Evaluation of the Hemodynamic Response during Laryngoscopy and Intubation using McCOY and Macintosh Laryngoscope Blades

Abstract

Basic elements of general anesthesia include
unconsciousness, amnesia, analgesia, muscle relaxation,
diminished motor response to noxious stimuli, and reversibility.
Muscle relaxation necessitates securing ventilation with
endotracheal intubation. Laryngoscopy forms an important
part of general anaesthesia and endotracheal intubation.
Laryngoscopes are used to view the larynx and adjacent
structures for inserting an endotracheal tube into the trachea.
Laryngoscopy aims to obtain good visualization of the vocal
cords to facilitate smooth endotracheal intubation. The direct
laryngoscopic view is best seen in sniffing in the morning air
position, improving the glottis view. Laryngoscopy triggers major
stress responses, one due to sympathetic stimulation releasing
catecholamines that leads to tachycardia and hypertension,
which increases the myocardial oxygen demand, and the other
due to vagal stimulation leading to parasympathetic activation
that manifests as bradycardia and hypotension. Both may be
catastrophic in patients with a known history of ischemic heart
disease.
Materials and Methods: This hospital-based prospective,
observational study was carried out in the Department of
Anaesthesiology, Shri Ram Murti Smarak Institute of Medical
Sciences, Bareilly over 112 patients of ASA physical status I
and II, undergoing elective surgery under general anaesthesia
during a period of 18 months (February 2021 to June 2022).
Results: In our study, a total of 112 patients were included,
50.0% of cases were managed by Macintosh blade those
consisting of group I, and 50.0% of cases were managed by
McCoy blade, those consisting of group II. Pre-op Heart rate
(HR) was 80.56 ± 11.48 and 76.79 ± 10.90 in group I and II,
respectively and it was reduced pre-intubation in both groups
and it increased significantly during laryngoscopy (p <0.05).
Pre-op systolic blood pressure (SBP) was 116.56 ± 11.55 and
119.48 ± 11.41 in group I and II, respectively and it was reduced
at pre-intubation in both groups and it increased significantly
during laryngoscopy (p <0.05). Pre-op diastolic blood pressure
(DBP) was 73.17 ± 8.54 and 73.61 ± 10.29 in group I and II,
respectively and it decreased at pre-intubation and again, it was
increased during laryngoscopy (p <0.05). Pre-op mean arterial
pressure (MAP) was 87.79 ± 8.64 and 89.28 ± 9.0 in group I
and II, respectively and it was decreased at pre-intubation
and again, it was increased during laryngoscopy (p<0.05).
ECG was found normal in both groups at all time duration with
tachycardia, but no change in the ST segment was noticed in
any group.
Conclusion: Our study concludes that the McCoy blade
produces significantly lesser marked hemodynamic changes.
The vitals like heart rate, systolic blood pressure, diastolic
blood pressure and mean arterial pressure all rise in both
groups following the laryngoscopy and intubation but increases
with McCoy were less and insignificant than Macintosh
laryngoscopes.