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ORIGINAL ARTICLE
Year : 2023 | Volume
: 24
| Issue : 1 | Page : 43-48
Comparison of McGrath videolaryngoscope with conventional Macintosh laryngoscope for tracheal intubation in pediatric patients with normal airway
Stuti Bhamri, Devyani Desai, Darshit Chauhan, Neha Cheraya
Department of Anaesthesiology, Government Medical College, Vadodara, Gujarat, India
Correspondence Address:
Dr. Devyani Desai
Department of Anaesthesiology, Government Medical College, Vadodara, Gujarat
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/TheIAForum.TheIAForum_104_22
Background and Aims: Videolaryngoscopes have attained prime importance in securing the airway in children in the present era. McGrath videolaryngoscope is available with single-use non-channeled fog-free disposable blades of various sizes showing its efficacy for intubation in adults but still lacunae in data related to children.
Materials and Methods: In this prospective randomized controlled trial, a total of 88 children of the American Society of Anesthesiologists Grade I and II aged 1–10 years, weighing 10–20 kg undergoing general anesthesia were enrolled. Using the sealed envelope technique, the children were randomly allocated between Group G, in whom McGrath videolaryngoscope and Group M, in whom Macintosh laryngoscope was used for intubation. The primary aim was to compare intubation time between the two videolaryngoscopes. The secondary outcomes included glottic exposure time, Cormack and Lehane grading, number of attempts of intubation, intubation difficulty scale and complications. Statistical analysis was done using MedCalc software. The Student's t-test and Chi-square test were used for quantitative and categorical data, respectively.
Results: The mean intubation time was comparable in both the groups (18.14 ± 17.80 s in Group G vs. 17.30 ± 16.74 s in Group M, P = 0.821). The mean time to glottic exposure was shorter (5.66 ± 4.58 vs. 8.50 ± 5.59 s, P = 0.0108) with decreased number of attempts of tube insertion and less incidences of trauma observed in patients with Group G as opposed to Group M. The Cormack and Lehane grading showed better glottic view in Group G.
Conclusion: McGrath videolaryngoscope is as useful as the Macintosh laryngoscope for intubation in children with the added advantages of a better view of the larynx, lesser attempts to intubation, and fewer incidence of trauma.
Keywords: Endotracheal intubation, macintosh laryngoscope, McGrath videolaryngoscope, pediatric
The quality airway management technique is crucial for an anesthesiologist taking care of children during surgery. The incidence of difficult direct laryngoscopy ranges from 0.06% to 3%.[1] Anticipated or unanticipated difficulties leading to failure to intubate are the leading elements for anesthesia-related morbidity and mortality in the pediatric population.[2] Routine bedside screening tests have limited power to predict these difficulties. Remarkable progress in airway assessment tools, difficult airway algorithms, newer modalities for managing the airway, and the evolution of newer airway devices especially video-laryngoscopes (VLs) suitable for pediatric patients affected the perioperative management in this age group. Enlarged field of vision from 15° to 80° resulting in augmented eyesight reaching beyond the capacity of a Macintosh blade, and minimal manipulation leading to reduced chances of noxious stimulus and trauma are the advantages of video laryngoscopy-assisted intubation in children.[2]
Prior literature analyzing different video laryngoscopes with direct laryngoscope for tracheal intubation demonstrated a superior view of the glottis with a comparable success rate and reduced time to intubate in children presenting with difficult intubation.[3],[4],[5],[6],[7],[8] McGrath is a recently introduced VL, with pediatric and adult-sized non-channeled blades. Relatively in nascent stages of development, its use in the pediatric age group is still emerging. Therefore, we decided to look for its usefulness in children aged 1–10 years. Primarily, the intubation time was compared using McGrath VL and Macintosh laryngoscope and glottic exposure time, Cormack–Lehane grading, number of attempts to successful intubation, intubation difficulty scale (IDS), vital parameters, and complications were secondary parameters.
