Video-Assisted Intubating Stylet Technique for Difficult Intubation: A Case Series Report

Induction of anesthesia can be challenging for patients with difficult airways and head or neck tumors. Factors that could complicate airway management include poor dentition, limited mouth opening, restricted neck motility, narrowing of oral airway space, restricted laryngeal and pharyngeal space, and obstruction of glottic regions from the tumor. Current difficult airway management guidelines include awake tracheal intubation, anesthetized tracheal intubation, or combined awake and anesthetized intubation. Video laryngoscopy is often chosen over direct laryngoscopy in patients with difficult airways because of an improved laryngeal view, higher frequency of successful intubations, higher frequency of first-attempt intubation, and fewer intubation attempts. In this case series report, we describe the video-assisted intubating stylet technique in five patients with difficult airways. We believe that the intubating stylet is a feasible and safe airway technique for anesthetized tracheal intubation in patients with an anticipated difficult airway.


Introduction
A difficult airway is always challenging for the airway operator. The incidence of failed tracheal intubation varies from 0.1% to 11% depending on patients' conditions and clinical scenarios [1,2]. Difficult airway guidelines have been developed and periodically revised to provide recommendations for clinicians. In clinical practice, video-laryngoscopes, fiberoptic bronchoscopes, supraglottic devices, or combined tools techniques are commonly used for elective/routine and emergency tracheal intubation [3][4][5].
A plethora of clinical studies have shown the advantages of commercial videolaryngoscopes over conventional direct laryngoscopes [6,7]. The comparisons were made in different clinical scenarios (e.g., elective and emergency intubation), distinct environments (e.g., operating rooms and intensive care units), various patients' conditions (e.g., adult, pediatrics, pregnancy, anesthetized or awake), and airway status (normal airway, expected and unanticipated difficult airway). The comparison parameters include the time taken to intubate, the success rate of the first attempt, the overall success rate, alternative rescue methods, and the complications rate.
In the past decades, since the video-assisted rigid intubating stylet was designed by Shikani [8] and modified by Levitan [9], numerous articles have been published detailing the safety and advantages of the Shikani video-assisted optical stylet tracheal intubation Healthcare 2022, 10, 741 2 of 11 method both in routine and unanticipated difficult airway management [10,11]. In this case series report, the objective was to share our experience using the Shikani video-assisted intubating stylet technique in five anticipated but challenging, difficult airway situations. There are four different brands of intubating stylets in our hands ( Figure 1) and each of them suits its purpose perfectly. In this case series report, all the tracheal intubations were performed using the Video Intubation Light Stylet because of its unique feature of wireless transmission of the images onto a separate screen. Video Intubation Light Stylet (Trachway) is the same product as the Clarus Video System (CVS) and Optiscope Video Stylet (Clarus Medical LLC, Minneapolis, MN, USA) under different brand names. The airway operator was the same one for all these five cases, who is a certified anesthesiologist with 40 years of experience (including 16 years and 6 years of experience with video laryngoscopy and the intubating stylet technique, respectively). In an anesthetized human subject without anticipated airway problems, tracheal intubation using Video Intubation Light Stylet was shown to be smooth, swift, and accurate ( Figure 2 and Supplementary Material Video S1).
the safety and advantages of the Shikani video-assisted optical stylet trachea method both in routine and unanticipated difficult airway management [10 case series report, the objective was to share our experience using the Shika sisted intubating stylet technique in five anticipated but challenging, difficul uations. There are four different brands of intubating stylets in our hands (F each of them suits its purpose perfectly. In this case series report, all the trac tions were performed using the Video Intubation Light Stylet because of its un of wireless transmission of the images onto a separate screen. Video Intubatio let (Trachway) is the same product as the Clarus Video System (CVS) and Opti Stylet (Clarus Medical LLC, Minneapolis, MN, USA) under different brand airway operator was the same one for all these five cases, who is a certified a gist with 40 years of experience (including 16 years and 6 years of experience laryngoscopy and the intubating stylet technique, respectively). In an anesthet subject without anticipated airway problems, tracheal intubation using Vide Light Stylet was shown to be smooth, swift, and accurate ( Figure 2 and Sup Material Video S1).

