Study on Haemodynamic Response to Laryngoscopy and Intubation using McCOY and Macintosh Laryngoscopes: A Comparative Approach

Introduction: Laryngoscopy and endotracheal intubation are known to cause increase in arterial blood pressure, heart rate and may be associated with various dysarythmias. This study is done to compare the hemodynamic changes with McCOY laryngoscope and Macintosh laryngoscope in 120 patients who were divided into 2 groups. Methods: A positive correlation has been demonstrated between force exerted at laryngoscopy and patient's height, weight, body mass index (BMI) and presence of maxillary incisors but it was seen that effect of these factors on force exerted with the McCOY blade is not as important as with Macintosh blade. So this study was done to compare the hemodynamic response to laryngoscopy and intubation using McCOY and Macintosh laryngoscope in stress attenuation. Results: Maximum increase in heart rate from the baseline after laryngoscopy in group 2 and a least rise in heart rate from base line in group 1.Group 1 has 9 % increase in heart rate from basal value. Group 2 has 22 % increases in heart rate from basal value. Group 1 has 6 % increase in Original Research Article


INTRODUCTION
The induction of anaesthesia, laryngoscopy, endotracheal intubation and surgical stimulation is reported to evoke cardiovascular response characterized by alterations in systemic blood pressure, heart rate and cardiac rhythm [1]. Some clinical consequences in healthy patients are sympathoadrenergic responses.They generally cause failure of ventricular functioning, myocardial ischemia, haemorrhage in cerebrum, All these together cause sudden rise in arterial blood pressure and increase in heart rate. All these complications are reported to be noticed in preexisting hypertensive patients.in such cases disturbances in cardiac rhythm and systemic arterial blood pressure needs to be suppressed. These complications are common in hypertensive patients. The present concept of a definitive sympathetic overactivity during laryngeal intubation clearly shows that a mere protection against vagal overactivity and the use of anticholinergic drugs alone may not be sufficient.Those techniques which require prior laryngoscopy to administer the local anesthetic solution are likely to be of limited value. Narcotics, vasodilators, Betablockers, Calcium channel blockers, lidocain e, . modification of instruments and use of other intubating devices (e.g. LMA) have been tried to obtund this haemodynamic response to laryngoscopy and intubation [2,3].These hemodynamic response during laryngoscopy and endotracheal intubation should be abolished to balance the myocardial 0 2 supply and demand which is very important in the safe conduct of anaesthesia. Hence this study aims to compare the hemodynamic response to laryngoscopy and intubation using McCOY and Macintosh laryngoscopic blade [4].

Study Design
120 patients of ASA physical status I undergoing elective surgical procedure under general anaesthesia with endotracheal intubation was included in the study.
Patients belonging to age groups of 18 -60 years of both sexes were included. It is a prospective randomized controlled study.

Inclusion Criteria:
ASA I physical status-

t) Patient's refusal.
One of the anesthesiologists, who was blinded to the type of laryngoscope used gave all the drugs. The third anesthesiologist who was blinded to the haemodynamic parameters did the laryngoscopy and intubation. Patients of both sexes of ASA physical status I undergoing surgical procedure were randomly allocated into 2 groups (Group 1: McCOY laryngoscope, Group 2: Macintosh laryngoscope). One of the anesthesiologists, who was blinded to the type of laryngoscope used gave all the drugs. Another anesthesiologist took note of the heart rate and blood pressure at different point of times. The third anesthesiologist who was blinded to the haemodynamic parameters did the laryngoscopy and intubation. The McCOY laryngoscope was used with full lever on and it was never used as Macintosh laryngoscope.
Once the vocal cords were visualized, the intubation was done. Both Laryngoscopic and intubation time was measured. The heart rate (HR), systolic blood pressure (SBP), and the diastolic blood pressure (DBP) were noted at different time points-baseline, after induction, immediately after intubation, and subsequently at one-minute interval after intubation. The information collected regarding all the selected cases were recorded in a Master Chart. Data analysis was done with the help of computer using statistical software called PASW Statistic Version 21.0 by applying statistical tools like paired t test, chi square test, ANOVA.A 'p' value less than 0.05 is taken to denote significant relationship.

RESULTS
Heart rate, systolic blood pressure were recorded before induction, prelaryngoscopy, post intubation, and 1 min intervals for 7 min thereafter. Comparison of preoperative heart rate (HR) , blood pressure(BP) and mean arterial pressure (MAP)at various time intervals in two groups were analyzed (Fig 1,2&  3).

DISCUSSION
Laryngoscopy and endotracheal intubation are reported to cause increase in arterial blood pressure, heart rate and may be associated with various dysarythmias. Methods may be many but obtunding this reflex response during laryngoscopy and intubation remains a major concern for the anesthesiologists.

CONCLUSION
McCOY laryngoscope produces significantly less or more Hemodynamic parameters when compared with Macintosh blade. So this nonpharmacological intervention of McCOY blade can be utilized as a tool for obtunding hemodynamic responses to laryngoscopy and intubation.

DISCLAIMER
The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts of the authors.

ETHICAL APPROVAL AND CONSENT
The study was conducted after getting approval by our institution ethical committee and after obtaining written informed consent from the patient. The surgeon was also duly informed of the study.