Materials and MethodsAfter taking permission from the Institutional Scientific and Ethical Research Committee and registered in the national Clinical Trial Registry, (CTRI/2019/10/021568), this study was conducted from September 2019 to October 2020, at the tertiary care hospital. Eighty-eight patients aged between 1 and 10 years of either sex, weighing 10–20 kg, American Society of Anesthesiologists (ASA) physical status I or II, with mouth opening >20 mm underwent elective surgical procedures and received general anesthesia were included. Patients with any of the following: difficult airways such as Mallampati Grade III or IV, receding mandible, abnormal airway anatomy, pre-existing laryngeal or tracheal pathology, upper respiratory tract infection, or unwillingness to participate were excluded. Pre-anesthetic check-up including basic laboratory investigations was performed. The patient's parents/guardians were explained in detail about the purpose, procedure, and possible adverse effects of the study and written informed consent was obtained from them and were instructed to keep the child in a fasting state for 6 h before surgery.
All patients were randomly allocated to two groups by the computer-generated random numbers which were then sealed in an opaque envelope. All Group G (n = 44) patients were intubated using McGrath VL while in Group M (n = 44), a Macintosh laryngoscope was used for endotracheal intubation. The envelope was opened after taking the patient inside the operation theatre, just before induction of anesthesia. For McGrath VL, pediatric non-channeled blade was mounted on the handle (containing battery) and the performance of the device was examined by viewing the clarity of the image on the monitor. A Macintosh laryngoscope with an appropriately sized pediatric blade mounted on the handle was also kept ready. On arrival at the operation theater, a multipara monitor was attached and baseline vital parameters such as pulse rate (PR), mean arterial pressure (MAP), and oxygen saturation (SpO2) were recorded. Patients were premedicated using glycopyrrolate 5 μg/kg, fentanyl 2 μg/kg, and ondansetron 0.1 mg/kg intravenously 5 min before induction. All patients were induced with increasing concentrations of sevoflurane (starting from 1%) with 100% O2 at 6 L/min flow using the Jackson-Rees circuit. The sevoflurane concentration was increased by 1% at every 2nd to 3rd breath. After achieving loss of eyelash reflex, an intravenous injection of atracurium 0.3-–.5 mg/kg was administered. Controlled positive pressure mask ventilation was initiated as soon as the patient became apneic and was continued with the help of capnography to maintain EtCO2 in the range of 35–45 cm H2O. After 3 minutes of mask ventilation, patients in Group G were intubated with the head kept in a neutral position. McGrath VL with pediatric size 2 blade was forwarded from the center of the tongue to the glottis while viewing the screen of the monitor attached to the handle so that it barely lifted the epiglottis with the tip of the blade. Once the glottic view was visible, the time of glottic exposure and Cormack and Lehane grading was noted. The endotracheal tube was advanced into the trachea from the side of the mouth with preloaded stylet under direct observation on the screen. If impingement of the tube occurred, then manipulation maneuvers were done in the form of rotation of the tube in a clockwise or anticlockwise direction, slight withdrawal or advancement of scope, or application of external laryngeal pressure. In Group M, the patients were intubated using the Macintosh laryngoscope with a size 2 blade after keeping the head in the morning sniffing position. The glottic view was rated according to Cormack and Lehane grading, the glottic exposure time was noted and the tube was advanced into the trachea. Any external optimizing maneuvers if required, were documented. The endotracheal tube was attached to the anesthesia breathing circuit and tracheal intubation was confirmed with bilateral equal air entry and capnography. The intubation time, glottic exposure time, Cormack and Lehane grading, number of attempts of intubation, and IDS [Table 1] were noted. Vital parameters such as heart rate, MAP, and SpO2 were noted at induction, 1 min and 5 min after intubation. Intubation time was calculated as the time from insertion of the blade between the teeth until the first effective ventilation confirmed by capnography. Glottic exposure time was calculated as a time from the introduction of the laryngoscope from teeth/gum to visualization of the glottic aperture. Maximum attempts with the selected laryngoscope were limited to two. When the patient could not be intubated after applying optimization maneuvers or requiring >120 s for intubation, it was considered as failed intubation. These patients were excluded from the study.
Intraoperative anesthesia was maintained using O2 and N2O (50:50) with sevoflurane and intermittent intravenous atracurium. Around 10 minutes before the end of the surgery, N2O and sevoflurane were stopped and the patient was ventilated with 100% oxygen. After returning spontaneous respiration, the residual neuromuscular blockade was reversed with intravenous neostigmine and glycopyrrolate. The patient was extubated following the establishment of a regular spontaneous breathing pattern as well as response to command and shifted to post-anesthesia care unit afterward. Perioperative complications such as laryngospasm, bronchospasm, tachycardia (>140 breaths/minute), bradycardia (<100 breaths/min), desaturation (SpO2 <95%), esophageal intubation, and oropharyngeal trauma were looked for and treated accordingly.
