Effect of Neuromuscular Blocking Agent Use on Video Laryngeal Mask Airway Insertion

Background and Rationale Supraglottic airway devices are widely used for airway management during general anesthesia. Although these devices may provide adequate ventilation even when anatomical positioning is suboptimal, previous studies have reported suboptimal positioning in approximately 50-80% of blindly inserted supraglottic airway devices. Such malpositioning may contribute to airway leakage, gastric aspiration, and airway trauma.

Third-generation video laryngeal mask airways (video LMAs) incorporate an integrated visualization system that enables direct observation of hypopharyngeal structures during insertion. This allows real-time assessment of device positioning and corrective maneuvers when necessary.

Neuromuscular blocking agents may facilitate supraglottic airway insertion by reducing upper airway muscle tone, improving mandibular relaxation and mouth opening, and suppressing laryngeal reflexes. These effects may improve insertion conditions, reduce insertion attempts, and facilitate optimal anatomical positioning. However, adequate insertion conditions can also be achieved without neuromuscular blockade when sufficient anesthetic depth is provided. Previous studies investigating the effects of neuromuscular blocking agents on first- and second-generation laryngeal mask airways have reported conflicting findings.

The aim of this study is to evaluate the effects of neuromuscular blockade on the visual placement quality and clinical parameters of third-generation video LMAs during general anesthesia.

Study Design and Participants This is a single-center, prospective, randomized, parallel-group, outcome assessor-blinded superiority trial conducted at Hacettepe University Faculty of Medicine, Department of Anesthesiology and Reanimation.

The study is planned to be conducted between February 1, 2027, and February 1, 2028, following authorization from the Turkish Medicines and Medical Devices Agency.

A total of 128 adult patients aged 18-80 years, with American Society of Anesthesiologists (ASA) physical status I-II, scheduled for elective surgery under general anesthesia with planned LMA airway management, will be enrolled.

Patients with a predicted difficult airway, body mass index greater than 35 kg/m², ASA physical status III-IV, or those undergoing emergency surgery will be excluded.

Randomization and Blinding Participants will be randomly allocated in a 1:1 ratio to the rocuronium group (Group R, n=64) or the control group (Group K, n=64).

The randomization sequence will be generated electronically using simple or block randomization. Group assignments will be placed in sequentially numbered, opaque, sealed envelopes. Following preoperative assessment and written informed consent, the corresponding envelope will be opened in the operating room to determine group allocation.

Only the anesthesiologist administering the induction medications will be aware of group allocation. The investigator inserting the video LMA, the investigator assessing the hypopharyngeal view, investigators performing intraoperative and postoperative assessments, and participants will remain blinded to group allocation.

Anesthesia Protocol and Interventions Standard monitoring, including electrocardiography, non-invasive blood pressure measurement, and peripheral oxygen saturation monitoring, will be performed before anesthesia induction.

Patients will receive one of the following induction regimens:

• Group R (Rocuronium Group): Intravenous propofol 2-2.5 mg/kg, remifentanil 1 mcg/kg, and rocuronium 0.6 mg/kg.
• Group K (Control Group): Intravenous propofol 2-2.5 mg/kg and remifentanil 1 mcg/kg, without neuromuscular blockade.

Following anesthesia induction, patients in both groups will be ventilated with 100% oxygen for 3 minutes.

A single-use third-generation video laryngeal mask airway (SafeLM FlexiView) will be inserted using the SafeLM MGL-SP-6 videoscope.

Device size will be selected according to the manufacturer's weight-based recommendations: size 3 for patients weighing 30-50 kg, size 4 for 50-70 kg, and size 5 for 70-100 kg. The cuff will be inflated to the volume recommended by the manufacturer.

The same video LMA system will be used in both groups. The study will not compare the safety or performance of different airway devices; rather, it will evaluate the effects of neuromuscular blockade on device placement quality.

Following insertion and assessment of the hypopharyngeal view, anesthesia will be maintained with sevoflurane at 1 minimum alveolar concentration (MAC) in a mixture of 40% oxygen and 60% air, together with intravenous remifentanil infusion at 0.02-0.07 mcg/kg/min.

Approximately 30 minutes before the end of surgery, all patients will receive standard postoperative analgesia consisting of intravenous paracetamol 1 g, ibuprofen 400 mg, and tramadol 1 mg/kg.

