Comparison of Glottic View and Haemodynamic Stress Response Associated with Laryngoscopy using the Macintosh, McCoy and Miller Blades in Adult Patients

Introduction: Laryngoscopy induces haemodynamic responsewhich has implications for patients with cardiovascularillnesses. We devised this study to compare the laryngoscopicview of the glottis obtained with the Macintosh, McCoy andMiller blades, and corresponding haemodynamic changes.Material and Methods: 105 ASA grade I and II patientsrandomly divided into three groups were intubated usingMacintosh, McCoy and Miller blade respectively. Cormackand Lehane grade of glottic view obtained, heart rate, systolicand diastolic blood pressure at baseline, immediately beforeinduction, following induction, and at 1, 3 and 10 minutesafter intubation were noted. Epi Info 7.2 was used forstatistical analysis. Chi square and ANOVA tests were appliedto compare haemodynamic parameters.Results: 18 patients (51.4%) were CL grade I and 17 (48.6%)were CL grade II in Macintosh, 24 (68.6%) were CL gradeI and 11 (31.4%) were CL II in McCoy and, 32 (91.4%)were CL I and 3 (8.6%) were CL II in Miller group. Risein heart rate following intubation was greatest with Millerblade, followed by Macintosh and least with McCoy, andwas statistically significant (P< 0.01). Rise in both, systolicand diastolic blood pressure following intubation was highestwith the Miller blade, followed by Macintosh and least withMcCoy, and the difference compared with baseline values wasstatistically significant (P<0.01).Conclusions: Miller blade provides best visualization of larynxbut McCoy blade produced least haemodynamic response,hence the latter is preferable when less haemodynamicresponse is desired.

Effects of the modified blade on reducing the risk of dental trauma by novice laryngoscopists in anticipated difficult airway / 대한마취과학회지

BACKGROUND: Dental trauma is one of the most common complications during laryngoscopy, especially by novice. As the chance of making direct contact with the teeth is decreased during laryngoscopy, the chance of applying direct pressure to the teeth is decreased, thus the injury by the blade also can be decreased. The purpose of this study was to determine the effectiveness of a modified Macintosh blade on reducing dental contact and the risk of dental trauma by novice laryngoscopists in anticipated difficult airway. METHODS: Sixty-six patients scheduled for elective surgery were divided into Easy group and Difficult group according to Wilson's risk sum score. Laryngoscopy was performed twice on each patient by novice, once with a regular Macintosh 3 blade and once with a blade in which the flange was partially removed (Callander modification). The distance between the flange of the blade and the upper incisors at glottic exposure was measured. We compared the blade-tooth distances and the chance of directly contacting the tooth between two blades. RESULTS: The modified blade provided more distance than the regular Macintosh blade in both group (P < 0.001). It is also associated with decreased chance of directly contacting the teeth, especially in Difficult group (73.7% with regular blade vs 10.6% with the modified blade) (P < 0.001). CONCLUSIONS: The modified Macintosh blade used in this study proved to be an effective device for novice laryngoscopists in reducing likelihood of dental injuries in anticipated difficult intubation.

Effects of the modified blade on reducing the risk of dental trauma by novice laryngoscopists in anticipated difficult airway / 대한마취과학회지

BACKGROUND: Dental trauma is one of the most common complications during laryngoscopy, especially by novice. As the chance of making direct contact with the teeth is decreased during laryngoscopy, the chance of applying direct pressure to the teeth is decreased, thus the injury by the blade also can be decreased. The purpose of this study was to determine the effectiveness of a modified Macintosh blade on reducing dental contact and the risk of dental trauma by novice laryngoscopists in anticipated difficult airway. METHODS: Sixty-six patients scheduled for elective surgery were divided into Easy group and Difficult group according to Wilson's risk sum score. Laryngoscopy was performed twice on each patient by novice, once with a regular Macintosh 3 blade and once with a blade in which the flange was partially removed (Callander modification). The distance between the flange of the blade and the upper incisors at glottic exposure was measured. We compared the blade-tooth distances and the chance of directly contacting the tooth between two blades. RESULTS: The modified blade provided more distance than the regular Macintosh blade in both group (P < 0.001). It is also associated with decreased chance of directly contacting the teeth, especially in Difficult group (73.7% with regular blade vs 10.6% with the modified blade) (P < 0.001). CONCLUSIONS: The modified Macintosh blade used in this study proved to be an effective device for novice laryngoscopists in reducing likelihood of dental injuries in anticipated difficult intubation.

The Effectiveness of a Modified Laryngoscope Blade on Reducing the Potential of Dental Trauma / 대한마취과학회지

BACKGROUND: Despite progress in intubation techniques, dental trauma is one of the most common complications of general anesthesia. As the flange of the Macintosh blade appears responsible for most dental injuries, we modified the ordinary Macintosh blade by partially removing its flange and evaluated the effectiveness of the modified blade in terms of reducing potential of dental injuries. METHODS: Four hundred and eighty-three patients scheduled for elective surgery requiring general anesthesia with endotracheal tube placement were included in this prospective study. Laryngoscopy was performed twice, once using an ordinary Macintosh No. 3 blade and once using the modified Macintosh blade. The modification consisted of reducing the height of the flange by partial removal, as described by Callander et al. When optimum visibility of the glottis was obtained, the distance between the flange of the blade and the upper incisor was measured. We compared blade-tooth distances and laryngoscopic views for the two blades. RESULTS: The modified blade with low-height flange provided more distance than the ordinary type of blade (P<0.01). The incidence of direct contact between the blade and the upper tooth was 20.3% when the ordinary blade was used, and nearly 80% of these did not involve direct contact when using the modified blade. In addition, the modified blade provided a greater field of view than the ordinary blade (P<0.01). CONCLUSIONS: The modified Macintosh blade used in this study proved to be a useful device, which could reduce dental injuries and provide a better laryngoscopic view during laryngoscopy.