Abstract

Objective

GlideScope^® provides better laryngoscopic view and is advantageous in tracheal intubation in ankylosing spondylitis patients with difficult airway.

Methods

This study was performed to investigate the use of the GlideScope^® for tracheal intubation in 15 patients wearing halo vests scheduled for elective surgery under general anesthesia. Preoperative airway assessments were evaluated to predict the difficulty of tracheal intubation. Before intubation, all patients were given a modified Cormack and Lehane (MCLS) grade and percentage of glottic opening (POGO) score by the intubating anesthesiologist having resorted to direct laryngoscopy (DL) with a Macintosh Size 3 blade depiction. Then intubation with the GlideScope^® was performed, during which the larynx was inspected and given another MCLS grade and POGO score.

Results

Fourteen of the 15 patients had MCLS Grade III or IV by direct Macintosh laryngoscopy and were considered to have a difficult laryngoscopy. Nasal tracheal intubation by the GlideScope^® was successful on all occasions. The GlideScope^® improved the MCLS grade and POGO score in all patients who had put on a halo vest as compared with those on DL (p < 0.01). The GlideScope^® also provided a better laryngoscopic view than that by a DL. All of the patients who wore halo vests and presented with suspected difficult airways could be intubated successfully with the GlideScope^®.

Conclusion

The use of the GlideScope^® for tracheal intubation could be an alternative option in patients with a difficult airway, whose surgery was circumscribed under general anesthesia with tracheal intubation.

Keywords

intubation, intratracheal; laryngoscopy; laryngoscopes: GlideScope®; orthotic devices: halo vest;

1. Introduction

The GlideScope^® (Verathon Medical B.V. Boerhaaveweg, Ijsselstein, The Netherlands) is a video laryngoscope developed for difficult airway management.¹ The device consists of a light source and video camera located in the blade of a rigid plastic laryngoscope, which is connected to a separate liquid crystal display monitor. Previous studies have demonstrated that the GlideScope^® may provide a better laryngoscopic view than that by a direct laryngoscope² (DL) and has a particular advantage over other devices for tracheal intubation in patients with difficult airway.³ Our previous investigation has demonstrated that the use of the GlideScope^® for tracheal intubation in patients with ankylosing spondylitis could be promising.⁴ Most of them presenting with difficult airways by DL could be successfully intubated nasally with the GlideScope^® for general anesthesia.

Because DL in patients who wear a halo vest is difficult for anesthesiologist to manipulate, successful intubation in such a circumstance is quite impossible. Moreover, the patients are frequently subject to failure of intubation with DL because of limited neck motility and mouth opening.⁵ Awake fiberoptic intubation is ideal in these patients because neck mobilization and wide mouth opening are unnecessary.⁶ However, this procedure will cause bodily suffering, and some patients may utterly refuse awake intubation. Furthermore, patients with cervical spine injuries often require urgent intubation under suboptimal conditions. The aim of the study was to investigate the use of GlideScope^® for tracheal intubation in patients who had worn a halo vest and preferred their surgery to be carried out under general anesthesia with intubation.

2. Methods

After obtaining the approval of Hospital Ethics Committee and patient written informed consent, 15 consecutive patients who had to wear halo vests and were scheduled for elective surgery under general anesthesia with tracheal intubation in the period between December 2005 and November 2007 were recruited for the study. Preoperative airway assessments included Mallampati classification,⁷ thyromental distance, interincisor gap, and atlanto-occipital extension. The Mallampati score was recorded in the sitting position with mouth opened and tongue protruded. Thyromental distance was measured as the distance between the anterior chin and the thyroid notch. All examinations were performed by an anesthesiologist who was not involved in airway management. The tests for conditions of airway that foretold the likelihood of difficult intubation included the following: Mallampati classification ≥3; thyromental distance ≤6.5 cm; interincisor gap ≤4 cm; or atlanto-occipital extension was limited. After the airway assessments, the anesthesiologist was requested to complete an airway assessment sheet and predict the ease of tracheal intubation as difficult or nondifficult.

A standard anesthesia protocol was followed, and routine monitoring was applied. Patients were placed in the semisitting position having worn the halo vest. After preoxygenation through face mask with 100% oxygen for 5 minutes, inhalational induction of anesthesia with sevoflurane in oxygen was started without premedication. When the eyelash reflex disappeared, the end-tidal sevoflurane concentration was 4.5%. After ensuring that mask ventilation was smooth, 1.5 mg/kg succinylcholine was given intravenously. As full neuromuscular blockade was achieved, all patients underwent an initial DL with Size 3 blade of Macintosh (Heine, Germany) laryngoscope, and the laryngeal views were scored in accordance with the modified Cormack and Lehane (MCLS) grading system⁸ and percentage of glottic opening (POGO).⁹ These were performed by an anesthesiologist who did not participate in preoperative airway assessment. After initial laryngoscopy, positive pressure ventilation was continued through a face mask, and then, the trachea was intubated with the GlideScope^®. Our previous experience revealed that the tracheal intubation with the GlideScope^® would be more smooth and easy through nasal but not oral passage.⁵ Nasotracheal intubations were performed by the sole anesthesiologist who had experience in anesthesia for more than 20 years and was seasoned in the use of the GlideScope^® (>1000 intubations). A Parker Flex-It™ (Parker Medical, USA) articulating tracheal tube stylet¹⁰ was used for assisting the intubation (Fig. 1). During intubation, the larynx was inspected and given a second MCLS grade and POGO score. A difficult tracheal intubation is defined as an MCLS Grade ≥III or a POGO score of 0.

