European Journal of Cardiovascular Medicine

Endotracheal intubation using a laryngoscope remains the preferred method for securing airways during general anesthesia. This technique offers several benefits, including the separation of respiratory and digestive systems, which minimizes aspiration risks. It also facilitates controlled ventilation, enables the delivery of anesthetic agents, and aids in maintaining respiratory hygiene. ^[1]

Despite advancements in anesthesiology, unsuccessful tracheal intubation attempts continue to be a significant source of complications in clinical settings. These complications can range from airway injuries and inadvertent esophageal intubation to more severe outcomes such as pulmonary aspiration and systemic issues resulting from oxygen deprivation and unexpected cardiovascular fluctuations. Traditional direct laryngoscopy, typically performed with a curved Macintosh blade in adult patients, relies on obtaining an unobstructed view of the larynx. ^[2]

Effective visualization during direct laryngoscopy depends on several factors. These include adequate lateral displacement of the tongue, proper positioning of the patient's head & neck in the "sniffing position" and optimal alignment of the oral, pharyngeal, and laryngeal axes. This position involves slight flexion of the neck, often achieved by placing a pillow under the head, combined with extension at the atlantooccipital joint. ^[3]

The advent of video laryngoscopes has introduced new possibilities in airway management. These devices offer enhanced glottic views without necessitating extensive tongue manipulation, precise head and neck positioning, or the use of additional intubation aids. However, it's important to note that airway instrumentation, regardless of the method, can trigger adverse cardiovascular responses. Significant fluctuations in blood pressure and heart rate can be particularly dangerous for patients with pre-existing conditions such as hypertension, coronary artery disease, or neurological disorders. These changes may lead to serious complications including myocardial ischemia, cardiac failure, or increased intracranial pressure. ^[4]

Video-assisted devices, by potentially reducing the need for forceful airway manipulation, may offer improved hemodynamic stability. This advantage has led to their increasing adoption in managing both normal and challenging airways. The ideal laryngoscopic technique should provide a clear view of the glottis, allowing for accurate endotracheal tube placement with minimal effort, reduced time, and lower risk of patient injury. Research has consistently shown that video laryngoscopes can enhance laryngeal visualization and improve intubation success rates. ^[5]

The McGrath Video Laryngoscope features a slim, disposable blade that closely resembles the Macintosh design, coupled with a compact LCD screen on the handle. Its lightweight construction and ergonomic design may contribute to easier and quicker tracheal intubation. A key advantage of the McGrath MAC is its ability to display a clear view of the glottis, vocal cords, and surrounding structures on its screen without requiring the precise alignment of airway axes, making it suitable for both routine and potentially difficult intubations. ^[6]

In contrast, the traditional Macintosh Laryngoscope utilizes a curved blade design. It functions by positioning the blade tip in the vallecula, anterior to the epiglottis, and then lifting to expose the larynx. This approach aims to simplify laryngeal exposure for endotracheal tube insertion. However, it typically requires the patient to be in the sniffing position to align the oral, pharyngeal, and laryngeal axes. ^[7-10]

This study aims to evaluate and compare the performance of the McGrath MAC Video Laryngoscope against the standard Macintosh Laryngoscope in adult patients. Key parameters for comparison include the time required for intubation, the number of attempts needed, any additional maneuvers required, overall ease of use, and the impact on cardiovascular stability during the intubation process.

AIMS AND OBJECTIVES

• The primary aim of this study is to conduct a comparative analysis of the McGrath MAC Video Laryngoscope and the Macintosh Laryngoscope in adult patients. Our main focus is on two key aspects:
• Measuring and comparing the total duration required for successful endotracheal intubation, recorded in seconds.
• Assessing and contrasting the hemodynamic stability of patients during and immediately following the insertion of the endotracheal tube.
• Our secondary objectives encompass a broader range of intubation-related factors:
• Evaluating the number of attempts required to achieve successful intubation with each device.
• Identifying and comparing the frequency of additional assistance needed, such as the use of a stylet or the application of external laryngeal pressure.
• Determining if any alternative intubation techniques were necessary for either device.
• Monitoring and recording any complications that arose during the induction phase or in the post-operative period associated with the use of these devices.

