Optimal Concentration of Remifentanil for NIM Tube Intubation With Low-dose NMBA

Study Overview
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Brief Summary
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During thyroid surgery, Intraoperative Neuromonitoring (IONM) plays a crucial role in preventing serious complications such as bilateral vocal cord paralysis. It achieves this by detecting damage to the recurrent laryngeal nerve (RLN) and predicting the RLN's functional status. The utilization of Nerve Integrity Monitoring tubes (NIM tubes) is on the rise for effective IONM. As IONM relies on observing electromyographic (EMG) responses to direct electrical nerve stimulation, the routine use of neuromuscular blocking agents (NMBAs) in general anesthesia can impact the interpretation of IONM results and potentially reduce sensitivity to nerve responses to stimulation. However, the use of NMBAs is essential for ensuring smooth endotracheal intubation in patients undergoing general anesthesia. Numerous studies suggest that NMBA usage provides superior intubation conditions and reduces vocal cord complications compared to scenarios without NMBA. Various regimens for neuromuscular blockade methods are employed during IONM in thyroid surgery, ranging from not using NMBAs at all to using a full dose of NMBA for intubation. This is followed by the administration of sugammadex, an NMBA reversal agent, before nerve monitoring. One of the methods known for providing satisfactory intubation conditions while ensuring the quality of EMG signals during IONM in thyroid surgery is using rocuronium at an ED95 dose of 0.3 mg/kg. This approach is considered suitable for most IONM scenarios. However, when adequate muscle relaxation is not achieved, not all patients can undergo intubation, necessitating a strategy for appropriate intubation conditions. Historically, it has been reported that achieving satisfactory intubation conditions without the use of NMBA during general anesthesia requires higher amounts of propofol and opioids. Therefore, the assumption is made that using remifentanil, an opioid used in total intravenous anesthesia (TIVA), at an appropriate concentration can provide acceptable intubation conditions with minimal NMBA use for patients undergoing IONM. This study aims to determine the optimal concentration of remifentanil needed to achieve excellent intubation conditions in patients undergoing thyroid surgery with IONM using rocuronium 0.3 mg/kg as the NMBA during TIVA

Official Title
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Optimal Concentration of Remifentanil for Achieving Excellent Intubating Condition During Low-dose Neuromuscular Blocking Agent Administration for Intraoperative Neuromonitoring Using Nerve Integrity Monitoring Tube

Conditions
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Thyroidectomy

Intervention / Treatment
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* Drug: Remifentanil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All female aged 20-60 ASA (American Society of Anesthesiologists) physical status I or II who scheduled for thyroidectomy under intraoperative neuromonitoring with a nerve integrity monitoring tube (NIM tube) Exclusion Criteria: Patients anticipated to experience challenging intubation. Patients who have had an upper respiratory tract infection within the past 2 weeks. Patients with a history of heart, lung, and kidney diseases. Patients with a body mass index (BMI) of 30 kg/m² or higher. Patients currently taking analgesics. Patients expressing a desire not to participate in the study.

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Intervention Model: Sequential Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Remifentanil for NIM tube intubation<br> | Drug: Remifentanil<br>* Following a sequential allocation scheme, the predetermined Ce of remifentanil for each patient will be determined by the Dixon up-and-down method. The Ce of remifentanil for the first patient will be 4.0 ng/ml, and then the remifentanil Ce will be increased or decreased in 0.5 ng/ml increments for subsequent patients depending on the success or failure of intubation. The Ce of remifentanil to provide acceptable intubation at low dose neuromuscular blockade, the primary outcome, will be determined by obtaining seven crossovers of patients with acceptable intubation/unacceptable intubation and then calculating the mean of the midpoint doses for each independent pair of patients. According to previous studies that estimated EC50 by Dixon's up-and-down method, 6-8 failure/success crossover pairs are required, so this study aims to collect independent data of 7 pairs of intubation acceptable/unacceptable patients.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Optimal effect-site concentration (Ce) of remifentanil | Finding the Ce of remifentanil that provides acceptable condition of tracheal intubation when administering a low-dose NMBA is the aim of the study. The Ce of remifentanil for the first patient is 4.0 ng/ml, and then the Ce is increased or decreased in 0.5 ng/ml increments for subsequent patients depending on the success or failure of intubation. About 3 minutes after administering rocuronium 0.3 mg/kg, NIM tube will be intubated. At this time, the intubation condition will be evaluated using the grading system described by Fuchs-Buder. There are 4 items (jaw relaxation, vocal cord position, cough response, and limb movement) that are evaluated, and a total score can be calculated based on them: 1 point if all items are E, 3 points if even one item is P, and 2 points for the rest. A tracheal intubation condition rating of 1 or 2 indicates that the intubation is acceptable (successful), and a rating of 3 indicates that the intubation is unacceptable (unsuccessful). | During the tracheal intubation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The rating of each item of the grading system of the tracheal intubation condition | There are 4 items (jaw relaxation, vocal cord position, cough response, and limb movement) in the grading system described by Fuchs-Buder. We will also evaluate the grade of these items. | During the tracheal intubation | 
| Total dose of remifentanil administered until tracheal intubation |  | From the start of the anesthesia induction to tracheal intubation | 
| Incidence of hypotension and bradycardia |  | From the start of the anesthesia induction to tracheal intubation | 
| Doses of agents (ephedrine and atropine) administered to treat hypotension and bradycardia |  | From the start of the anesthesia induction to tracheal intubation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Neuromuscular blocking agents, Remifentanil, Intraoperative nerve monitoring