A comparison between the GlideScope Ò Video Laryngoscope and direct laryngoscope in paediatric patients with difficult airways a pilot study

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1 doi: /j x ORIGINAL ARTICLE A comparison between the GlideScope Ò Video Laryngoscope and direct laryngoscope in paediatric patients with difficult airways a pilot study C. Karsli, 1 J. Armstrong 2 and J. John 3 1 Assistant Professor, University of Toronto & Staff Anesthesiologist, 2 Fellow Anesthesiologist, The Hospital for Sick Children, Toronto, Canada 3 Assistant Professor, Eastern Virginia Medical School & Staff Anesthesiologist, Children s Hospital of the King s Daughters, Norfolk, USA Summary The GlideScope Ò Video Laryngoscope may improve the view seen at laryngoscopy in adults who have a difficult airway. Manikin studies and case reports suggest it may also be useful in children, although prospective studies are limited in number. We hypothesised that the paediatric GlideScope will result in an improved view seen at laryngoscopy in children with a known difficult airway, compared to direct laryngoscopy. Eighteen children with a history of difficult or failed intubation were prospectively recruited. After inhalational induction, each patient had laryngoscopy performed using a standard blade followed by GlideScope videolaryngoscopy. The GlideScope yielded a significantly improved laryngoscopic view, both with (p = 0.003) and without (p = 0.004) laryngeal pressure. The mean (SD) time taken to achieve the optimal view was 20 (8)s using conventional laryngoscopy and 26 (22)s using the GlideScope Ò (p = 0.5). The GlideScope Ò significantly improves the laryngoscopic view obtained in children with a difficult airway.... Correspondence to: Dr James Armstrong jama@doctors.org.uk Accepted: 27 January 2010 The paediatric GlideScope Ò Video Laryngoscope (Verathon Medical Inc., Bothell, WA, USA) is a laryngoscopic instrument that may improve the view of the glottis during tracheal intubation in adults and children. The 60 angle of the blade is designed to provide an improved view of the glottis, without requiring alignment of the oral, pharyngeal and tracheal axes, and also without requiring any additional lifting force. In a series of 60 adults with tumours of the upper airway, the GlideScope improved the Cormack and Lehane [1] view in 82% of the patients, when compared with the MacIntosh blade [2]. A small number of case reports have been published reporting successful use of the GlideScope in paediatric patients with Treacher Collins syndrome [3], Beckwith Wiedemann syndrome [4] and Goldenhar syndrome [5]. Prospective studies comparing the GlideScope with direct laryngoscopy in children with a known difficult airway are limited. The aim of this pilot study was to assess the laryngoscopic view in children known to have a difficult airway, using the paediatric GlideScope when compared with conventional direct laryngoscopy using the Macintosh blade. Our secondary aim was to compare the time taken to achieve the best possible view with each technique. Methods Following Research Ethics Board approval and written informed consent, children between 2 and 16 years of age with a known difficult airway, were enrolled over an 18-month period. All participants were scheduled for operative procedures requiring general anaesthesia and tracheal intubation. Prospective patients were identified pre-operatively in the anaesthesia consultation clinic or surgical booking office. A patient was considered suitable Journal compilation Ó 2010 The Association of Anaesthetists of Great Britain and Ireland 353

2 C. Karsli et al. Æ GlideScope Ò Video Laryngoscope vs direct laryngoscopy in children Anaesthesia, 2010, 65, pages for enrollment if there was documentation on a previous anaesthetic record indicating that intubation had been difficult (defined as Cormack and Lehane grade 3 or higher, or previous failed intubation). Patients with severely limited (< 2 cm) mouth opening, compromised cardiac or respiratory status or with cervical spine injury were excluded. In each case, the difficult airway cart was present in the operating room, and routine monitoring for general anaesthesia was applied. Induction of anaesthesia was achieved via inhalation of 8% sevoflurane in oxygen, and spontaneous ventilation was maintained throughout the induction period. An intravenous cannula was then inserted and the patient s head was maintained in the standard sniffing position. Direct laryngoscopy using a conventional laryngoscope with an appropriately sized Macintosh blade (Heine, Germany) was performed by one of two staff anaesthetists. The type and size of blade was left to the discretion of the anaesthetist performing the laryngoscopy. The best laryngoscopic view was graded according to the Cormack and Lehane scale both with and without backwards, upwards