The sample size was calculated using the parameter “intubation time” taken from the previous study.[8] To estimate the mean difference of total time for intubation between the two groups by 6 s with a standard deviation (SD) of 10 s at 95% confidence and 80% power, a total of 88 patients had to be studied. All data were compiled into Microsoft Excel. The statistical analysis was done utilizing MedCalc (version 12.5. The Medtronic, Covidien, MA, USA). All continuous variables such as time to intubation, time to glottic exposure, and demographic variables were presented as mean ± SD and analyzed using the Student's t-test. The χ2 test was applied for categorical data such as gender, ASA grading, attempts to intubation, Cormack–Lehane grading of laryngeal view, and complications. P <0.05 was considered statistically significant.
ResultsAll patients were analyzed as there were no dropouts [Figure 1]. Both groups were similar demographically [Table 2]. The time to intubation using McGrath VL and Macintosh laryngoscope was comparable (P = 0.821) [Table 3]. Less time was required for glottic exposure in Group G (5.66 ± 4.58 s) as opposed to Group M (8.50 ± 5.59 s) and was statistically significant (P = 0.0108) [Table 4]. Evaluating the vocal cords by Cormack–Lehane grading revealed a Grade I/II/III view in 32/9/3 cases with McGrath VL and in 22/18/4 cases of Macintosh laryngoscope, suggesting a better view of glottis in Group G compared to Group M (P = 0.0295, Grade I, P = 0.0386, Grade II) [Table 4]. A statistically significant difference was found in intubation at the first attempt comparing Group G against Group M (40/44 [90.91%] vs. 36/44 [81.81%] patients [P < 0.0001]) [Table 4]. IDS was comparable in both groups (0.47 + 0.59 vs. 0.95 + 0.73, P = 0.4) [Table 4]. maneuvers like external laryngeal manipulation were required in 12 and 10 patients, respectively, in Group G and Group M, while rotation of the endotracheal tube was necessary for 19 patients in Group G and 16 patients in Group M to facilitate intubation (P = 0.6). Hemodynamically, both groups were comparable at 0, 1, and 5 minutes after intubation (P > 0.05) [Graph 1]. After the removal of the airway device, 3 cases versus 12 cases of oropharyngeal trauma were found in Group G and Group M respectively which was again statistically significant (P = 0.0119) [Table 4]. No other complications such as laryngospasm, bradycardia, tachycardia, or esophageal intubation were seen in either group.
The study resulted in identical intubation times between both groups (P = 0.821). A similar finding has been reported by Su et al., Kim et al. and Ray et al. while using these scopes in children.[6],[8],[9] Giraudon et al., Sun et al. and Wallace et al., however, found a shorter time to intubation using direct laryngoscopy as the tube passage time was shorter with Macintosh laryngoscope.[10],[11],[12] Ray et al. and Giraudon et al. also found that using McGrath videolaryngoscopy, a novice laryngoscopist initially required more time to intubation which decreased after gaining experience.[9],[10] Contrary to this, Orliaguet et al. found McGrath VL superior to direct laryngoscopy while comparing intubation time.[7] The McGrath VL can be a superior guide to intubation when used by expert operators, even in cases of difficult awake intubation as stated by Raza et al.[13]
In our study, glottic exposure time was found to be less with McGrath VL compared to direct laryngoscopy. We observed that in Group G, no tongue displacement was required and hence, the blade could be inserted quickly in the midline. The epiglottis was also not required to be elevated forcefully to view the glottic opening. Both these factors helped in reducing time to the best glottic view using McGrath VL compared to the Macintosh laryngoscope. In consensus with our study, Kim et al., Ross et al. and Yung-Cheng Su et al. reported less time to view the glottis with McGrath VL in comparison to direct laryngoscopy.[6],[8],[14] On the other hand, Giraudon et al. and Sun et al. found a similar time to get the best glottic view comparing both these scopes.[10],[11] During intubation with McGrath VL using a pediatric blade, the tongue is not displaced which may obstruct the passage of the tube, hence separate insertion maneuvering is required. Furthermore, all video laryngoscopes require hand-eye coordination in terms of simultaneous handling of the VL and endotracheal tube while maintaining a proper glottic view on the screen. These factors might have contributed to the prolongation of total intubation time despite having shorter glottic exposure time with the McGrath video laryngoscope as compared to the Macintosh laryngoscope.
