The GlideScope® video laryngoscope (GVL) (Verathon Medical Inc., Bothell, WA, USA) is widely used for nasotracheal intubation in dental and facial plastic surgery.1 Magill forceps are often used when performing nasotracheal intubation with direct laryngoscopy, but the angle of these forceps is different from that of the GVL blade, which can complicate the procedure. In contrast, vascular forceps have an angulation similar to that of the GVL blade (Fig. 1).2

Fig. 1
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Demonstration of different angles of a GlideScope blade (#4), b Vascular forceps, and c Magill forceps

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There are reports of conversion from oral to nasal intubation using endotracheal tube exchangers3,4; however, it remains unclear if tube exchangers facilitate nasotracheal intubation.

The purpose of this study was to compare the effectiveness of using the GVL with Magill forceps (group M) vs with vascular forceps in conjunction with a tube exchanger (group V) for nasotracheal intubation. We hypothesized that total intubation time would be significantly shorter in group V than in group M. In addition, we expected a lower incidence of epistaxis in group V than in group M.

Methods

This study was approved by the Hanyang University Guri Hospital Institutional Review Board on Human Subjects Research and Ethics Committees (GURI 2014-16). All patients provided written informed consent prior to enrolment. Sixty patients (aged 18–65 years) scheduled for elective surgery and classified as American Society of Anesthesiologists physical status I or II were included in the study. Exclusion criteria were patients with a history of difficult intubation, larynx surgery, or larynx radiotherapy; anticipated esophago-tracheal reflux; Mallampati view 3 or 4; frequent episodes of epistaxis; or bleeding tendency. On preoperative visits, residents evaluated the patients for the presence of nasal injury, dyspnea, sinusitis, allergic rhinitis, and a history of smoking.

Upon the patient’s arrival at the operating room, a nurse, who was blinded to the study, opened an envelope containing the randomization numbers and group information—i.e., Magill forceps (M) or vascular forceps (V). The following patient characteristics were measured and recorded: age, sex, weight, height, body mass index, Mallampati view, thyromental distance, maximal mouth opening, and neck circumference. Elective monitoring was performed. A bispectral index (BIS) monitor (A-2000TM, version 3.3; Aspect Medical System Inc., Newton, MA, USA) was used to monitor the depth of anesthesia.

Before induction of anesthesia, one side of the patient’s nostril was blocked. The patient was then instructed to sneeze through the opposite nostril to confirm that the nostril was blocked, and the selected nostril was packed with gauze containing epinephrine. Denitrogenation was performed by having the patients breathe 100% oxygen for three minutes to remove all nitrogen gas from their airway. After acquiring intravenous access and completing denitrogenation, remifentanil and 2% propofol were administered by an Orchestra® Base Primea infusion device (Fresenius Kabi, France). Rocuronium 0.6 mg kg−1 iv was administered when the BIS value was < 60 and verbal response was absent. An Innervator nerve stimulator (Fisher & Paykel Healthcare, Auckland, New Zealand) was placed along the ulnar nerve to monitor the train-of-four reactions, and nasotracheal intubation was initiated once the train-of-four reaction was zero.

Nasotracheal tubes (NTTs) (Mallinckrodt Medical, Covidien, Ireland) with an internal diameter of 7.0 and 6.5 mm were used for males and females, respectively. The tubes were placed into sterile saline maintained at 45°C and then lubricated with water-soluble gel. In group M, the NTT was oriented with the concavity facing caudally, and the tube was advanced along the nasal floor to the posterior nasopharyngeal wall. The GlideScope blade was then placed into the patient’s mouth, and the tip of the NTT was inserted into the trachea using Magill forceps via the GVL monitor (Fig. 1). In group V, a lubricated Sheridan T.T.X.™ endotracheal tube exchanger (Teleflex Medical, Durham, NC, USA) was inserted into the NTT with the tip of the tube exchanger protruding approximately 15 cm from the distal end of the NTT (Fig. 2). A tube exchanger lubricated with water-soluble gel was inserted into the nasal cavity, and the GlideScope blade was then placed into the patient’s mouth. Using vascular forceps, the tube exchanger was advanced along the lower pathway of the nasal airway and passed through the glottis. The NTT was then advanced along the tube exchanger via the GVL monitor. Three anesthesiologists (M.K.O., W.J.J., and S.Y.C.) performed the nasotracheal intubations.

Fig. 2
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Demonstration of tube exchanger positioning during the study (with approximately 15 cm of the exchanger protruding from the distal end of the nasotracheal tube)

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Total intubation time was defined as the time from when the anesthesiologist picked up the device to when three successive end-tidal CO2 waves were obtained following intubation. Immediately after extubation, the patient’s airway was assessed for blood in the intubation tube, the presence of damaged oral tissue, damage to the teeth, and other complications. A blinded observer assessed the patients for sore throat at one and 24 hr postoperatively.

To calculate the sample size, we used the average (standard deviation [SD]) intubation time obtained from a pilot study—i.e., 66.1 (15.5) sec. We needed 28.8 patients to detect a 20% difference between the groups. Assuming a 2% dropout rate, this study required 60 patients. We used IBM® SPSS® Statistics 21.0 for Windows for statistical analyses (SPSS Inc., Chicago, IL, USA). Unpaired Student’s t tests were used to compare the numerical data of the two groups. The mean difference and the 95% confidence interval (CI) of the mean difference were calculated. Categorical data (ratio of sore throat, epistaxis) were analyzed using Fisher’s exact test. The relative risks of the proportion of categorical data and 95% CI were calculated.