This prospective study was conducted at M.P. Shah Medical College, Jamnagar, from March 2021 to August 2022, after obtaining Institutional approval no. 51/01/2023, dated 11/04/2023). We enrolled 60 adult patients scheduled for elective surgeries, adhering to strict inclusion and exclusion criteria. Eligible participants were between 18-60 years old, classified as ASA II-III, with a BMI of 18.5-29.9 kg/m2. We excluded patients with obesity (BMI >30 kg/m2), predicted difficult airways, active respiratory infections, cardiovascular diseases, coagulation disorders, elevated intracranial pressure, known drug allergies, and those undergoing emergency procedures.

Randomization and Allocation: Study participants were divided equally into two groups using a randomization protocol generated through the StatTrek online random number generator (https://stattrek.com/statistics/random-number-generator.aspx). To ensure allocation concealment and prevent selection bias, an independent physician managed the randomization sequence using a secure envelope system. Each assignment was placed in sequentially numbered envelopes that were made sealed, opaque and stapled to maintain confidentiality. The group allocations remained concealed until each participant completed their baseline assessments and was cleared for intervention assignment.

Pre-anesthetic Preparation: All patients underwent a comprehensive pre-anesthetic evaluation, including a detailed medical history, systemic examination, and relevant investigations. Patients were kept nil by mouth for a minimum of 6 hours prior to the procedure. Upon arrival in the preoperative area, baseline parameters including pulse and respiratory rate, SpO2 and non-invasive BP were recorded.

Anesthetic Management: Patients received standard premedication, including intramuscular injections of Pentazocine (0.5mg/kg), Promethazine (0.5mg/kg) and Glycopyrrolate (4μg/kg) 30 minutes before induction. Intravenous administration of Ondansetron (0.1mg/kg) and Midazolam (20μg/kg) was given 10 minutes prior to induction.

Standard monitoring protocols were implemented in the operating room with continuous ECG, SpO2 monitoring and automated blood pressure measurements. Anesthesia was initiated with intravenous Propofol administration (1.5-2.0 mg/kg) followed by neuromuscular blockade using Succinylcholine (2.0 mg/kg IV) to facilitate intubation conditions.

Intubation Procedure: Patients in Group M underwent intubation using a conventional Macintosh, while those in Group G were intubated using the McGrath MAC video laryngoscope. The appropriate blade size and endotracheal tube (sizes 6.5 to 8.5) were selected based on patient characteristics.

Data Collection: During the intubation process, we recorded:

• Number of intubation attempts
• Time taken for device insertion
• Time taken for endotracheal tube insertion
• Total intubation time
• Need for alternative techniques or additional assistance
• Requirement for external laryngeal pressure
• Use of a stylet

Hemodynamic parameters like BP, heart rate and SpO2 were monitored at regular intervals: baseline, and at 0, 30 seconds, 1, 3, 5, 10, 15, 20, 25, 30, 60, and 90 minutes post-intubation.

Statistical Analysis

All data processing and calculations were performed using Epi Info version 22.0 statistical software. Numerical data were presented as means with standard deviations, and categorical variables were reported as frequencies and proportions. Statistical comparisons between groups for quantitative measurements utilized independent t-tests. Statistical significance was established at p<0.05. Sample size determination was informed by a preliminary pilot study, with 30 participants per group calculated to achieve 80% statistical power at an alpha significance level of 0.05.

Our study, conducted at M.P. Shah Medical College, Jamnagar from March 2021 to August 2022, included 60 patients equally divided into two groups. Demographic profile showed statistically no significant difference among both the groups (Table 1). The total duration of  endotracheal intubation revealed a statistically significant difference, with Group G (McGrath MAC) performing better at 14.66 ± 4.02 seconds compared to Group M (Macintosh) at 23.01 ± 1.81 seconds (Table 2).

Table 3 indicates that no patients in either group required a second attempt or alternative intubation technique. However, fewer patients in Group G needed external laryngeal pressure (2 vs 7) and stylet use (18 vs 23) compared to Group M. Hemodynamic responses showed notable differences, with statistically significant variations in mean pulse rates between the groups at 30 seconds, 1, 3, 5, 10, and 15 minutes post-intubation (P < 0.05) (Table 4).

Similarly, Figure 3 demonstrates significant differences in Mean Arterial Pressure between the groups at 30 seconds, 1, 3, 5, and 10 minutes post-intubation (P<0.05). Importantly, no complications were observed in either group during the perioperative or postoperative periods (Table 5).

