A Prospective study to predict difficult airway in adult patients by using preoperative ultrasound based measurements of airway parameters at sms medical college jaipur

All patients will be visited on the day prior to surgery and explained about the anaesthetic technique and perioperative course. Each patient will have a pre anaesthetic checkup that includes:

1.Any significant present/past medical or surgical history, any drug allergy history will  be noted.

2.General physical examination will be done.

3.Airway examination include Mallampati scores (MMP) , inter incisor distances and will be measured. Mallampati grading 1and 2 and inter incisor gap more than 3 fingers will be taken for study.

4.Vital parameters like Blood pressure, Pulse, SpO2, Temperature, Respiratory rate will be measured.

5.Routine investigations like Hb, TLC, DLC, Bleeding Time, Clotting Time, PT-INR, Fasting blood sugar, Serum urea, Serum creatinine, SGOT, SGPT, Serum Electrolytes, Chest X-Ray, ECG to be done.

6.Written and informed consent will be obtained for general anaesthesia after complete explanation about the study protocol.

7.The antihypertensive medications used by the patients will be recorded.

8.An assessment of the airway using ultrasonography (USG) will be performed preoperatively. Patients will be positioned supine with their heads in a neutral position without any support, chin lifted, mouth closed, and tongue touching the floor of the mouth. They will be instructed to look straight ahead and refrain from making any movements. A linear high-frequency probe will be placed in the submandibular area in the midline to obtain measurements of the thickness of the anterior soft tissue in the transverse view at two levels which are the level of the hyoid bone (Distance from Hyoid Bone to Skin (DSHB)) and the level of the thyrohyoid membrane (distance from the skin to the epiglottis midway between the hyoid bone and the thyroid cartilage (DSEM)).

9.Parameters to be observed will include the thickness of the anterior neck soft tissue in the transverse view at the level of the hyoid bone (Distance from Hyoid Bone to Skin (DSHB)) and the thickness of the anterior neck soft tissue in the transverse view at the level of the thyrohyoid membrane (distance from the skin to the epiglottis midway between the hyoid bone and the thyroid cartilage (DSEM)).

10.Following clinical and USG airway assessment, patients will be classified as having a difficult or easy laryngoscopy based on predetermined criteria for the USG parameters. A distance from the skin to the epiglottis midway between the hyoid bone and the thyroid cartilage (DSEM) value greater than 2.03 cm will be classified as a difficult airway, while a value less than 2.03 cm will be classified as an easy airway. A Distance from Hyoid Bone to Skin (DSHB) value greater than 0.66 cm will be categorized as a difficult airway, while a value less than 0.66 cm will be categorised as an easy airway.

11.Upon arrival in the operating room, an intravenous (IV) line will be secured, and patients will be pre-medicated with injections of glycopyrrolate 0.005 mg per kg and fentanyl 2 mcg per kg, followed by preoxygenation with 100 percent oxygen for three minutes. Induction will be performed using Injection propofol 2 mg per kg, and neuromuscular blockade will be achieved with Injection succinyl choline 2 mg per kg IV. Direct laryngoscopy will be conducted by an anaesthesiologist using an appropriately sized curved Macintosh blade, and the Cormack Lehane (CL) grade will be recorded. Cormack Lehane grades I and II will be considered as easy laryngoscopies. Following laryngoscopy, patients will be intubated with an appropriately sized endotracheal tube laryngoscopy, patients will be intubated with an appropriately sized endotracheal tube and prepared for surgery to commence.