intubation (5 points: resistance
movement of the head or limbs; 4 points: verbal protest; 3 points:
severe painful expression; 2 points: slight painful expression; 1 point:
no response).
Tracheal tube tolerance after successful intubation (3 points: strong
resistance
requiring
immediate
general
anesthesia;
2
points:
restlessness and mild resistance; 1 point: cooperative).
Assessment of superior laryngeal nerve blockade effectiveness based
on clinical diagnostic criteria: nability to produce high-pitched sounds,

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monotone voice.
Morphological
changes
in
the
vocal
cords
observed
during
laryngoscopy (e.g., irregular vocal cord surface, wrinkles, malposition,
reduced mobility).
Absence of neural reflex upon touching the mucosa above the vocal
cords.
Meeting two of the above diagnostic criteria indicates excellent
superior laryngeal nerve blockade effectiveness.
Eight: Observation, Recording, and Management of Adverse Events
In the event of oxygen saturation dropping below 90% during the
experiment, the procedure will be halted. Patients will be instructed to
take deep breaths or receive oxygen supplementation via a mask with
increased pressure.
Nine: Quality Control and Quality Assurance of the Study
No specific quality control or quality assurance measures are outlined for
this study.
Ten: Data Security Monitoring
Clinical research will establish an appropriate data security monitoring
plan based on the level of risk. All adverse events will be meticulously
documented, appropriately addressed, and tracked until resolution or
stabilization. Serious adverse events and unexpected events will be
reported to the ethics committee, regulatory authorities, sponsors, and

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drug regulatory authorities in accordance with regulations and guidelines.
The principal investigator will periodically conduct cumulative reviews
of all adverse events, and if necessary, convene investigator meetings to
assess the risks and benefits of the study. In double-blind trials,
emergency unblinding may be performed if necessary to ensure subject
safety and rights.
Eleven: Statistical Analysis
Statistical analysis will be conducted using SPSS 22.0 software.
Normally distributed continuous data will be presented as mean ±
standard deviation (x±s), and group comparisons will be made using
analysis of variance (ANOVA). Categorical data will be presented as
counts or percentages, and group comparisons will be made using the X2
test. A significance level of P<0.05 will be considered statistically
significant.
Twelve: Ethical Principles and Requirements for Clinical Research
This clinical research will adhere to ethical principles and requirements
outlined in the World Medical Association's "Declaration of Helsinki" and
the regulations set forth by the National Health and Family Planning
Commission of the People's Republic of China, including the "Ethical
Review Measures for Biomedical Research Involving Human Subjects."
Specific measures will include informed consent, privacy protection, free
participation in research, risk control, protection of special subjects, and

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compensation for research-related harm. Prior to commencing the study,
the research protocol must receive approval from the ethics committee.
Before enrollment, every subject will be provided with comprehensive
information about the study's purpose, procedures, and potential risks.
They will sign a written informed consent form. Subjects will be
informed that participation in the clinical research is entirely voluntary,
and they have the right to refuse or withdraw from the study at any stage
without discrimination or retaliation. Their medical treatment and rights
will not be affected. Informed consent forms will be retained as part of
the clinical research documents, ensuring the protection of subjects'
personal privacy and data confidentiality.
References
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