Case 1: Giant Cemento-Ossifying Fibroma
A 26-year-old man (158 cm, 52 kg, body mass index [BMI] 20.8 kg/m 2 ) was referred to our medical center for an oculofacial tumor for four years. The preoperative tumor biopsy indicated a diagnosis of cemento-ossifying fibroma. A combined operation with wide excision, free fibular flap, and vastus lateralis muscle flap was scheduled in 2021. Because the tumor was extensive (14 cm × 11 cm × 10 cm in size) and invaded the left eye, nose, paranasal sinus, maxilla, and oral cavity, the flexible fiberoptic intubation through the nasotracheal path was impossible ( Figure 3A-C). An awake surgical tracheostomy was refused by the patient as the first choice. After evaluation of the airway and ventilation status, oral tracheal intubation with the Shikani video-assisted intubating stylet technique was performed. The surgeons stood by for the possibility of surgical airway intervention. The patient first received pre-medication and high-flow nasal cannula oxygenation, followed by routine induction agents for anesthesia (glycopyrrolate, lidocaine, fentanyl, propofol, and succinylcholine). Tracheal intubation was planned using the videoassisted intubating stylet technique (with the Video Intubation Light Stylet). Although the oral cavity space was not wide enough, the stylet still could reach the epiglottis and then slipped under it. Eventually, a clear and full-size glottis view was obtained and the endotracheal tube was smoothly and swiftly railroaded into the trachea ( Figure 3D). The tracheal intubation was confirmed, secured and mechanical ventilation was initiated without complications. The whole intubation process is demonstrated in Supplementary Material Video S2.

Case 1: Giant Cemento-Ossifying Fibroma
A 26-year-old man (158 cm, 52 kg, body mass index [BMI] 20.8 kg/m 2 ) was referred to our medical center for an oculofacial tumor for four years. The preoperative tumor biopsy indicated a diagnosis of cemento-ossifying fibroma. A combined operation with wide excision, free fibular flap, and vastus lateralis muscle flap was scheduled in 2021. Because the tumor was extensive (14 cm × 11 cm × 10 cm in size) and invaded the left eye, nose, paranasal sinus, maxilla, and oral cavity, the flexible fiberoptic intubation through the nasotracheal path was impossible ( Figure 3A-C). An awake surgical tracheostomy was refused by the patient as the first choice. After evaluation of the airway and ventilation status, oral tracheal intubation with the Shikani video-assisted intubating stylet technique was performed. The surgeons stood by for the possibility of surgical airway intervention. The patient first received pre-medication and high-flow nasal cannula oxygenation, followed by routine induction agents for anesthesia (glycopyrrolate, lidocaine, fentanyl, propofol, and succinylcholine). Tracheal intubation was planned using the video-assisted intubating stylet technique (with the Video Intubation Light Stylet). Although the oral cavity space was not wide enough, the stylet still could reach the epiglottis and then slipped under it. Eventually, a clear and full-size glottis view was obtained and the endotracheal tube was smoothly and swiftly railroaded into the trachea ( Figure 3D). The tracheal intubation was confirmed, secured and mechanical ventilation was initiated without complications. The whole intubation process is demonstrated in Supplementary Material Video S2.

Case 2: Enlarged Palatine Tonsils
A 12-year-old girl (158 cm, 95 kg, BMI 38.0 kg/m 2 ) was diagnosed with obstructive sleep apnea syndrome (OSAS) caused by enlarged tonsils (grade 3) and a redundant uvula. She was scheduled to undergo uvulo-palato-pharyngoplasty (UPPP) under general anesthesia in 2021. Routine vital signs monitoring was implemented, and anesthesia was induced with fentanyl, lidocaine, propofol, and rocuronium. Oral tracheal intubation was performed using the Shikani video-assisted intubating stylet technique (with the Video Intubation Light Stylet) with a 6.5 mm diameter endotracheal tube. Due to copious saliva and secretion in her oropharyngeal cavity, a suction tube was applied to clear the airway

Case 2: Enlarged Palatine Tonsils
A 12-year-old girl (158 cm, 95 kg, BMI 38.0 kg/m 2 ) was diagnosed with obstructive sleep apnea syndrome (OSAS) caused by enlarged tonsils (grade 3) and a redundant uvula. She was scheduled to undergo uvulo-palato-pharyngoplasty (UPPP) under general anesthesia in 2021. Routine vital signs monitoring was implemented, and anesthesia was induced with fentanyl, lidocaine, propofol, and rocuronium. Oral tracheal intubation was performed using the Shikani video-assisted intubating stylet technique (with the Video Intubation Light Stylet) with a 6.5 mm diameter endotracheal tube. Due to copious saliva and secretion in her oropharyngeal cavity, a suction tube was applied to clear the airway before tracheal intubation. The epiglottis was reached, and a clear glottis view was obtained without difficulty ( Figure 4). The whole process of tracheal intubation was smooth and swift (as shown in Supplementary Material Video S3).