Comparing the quality of visualization of glottis as assessed by Cormack and Lehane grading, Group G had a superior view of the glottis (P = 0.0108). Similar to our study, Kim et al. too, found a better percentage of glottic opening (POGO) score using the McGrath video laryngoscope as compared to the conventional scope in the pediatric population (95% vs. 74%, P = 0.013).[8] This was attributed to a high-resolution complementary metal oxide semiconductor camera in-built into the McGrath VL providing a panoramic view which significantly improved the glottic view. Using a new size-1 blade for the McGrath VL to facilitate intubation in neonates by Ross and Baxter found an improved video laryngoscopy view over that obtained under direct laryngoscopy.[14] In the magnified view of the larynx, facilitation of intubation was best achieved with a pre-loaded stylet inside the tracheal tube as the pediatric larynx is anterior and cephalad, An emulation of the blade to the traditional Macintosh laryngoscope in both, the design and a standard handle allowing application of different blades is an added advantage.[10] As opposed to our study, comparable Cormack and Lehane grade or POGO scores were found by Giraudon et al.[10]
Less number of attempts of intubation was required with McGrath VL. Intubation was done in the first attempt in 90.91% of patients and only 9.09% of patients required the second attempt of intubation in Group G. In Group M, 81.81% of patients had a successful first attempt of intubation while a second attempt was required in 18.19% of patients (P < 0.0001). Similar to our study, Kim et al. also found better results at the first attempt of intubation using the McGrath VL.[8] Ray et al. observed a higher overall rate of successful tracheal intubation using McGrath VL even when used by novice laryngoscopists.[9]
Our study revealed comparable IDS in both groups (P = 0.4). Kim et al. reported lower median IDS in the McGrath group (0 [0–0] vs. 0 [0–1], P = 0.018).[8] 12 patients in Group G and 10 patients in Group M required external laryngeal manipulation, while rotation of the endotracheal tube was necessary for 19 patients in Group G and 16 patients in Group M to facilitate intubation (P = 0.6).
Hemodynamic responses attributed to laryngoscopy and tracheal intubation increases with the force and duration of laryngoscopy. The alignment of the oral, pharyngeal, and laryngeal axes for visualization of the glottis and intubation is not needed while using videolaryngoscope, minimizing the stimulation thought to reduce the pressure response as observed by Shribman et al.[15] However, we found comparable mean PR and blood pressure among both groups. Kim et al. and Tempe et al. were also unable to find the advantage of hemodynamic stability using video laryngoscopes in the pediatric population.[8],[16] This can be attributed to the longer time to intubation due to decreased proficiency in using video laryngoscopes by anesthetists.[16]
The smooth blade with no sharp edges as well as requiring minimal force to elevate the epiglottis may reduce the incidence of oropharyngeal trauma while using McGrath VL. It was significantly less in Group G, with 3 cases against 12 cases of oropharyngeal trauma in Group M, with a P = 0.0119. There were no other significant complications observed in either of the two groups. Kim et al. also noted lesser instances of trauma while using McGrath VL than conventional Macintosh scope.[8] Ray et al. observed avoidance of esophageal intubation and less dental trauma using McGrath VL.[9]
Being the device used for laryngoscopy, blinding was difficult. This could have led to some bias which we tried to reduce by the inclusion of experienced anesthesiologists who have used Mcgrath VL for at least 25 intubations in children previously. This is a single-center study using McGrath VL in pediatric patients with normal airways. Further multicentric research requires to study this device in children having difficult airways.
ConclusionMcGrath VL is as useful as the Macintosh laryngoscope for intubation in children aged 1–10 years having anatomically normal airways, with additional advantages of a better view of the larynx, lesser attempts to intubation and fewer instances of trauma.
Acknowledgment
We would like to acknowledge Dr. MR Upadhyay, Ex-Professor and HOD, Department of Anaesthesia, Government Medical College, Vadodara, Gujarat, for giving his valuable suggestions throughout the study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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