Hemodynamic responses to laryngoscopy and intubation using Macintosh, Miller and McCoy blades

Abstract

Background: Direct Laryngoscopy and endotracheal intubation are essential components of administration of general anaesthesia but trigger major stress response, in the form of in­creased catecholamines leading to tachycardia and hypertension. This study is designed to compare the haemodynamic stress response with the Macintosh, McCoy and Miller blades.

Methods: This prospective comparative study was conducted in 150 ASA grade I and II pa­tients, undergoing laparoscopic cholecystectomy under general anaesthesia from March 2017, were randomly divided into three groups using Macintosh, McCoy and Miller blade for endotracheal intubation respectively.

Results: The groups were also comparable in respect to gender, mean age, ASA grade, Cor­mack and Lehane grade, Laryngoscopic intubation time, baseline heart rate, heart rate before laryngoscopy, baseline mean arterial pressure and Mean Arterial Pressure before laryngos­copy. The mean heart rates at end of 1, 3 and 5 minute were 93.58±13.11, 88.28±11.57 and 83.64±10.94 bpm with Macintosh blade; 93.08±12.09, 94.54±11.87 and 87.50±10.72 bpm with McCoy blades; 108.20±13.94, 95.18±12.75 and 93.22±12.32 bpm with Miller blades. Rise in heart rate as well as mean arterial pressure following intubation was greatest with Miller blade, followed by Macintosh blade and least with McCoy blade and was statistically significant (P< 0.01).

Conclusions: Miller blade produced maximum haemodynamic stress response, followed by Macintosh blade and McCoy blade produced the least haemodynamic response, hence the latter is preferable when less haemodynamic response is desired.