and right laryngeal pressure. Sevoflurane in oxygen was once again provided for 30 s followed by laryngoscopy. Grading of the view (as seen on the monitor) using the paediatric GlideScope (size 3, reusable blade) was done by the second anaesthetist, both with and without backwards, upwards and right laryngeal pressure. The second anaesthetist was blinded to the Cormack Lehane laryngoscopy score given by the first anaesthetist. Each of the two anaesthetists was randomly assigned the technique they were to use (GlideScope or direct laryngoscopy) before the case was started. The time to the best laryngoscopic view with each technique was recorded. This was defined as the time from when the laryngoscope blade entered the patient s mouth to the time the anaesthetist determined that the best possible view had been achieved. Tracheal intubation was performed using the paediatric GlideScope. If intubation was not possible on the first attempt with the GlideScope, the patient s airway was then managed at the discretion of the anaesthetist, and in accordance with the difficult airway algorithm. The data from each patient were split into two groups, to allow analysis of the Cormack and Lehane grades obtained with and without backwards, upwards, right laryngeal pressure. Data were then analysed using a twotailed Wilcoxon signed rank sum test to examine pairs of Cormack and Lehane grades for each patient. The data for time to best laryngoscopic view data were analysed using the Mann Whitney U test. A p value < 0.05 was considered statistically significant. Results Eighteen patients were recruited, with mean (SD) age of 11 (5) years and weight of 35 (22) kg. All but one patient (who had received radiation therapy for mandibular sarcoma) had a developmental syndrome associated with difficult airway management and intubation (e.g. Goldenhar, Pierre-Robin, Apert, Russell-Silver, Townes- Brock or Cornelia DeLange syndrome). The best views obtained by each method of laryngoscopy, with and without backwards, upwards and right laryngeal pressure, and the time to achieve that view, are shown in Table 1. There was a significant improvement in the laryngoscopic grade obtained using the GlideScope compared with direct laryngoscopy, both with (p = 0.003) and without (p = 0.004) backwards, upwards, right laryngeal pressure. There was no significant difference between the time required to generate the best view using direct laryngoscopy (mean (SD) 20 (8) s) and the GlideScope (26 (22) s); p = 0.5. The tracheas of all but three of the patients were intubated using the GlideScope on the first attempt. In patient L, the GlideScope yielded the best Table 1 Cormack and Lehane laryngoscopy grades and time to achieve an optimal view in paediatric patients, using direct laryngoscopy or the GlideScope, with and without backward, upward, and right laryngeal pressure (BURP). Values are actual number. Patient Direct laryngoscopy Glidescope Intubation method No BURP BURP Time (s) No BURP BURP Time (s) (if not Glidescope) A B C D E F G H I J K L Fiberoptic M Direct Laryngoscopy N O P Fiberoptic (through LMA) Q R Mean SD 8 22 LMA, laryngeal mask airway. 354 Journal compilation Ó 2010 The Association of Anaesthetists of Great Britain and Ireland

3 C. Karsli et al. Æ GlideScope Ò Video Laryngoscope vs direct laryngoscopy in children view. However, there was insufficient room in this patient s mouth for both the GlideScope and the tracheal tube, and flexible fiberoptic intubation was required. Direct laryngoscopy provided the best view in patient M. In patient P, intubation was unsuccessful with both the GlideScope and direct laryngoscopy, and therefore fiberoptic intubation was performed using a laryngeal mask airway as a guide. Oxygen saturation was maintained above 95% in all patients throughout the study period, and there were no other complications recorded. Discussion The most interesting finding in the current study was that the paediatric GlideScope yielded a better view of the glottis in 14 of the 18 patients (78%), as compared to direct laryngoscopy with the MacIntosh blade. This degree of improvement was shown to be significant both with (p < 0.003) and without (p < 0.004) backwards, upwards, right laryngeal pressure. Two further patients (11%) had the same view recorded with each technique. In 15 of the 18 patients (83%), tracheal intubation was noted to be easy with the paediatric GlideScope, despite the fact that all patients had been previously graded as having difficult laryngoscopy and intubation by an experienced paediatric anaesthetist. This was confirmed by the initial results of direct laryngoscopy (without laryngeal pressure) in our study, with nine patients being graded Cormack and Lehane grade 3 and nine grade 4. There has been extensive work evaluating the Glide- Scope in the adult population. Initial manikin studies [6] and