To compare the haemodynamic stress response of direct laryngoscopy and oro-tracheal intubation using McCoy and Macintosh blade in general anaesthesia

Abstract

Maiti and Moitra: To compare the haemodynamic stress response using McCoy and Macintosh blade Asian Journal of Medical Sciences | Mar 2021 | Vol 12 | Issue 3 29 There are various studies to understand the technique of laryngoscopy9 and the physiological changes caused by it.10 Direct Laryngoscopy and intubation lead to extensive stress response and sympathetic stimulation in the body which can be critical for some patient subsets like cardiac ischemia, raised intracranial tension, cerebral aneurysm, open globe injury, glaucoma etc. Hence reduction of the intense stress response is of utmost importance for a stable and safe hemodynamics in those patients. Various pharmacological measures have been used to blunt this stress response. Various adaptations in the designs of the laryngoscope blades have also been tried. The time duration of laryngoscopy also contributes to the stress response and hence duration of less than 15 seconds is said to be ideal. No technique has yet proved to be perfect. Thus it is a must for all anesthesiologists to understand the physiology of this stress response and also to know the measures to reduce it. Various studies have been carried out in the past and they have shown that the difference in amount of stretch and force caused by different designs of blades leading to varied degrees of stress responses.11 It is interesting to see how this simple technique of changing the laryngoscope blade design changes the degree of stress response. As laryngoscope blades are reused, therefore it is also a very cost effective measure. There have been various studies on the stress response. But as mostly no consensus came from those studies, this study was undertaken amongst the West Bengal population in India to compare the results of the two laryngoscopic blades. MATERIALS AND METHODS The study was conducted in a government medical college of West Bengal for a period of approximately one year (March 2011 to February 2012) on 60 patients (male and female in equal numbers) of ASA grade 1 and 2 and within the age group of 20 to 55 years, posted for elective surgery under general anesthesia with orotracheal intubation. Patients with anticipated difficult intubation, ASA grade 3 and 4, suffering from hypertension, diabetes or other systemic diseases, taking antihypertensive drugs were discarded. It is a prospective randomized observational single blind study. Ethical committee clearance was obtained before commencement of the study. The patients were explained about the whole procedure and a written consent was obtained from each patient. Among 60, 30 males and 30 female patients were selected and divided randomly into group 1 and 2 such that each group contains 15 males and 15 female patients. A detailed pre-anaesthetic check-up was done on the day before surgery including history of present illness and its management, previous medical and surgical illness, previous anaesthetic exposure, drug and allergy history. A detailed examination of the airway, other systems of the body and spine were also done. All routine blood investigations, ECG and chest X ray were checked. The height and weight of the patient were also recorded. All patients were given suggestions regarding the preoperative preparations. After patient identification and checking the consent for surgery and anesthesia the patients were shifted to the operating table with an intravenous line for infusing Ringer’s Lactate. Monitors like noninvasive blood pressure cuff, pulse oximeter, 12 lead ECG, capnograph and temperature probe were attached to the patients. All patients were given intravenous Ondansetron 4mg, injection Fentanyl 2 mcg / kg, three minutes before induction of anaesthesia. Pre-oxygenation was done for 5 minutes and then induction of Anaesthesia was done with Injection 2% Propofol 2mg/kg and Injection Atracurium 0.5mg/kg was used as muscle relaxant. After 3 minutes of bag mask ventilation laryngoscopy and intubation were done. Laryngoscopy was done in less than 15 seconds in all cases. Endotracheal tube size 7.5 mm was used for females and 8.5mm was used for males. The tube was secured with adhesive tapes after the tube position was being confirmed by auscultation and capnography. Anaesthesia was maintained with 66 percent N2O and 33 percent O2 with intermittent intravenous Fentanyl and Atracurium as required. Monitoring 1) Heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure before and after induction, 1 minute, 3 minute and 6 minute after intubation. 2) ECG lead 2 and lead 5 continuously for any rhythm disturbance. 3) End tidal CO2 by capnography. Data analysis Data was analyzed by SPSS version 19. Student’s t-test was applied to find the difference between the mean values of the parameters of the two groups at the base line and after induction with Propofol. Two-way mixed model repeated measures ANOVA was used to find the main effect of the influence of time on the mean values of the parameters averaged across both the groups, the group x time interaction and between group effects. Greenhouse-Geisser’s correction for the degrees of freedom was considered where assumption of sphericity was violated. A ‘p’ value less than .05 was considered to be significant. Maiti and Moitra: To compare the haemodynamic stress response using McCoy and Macintosh blade 30 Asian Journal of Medical Sciences | Mar 2021 | Vol 12 | Issue 3 RESULTS The mean age in the two groups (38.63 ± 6.53 vs. 38.77 ± 5.56) did not vary significantly [t (58) = .085 p = .933].