These results suggest that the McGrath MAC video laryngoscope offers advantages in terms of intubation speed, reduced need for optimization maneuvers, and potentially better hemodynamic stability compared to the Macintosh laryngoscope (Table 5).

Figure1: Insertion of McGrath MAC blade and view of vocal cord in McGrath MAC LCD scree

Figure 2: CONSORT diagram

Figure 3: shows line diagram of statistical analysis of changes in mean arterial pressure during surgery in both groups

TABLE 1: DEMOGRAPHIC DATA IN MACINTOSH &MCGRATH MAC VIDEOLARYNGOSCOPE GROUPS

TABLE 2: COMPARISION OF TOTAL TIME (DURATION) OF ENDOTRACHEAL INTUBATION BETWEEN TWO GROUPS.

TABLE 3: COMPARISON OF ANY ALTERNATIVE MANEUVER REQUIRED BETWEEN TWO GROUPS

TABLE 4: COMPARISION OF MEAN PULSE RATE AT DIFFERENT TIME INTERVAL BETWEEN TWO GROUPS

TABLE 5: COMPLICATIONS PERIOPERATIVE AND POSTOPERATIVELY

Airway management, particularly in challenging cases, has long been a critical concern in anesthesiology. The past decade has witnessed significant advancements with the introduction of video-assisted airway devices and specialized laryngeal mask airways, greatly enhancing clinical outcomes for adult patients. Among these innovations, a select few, including the AIRTRAQ Optical Laryngoscope, Glide Scope Video Laryngoscope, True View Video laryngoscope, McGrath Mac video laryngoscope, Pentax AWS, and Fastrach Laryngeal intubating LMA, are now available in various sizes to accommodate diverse patient needs. ^[11]

Video laryngoscopy represents a paradigm shift in tracheal intubation techniques, offering a distinctly different approach compared to traditional Macintosh laryngoscopy. This novel method requires a unique skill set, diverging significantly from the techniques employed in direct laryngoscopy with Macintosh or Miller blades. While conventional methods demand extensive practice to achieve proficiency, video laryngoscopy (VL) has demonstrated a remarkably shorter learning curve. This accessibility allows even less experienced practitioners to perform successful laryngoscopy and intubation, potentially revolutionizing airway management practices and improving patient safety. ^[12,13]

DEMO GRAPHICAL DISTRIBUTION

Our investigation encompassed two cohorts, each consisting of 30 participants. In the Macintosh group (M), the average age was 34.53 years, mean weight 58.66 kg, with a male-to-female ratio of 12:18. The McGrath MAC group (G) exhibited an average age of 35.06 years, mean weight of 59 kg, and a male-to-female ratio of 14:16. The demographic characteristics were statistically comparable across both groups, ensuring a balanced foundation for our analysis.

INTUBATION CRITERIA

Our study revealed a notable disparity in the duration required for endotracheal intubation between the two groups. Participants in group M required an average of 23.01 seconds (SD 1.81) for intubation, while those in group G achieved intubation in just 14.66 seconds (SD 4.02) (P<0.001). The McGrath Mac video laryngoscope's superior efficiency compared to the conventional Macintosh laryngoscope. Notably, no participants in either group necessitated a second attempt or alternative intubation technique. The significant reduction in intubation time with the McGrath Mac laryngoscope (P < 0.001) can be attributed to the indirect laryngeal view it provides, which, despite requiring hand-eye coordination, facilitated faster tube placement.

In 2014, Bhola, Ruchi; Bhalla et al conducted a comparative study of the McGrath video and TruviewEVO2 laryngoscope for tracheal intubations in patients with the cervical spine immobilization. Their findings revealed shorter intubation times with the McGrath video laryngoscope compared to the Truview (30.02s vs.38.72s). While laryngoscopic views were similar between the devices, the McGrath Video laryngoscope demonstrated fewer hemodynamic alterations during intubation. Both devices achieved a 100 percent success rate and provided good glottic views in simulated cervical spine injury scenarios using manual in-line stabilization. ^[14]

These results align with our observations, confirming that the McGrath MAC video laryngoscope offers superior vocal cord visualization and facilitates easier intubation. In our study, the endotracheal intubation duration was significantly shorter with McGrath MAC video laryngoscope (GROUP G - 14.66 ± 4.02 seconds) compared to the Macintosh laryngoscope (GROUP M - 23.01 ± 1.81 seconds).