Results

Sixty patients were enrolled in our study from November 2014 to September 2015. No patients were excluded during the study (Fig. 3). There were no significant differences between the two groups with regard to demographic data (Table 1). Thyromental distance, neck circumference, and mouth opening were also similar between the groups (Table 1). There were no cases of hypoxemia or desaturation in either group during nasotracheal intubation. The glottic views obtained by GVL were not significantly different between the two groups (Table 2).

Fig. 3
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Study flow diagram

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Table 1 Demographic data
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Table 2 Characteristics of nasotracheal intubation and associated complications
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There was a significant difference in total intubation time between the two groups (group M, 96.1 sec vs group V, 78.1 sec; mean difference, 18 sec; 95% CI, 13.7 to 49.7) (Table 2). There was a lower numerical incidence of sore throat in group V than in group M, both in the recovery room (16.7% vs 6.7%, respectively) and at 24 hours (16.7% vs 3.3%, respectively; relative risk, 2.5 at 24 hr), although the differences were not significant (Table 2).

There was a significantly lower incidence of epistaxis in group V than in group M (46.7% vs 16.7%; relative risk, 2.8; 95% CI, 1.2 to 6.8) (Table 2).

Discussion

In this study, we found that the total intubation time for nasal intubation was significantly shorter using the GVL and vascular forceps-guided tube exchanger than using the GVL with Magill forceps. The incidence of epistaxis was significantly lower in the vascular forceps group. All nasal intubations were successfully completed.

Compared with the direct laryngoscope, the tip of the GVL was directed toward the vallecula. This enhanced the glottic view and eventually resulted in an increase in the success rate of endotracheal intubation in the difficult airway.5 In a difficult airway, such as in patients with a cervical collar or restricted cervical movement, the GVL acquired a good laryngeal view and shortened the time for endotracheal intubation.6 Nevertheless, despite a good glottic view, there were several cases of difficult intubation due to restricted neck movement.7 Several methods were investigated to overcome this difficulty. In routine use, the GVL has a 60° angled stylet; however, use of a 90° angled stylet resulted in easier endotracheal intubation.8 Prior studies using a fibreoptic scope with the GVL showed effective endotracheal intubation.9,10 In patients under general anesthesia, the fibreoptic endoscope is used as a controllable stylet. In contrast, in patients under conscious sedation, the fibreoptic bronchoscope enters the airway along the GVL blade according to adjustments of its positional camera. In other studies,2,11 the angle of the vascular forceps was similar to that of the GVL blade, and the tube exchanger served as a guide for introducing the endotracheal tube. Ultimately, endotracheal intubation was effective using the vascular forceps along with the tube exchanger.

Compared with the direct laryngoscope, the GVL facilitates routine nasotracheal intubation.1,12 There are many studies regarding facilitating nasotracheal intubation with additional tools or techniques. 13,14,15 For instance, thermosoftening the nasotracheal tube can improve flexibility and navigability though the nasal pathway. Nasogastric tubes can pass through the lower pathway of the nasal cavity due to their flexibility and pliability. In a previous study from our group,2 we found that using a forceps-guided tube exchanger could be advantageous when using the GVL. In this study, the total intubation time in group V was significantly shorter than that in group M. This difference might be due to the flexibility and pliability of a tube exchanger and the easy passage of the nasotracheal tube through the glottis using vascular forceps.

Many methods have been introduced to reduce the incidence of epistaxis. 13,14,15,16,17 Thermosoftening the tube, as mentioned above, resulted in tube misplacement into the upper pathway in 73.3% of cases.15 This misplacement caused trauma to the middle turbinate and massive bleeding. Flexible nasogastric tube insertion can ensure that tubes pass into the lower pathway, reducing the bleeding. Another method is the use of the nasopharyngeal airway (Wendl tube) as a pathfinder, in which a soft and flexible airway is gently inserted into the nasopharynx along the floor of the nasal cavity. In our study, use of the conventional method in group M by tube warming with 45°C saline and Magill forceps resulted in more nasal bleeding than in group V with the tube exchanger and vascular forceps (46.7% vs 16.7%, respectively). This discrepancy might be due to the flexibility and pliability of the tube exchanger which allowed it to pass into the lower pathway.

Sore throat is a common complication of nasotracheal intubation resulting from direct pharyngeal trauma caused by the Magill forceps. In a previous study,2 there was a lower incidence of sore throat using a tube exchanger and vascular forceps vs using a stylet. In this study, the incidence of sore throat tended to be lower in group V than in group M, although the difference was not significant.

This study has several limitations. For instance, the participating anesthesiologists were not blinded to the assigned groups, and they were more familiar with using Magill forceps than they were with using vascular forceps. In addition, although we analyzed the incidence of epistaxis, we did not evaluate its severity. Finally, a larger sample size is needed to evaluate the incidence of sore throat with regard to different intubation techniques.

This study shows that total intubation time was significantly lower when using a GVL with a tube exchanger and vascular forceps (group V) vs when using a GVL with Magill forceps (group M). The incidence of epistaxis was also significantly lower in group V than in group M. Therefore, when a GVL is used, nasotracheal intubation with a tube exchanger and vascular forceps offers advantages over the Magill forceps.