Case 2: Enlarged Palatine Tonsils
A 12-year-old girl (158 cm, 95 kg, BMI 38.0 kg/m 2 ) was diagnosed with ob sleep apnea syndrome (OSAS) caused by enlarged tonsils (grade 3) and a re uvula. She was scheduled to undergo uvulo-palato-pharyngoplasty (UPPP) unde anesthesia in 2021. Routine vital signs monitoring was implemented, and anesth induced with fentanyl, lidocaine, propofol, and rocuronium. Oral tracheal intuba performed using the Shikani video-assisted intubating stylet technique (with th Intubation Light Stylet) with a 6.5 mm diameter endotracheal tube. Due to copio and secretion in her oropharyngeal cavity, a suction tube was applied to clear th before tracheal intubation. The epiglottis was reached, and a clear glottis view tained without difficulty ( Figure 4). The whole process of tracheal intubation wa and swift (as shown in Supplementary Material Video S3).

Case 3: Lower Gum Carcinoma with Neck Radiation Fibrosis
A 68-year-old man (164 cm, 40 kg, BMI 14.8 kg/m 2 ) with right lower gum squamous cell carcinoma (pT4aN0) was scheduled to undergo a wide tumor excision (Commando operation), mandibulectomy, suprahyoid neck dissection, and tracheostomy in 2021. He was previously diagnosed with buccal and soft palate cancer 20 years ago and had undergone surgical resection and radiotherapy. Although post-radiotherapy neck muscle atrophy and soft-tissue fibrosis were noticed, the patient did not demonstrate any stridor or difficult breathing before induction of anesthesia. The mouth opening was restricted and only two-finger wide ( Figure 5A,B). Although awake tracheostomy was not impossible, the surgical team preferred tracheal intubation to secure the airway first. We felt that a flexible fiberoptic intubation technique via the nasal path would be an option, however, we anticipated difficulty with increased secretions and bleeding along with the distorted anatomy with potential difficulty in advancing the tracheal tube. Oral tracheal intubation with the Shikani video-assisted intubating stylet technique was chosen (with the Video Intubation Light Stylet). Anesthesia was induced with fentanyl, lidocaine, propofol, and rocuronium. Sugammadex was ready for rescue if any difficult airway was encountered. The intubating procedure ended up being smooth and swift ( Figure 5C,D also shown in Supplementary Material Video S4).

Case 4: Hypopharyngeal Cancer
A 63-year-old man (169 cm, 62 kg, BMI 21.7 kg/m 2 ) was in his usual health status until 2 months prior to surgery when hoarseness was noted. A further examination and biopsy showed stage IV hypopharyngeal squamous cell carcinoma involving the left pyriform sinus cancer (T4aN2b) with extranodal extension (Figure 6A-C). The patient was scheduled to undergo a total laryngectomy with type II modified radical neck dissection, right selective neck dissection (II, III, IV), and free flap reconstruction in 2021. The standard monitoring was implemented and preoxygenation was applied. Oro-tracheal intubation was planned using the Shikani video-assisted intubating stylet technique (with the Video Intubation Light Stylet) and was done with a 7.5 mm diameter endotracheal tube ( Figure 6D,E). The surgeons were on standby for a possible surgical tracheotomy, however, this was not needed. Anesthesia was induced with glycopyrrolate, fentanyl, lidocaine, propofol, and succinylcholine. A suction tube through a nasal airway was inserted to clear the secretion inside the oropharyngeal space. The intubating process was done via the Shikani videoassisted stylet intubating technique in a smooth, swift, and uneventful fashion (shown in Supplementary Material Video S5).
Healthcare 2022, 10, 741 6 of 11 Intubation Light Stylet) and was done with a 7.5 mm diameter endotracheal tube ( Figure  6D,E). The surgeons were on standby for a possible surgical tracheotomy, however, this was not needed. Anesthesia was induced with glycopyrrolate, fentanyl, lidocaine, propofol, and succinylcholine. A suction tube through a nasal airway was inserted to clear the secretion inside the oropharyngeal space. The intubating process was done via the Shikani video-assisted stylet intubating technique in a smooth, swift, and uneventful fashion (shown in Supplementary Material Video S5).