subsequent work on patients with a Cormack and Lehane grade 1 2, have shown that the GlideScope is consistently able to yield equal or better views of the glottis than direct laryngoscopy [7 9]. This is the case even with inexperienced operators. Studies that examined time to intubation [7] have indicated that use of the GlideScope prolongs the time before tracheal intubation is achieved. A recent meta-analysis [10], analysing a range of nonstandard laryngoscopes and fiberoptic intubation aids, identified seven studies examining aspects of the Glide- Scope in adult patients [7 9], [11 14], (Sorbello M, Zingale S, Cutuli M, et al. Evaluation of glottic vision and intubation success rate with GlideScope and conventional Macintosh laryngoscopy with head fixed in neutral position: study in 500 patients. Presented at the Difficult Airway Society Annual Meeting, Dublin, 2006). A total of 1076 patients with a normal airway and 213 patients with a predicted or actual difficult airway were included in this analysis. The results revealed a 96.4% first time success rate (95% CI 95 97%, n = 1076) and a overall success rate of 99.8% (95% CI %, n = 1076) in normal patients, compared to a 92.3% first time success rate (95% CI 79 98%, n = 39) in patients with a predicted or difficult intubation. The meta-analysis also showed an average 69% improvement in laryngoscopic view with the GlideScope, when compared with the Macintosh 3 laryngoscope blade. However, the heterogeneous nature of the studies in this meta-analysis made comparisons more imprecise. These results are similar to those obtained in our study, where 89% of patients had the same or better views with the GlideScope. The first time intubation success rate in our patient group was 83%, slightly lower than the metaanalysis results, but within the same confidence ranges. We only allowed one attempt with the GlideScope; therefore results for overall success are not comparable. The initial work in normal paediatric populations showed similar results, with an equal or better view of the glottis, but an increased time to intubation with the GlideScope [15, 16]. However, a recent study by Redel and colleagues [17] also showed improved intubating conditions, but with no difference in the time to intubation. The current pilot study was not designed to assess or compare the time to intubation with the GlideScope vs direct laryngoscopy. This was unavoidable as tracheal intubation was only carried out after the second laryngoscopy with the GlideScope. Despite this, internal consistency was preserved as much as possible, by having the same two investigators perform all the laryngoscopies. The time taken to achieve the optimal view with either technique was assessed, and found not to be significantly different. This raises an important point when considering the GlideScope, and indeed all videolaryngoscopes. All these devices place the virtual eyeball close to the glottis, theoretically making obtaining a view easier. This does not necessarily mean that passing the tracheal tube through the vocal cords will be as easy. Often, careful manipulation may be required to approximate the tip of the tube and the glottic opening. The GlideScope may facilitate tracheal intubation in patients with abnormal upper airways not only by improving the laryngoscopic view, but by virtue of its indirect (videoscopic) nature. In patients with a small mouth, retrognathia or micrognathia direct laryngoscopy may reveal an adequate view of the vocal cords. However, insertion of a tracheal tube into the oropharynx may then obliterate that view, making intubation difficult. In contrast, laryngoscopy using the GlideScope may allow for an improved continuous view even as the tracheal tube is inserted in the mouth. In our opinion, this mechanism accounts for the improved view often afforded by videolaryngoscopes such as the GlideScope Ò. More recently, studies have been carried out looking at the use of the GlideScope in children with a difficult Journal compilation Ó 2010 The Association of Anaesthetists of Great Britain and Ireland 355

4 C. Karsli et al. Æ GlideScope Ò Video Laryngoscope vs direct laryngoscopy in children Anaesthesia, 2010, 65, pages airway. A manikin study by White and colleagues [18] compared the new paediatric GlideScope with the Miller laryngoscope in simulated 3 6-month-olds, under normal and difficult airway conditions. No difference in time to intubation was found, and subjective evaluation of ease of use and quality of field of view was comparable. A small number of case reports have been published reporting successful use of the GlideScope in patients with Treacher Collins syndrome [3], Beckwith Wiedemann syndrome [4] and Goldenhar syndrome [5]. All of these patients previously had difficult or failed intubations with no glottic structures easily visible with direct laryngoscopy. Use