Effect Of Conventional Direct Laryngoscopy And Left Head Rotation Technique On Laryngeal View In Patients Undergoing Surgery Under The General Anaesthesia– A Prospective, Randomized Cross Over Study

In this prospective randomised cross-over study, patients will be enrolled based on the aforementioned inclusion and exclusion criteria. All the selected subjects will be assessed preoperatively and will be explained about the study in their vernacular language. A detailed patient information sheet (PIS) will be given to the patients or their next of kin. Written informed consent will be taken from the patients prior to enrolment. Detailed history and physical examination of patients will be done preoperatively. On the day of the surgery, patients will be shifted to the operation theatre and standard ASA monitors including Non-invasive blood pressure (NIBP), electrocardiography (ECG) and pulse oximetry (SpO2) monitoring will be attached. Blood pressure will be monitored at an interval of 1 minute during induction of anaesthesia as well as the total laryngoscopy sequence. Bispectral Index (BIS) monitoring sensors will be placed on the forehead after cleaning the forehead with an alcohol-based solution. BIS will be maintained between 40 and 60. A wide-bore intravenous (IV) cannula will be inserted.

Following preoxygenation for 3 minutes, induction of anaesthesia will be done with intravenous midazolam(0.02mg/kg), Lignocaine hydrochloride 2% (1.5 mg/kg), propofol(1-2mg/kg), Fentanyl (2mcg/kg) and vecuronium (0.1mg/kg). The sequence of laryngoscopy will be determined using computer generated randomisation sequence as AB or BA (A – Laryngoscopy with Sniffing position technique and B-Laryngoscopy with LeHeR technique)  in order to avoid bias in favour of either laryngoscopy techniques.

In the Sniffing position technique, patients will be placed in the supine position and a pillow will be placed under the patient’s occiput to facilitate cervical flexion and the head will be extended to attain extension of the atlanto-occipital joint. In the LeHeR technique, patients will be placed in supine position with simple neck extension and head rotated to the left up to 45 degrees with the aid of a Goniometer or protractor. Following pre-oxygenation and induction, direct laryngoscopy with the first technique as per the assigned sequence will be done and an assessment of CL grading will be done. After assessment of CL grading, the laryngoscope will be removed and mask ventilation will be done for 3 minutes. Laryngoscopy with the second technique as per the assigned sequence will be done and CL grading will be assessed. The final intubation will be done after the completion of the second laryngoscopy technique. Intubation Difficulty Scale (IDS) Score will be assessed for the technique used.

Titrated doses of propofol at a rate of 100 to 200 mcg/kg/min will be used for maintenance (BIS between 40-60) until the laryngoscopy sequences and intubation are completed.  A bolus of propofol (0.5 mg/kg) will be administered if SBP is increased by more than 20% from the previous reading during the laryngoscopy sequence. After intubation, the further course of anaesthesia will be decided as per the discretion of the anaesthesiology in charge of that case.