Case 5: Vocal Cord Granuloma
A 46-year-old woman (160 cm and 72 kg, BMI 28.1 kg/m 2 ) received a craniectomy due to intracerebral hemorrhage under general anesthesia with tracheal intubation with mechanical ventilation during the course of treatment. One year later, she suffered from hoarseness and was diagnosed with a very large vocal cord granuloma, obstructing a good portion of the glottis. After making her own decision with some delay, she eventually was willing to receive laryngo-microsurgery (LMS) to remove the granuloma in 2019. After implementing standard monitoring and adequate preoxygenation, anesthesia was induced with routine medications, including glycopyrrolate, lidocaine, fentanyl, propofol, and succinylcholine. The ENT team was on standby for possible surgical airway management, however, this was not needed. Oral tracheal intubation was then performed with the Shikani video-assisted intubating technique (with the Video Intubation Light Stylet) and a 6.5 mm endotracheal tube. The tracheal intubation was swift and successful on the first attempt ( Figure 7A,B, also shown in Supplementary Material Video S6). Resection of the granuloma by LMS was smooth and uneventful ( Figure 7C,D).

Case 5: Vocal Cord Granuloma
A 46-year-old woman (160 cm and 72 kg, BMI 28.1 kg/m 2 ) received a craniectomy due to intracerebral hemorrhage under general anesthesia with tracheal intubation with mechanical ventilation during the course of treatment. One year later, she suffered from hoarseness and was diagnosed with a very large vocal cord granuloma, obstructing a good portion of the glottis. After making her own decision with some delay, she eventually was willing to receive laryngo-microsurgery (LMS) to remove the granuloma in 2019. After implementing standard monitoring and adequate preoxygenation, anesthesia was induced with routine medications, including glycopyrrolate, lidocaine, fentanyl, propofol, and succinylcholine. The ENT team was on standby for possible surgical airway management, however, this was not needed. Oral tracheal intubation was then performed with the Shikani video-assisted intubating technique (with the Video Intubation Light Stylet) and a 6.5 mm endotracheal tube. The tracheal intubation was swift and successful on the first attempt ( Figure 7A,B, also shown in Supplementary Material Video S6). Resection of the granuloma by LMS was smooth and uneventful ( Figure 7C,D).

Discussion
We reported five cases of anticipated difficult airways with various presentatio from facial-oral lesions to glottis abnormalities. Among the recommendations and the u date in difficult airway guidelines made by the American Society of Anesthesiologi some strategies have been proposed for the anticipated difficult intubation, depending the patient's factors and condition, and the anesthesiologist's experience, skills, and pr erences regarding airway management [12,13]. For example, in a situation where a di cult airway is anticipated but the patient can be adequately ventilated and oxygenat awake intubation may not always be the first option. Instead, intubation under gene anesthesia may be safer. In this case, the video laryngoscopy has been reported to be s cessful in various difficult airway scenarios (including morbid obesity, ankylosing sp dylitis, congenital facial maxillary anomalies, giant thyroid goiter, oropharyngeal or l yngeal mass or tumor) [14,15].
In this report, we demonstrated the role of the Shikani video-assisted intubating s let technique (Figures 1 and 2) in five patients with different airway challenges (from facial-oral tumor to a glottis lesion, Figures 3-7). Although this case series report was designed as a comparative clinical study between video laryngoscopy and the videosisted intubating stylet technique, it is important to mention that we were successful the first attempt using the aforementioned video-assisted intubating stylet in all these tients while we had real concerns about potentially facing difficulty with the other te nique. In addition to the high success rate of the first attempt, the advantages of the in bating stylet technique include the short time to complete intubation, a low incidence soft-tissue injuries and sympathetic reflexion (Table 1). Above all, the satisfaction le was high among the operators using the video-assisted intubating stylet technique.