of the GlideScope resulted in a Cormack and Lehane grade-1 view in the first two cases, and a grade-2 view (with aid from backwards, upwards and right laryngeal pressure maneuver) in the third case. In all three children, the tracheas were intubated without difficulty. The results obtained from the current study support those of the manikin study mentioned above [18], and the case reports of children with syndromes associated with airway abnormalities. Twelve of the 18 patients (67%) examined had a Cormack and Lehane view of 3 or 4, i.e. with no glottic structures visible, using direct laryngoscopy with laryngeal pressure. With the GlideScope, only nine patients (50%) had a grade-3 or -4 view on initial assessment, and this decreased to five (28%) with the application of laryngeal pressure. Although our results with the GlideScope showed a statistically significant difference in the view obtained without laryngeal pressure, 50% of patients still had a Cormack and Lehane grade 3 or 4, essentially still equating to a blind intubation. However, with laryngeal pressure, the GlideScope was able to enhance a Cormack and Lehane grade-3 or -4 view to a grade-1 or -2 view. Of equal importance is to examine the features of the patients whose laryngoscopic views were not able to be improved with the GlideScope. Two of the three patients with failed GlideScope intubations (patients L and M) had syndromes associated with short, immobile necks (Kippel-Feil and Noonan s syndromes). The other patient who failed to yield an improved view with the Glide- Scope (patient P), had an extremely large tongue as the result of Hunter s syndrome (a lysosomal storage disease), which hampered the glottic view, although intubation was still possible. These results suggest that the Glide- Scope may be less useful in patients with short necks, restricted neck movement or significant macroglossia. However, more patients with these characteristics would need to be studied to confirm this. There are some important sources of bias inherent in this study that must be addressed. By definition, the grading of Cormack and Lehane views is subjective. The current study was designed so that each of the investigators was blinded to the laryngoscopic grade assigned by the other investigator, and each was randomly assigned a technique (direct laryngoscopy or GlideScope) before the case started. The disadvantage of having two observations made by two different investigators includes potentially increasing the chance of inter-observer variability. Such variability is potentially compounded by the fact that there was no independent corroboration of the glottic view in each case. The time points recorded were also subjective, although we aimed to minimise this by only having two investigators perform the laryngoscopies. In this study, each patient underwent direct laryngoscopy first, followed by the GlideScope (i.e. the order was not randomised). Although this may introduce bias, it was felt to be appropriate as all the patients were proven difficult direct laryngoscopies. In this study, it was proposed the GlideScope would generate a better view. Therefore, by using the GlideScope first, followed by direct laryngoscopy, and then having to repeat the GlideScope to intubate the trachea, would mean that the patient would be exposed to unnecessary interventions. The fact that only three patients needed further interventions after the GlideScope supports this rationale. The risk of operator bias must also be considered. This is very difficult to control for, as it is impossible to blind the anaesthetist to which instrument is in his hand. The only way to address some of these issues would be to redesign the study to allow for independent grading of the view obtained using both techniques by more than one independent observer. This study indicates that, in children who are known to have a difficult airway, the use of the GlideScope video laryngoscope, with and without laryngeal pressure, significantly improves the Cormack and Lehane grade at laryngoscopy. Consequently, the GlideScope may prove a useful tool either in patients who are known to have a difficult airway, or in patients with a suspected difficult airway, where no previous anaesthetics have been performed to confirm this. Acknowledgements We are grateful to Dr Mark Crawford MD, Department of Anesthesia, The Hospital for Sick Children, Toronto, Ontario, Canada, for statistical assistance. Competing interests This work has not been funded by any sources. No ethical, financial or other conflict of interest exists with the subject matter or materials. No person involved in this study has any financial relationship with the GlideScope or Verathon Medical Inc. 356 Journal compilation Ó 2010 The Association of Anaesthetists of Great Britain and Ireland

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