At the end of surgery, patients in Group R will receive intravenous sugammadex 200 mg before removal of the airway device, according to the approved study protocol.

Primary Outcome The primary outcome is the proportion of patients achieving optimal anatomical positioning of the video LMA, defined as a Brimacombe-Berry score of 4.

Following insertion, a blinded investigator will evaluate the hypopharyngeal view using the integrated videoscope and classify device positioning according to the following scoring system:

• Score 4: Only the vocal cords are visible (optimal positioning).
• Score 3: The vocal cords and posterior epiglottis are visible.
• Score 2: The vocal cords and anterior epiglottis are visible.
• Score 1: The vocal cords are not visible, but the device remains functional.
• Score 0: The device is nonfunctional. The proportion of patients achieving a score of 4 will be compared between the two groups.

Secondary Outcomes Secondary outcomes will include oropharyngeal leak pressure, insertion characteristics, ventilation parameters, hemodynamic responses, airway complications, and postoperative adverse effects.

Oropharyngeal leak pressure will be measured following device insertion. Insertion time will be defined as the interval from the moment the investigator places a hand on the patient's chin until the hand is removed from the LMA following insertion.

Insertion difficulty will be evaluated by the inserting investigator using a 0-100 mm visual analog scale (VAS), where 0 indicates extremely easy insertion and 100 indicates extremely difficult insertion.

Additional insertion-related outcomes will include the size of the LMA used, first-attempt insertion success, total number of insertion attempts, and the minimum and maximum heart rate and blood pressure values recorded during insertion.

Insertion-related complications, including airway bleeding, laryngospasm, and oxygen desaturation, will be documented.

Successful ventilation will be confirmed by the presence of an appropriate capnographic waveform.

Five minutes after initiation of mechanical ventilation, peak airway pressure (Ppeak), mean airway pressure (Pmean), and ventilation leak volume, defined as the difference between inspired and expired tidal volumes, will be recorded.

The presence of blood on the LMA after device removal and the durations of anesthesia and surgery will also be documented.

Postoperative adverse effects, including hoarseness, dysphagia, sore throat, nausea, and vomiting, will be assessed at 20 minutes and 6 hours postoperatively through face-to-face interviews. Each symptom will be recorded as present or absent.

Sample Size Calculation The sample size was calculated based on the primary outcome of achieving a Brimacombe-Berry score of 4.

Based on previous literature and clinical observations, the proportion of patients achieving optimal positioning was assumed to be approximately 50% in the control group and 75% in the rocuronium group.

An a priori sample size calculation was performed using G*Power version 3.1.9.6, based on a two-sided Fisher's exact test, a significance level of 0.05, and statistical power of 80%.

According to the study protocol, 64 participants per group, resulting in a total sample size of 128 patients, were determined to be sufficient.

Statistical Analysis Statistical analyses will be performed using IBM SPSS Statistics version 25. The distribution of continuous variables will be evaluated using the Kolmogorov-Smirnov test, and homogeneity of variances will be assessed using Levene's test.

Normally distributed continuous variables will be presented as mean ± standard deviation, whereas non-normally distributed variables will be presented as median (minimum-maximum). Categorical variables will be reported as frequencies and percentages.

Continuous variables will be compared between groups using the independent-samples t-test when parametric assumptions are satisfied and the Mann-Whitney U test otherwise.

Categorical variables will be analyzed using Pearson's chi-square test, continuity-corrected chi-square test, Fisher's exact test, or Fisher-Freeman-Halton test, as appropriate.

The primary outcome, defined as the proportion of patients achieving a Brimacombe-Berry score of 4, will be compared between groups using Pearson's chi-square test or Fisher's exact test, depending on expected cell frequencies.

Repeated measurements, including intraoperative hemodynamic parameters and postoperative assessments, will be analyzed using repeated-measures analysis of variance with Wilks' lambda when parametric assumptions are satisfied, or the Friedman test otherwise. Appropriate post hoc tests with Bonferroni correction will be applied when necessary.

Exploratory logistic regression analysis will be performed to investigate clinical factors associated with optimal video LMA positioning. Results will be reported as odds ratios with 95% confidence intervals.

Unless otherwise specified, a p-value below 0.05 will be considered statistically significant. Appropriate adjustments will be applied for multiple comparisons.