MEAN PULSE RATE

Our analysis revealed that in group G, the mean pulse rate was 84.4/min (SD 8.66), while in group M, it was 89.03/min (SD 12.21) after premedication but before intubation. This differences was statistically not significant (p=0.095). Post-intubation, we observed statistically significant differences in mean pulse rates between the two groups at 0, 30 sec. and 1,2,3,5,10 and 15 minutes (P<0.05). However, these differences became statistically insignificant at 20, 25, 30, and 60 minutes (P>0.05). These findings suggest that Group G demonstrated better hemodynamic stability compared to group M.

MEAN ARTERIAL BLOOD PRESSURE

In our investigation, group G exhibited a Mean Arterial Pressure of 89.8mmHg (SD 8.38), while group M showed 92.77mmHg (SD 6.34) after premedication but prior to intubation. This difference was not statistically significant (p value 0.12). Following intubation, we observed statistically significant differences in Mean Arterial Pressure between the two groups at 0, 30 seconds, 1, 2, 3, 5, and 10 minutes (P value < 0.05). However, these differences became statistically insignificant at 15, 20, 25, 30, and 60 minutes (P value > 0.05). These results further support the conclusion that Group G demonstrated superior hemodynamic stability compared to group M.

A 2018 randomized controlled investigation by Kim and colleagues evaluated pediatric airway management comparing traditional Macintosh and McGrath MAC video laryngoscopy techniques. The study enrolled 84 children between ages 1-10 years, assessing various intubation metrics. While intubation duration was comparable between devices, the McGrath MAC demonstrated superior glottic visualization with more frequent Cormack Lehane grade 1 views. The video laryngoscope also achieved better Intubation Difficulty Scores and demonstrated more favorable cardiovascular responses during the procedure compared to conventional direct laryngoscopy. ^[15]

These findings corroborate our results, demonstrating that the McGrath MAC video laryngoscope offers improved hemodynamic stability compared to the Macintosh laryngoscope.

A recent investigation by Abhyankar, Sabharwal and colleagues (2023) assessed three different laryngoscopy techniques in adult surgical patients. Their prospective trial enrolled 180 participants, equally distributed among traditional Macintosh laryngoscopy (Group-A), C-MAC video laryngoscopy (Group-B), and McGrath MAC video laryngoscopy (Group-C). The researchers evaluated multiple performance metrics, with first-pass success rate as their primary endpoint. Secondary measures encompassed glottic visualization quality using Cormack-Lehane grading, temporal parameters including laryngoscopy and intubation duration, procedural difficulty assessment, requirement for airway optimization techniques, and the frequency of endotracheal tube insertion attempts. ^[16]

Their study comparing Macintosh, C-MAC, and McGrath MAC laryngoscopes in 180 surgical patients found that video laryngoscopes achieved better first-attempt success rates and superior glottic visualization (C-MAC: 100%, McGrath: 90%, Macintosh: 41.7%). However, traditional Macintosh demonstrated faster procedure times for both laryngoscopy (9.9±2.5s) and intubation (24.4±12s) compared to video laryngoscopes, though more optimization maneuvers were required. ^[17]

These findings align with our observations, confirming that the McGrath MAC video laryngoscope offers improved hemodynamic stability compared to the Macintosh laryngoscope and achieves shorter intubation times.

The McGrath MAC video laryngoscope demonstrates superior performance compared to the Macintosh laryngoscope in managing challenging intubations. However, it's important to note that proficiency with this device requires specialized training, which can be acquired through practice on patients with normal airways. Our investigation reveals that the McGrath MAC Video laryngoscope facilitates smoother intubation, offers improved hemodynamic stability, and significantly reduces the overall intubation duration when compared to the traditional Macintosh Laryngoscope. As a newer airway management tool, the McGrath MAC video laryngoscope proves to be more intuitive, straightforward, and user-friendly than its conventional counterpart.