Discussion
We reported five cases of anticipated difficult airways with various presentations, from facial-oral lesions to glottis abnormalities. Among the recommendations and the update in difficult airway guidelines made by the American Society of Anesthesiologists, some strategies have been proposed for the anticipated difficult intubation, depending on the patient's factors and condition, and the anesthesiologist's experience, skills, and preferences regarding airway management [12,13]. For example, in a situation where a difficult airway is anticipated but the patient can be adequately ventilated and oxygenated, awake intubation may not always be the first option. Instead, intubation under general anesthesia may be safer. In this case, the video laryngoscopy has been reported to be successful in various difficult airway scenarios (including morbid obesity, ankylosing spondylitis, congenital facial maxillary anomalies, giant thyroid goiter, oropharyngeal or laryngeal mass or tumor) [14,15].
In this report, we demonstrated the role of the Shikani video-assisted intubating stylet technique (Figures 1 and 2) in five patients with different airway challenges (from a facial-oral tumor to a glottis lesion, Figures 3-7). Although this case series report was not designed as a comparative clinical study between video laryngoscopy and the videoassisted intubating stylet technique, it is important to mention that we were successful on the first attempt using the aforementioned video-assisted intubating stylet in all these patients while we had real concerns about potentially facing difficulty with the other technique. In addition to the high success rate of the first attempt, the advantages of the intubating stylet technique include the short time to complete intubation, a low incidence of soft-tissue injuries and sympathetic reflexion (Table 1). Above all, the satisfaction level was high among the operators using the video-assisted intubating stylet technique. The glottic view quality was judged by either the Cormack-Lehane grades or POGO scores. The degree of difficulty for intubation was evaluated subjectively and confirmed by reviewing the video-recording images (Supplementary Materials Videos S1-S6).
Post-operative sore throat (POST) and hoarseness were not evaluated in these five head-neck surgical cases.
If the operator is not sure about the airway, it is generally recommended to keep the patient awake and maintain spontaneous respiration. In those cases, blade laryngoscopy intubation, which requires general anesthesia, is best avoided. Fiberoptic nasotracheal intubation and intubating stylet video laryngoscopy may be safer options in difficult airways. If the airway is potentially unstable, a planned surgical airway (tracheotomy) with the surgeon on standby could be considered. It has been our experience though, that intubation using the Shikani video-assisted intubating stylet technique has allowed us to avoid emergency tracheotomies in the great majority of difficult airway cases that we have encountered, even critical ones. This technique has shown to be superior to the Macintosh blade intubation in the literature [31][32][33][34][35][36][37][38].
In this case series, we report that the Shikani video-assisted intubating stylet technique is an easy and safe way to secure a variety of airway pathologies, including enlarged tonsils, radiation fibrosis of the upper airway and neck, hypopharyngeal cancer, vocal polyps, and granulomas. This is the first time that the use of the video-assisted intubating stylet technique has been reported in maxillofacial surgery. Difficult airways using conventional laryngoscopy were reported in maxillofacial surgery with a prevalence rate of 15.4% (against 1% to 4% in overall incidence) [13,14,39]. We have found that the video-intubating stylet technique is smooth and successful for patients undergoing large maxillofacial surgery ( Figure 3, Table 1). It is also relevant to mention that the Shikani intubating stylet technique has also been described as advantageous in restricted neck movement and limited mouth opening [31][32][33][34][35][36][37][38][39][40]. It is less traumatic, being able to be used in patients with small mouth openings, thus requiring fewer neck or laryngeal manipulations [41][42][43][44].
Furthermore, it is worth mentioning that the airway operator might encounter some troubles while using the intubating stylet technique, such as an obstructed view by the soft tissues, difficulty finding the correct path to insert, blockade by the epiglottis, fogging of the lens, obstruction of the optics by saliva, mucous plugs, or blood, difficulty railroading the endotracheal tube into the trachea, etc. Fortunately, according to our own experiences, the time course for developing competency/proficiency in intubating using the stylet technique is comparable to video laryngoscopy. Moreover, it should be emphasized that the outcomes of using the intubating stylet technique in anticipated difficult airway scenarios depend on various factors and conditions. While some airway operators with vast use experience and skills found the intubating stylet technique to be easy, others might not feel so at ease with dealing with such a technique. Therefore, a Plan B for airway management in such patient populations with potentially difficult airways should always be prepared in advance.
We found the Shikani video-assisted intubating stylet technique to be safe and reliable in a variety of airway management cases. We recommend that the airway operator add this technique to their armamentarium for managing the difficult airway. Initial training with simple cases is recommended before handling difficult ones.