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Fig. 1. A Parker Flex-It™ articulating tracheal tube stylet was used for assisting nasotracheal intubation with the GlideScope®.

Data were analyzed using the McNemar χ² test for matched pairs to examine MCLS grades between DL and GlideScope^®.³ A p value <0.05 was considered statistically significant.

3. Results

Patients’ characteristics and the preoperative airway assessment data are shown in Table 1. The order of listing patients in Table 1 is sequential to the order of difficulties in tracheal intubation. After evaluation of preoperative airway by DL, all 15 patients were judged to have difficult airway, of whom 14 showed MCLS Grade III or IV. Table 2 shows the comparison of MCLS grades between DL and GlideScope^®. All patients (100%) had improvement in the MCLS grade (p < 0.01) as seen with the GlideScope^®, and they could be nasally intubated successfully at the first attempt by GlideScope^®.

Table 1. Patient characteristics and airway assessment by direct laryngoscopy and GlideScope®.

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Table 2. Comparison of MCLS grades between DL and GS (n = 15).

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4. Discussion

The present account is a report about a study chiefly for demonstrating the effectiveness of the GlideScope^® for management of difficult airway in patients wearing halo vests.

Airway management and tracheal intubation in patients who had put on halo vests could be difficult and challenging. In design, the halo vest projects from the shoulders and holds the head in rigid fixation with four metallic struts and a metallic “halo” affixed to the skull with bolts. This cumbersome device, although restricts the movement of head and neck, prevents easy access by the anesthesiologist to the patient’s airway and rendering even mild neck extension, for aiding visualization of the larynx in conventional DL impossible.⁵ Awake fiberoptic tracheal intubation can be helpful to overcome the difficulties in general situation but not in pressing condition. Cricothyroidotomy is too invasive and may be enforced only in the emergent setting. Besides, Kitamura et al⁶ reported on fiberoptic intubation through laryngeal mask airway by using a tube exchange catheter under general anesthesia in Japanese patients wearing halo vests. Lu et al¹¹ reported that the intubating laryngeal mask airway would be an alternative choice in patients with severe ankylosing spondylitis. However, nonanesthetic practitioners could be unfamiliar with the aforementioned equipments and techniques that need professional expertise. The GlideScope^® provides a better intubating condition in these patients, especially in emergent condition or when nasotracheal intubation is needed.

In our previous study, we used the same predictor tests to evaluate the airway condition preoperatively in patients wearing halo vests and could predict the difficulties of tracheal intubation.⁴ We also found that the predictions were highly consistent with the MCLS grades disclosed by DL but not by GlideScope^®. This finding was similar to that of our study in ankylosing spondylitis patients, and it meant that the conventional airway assessment tests to predict difficulty of tracheal intubation cannot be substituted by GlideScope^® in most patients.

After we first described successful nasotracheal intubation with the GlideScope^®, other reports12, 13, 14 also revealed that the main limitation in using the GlideScope^® was its inability of getting a good view of the glottis, but it could be helpful in manipulating the tracheal tube to pass the vocal cords, especially in patients wearing halo vests or those with restricted mouth opening. We have to emphasize again that nasal intubation could carry possibly significant morbidities, such as epistaxis and subsequent sinusitis. Thus, a thorough preparation before nasal intubation is imperative and should be taken into consideration while it is chosen.

Comparing with the conventional DL, the GlideScope^® has the following characteristics: it provides better glottic view and does not need the three axes close in-line for tracheal intubation. However, the time for tracheal intubation with GlideScope^® is longer than that for DL in patients with normal airways, and manipulating it needs experience and skill.15, 16 Furthermore, several articles have reported the clinical complications, such as tonsilar and palatal injuries, during the use of the GlideScope^®, and thus, its use is considerably limited.17, 18, 19

Videolaryngoscopy is rapidly becoming an established technique that can provide a good view of the larynx when conventional DL fails. It would change our conventional concepts of airway management: that preoperative airway assessments could not predict the difficulties of tracheal intubation by videolaryngoscopes is denied; decision making in difficult-airway algorithm during recognized or anticipated difficult condition should also be modified, to wit-, patients with difficult airways must have the trachea intubated only with awake fiberoptic bronchoscopy may be too arbitrary.

5. Conclusion

Our study showed that GlideScope^® for tracheal intubation for general anesthesia in patients wearing halo vests could provide a better view of the larynx than DL and facilitate successful nasotracheal intubation. It also demonstrated the growing information regarding the applicability of the GlideScope^® in patients with recognized difficult airways revealed by prior DL.

Acknowledgments

This study was supported by a research grant (TCDR-94A-38) from the Tzu Chi Charity Foundation. No person involved in this study has any financial relationship with the GlideScope^® or Saturn Biomedical Systems.