LIMITATIONS OF THIS STUDY

Several constraints should be acknowledged when interpreting our findings. Firstly, due to the nature of the devices, it was not feasible to blind the anesthetist performing the intubation to the study group, potentially introducing bias. Secondly, our investigation was limited by a relatively small sample size. To fully establish the significance of this technique in operative settings, more extensive studies encompassing larger patient populations are necessary. Lastly, it's worth noting that the anesthetists involved in the study possessed considerably more experience with the Macintosh laryngoscope compared to the McGrath MAC video laryngoscope, which may have influenced the results. Future research should aim to address these limitations to provide more robust and generalizable conclusions.

CONFLICT OF INTEREST

There are no conflicts of interest.

FINANCIAL SUPPORT AND SPONSORSHIP

  Nil

1. Zaouter C, Calderon J, Hemmerling TM. Videolaryngoscopy as a new standard of care. Br J Anaesth. 2015 Feb 1;114(2):181–3.
2. Saxena A, Madan M, Shrivastava U, Mittal A, Dwivedi Y, Agrawal A, et al. Role of the Truview EVO2 laryngoscope in the airway management of elective surgical patients: A comparison with the Macintosh laryngoscope. Indian J Anaesth. 2013;57(3):276.
3. Nasim S, Maharaj CH, Butt I, Malik MA, O’ Donnell J, Higgins BD, et al. Comparison of the Airtraq and Truview laryngoscopes to the Macintosh laryngoscope for use by Advanced Paramedics in easy and simulated difficult intubation in manikins. BMC Emerg Med. 2009 Feb 1;9:2.
4. Soma Tech Intl’s Blog [Internet]. [cited 2024 Jun 24]. McGRATH Series 5 Video Laryngoscope | Adjustable Blade. Available from: https://www.somatechnology.com/video-laryngoscopes/mcgrath-series-5/
5. Channa AB. Video laryngoscopes. Saudi J Anaesth. 2011 Oct;5(4):357–9.
6. Doyle J. A brief history of clinical airway management. 2009;4.
7. Jackson C. Direct laryngoscopes. The Laryngoscope. 1913;23(6):708–9.
8. Miller RA. A NEW LARYNGOSCOPE. Anesthesiology. 1941 May 1;2(3):317–20.
9. Macintosh RR. A NEW LARYNGOSCOPE. The Lancet. 1943 Feb 13;241(6233):205.
10. Liban JB. Innovations, inventions and Dr Archie Brain. Anaesthesia. 2012;67(12):1309–13.
11. van Zundert TCRV, Brimacombe JR, Ferson DZ, Bacon DR, Wilkinson DJ. Archie Brain: celebrating 30 years of development in laryngeal mask airways. Anaesthesia. 2012 Dec;67(12):1375–85.
12. Savoldelli GL, Schiffer E, Abegg C, Baeriswyl V, Clergue F, Waeber JL. Comparison of the Glidescope, the McGrath, the Airtraq and the Macintosh laryngoscopes in simulated difficult airways*. Anaesthesia. 2008 Dec;63(12):1358–64.
13. McGRATHTM MAC Video Laryngoscope | Medtronic [Internet]. [cited 2024 Jun 24]. Available from: https://www.medtronic.com/covidien/en-us/products/intubation/mcgrath-mac-video-laryngoscope.html
14. Bhola R, Bhalla S, Gupta R, Singh I, Kumar S. Tracheal intubation in patients with cervical spine immobilization: A comparison of McGrath(®) video laryngoscope and Truview EVO2(®) laryngoscope. Indian J Anaesth. 2014 May;58(3):269–74.
15. Kim JE, Kwak HJ, Jung WS, Chang MY, Lee SY, Kim JY. A comparison between McGrath MACvideolaryngoscopy and Macintosh laryngoscopy in children. Acta Anaesthesiol Scand. 2018 Mar;62(3):312–8.
16. Abhyankar P, Sabharwal N, Gupta A, Das AK. Comparative evaluation of C-MAC and McGrath MAC videolaryngoscopes with Macintosh direct laryngoscope for endotracheal intubation in adult patients undergoing elective surgeries. J Anaesthesiol Clin Pharmacol. 2023;39(3):422–8.
17. mcgrath-mac-enhanced-direct-laryngoscope-product-brochure.pdf [Internet]. [cited 2024 Jun 24]. Available from: https://www.medtronic.com/content/dam/medtronic-wide/public/united-states/products/respiratory/mcgrath-mac-enhanced-direct-laryngoscope-product-brochure.pdf