Craniotomy: Comparison between Macintosh and Mccoy Laryngoscope Blades, with Monitoring of Entropy

What is it about?

Craniotomy: Comparison between Macintosh and Mccoy Laryngoscope Blades, with Monitoring of Entropy

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Photo by National Cancer Institute on Unsplash

Photo by National Cancer Institute on Unsplash

Why is it important?

Aim: To compare the haemodynamic responses, during laryngoscopy and intubation, using Macintosh and McCoy blades, in patients of ASA grades I and II, undergoing craniotomy for supratentorial lesions, under general anaesthesia, with monitoring of entropy, to ensure uniform depth of anaesthesia. Methodology: A prospective, randomized, comparative study conducted at Nizam’s Institute of Medical Sciences , between January 2013 and April 2013 . Total 60 patients were included in study with 30 patients in each group divided as Group A - Macintosh laryngoscope was used & Group B -- McCoy laryngoscope was used. Patients included were undergoing elective supratentorial lesion surgery, aged between 18 to 60 years & belonged to ASA grade I & II. Depth of anaesthesia by monitoring entropy was kept uniform during laryngoscopy and intubation (Between 40 to 60). Airway assessment and difficult intubation scoring systems and also intubation related parameters were noted and compared between the 2 groups . Heart rate, Invasive blood pressure, which included systolic, diastolic and mean arterial pressure, RE and SE were recorded and compared at the following time points: preinduction (baseline Tb), before laryngoscopy (T0), during laryngoscopy (TL) , during intubation (In), post intubation at 1, 2, 3, 4 and 5 minutes (T1-T5) , between the 2 groups. Results: Haemodynamic response consisting of an increase in HR, SBP, DBP and MAP were seen during laryngoscopy and intubation, using Macintosh and McCoy blades in this study. It was also observed that, the haemodynamic responses to laryngoscopy and intubation was slightly greater with Macintosh blade than with McCoy blade. This was due to better laryngeal visualization and shorter time of ETT insertion with the McCoy balde, than with the Macintosh and this was contributory to the lower haemodynamic responses seen with the McCoy blade. But these responses were statistically insignificant between the two blades (p>0.05), when depth of anaesthesia by monitoring entropy was kept uniform throughout the study (Between 40 to 60 ). The stress responses were also short lived in both groups, as uniform depth of anaesthesia using entropy monitoring, blunted the overall responses to laryngoscopy and intubation, and the awareness component, which could have occurred if not monitored. Conclusion: We conclude that, although McCoy blade was superior in terms of better glottic visualization, ease of intubation and overall operability, the haemodynamic responses produced during laryngoscopy, intubation and post intubation were similar and comparable with the Macintosh blade and statistically insignificant (p>0.05), when depth of anaesthesia is uniform and adequate.

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